nncmpp/nncmpp.c

/*
 * nncmpp -- the MPD client you never knew you needed
 *
 * Copyright (c) 2016 - 2024, Přemysl Eric Janouch <p@janouch.name>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 */

#include "config.h"

// We "need" to have an enum for attributes before including liberty.
// Avoiding colours in the defaults here in order to support dumb terminals.
#define ATTRIBUTE_TABLE(XX)                              \
	XX( NORMAL,      normal,       -1, -1, 0           ) \
	XX( HIGHLIGHT,   highlight,    -1, -1, A_BOLD      ) \
	/* Gauge                                          */ \
	XX( ELAPSED,     elapsed,      -1, -1, A_REVERSE   ) \
	XX( REMAINS,     remains,      -1, -1, A_UNDERLINE ) \
	/* Tab bar                                        */ \
	XX( TAB_BAR,     tab_bar,      -1, -1, A_REVERSE   ) \
	XX( TAB_ACTIVE,  tab_active,   -1, -1, A_BOLD      ) \
	/* Listview                                       */ \
	XX( HEADER,      header,       -1, -1, A_UNDERLINE ) \
	XX( EVEN,        even,         -1, -1, 0           ) \
	XX( ODD,         odd,          -1, -1, 0           ) \
	XX( DIRECTORY,   directory,    -1, -1, 0           ) \
	XX( SELECTION,   selection,    -1, -1, A_REVERSE   ) \
	/* Cyan is good with both black and white.
	 * Can't use A_REVERSE because bold'd be bright.
	 * Unfortunately ran out of B&W attributes.       */ \
	XX( MULTISELECT, multiselect,  -1,  6, 0           ) \
	/* This ought to be indicative enough.            */ \
	XX( DEFOCUSED,   defocused,    -1, -1, A_UNDERLINE ) \
	XX( SCROLLBAR,   scrollbar,    -1, -1, 0           ) \
	/* These are for debugging only                   */ \
	XX( WARNING,     warning,       3, -1, 0           ) \
	XX( ERROR,       error,         1, -1, 0           ) \
	XX( INCOMING,    incoming,      2, -1, 0           ) \
	XX( OUTGOING,    outgoing,      4, -1, 0           )

enum
{
#define XX(name, config, fg_, bg_, attrs_) ATTRIBUTE_ ## name,
	ATTRIBUTE_TABLE (XX)
#undef XX
	ATTRIBUTE_COUNT
};

// My battle-tested C framework acting as a GLib replacement.  Its one big
// disadvantage is missing support for i18n but that can eventually be added
// as an optional feature.  Localised applications look super awkward, though.

// User data for logger functions to enable formatted logging
#define print_fatal_data    ((void *) ATTRIBUTE_ERROR)
#define print_error_data    ((void *) ATTRIBUTE_ERROR)
#define print_warning_data  ((void *) ATTRIBUTE_WARNING)

#define LIBERTY_WANT_POLLER
#define LIBERTY_WANT_ASYNC
#define LIBERTY_WANT_PROTO_HTTP
#define LIBERTY_WANT_PROTO_MPD
#include "liberty/liberty.c"

#ifdef WITH_X11
#define LIBERTY_XUI_WANT_X11
#endif // WITH_X11
#include "liberty/liberty-xui.c"

#include <dirent.h>
#include <locale.h>
#include <math.h>

// We need cURL to extract links from Internet stream playlists.  It'd be way
// too much code to do this all by ourselves, and there's nothing better around.
#include <curl/curl.h>

// The spectrum analyser requires a DFT transform.  The FFTW library is fairly
// efficient, and doesn't have a requirement on the number of bins.
#ifdef WITH_FFTW
#include <fftw3.h>
#endif  // WITH_FFTW

// Remote MPD control needs appropriate volume controls.
#ifdef WITH_PULSE
#include "liberty/liberty-pulse.c"
#include <pulse/context.h>
#include <pulse/error.h>
#include <pulse/introspect.h>
#include <pulse/subscribe.h>
#include <pulse/sample.h>
#endif  // WITH_PULSE

#define APP_TITLE  PROGRAM_NAME         ///< Left top corner

#include "nncmpp-actions.h"

// --- Utilities ---------------------------------------------------------------

static void
shell_quote (const char *str, struct str *output)
{
	// See SUSv3 Shell and Utilities, 2.2.3 Double-Quotes
	str_append_c (output, '"');
	for (const char *p = str; *p; p++)
	{
		if (strchr ("`$\"\\", *p))
			str_append_c (output, '\\');
		str_append_c (output, *p);
	}
	str_append_c (output, '"');
}

static bool
xstrtoul_map (const struct str_map *map, const char *key, unsigned long *out)
{
	const char *field = str_map_find (map, key);
	return field && xstrtoul (out, field, 10);
}

static const char *
xbasename (const char *path)
{
	const char *last_slash = strrchr (path, '/');
	return last_slash ? last_slash + 1 : path;
}

static char *xstrdup0 (const char *s) { return s ? xstrdup (s) : NULL; }

static char *
latin1_to_utf8 (const char *latin1)
{
	struct str converted = str_make ();
	while (*latin1)
	{
		uint8_t c = *latin1++;
		if (c < 0x80)
			str_append_c (&converted, c);
		else
		{
			str_append_c (&converted, 0xC0 | (c >> 6));
			str_append_c (&converted, 0x80 | (c & 0x3F));
		}
	}
	return str_steal (&converted);
}

static void
str_enforce_utf8 (struct str *self)
{
	if (!utf8_validate (self->str, self->len))
	{
		char *sanitized = latin1_to_utf8 (self->str);
		str_reset (self);
		str_append (self, sanitized);
		free (sanitized);
	}
}

static void
cstr_uncapitalize (char *s)
{
	if (isupper (s[0]) && islower (s[1]))
		s[0] = tolower_ascii (s[0]);
}

static int
print_curl_debug (CURL *easy, curl_infotype type, char *data, size_t len,
	void *ud)
{
	(void) easy;
	(void) ud;
	(void) type;

	char copy[len + 1];
	for (size_t i = 0; i < len; i++)
	{
		uint8_t c = data[i];
		copy[i] = !iscntrl_ascii (c) || c == '\n' ? c : '.';
	}
	copy[len] = '\0';

	char *next;
	for (char *p = copy; p; p = next)
	{
		if ((next = strchr (p, '\n')))
			*next++ = '\0';
		if (!*p)
			continue;

		if (!utf8_validate (p, strlen (p)))
		{
			char *fixed = latin1_to_utf8 (p);
			print_debug ("cURL: %s", fixed);
			free (fixed);
		}
		else
			print_debug ("cURL: %s", p);
	}
	return 0;
}

static char *
mpd_parse_kv (char *line, char **value)
{
	char *key = mpd_client_parse_kv (line, value);
	if (!key)  print_debug ("%s: %s", "erroneous MPD output", line);
	return key;
}

static void
mpd_read_time (const char *value, int *sec, int *optional_msec)
{
	if (!value)
		return;

	char *end = NULL;
	long n = strtol (value, &end, 10);
	if (n < 0 || (*end && *end != '.'))
		return;

	int msec = 0;
	if (*end == '.')
	{
		// In practice, MPD always uses three decimal digits
		size_t digits = strspn (++end, "0123456789");
		if (end[digits])
			return;

		if (digits--) msec += (*end++ - '0') * 100;
		if (digits--) msec += (*end++ - '0') * 10;
		if (digits--) msec +=  *end++ - '0';
	}

	*sec = MIN (INT_MAX, n);
	if (optional_msec)
		*optional_msec = msec;
}

// --- cURL async wrapper ------------------------------------------------------

// You are meant to subclass this structure, no user_data pointers needed
struct poller_curl_task;

/// Receives notification for finished transfers
typedef void (*poller_curl_done_fn)
	(CURLMsg *msg, struct poller_curl_task *task);

struct poller_curl_task
{
	CURL *easy;                         ///< cURL easy interface handle
	char curl_error[CURL_ERROR_SIZE];   ///< cURL error info buffer
	poller_curl_done_fn on_done;        ///< Done callback
};

struct poller_curl_fd
{
	LIST_HEADER (struct poller_curl_fd)
	struct poller_fd fd;                ///< Poller FD
};

struct poller_curl
{
	struct poller *poller;              ///< Parent poller
	struct poller_timer timer;          ///< cURL timer
	CURLM *multi;                       ///< cURL multi interface handle
	struct poller_curl_fd *fds;         ///< List of all FDs

	// TODO: also make sure to dispose of them at the end of the program

	int registered;                     ///< Number of attached easy handles
};

static void
poller_curl_collect (struct poller_curl *self, curl_socket_t s, int ev_bitmask)
{
	int running = 0;
	CURLMcode res;
	// XXX: ignoring errors, in particular CURLM_CALL_MULTI_PERFORM
	if ((res = curl_multi_socket_action (self->multi, s, ev_bitmask, &running)))
		print_debug ("cURL: %s", curl_multi_strerror (res));

	CURLMsg *msg;
	while ((msg = curl_multi_info_read (self->multi, &running)))
		if (msg->msg == CURLMSG_DONE)
		{
			struct poller_curl_task *task = NULL;
			hard_assert (!curl_easy_getinfo
				(msg->easy_handle, CURLINFO_PRIVATE, &task));
			task->on_done (msg, task);
		}
}

static void
poller_curl_on_socket (const struct pollfd *pfd, void *user_data)
{
	int mask = 0;
	if (pfd->revents & POLLIN)  mask |= CURL_CSELECT_IN;
	if (pfd->revents & POLLOUT) mask |= CURL_CSELECT_OUT;
	if (pfd->revents & POLLERR) mask |= CURL_CSELECT_ERR;
	poller_curl_collect (user_data, pfd->fd, mask);
}

static int
poller_curl_on_socket_action (CURL *easy, curl_socket_t s, int what,
	void *user_data, void *socket_data)
{
	(void) easy;
	struct poller_curl *self = user_data;

	struct poller_curl_fd *fd;
	if (!(fd = socket_data))
	{
		set_cloexec (s);

		fd = xmalloc (sizeof *fd);
		LIST_PREPEND (self->fds, fd);

		fd->fd = poller_fd_make (self->poller, s);
		fd->fd.dispatcher = poller_curl_on_socket;
		fd->fd.user_data = self;
		curl_multi_assign (self->multi, s, fd);
	}
	if (what == CURL_POLL_REMOVE)
	{
		// Some annoying cURL bug.  Never trust libraries.
		fd->fd.closed = fcntl(fd->fd.fd, F_GETFL) < 0 && errno == EBADF;

		poller_fd_reset (&fd->fd);
		LIST_UNLINK (self->fds, fd);
		free (fd);
	}
	else
	{
		short events = 0;
		if (what == CURL_POLL_IN)    events = POLLIN;
		if (what == CURL_POLL_OUT)   events =          POLLOUT;
		if (what == CURL_POLL_INOUT) events = POLLIN | POLLOUT;
		poller_fd_set (&fd->fd, events);
	}
	return 0;
}

static void
poller_curl_on_timer (void *user_data)
{
	poller_curl_collect (user_data, CURL_SOCKET_TIMEOUT, 0);
}

static int
poller_curl_on_timer_change (CURLM *multi, long timeout_ms, void *user_data)
{
	(void) multi;
	struct poller_curl *self = user_data;

	if (timeout_ms < 0)
		poller_timer_reset (&self->timer);
	else
		poller_timer_set (&self->timer, timeout_ms);
	return 0;
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

static bool
poller_curl_init (struct poller_curl *self, struct poller *poller,
	struct error **e)
{
	memset (self, 0, sizeof *self);
	if (!(self->multi = curl_multi_init ()))
		return error_set (e, "cURL setup failed");

	CURLMcode mres;
	if ((mres = curl_multi_setopt (self->multi,
			CURLMOPT_SOCKETFUNCTION, poller_curl_on_socket_action))
	 || (mres = curl_multi_setopt (self->multi,
			CURLMOPT_TIMERFUNCTION, poller_curl_on_timer_change))
	 || (mres = curl_multi_setopt (self->multi, CURLMOPT_SOCKETDATA, self))
	 || (mres = curl_multi_setopt (self->multi, CURLMOPT_TIMERDATA, self)))
	{
		curl_multi_cleanup (self->multi);
		self->multi = NULL;
		return error_set (e, "%s: %s",
			"cURL setup failed", curl_multi_strerror (mres));
	}

	self->timer = poller_timer_make ((self->poller = poller));
	self->timer.dispatcher = poller_curl_on_timer;
	self->timer.user_data = self;
	return true;
}

static void
poller_curl_free (struct poller_curl *self)
{
	curl_multi_cleanup (self->multi);
	poller_timer_reset (&self->timer);

	LIST_FOR_EACH (struct poller_curl_fd, iter, self->fds)
	{
		poller_fd_reset (&iter->fd);
		free (iter);
	}
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

/// Initialize a task with a new easy instance that can be used with the poller
static bool
poller_curl_spawn (struct poller_curl_task *task, struct error **e)
{
	CURL *easy;
	if (!(easy = curl_easy_init ()))
		return error_set (e, "cURL setup failed");

	// We already take care of SIGPIPE, and native DNS timeouts are only
	// a problem for people without the AsynchDNS feature.
	//
	// Unfortunately, cURL doesn't allow custom callbacks for DNS.
	// The most we could try is parse out the hostname and provide an address
	// override for it using CURLOPT_RESOLVE.  Or be our own SOCKS4A/5 proxy.

	CURLcode res;
	if ((res = curl_easy_setopt (easy, CURLOPT_NOSIGNAL,    1L))
	 || (res = curl_easy_setopt (easy, CURLOPT_ERRORBUFFER, task->curl_error))
	 || (res = curl_easy_setopt (easy, CURLOPT_PRIVATE,     task)))
	{
		curl_easy_cleanup (easy);
		return error_set (e, "%s", curl_easy_strerror (res));
	}

	task->easy = easy;
	return true;
}

static bool
poller_curl_add (struct poller_curl *self, CURL *easy, struct error **e)
{
	CURLMcode mres;
	// "CURLMOPT_TIMERFUNCTION [...] will be called from within this function"
	if ((mres = curl_multi_add_handle (self->multi, easy)))
		return error_set (e, "%s", curl_multi_strerror (mres));
	self->registered++;
	return true;
}

static bool
poller_curl_remove (struct poller_curl *self, CURL *easy, struct error **e)
{
	CURLMcode mres;
	if ((mres = curl_multi_remove_handle (self->multi, easy)))
		return error_set (e, "%s", curl_multi_strerror (mres));
	self->registered--;
	return true;
}

// --- Compact map -------------------------------------------------------------

// MPD provides us with a hefty amount of little key-value maps.  The overhead
// of str_map for such constant (string -> string) maps is too high and it's
// much better to serialize them (mainly cache locality and memory efficiency).
//
// This isn't intended to be reusable and has case insensitivity built-in.

typedef uint8_t *compact_map_t;         ///< Compacted (string -> string) map

static compact_map_t
compact_map (struct str_map *map)
{
	struct str s = str_make ();
	struct str_map_iter iter = str_map_iter_make (map);

	char *value;
	static const size_t zero = 0, alignment = sizeof zero;
	while ((value = str_map_iter_next (&iter)))
	{
		size_t entry_len = iter.link->key_length + 1 + strlen (value) + 1;
		size_t padding_len = (alignment - entry_len % alignment) % alignment;
		entry_len += padding_len;

		str_append_data (&s, &entry_len, sizeof entry_len);
		str_append_printf (&s, "%s%c%s%c", iter.link->key, 0, value, 0);
		str_append_data (&s, &zero, padding_len);
	}
	str_append_data (&s, &zero, sizeof zero);
	return (compact_map_t) str_steal (&s);
}

static char *
compact_map_find (compact_map_t data, const char *needle)
{
	size_t entry_len;
	while ((entry_len = *(size_t *) data))
	{
		data += sizeof entry_len;
		if (!strcasecmp_ascii (needle, (const char *) data))
			return (char *) data + strlen (needle) + 1;
		data += entry_len;
	}
	return NULL;
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

struct item_list
{
	compact_map_t *items;               ///< Compacted (string -> string) maps
	size_t len;                         ///< Length
	size_t alloc;                       ///< Allocated items
};

static struct item_list
item_list_make (void)
{
	struct item_list self = {};
	self.items = xcalloc ((self.alloc = 16), sizeof *self.items);
	return self;
}

static void
item_list_free (struct item_list *self)
{
	for (size_t i = 0; i < self->len; i++)
		free (self->items[i]);
	free (self->items);
}

static bool
item_list_set (struct item_list *self, int i, struct str_map *item)
{
	if (i < 0 || (size_t) i >= self->len)
		return false;

	free (self->items[i]);
	self->items[i] = compact_map (item);
	return true;
}

static compact_map_t
item_list_get (struct item_list *self, int i)
{
	if (i < 0 || (size_t) i >= self->len || !self->items[i])
		return NULL;
	return self->items[i];
}

static void
item_list_resize (struct item_list *self, size_t len)
{
	// Make the allocated array big enough but not too large
	size_t new_alloc = self->alloc;
	while (new_alloc < len)
		new_alloc <<= 1;
	while ((new_alloc >> 1) >= len
		&& (new_alloc - len) >= 1024)
		new_alloc >>= 1;

	for (size_t i = len; i < self->len; i++)
		free (self->items[i]);
	if (new_alloc != self->alloc)
		self->items = xreallocarray (self->items,
			sizeof *self->items, (self->alloc = new_alloc));
	for (size_t i = self->len; i < len; i++)
		self->items[i] = NULL;

	self->len = len;
}

// --- Spectrum analyzer -------------------------------------------------------

// See http://www.zytrax.com/tech/audio/equalization.html
// for a good write-up about this problem domain

#ifdef WITH_FFTW

struct spectrum
{
	int sampling_rate;                  ///< Number of samples per seconds
	int channels;                       ///< Number of sampled channels
	int bits;                           ///< Number of bits per sample
	int bars;                           ///< Number of output vertical bars

	int bins;                           ///< Number of DFT bins
	int useful_bins;                    ///< Bins up to the Nyquist frequency
	int samples;                        ///< Number of windows to average
	float accumulator_scale;            ///< Scaling factor for accum. values
	int *top_bins;                      ///< Top DFT bin index for each bar
	char *rendered;                     ///< String buffer for the "render"
	float *spectrum;                    ///< The "render" as normalized floats

	void *buffer;                       ///< Input buffer
	size_t buffer_len;                  ///< Input buffer fill level
	size_t buffer_size;                 ///< Input buffer size

	/// Decode the respective part of the buffer into the second half of data
	void (*decode) (struct spectrum *, int sample);

	float *data;                        ///< Normalized audio data
	float *window;                      ///< Sampled window function
	float *windowed;                    ///< data * window
	fftwf_complex *out;                 ///< DFT output
	fftwf_plan p;                       ///< DFT plan/FFTW configuration
	float *accumulator;                 ///< Accumulated powers of samples
};

// - - Windows - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

// Out: float[n] of 0..1
static void
window_hann (float *coefficients, size_t n)
{
	for (size_t i = 0; i < n; i++)
	{
		float sine = sin (M_PI * i / n);
		coefficients[i] = sine * sine;
	}
}

// In: float[n] of -1..1, float[n] of 0..1; out: float[n] of -1..1
static void
window_apply (const float *in, const float *coefficients, float *out, size_t n)
{
	for (size_t i = 0; i < n; i++)
		out[i] = in[i] * coefficients[i];
}

// In: float[n] of 0..1; out: float 0..n, describing the coherent gain
static float
window_coherent_gain (const float *in, size_t n)
{
	float sum = 0;
	for (size_t i = 0; i < n; i++)
		sum += in[i];
	return sum;
}

// - - Decoding  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

static void
spectrum_decode_8 (struct spectrum *s, int sample)
{
	size_t n = s->useful_bins;
	float *data = s->data + n;
	for (int8_t *p = (int8_t *) s->buffer + sample * n * s->channels;
		n--; p += s->channels)
	{
		int32_t acc = 0;
		for (int ch = 0; ch < s->channels; ch++)
			acc += p[ch];
		*data++ = (float) acc / s->channels / -INT8_MIN;
	}
}

static void
spectrum_decode_16 (struct spectrum *s, int sample)
{
	size_t n = s->useful_bins;
	float *data = s->data + n;
	for (int16_t *p = (int16_t *) s->buffer + sample * n * s->channels;
		n--; p += s->channels)
	{
		int32_t acc = 0;
		for (int ch = 0; ch < s->channels; ch++)
			acc += p[ch];
		*data++ = (float) acc / s->channels / -INT16_MIN;
	}
}

static void
spectrum_decode_16_2 (struct spectrum *s, int sample)
{
	size_t n = s->useful_bins;
	float *data = s->data + n;
	for (int16_t *p = (int16_t *) s->buffer + sample * n * 2; n--; p += 2)
		*data++ = ((int32_t) p[0] + p[1]) / 2. / -INT16_MIN;
}

// - - Spectrum analysis - - - - - - - - - - - - - - - - - - - - - - - - - - - -

static const char *spectrum_bars[] =
	{ " ", "▁", "▂", "▃", "▄", "▅", "▆", "▇", "█" };

/// Assuming the input buffer is full, updates the rendered spectrum
static void
spectrum_sample (struct spectrum *s)
{
	memset (s->accumulator, 0, sizeof *s->accumulator * s->useful_bins);

	// Credit for the algorithm goes to Audacity's /src/SpectrumAnalyst.cpp,
	// apparently Welch's method
	for (int sample = 0; sample < s->samples; sample++)
	{
		// We use 50% overlap and start with data from the last run (if any)
		memmove (s->data, s->data + s->useful_bins,
			sizeof *s->data * s->useful_bins);
		s->decode (s, sample);

		window_apply (s->data, s->window, s->windowed, s->bins);
		fftwf_execute (s->p);

		for (int bin = 0; bin < s->useful_bins; bin++)
		{
			// out[0][0] is the DC component, not useful to us
			float re = s->out[bin + 1][0];
			float im = s->out[bin + 1][1];
			s->accumulator[bin] += re * re + im * im;
		}
	}

	int last_bin = 0;
	char *p = s->rendered;
	for (int bar = 0; bar < s->bars; bar++)
	{
		int top_bin = s->top_bins[bar];

		// Think of this as accumulating energies within bands,
		// so that it matches our non-linear hearing--there's no averaging.
		// For more precision, we could employ an "equal loudness contour".
		float acc = 0;
		for (int bin = last_bin; bin < top_bin; bin++)
			acc += s->accumulator[bin];

		last_bin = top_bin;
		float db = 10 * log10f (acc * s->accumulator_scale);
		if (db > 0)
			db = 0;

		// Assuming decibels are always negative (i.e., properly normalized).
		// The division defines the cutoff: 8 * 7 = 56 dB of range.
		int height = N_ELEMENTS (spectrum_bars) - 1 + (int) (db / 7);
		p += strlen (strcpy (p, spectrum_bars[MAX (height, 0)]));

		// Even with slightly the higher display resolutions provided by X11,
		// 60 dB roughly covers the useful range.
		s->spectrum[bar] = MAX (0, 1 + db / 60);
	}
}

static bool
spectrum_init (struct spectrum *s, char *format, int bars, int fps,
	struct error **e)
{
	errno = 0;

	long sampling_rate, bits, channels;
	if (!format
	 || (sampling_rate = strtol (format, &format, 10), *format++ != ':')
	 || (bits          = strtol (format, &format, 10), *format++ != ':')
	 || (channels      = strtol (format, &format, 10), *format)
	 || errno != 0)
		return error_set (e, "invalid format, expected RATE:BITS:CHANNELS");

	if (sampling_rate < 20000 || sampling_rate > INT_MAX)
		return error_set (e, "unsupported sampling rate (%ld)", sampling_rate);
	if (bits != 8 && bits != 16)
		return error_set (e, "unsupported bit count (%ld)", bits);
	if (channels < 1 || channels > INT_MAX)
		return error_set (e, "no channels to sample (%ld)", channels);
	if (bars < 1 || bars > 12)
		return error_set (e, "requested too few or too many bars (%d)", bars);

	// All that can fail henceforth is memory allocation
	*s = (struct spectrum)
	{
		.sampling_rate = sampling_rate,
		.bits          = bits,
		.channels      = channels,
		.bars          = bars,
	};

	// The number of bars is always smaller than that of the samples (bins).
	// Let's start with the equation of the top FFT bin to use for a given bar:
	//   top_bin = (num_bins + 1) ^ (bar / num_bars) - 1
	// N.b. if we didn't subtract, the power function would make this ≥ 1.
	// N.b. we then also need to extend the range by the same amount.
	//
	// We need the amount of bins for the first bar to be at least one:
	//         1 ≤ (num_bins + 1) ^   (1 / num_bars) - 1
	//
	// Solving with Wolfram Alpha gives us:
	//   num_bins ≥ (2 ^ num_bars) - 1  [for y > 0]
	//
	// And we need to remember that half of the FFT bins are useless/missing--
	// FFTW skips useless points past the Nyquist frequency.
	int necessary_bins = 2 << s->bars;

	// Discard frequencies above 20 kHz, which take up a constant ratio
	// of all bins, given by the sampling rate.  A more practical/efficient
	// solution would be to just handle 96/192/... kHz rates as bitshifts.
	//
	// Filtering out sub-20 Hz frequencies would be even more wasteful than
	// this wild DFT size, so we don't even try.  While we may just shift
	// the lowest used bin easily within the extra range provided by this
	// extension (the Nyquist is usually above 22 kHz, and it hardly matters
	// if we go a bit beyond 20 kHz in the last bin), for a small number of bars
	// the first bin already includes audible frequencies, and even for larger
	// numbers it wouldn't be too accurate.  An exact solution would require
	// having the amount of bins be strictly a factor of Nyquist / 20 (stemming
	// from the equation 20 = Nyquist / bins).  Since log2(44100 / 2 / 20) > 10,
	// it would be fairly expensive, and somewhat slowly updating.  Always.
	// (Note that you can increase window overlap to get smoother framerates,
	// but it would remain laggy.)
	double audible_ratio = s->sampling_rate / 2. / 20000;
	s->bins = ceil (necessary_bins * MAX (audible_ratio, 1));
	s->useful_bins = s->bins / 2;

	int used_bins = necessary_bins / 2;
	s->rendered = xcalloc (s->bars * 3 + 1, sizeof *s->rendered);
	s->spectrum = xcalloc (s->bars, sizeof *s->spectrum);
	s->top_bins = xcalloc (s->bars, sizeof *s->top_bins);
	for (int bar = 0; bar < s->bars; bar++)
	{
		int top_bin = floor (pow (used_bins + 1, (bar + 1.) / s->bars)) - 1;
		s->top_bins[bar] = MIN (top_bin, used_bins);
	}

	s->samples = s->sampling_rate / s->bins * 2 / MAX (fps, 1);
	if (s->samples < 1)
		s->samples = 1;

	// XXX: we average the channels but might want to average the DFT results
	if (s->bits == 8)   s->decode = spectrum_decode_8;
	if (s->bits == 16)  s->decode = spectrum_decode_16;

	// Micro-optimize to achieve some piece of mind; it's weak but measurable
	if (s->bits == 16 && s->channels == 2)
		s->decode = spectrum_decode_16_2;

	s->buffer_size = s->samples * s->useful_bins * s->bits / 8 * s->channels;
	s->buffer = xcalloc (1, s->buffer_size);

	// Prepare the window
	s->window = xcalloc (s->bins, sizeof *s->window);
	window_hann (s->window, s->bins);

	// Multiply by 2 for only using half of the DFT's result, then adjust to
	// the total energy of the window.  Both squared, because the accumulator
	// contains squared values.  Compute the average, and convert to decibels.
	// See also the mildly confusing https://dsp.stackexchange.com/a/14945.
	float coherent_gain = window_coherent_gain (s->window, s->bins);
	s->accumulator_scale = 2 * 2 / coherent_gain / coherent_gain / s->samples;

	s->data = xcalloc (s->bins, sizeof *s->data);
	s->windowed = fftw_malloc (s->bins * sizeof *s->windowed);
	s->out = fftw_malloc ((s->useful_bins + 1) * sizeof *s->out);
	s->p = fftwf_plan_dft_r2c_1d (s->bins, s->windowed, s->out, FFTW_MEASURE);
	s->accumulator = xcalloc (s->useful_bins, sizeof *s->accumulator);
	return true;
}

static void
spectrum_free (struct spectrum *s)
{
	free (s->accumulator);
	fftwf_destroy_plan (s->p);
	fftw_free (s->out);
	fftw_free (s->windowed);
	free (s->data);
	free (s->window);
#if 0
	// We don't particularly want to discard wisdom.
	fftwf_cleanup ();
#endif

	free (s->rendered);
	free (s->spectrum);
	free (s->top_bins);
	free (s->buffer);

	memset (s, 0, sizeof *s);
}

#endif  // WITH_FFTW

// --- PulseAudio --------------------------------------------------------------

#ifdef WITH_PULSE

struct pulse
{
	struct poller_timer make_context;   ///< Event to establish connection
	pa_mainloop_api *api;               ///< PulseAudio event loop proxy
	pa_context *context;                ///< PulseAudio connection context
	uint32_t sink_candidate;            ///< Used while searching for MPD
	uint32_t sink;                      ///< The relevant sink or -1
	pa_cvolume sink_volume;             ///< Current volume
	bool sink_muted;                    ///< Currently muted?

	void (*on_update) (void);           ///< Update callback
};

static void
pulse_on_sink_info (pa_context *context, const pa_sink_info *info, int eol,
	void *userdata)
{
	(void) context;
	(void) eol;

	struct pulse *self = userdata;
	if (info)
	{
		self->sink_volume = info->volume;
		self->sink_muted = !!info->mute;
		self->on_update ();
	}
}

static void
pulse_update_from_sink (struct pulse *self)
{
	if (self->sink == PA_INVALID_INDEX)
		return;

	pa_operation_unref (pa_context_get_sink_info_by_index
		(self->context, self->sink, pulse_on_sink_info, self));
}

static void
pulse_on_sink_input_info (pa_context *context,
	const struct pa_sink_input_info *info, int eol, void *userdata)
{
	(void) context;
	(void) eol;

	struct pulse *self = userdata;
	if (!info)
	{
		if ((self->sink = self->sink_candidate) != PA_INVALID_INDEX)
			pulse_update_from_sink (self);
		else
			self->on_update ();
		return;
	}

	// TODO: also save info->mute as a different mute level,
	//   and perhaps info->index (they can appear and disappear)
	const char *name =
		pa_proplist_gets (info->proplist, PA_PROP_APPLICATION_NAME);
	if (name && !strcmp (name, "Music Player Daemon"))
		self->sink_candidate = info->sink;
}

static void
pulse_read_sink_inputs (struct pulse *self)
{
	self->sink_candidate = PA_INVALID_INDEX;
	pa_operation_unref (pa_context_get_sink_input_info_list
		(self->context, pulse_on_sink_input_info, self));
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

static void
pulse_on_event (pa_context *context, pa_subscription_event_type_t event,
	uint32_t index, void *userdata)
{
	(void) context;

	struct pulse *self = userdata;
	switch (event & PA_SUBSCRIPTION_EVENT_FACILITY_MASK)
	{
	case PA_SUBSCRIPTION_EVENT_SINK_INPUT:
		pulse_read_sink_inputs (self);
		break;
	case PA_SUBSCRIPTION_EVENT_SINK:
		if (index == self->sink)
			pulse_update_from_sink (self);
	}
}

static void
pulse_on_subscribe_finish (pa_context *context, int success, void *userdata)
{
	(void) context;

	struct pulse *self = userdata;
	if (success)
		pulse_read_sink_inputs (self);
	else
	{
		print_debug ("PulseAudio failed to subscribe for events");
		self->on_update ();
		pa_context_disconnect (context);
	}
}

static void
pulse_on_context_state_change (pa_context *context, void *userdata)
{
	struct pulse *self = userdata;
	switch (pa_context_get_state (context))
	{
	case PA_CONTEXT_FAILED:
	case PA_CONTEXT_TERMINATED:
		print_debug ("PulseAudio context failed or has been terminated");

		pa_context_unref (context);
		self->context = NULL;
		self->sink = PA_INVALID_INDEX;
		self->on_update ();

		// Retry after an arbitrary delay of 5 seconds
		poller_timer_set (&self->make_context, 5000);
		break;
	case PA_CONTEXT_READY:
		pa_context_set_subscribe_callback (context, pulse_on_event, userdata);
		pa_operation_unref (pa_context_subscribe (context,
			PA_SUBSCRIPTION_MASK_SINK | PA_SUBSCRIPTION_MASK_SINK_INPUT,
			pulse_on_subscribe_finish, userdata));
	default:
		break;
	}
}

static void
pulse_make_context (void *user_data)
{
	struct pulse *self = user_data;
	self->context = pa_context_new (self->api, PROGRAM_NAME);
	pa_context_set_state_callback (self->context,
		pulse_on_context_state_change, self);
	pa_context_connect (self->context, NULL, PA_CONTEXT_NOAUTOSPAWN, NULL);
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

static void
pulse_on_finish (pa_context *context, int success, void *userdata)
{
	(void) context;
	(void) success;
	(void) userdata;

	// Just like... whatever, man
}

static bool
pulse_volume_mute (struct pulse *self)
{
	if (!self->context || self->sink == PA_INVALID_INDEX)
		return false;

	pa_operation_unref (pa_context_set_sink_mute_by_index (self->context,
		self->sink, !self->sink_muted, pulse_on_finish, self));
	return true;
}

static bool
pulse_volume_set (struct pulse *self, int arg)
{
	if (!self->context || self->sink == PA_INVALID_INDEX)
		return false;

	pa_cvolume volume = self->sink_volume;
	if (arg > 0)
		pa_cvolume_inc (&volume, (pa_volume_t)  arg * PA_VOLUME_NORM / 100);
	else
		pa_cvolume_dec (&volume, (pa_volume_t) -arg * PA_VOLUME_NORM / 100);
	pa_operation_unref (pa_context_set_sink_volume_by_index (self->context,
		self->sink, &volume, pulse_on_finish, self));
	return true;
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

static void
pulse_init (struct pulse *self, struct poller *poller)
{
	memset (self, 0, sizeof *self);
	self->sink = PA_INVALID_INDEX;
	if (!poller)
		return;

	self->api = poller_pa_new (poller);

	self->make_context = poller_timer_make (poller);
	self->make_context.dispatcher = pulse_make_context;
	self->make_context.user_data = self;
	poller_timer_set (&self->make_context, 0);
}

static void
pulse_free (struct pulse *self)
{
	if (self->context)
		pa_context_unref (self->context);
	if (self->api)
	{
		poller_pa_destroy (self->api);
		poller_timer_reset (&self->make_context);
	}

	pulse_init (self, NULL);
}

#define VOLUME_PERCENT(x) (((x) * 100 + PA_VOLUME_NORM / 2) / PA_VOLUME_NORM)

static bool
pulse_volume_status (struct pulse *self, struct str *s)
{
	if (!self->context || self->sink == PA_INVALID_INDEX
	 || !self->sink_volume.channels)
		return false;

	if (self->sink_muted)
	{
		str_append (s, "Muted");
		return true;
	}

	str_append_printf (s,
		"%u%%", VOLUME_PERCENT (self->sink_volume.values[0]));
	if (!pa_cvolume_channels_equal_to (&self->sink_volume,
			self->sink_volume.values[0]))
	{
		for (size_t i = 1; i < self->sink_volume.channels; i++)
			str_append_printf (s, " / %u%%",
				VOLUME_PERCENT (self->sink_volume.values[i]));
	}
	return true;
}

#endif  // WITH_PULSE

// --- Application -------------------------------------------------------------

// Function names are prefixed mostly because of curses, which clutters the
// global namespace and makes it harder to distinguish what functions relate to.

// The user interface is focused on conceptual simplicity.  That is important
// since we use a custom toolkit, so code would get bloated rather fast--
// especially given our TUI/GUI duality.
//
// There is an independent top pane displaying general status information,
// followed by a tab bar and a listview served by a per-tab event handler.
//
// For simplicity, the listview can only work with items that are one row high.

// Widget identification, mostly for mouse events.
enum
{
	WIDGET_NONE = 0, WIDGET_BUTTON, WIDGET_GAUGE, WIDGET_VOLUME,
	WIDGET_TAB, WIDGET_SPECTRUM, WIDGET_LIST, WIDGET_SCROLLBAR, WIDGET_MESSAGE,
};

struct layout
{
	struct widget *head;
	struct widget *tail;
};

struct app_ui
{
	struct widget *(*padding) (chtype attrs, float width, float height);
	struct widget *(*label) (chtype attrs, const char *label);
	struct widget *(*button) (chtype attrs, const char *label, enum action a);
	struct widget *(*gauge) (chtype attrs);
	struct widget *(*spectrum) (chtype attrs, int width);
	struct widget *(*scrollbar) (chtype attrs);
	struct widget *(*list) (void);
	struct widget *(*editor) (chtype attrs);

	bool have_icons;
};

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

struct tab;

/// Try to handle an action in the tab
typedef bool (*tab_action_fn) (enum action action);

/// Return a line of widgets for the row
typedef struct layout (*tab_item_layout_fn) (size_t item_index);

struct tab
{
	LIST_HEADER (struct tab)

	char *name;                         ///< Visible identifier
	char *header;                       ///< The header, should there be any

	// Implementation:

	tab_action_fn on_action;            ///< User action handler callback
	tab_item_layout_fn on_item_layout;  ///< Item layout callback

	// Provided by tab owner:

	bool can_multiselect;               ///< Multiple items can be selected
	size_t item_count;                  ///< Total item count

	// Managed by the common handler:

	int item_top;                       ///< Index of the topmost item
	int item_selected;                  ///< Index of the selected item
	int item_mark;                      ///< Multiselect second point index
};

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

enum player_state { PLAYER_STOPPED, PLAYER_PLAYING, PLAYER_PAUSED };

// Basically a container for most of the globals; no big sense in handing
// around a pointer to this, hence it is a simple global variable as well.
// There is enough global state as it is.

static struct app_context
{
	// Event loop:

	struct poller poller;               ///< Poller
	struct poller_curl poller_curl;     ///< cURL abstractor
	bool quitting;                      ///< Quit signal for the event loop
	bool polling;                       ///< The event loop is running

	struct poller_fd tty_event;         ///< Terminal input event
	struct poller_fd signal_event;      ///< Signal FD event

	struct poller_timer message_timer;  ///< Message timeout
	char *message;                      ///< Message to show in the statusbar
	char *message_detail;               ///< Non-emphasized part

	// Connection:

	struct mpd_client client;           ///< MPD client interface
	struct poller_timer connect_event;  ///< MPD reconnect timer

	enum player_state state;            ///< Player state
	struct str_map playback_info;       ///< Current song info

	struct poller_timer elapsed_event;  ///< Seconds elapsed event
	int64_t elapsed_since;              ///< Last tick ts or last elapsed time
	bool elapsed_poll;                  ///< Poll MPD for the elapsed time?

	int song;                           ///< Current song index
	int song_elapsed;                   ///< Song elapsed in seconds
	int song_duration;                  ///< Song duration in seconds
	int volume;                         ///< Current volume

	struct item_list playlist;          ///< Current playlist
	uint32_t playlist_version;          ///< Playlist version
	int playlist_time;                  ///< Play time in seconds

	// Data:

	struct config config;               ///< Program configuration
	struct strv streams;                ///< List of "name NUL URI NUL"
	struct strv enqueue;                ///< Items to enqueue once connected
	struct strv action_names;           ///< User-defined action names
	struct strv action_descriptions;    ///< User-defined action descriptions
	struct strv action_commands;        ///< User-defined action commands

	struct tab *help_tab;               ///< Special help tab
	struct tab *tabs;                   ///< All other tabs
	struct tab *active_tab;             ///< Active tab
	struct tab *last_tab;               ///< Previous tab

	// User interface:

	struct app_ui *ui;                  ///< User interface interface
	int ui_dragging;                    ///< ID of any dragged widget

#ifdef WITH_FFTW
	struct spectrum spectrum;           ///< Spectrum analyser
	int spectrum_fd;                    ///< FIFO file descriptor (non-blocking)
	struct poller_fd spectrum_event;    ///< FIFO watcher
#endif  // WITH_FFTW

#ifdef WITH_PULSE
	struct pulse pulse;                 ///< PulseAudio control
#endif  // WITH_PULSE
	bool pulse_control_requested;       ///< PulseAudio control desired by user

	struct line_editor editor;          ///< Line editor

	// Terminal:

	bool use_partial_boxes;             ///< Use Unicode box drawing chars

	struct attrs attrs[ATTRIBUTE_COUNT];
}
g;

/// Shortcut to retrieve named terminal attributes
#define APP_ATTR(name) g.attrs[ATTRIBUTE_ ## name].attrs

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

static void
tab_init (struct tab *self, const char *name)
{
	memset (self, 0, sizeof *self);

	// Add some padding for decorative purposes
	self->name = xstrdup_printf (" %s ", name);
	self->item_selected = 0;
	self->item_mark = -1;
}

static void
tab_free (struct tab *self)
{
	free (self->name);
}

static struct tab_range { int from, upto; }
tab_selection_range (struct tab *self)
{
	if (self->item_selected < 0 || !self->item_count)
		return (struct tab_range) { -1, -1 };
	if (self->item_mark < 0)
		return (struct tab_range) { self->item_selected, self->item_selected };
	return (struct tab_range) { MIN (self->item_selected, self->item_mark),
		MAX (self->item_selected, self->item_mark) };
}

// --- Configuration -----------------------------------------------------------

static void
on_poll_elapsed_time_changed (struct config_item *item)
{
	// This is only set once, on application startup
	g.elapsed_poll = item->value.boolean;
}

static void
on_pulseaudio_changed (struct config_item *item)
{
	// This is only set once, on application startup
	g.pulse_control_requested = item->value.boolean;
}

static const struct config_schema g_config_settings[] =
{
	{ .name      = "address",
	  .comment   = "Address to connect to the MPD server",
	  .type      = CONFIG_ITEM_STRING,
	  .default_  = "\"localhost\"" },
	{ .name      = "password",
	  .comment   = "Password to use for MPD authentication",
	  .type      = CONFIG_ITEM_STRING },

	// NOTE: this is unused--in theory we could allow manual metadata adjustment
	// NOTE: the "config" command may return "music_directory" for local clients
	{ .name      = "root",
	  .comment   = "Where all the files MPD is playing are located",
	  .type      = CONFIG_ITEM_STRING },

#ifdef WITH_FFTW
	{ .name      = "spectrum_path",
	  .comment   = "Visualizer feed path to a FIFO audio output",
	  .type      = CONFIG_ITEM_STRING },
	// MPD's "outputs" command doesn't include this information
	{ .name      = "spectrum_format",
	  .comment   = "Visualizer feed data format",
	  .type      = CONFIG_ITEM_STRING,
	  .default_  = "\"44100:16:2\"" },
	// 10 is about the useful limit, then it gets too computationally expensive
	{ .name      = "spectrum_bars",
	  .comment   = "Number of computed audio spectrum bars",
	  .type      = CONFIG_ITEM_INTEGER,
	  .default_  = "8" },
	{ .name      = "spectrum_fps",
	  .comment   = "Maximum frames per second, affects CPU usage",
	  .type      = CONFIG_ITEM_INTEGER,
	  .default_  = "30" },
#endif  // WITH_FFTW

#ifdef WITH_PULSE
	{ .name      = "pulseaudio",
	  .comment   = "Look up MPD in PulseAudio for improved volume controls",
	  .type      = CONFIG_ITEM_BOOLEAN,
	  .on_change = on_pulseaudio_changed,
	  .default_  = "off" },
#endif  // WITH_PULSE

#ifdef WITH_X11
	{ .name      = "x11_font",
	  .comment   = "Fontconfig name/pattern for the X11 font to use",
	  .type      = CONFIG_ITEM_STRING,
	  .default_  = "`sans\\-serif-11`" },
#endif  // WITH_X11

	// Disabling this minimises MPD traffic and has the following caveats:
	//  - when MPD stalls on retrieving audio data, we keep ticking
	//  - when the "play" succeeds in ACTION_MPD_REPLACE for the same item as
	//    is currently playing, we do not reset g.song_elapsed (we could ask
	//    for a response which feels racy, or rethink the mechanism there)
	{ .name      = "poll_elapsed_time",
	  .comment   = "Whether to actively poll MPD for the elapsed time",
	  .type      = CONFIG_ITEM_BOOLEAN,
	  .on_change = on_poll_elapsed_time_changed,
	  .default_  = "on" },
	{}
};

static const struct config_schema g_config_colors[] =
{
#define XX(name_, config, fg_, bg_, attrs_) \
	{ .name = #config, .type = CONFIG_ITEM_STRING },
	ATTRIBUTE_TABLE (XX)
#undef XX
	{}
};

static const struct config_schema g_config_actions[] =
{
	{ .name      = "description",
	  .comment   = "Human-readable description of the action",
	  .type      = CONFIG_ITEM_STRING },
	{ .name      = "command",
	  .comment   = "Shell command to run",
	  .type      = CONFIG_ITEM_STRING },
	{}
};

static const char *
get_config_string (struct config_item *root, const char *key)
{
	struct config_item *item = config_item_get (root, key, NULL);
	hard_assert (item);
	if (item->type == CONFIG_ITEM_NULL)
		return NULL;
	hard_assert (config_item_type_is_string (item->type));
	return item->value.string.str;
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

static void
load_config_settings (struct config_item *subtree, void *user_data)
{
	config_schema_apply_to_object (g_config_settings, subtree, user_data);
}

static void
load_config_colors (struct config_item *subtree, void *user_data)
{
	config_schema_apply_to_object (g_config_colors,   subtree, user_data);

	// The attributes cannot be changed dynamically right now, so it doesn't
	// make much sense to make use of "on_change" callbacks either.
	// For simplicity, we should reload the entire table on each change anyway.
	const char *value;
#define XX(name, config, fg_, bg_, attrs_) \
	if ((value = get_config_string (subtree, #config))) \
		g.attrs[ATTRIBUTE_ ## name] = attrs_decode (value);
	ATTRIBUTE_TABLE (XX)
#undef XX
}

static int
app_casecmp (const uint8_t *a, const uint8_t *b)
{
	int res;
	// XXX: this seems to produce some strange results
	if (u8_casecmp (a, strlen ((const char *) a), b, strlen ((const char *) b),
		NULL, NULL, &res))
		res = u8_strcmp (a, b);
	return res;
}

static int
strv_sort_utf8_cb (const void *a, const void *b)
{
	return app_casecmp (*(const uint8_t **) a, *(const uint8_t **) b);
}

static void
load_config_streams (struct config_item *subtree, void *user_data)
{
	(void) user_data;

	// XXX: we can't use the tab in load_config_streams() because it hasn't
	//   been initialized yet, and we cannot initialize it before the
	//   configuration has been loaded.  Thus we load it into the app_context.
	struct str_map_iter iter = str_map_iter_make (&subtree->value.object);
	struct config_item *item;
	while ((item = str_map_iter_next (&iter)))
		if (!config_item_type_is_string (item->type))
			print_warning ("`%s': stream URIs must be strings", iter.link->key);
		else
		{
			strv_append_owned (&g.streams, xstrdup_printf ("%s%c%s",
				iter.link->key, 0, item->value.string.str));
		}
	qsort (g.streams.vector, g.streams.len,
		sizeof *g.streams.vector, strv_sort_utf8_cb);
}

static void
load_config_actions (struct config_item *subtree, void *user_data)
{
	(void) user_data;

	struct str_map_iter iter = str_map_iter_make (&subtree->value.object);
	while (str_map_iter_next (&iter))
		strv_append (&g.action_names, iter.link->key);
	qsort (g.action_names.vector, g.action_names.len,
		sizeof *g.action_names.vector, strv_sort_utf8_cb);

	for (size_t i = 0; i < g.action_names.len; i++)
	{
		const char *name = g.action_names.vector[i];
		struct config_item *item = config_item_get (subtree, name, NULL);
		hard_assert (item != NULL);
		if (item->type != CONFIG_ITEM_OBJECT)
			exit_fatal ("`%s': invalid user action, expected an object", name);

		config_schema_apply_to_object (g_config_actions, item, NULL);
		config_schema_call_changed (item);

		const char *description = get_config_string (item, "description");
		const char *command =  get_config_string (item, "command");
		strv_append (&g.action_descriptions, description ? description : name);
		strv_append (&g.action_commands, command ? command : "");
	}
}

static void
app_load_configuration (void)
{
	struct config *config = &g.config;
	config_register_module (config, "settings", load_config_settings, NULL);
	config_register_module (config, "colors",   load_config_colors,   NULL);
	config_register_module (config, "streams",  load_config_streams,  NULL);
	// This must run before bindings are parsed in app_init_ui().
	config_register_module (config, "actions",  load_config_actions,  NULL);

	// Bootstrap configuration, so that we can access schema items at all
	config_load (config, config_item_object ());

	char *filename = resolve_filename
		(PROGRAM_NAME ".conf", resolve_relative_config_filename);
	if (!filename)
		return;

	struct error *e = NULL;
	struct config_item *root = config_read_from_file (filename, &e);
	free (filename);

	if (e)
	{
		print_error ("error loading configuration: %s", e->message);
		error_free (e);
		exit (EXIT_FAILURE);
	}
	if (root)
	{
		config_load (&g.config, root);
		config_schema_call_changed (g.config.root);
	}
}

// --- Application -------------------------------------------------------------

static void
app_init_attributes (void)
{
#define XX(name, config, fg_, bg_, attrs_)      \
	g.attrs[ATTRIBUTE_ ## name].fg    = fg_;    \
	g.attrs[ATTRIBUTE_ ## name].bg    = bg_;    \
	g.attrs[ATTRIBUTE_ ## name].attrs = attrs_;
	ATTRIBUTE_TABLE (XX)
#undef XX
}

static bool
app_on_insufficient_color (void)
{
	app_init_attributes ();
	return true;
}

static void
app_init_context (void)
{
	poller_init (&g.poller);
	hard_assert (poller_curl_init (&g.poller_curl, &g.poller, NULL));
	g.client = mpd_client_make (&g.poller);
	g.song_elapsed = g.song_duration = g.volume = g.song = -1;
	g.playlist = item_list_make ();
	g.config = config_make ();
	g.streams = strv_make ();
	g.enqueue = strv_make ();
	g.action_names = strv_make ();
	g.action_descriptions = strv_make ();
	g.action_commands = strv_make ();

	g.playback_info = str_map_make (free);
	g.playback_info.key_xfrm = tolower_ascii_strxfrm;

#ifdef WITH_FFTW
	g.spectrum_fd = -1;
#endif  // WITH_FFTW

#ifdef WITH_PULSE
	pulse_init (&g.pulse, NULL);
#endif  // WITH_PULSE

	app_init_attributes ();
}

static void
app_free_context (void)
{
	mpd_client_free (&g.client);
	str_map_free (&g.playback_info);
	strv_free (&g.streams);
	strv_free (&g.enqueue);
	strv_free (&g.action_names);
	strv_free (&g.action_descriptions);
	strv_free (&g.action_commands);
	item_list_free (&g.playlist);

#ifdef WITH_FFTW
	spectrum_free (&g.spectrum);
	if (g.spectrum_fd != -1)
	{
		poller_fd_reset (&g.spectrum_event);
		xclose (g.spectrum_fd);
	}
#endif  // WITH_FFTW

#ifdef WITH_PULSE
	pulse_free (&g.pulse);
#endif  // WITH_PULSE

	line_editor_free (&g.editor);

	config_free (&g.config);
	poller_curl_free (&g.poller_curl);
	poller_free (&g.poller);
	free (g.message);
	free (g.message_detail);
}

static void
app_quit (void)
{
	g.quitting = true;

	// So far there's nothing for us to wait on, so let's just stop looping;
	// otherwise we might want to e.g. cleanly bring down the MPD interface
	g.polling = false;
}

// --- Layouting ---------------------------------------------------------------

static void
app_append_layout (struct layout *l, struct layout *dest)
{
	struct widget *last = dest->tail;
	if (!last)
		*dest = *l;
	else if (l->head)
	{
		// Assuming there is no unclaimed vertical space.
		LIST_FOR_EACH (struct widget, w, l->head)
			widget_move (w, 0, last->y + last->height);

		last->next = l->head;
		l->head->prev = last;
		dest->tail = l->tail;
	}

	*l = (struct layout) {};
}

/// Replaces negative widths amongst widgets in the layout by redistributing
/// any width remaining after all positive claims are satisfied from "width".
/// Also unifies heights to the maximum value of the run.
/// Then the widths are taken as final, and used to initialize X coordinates.
static void
app_flush_layout_full (struct layout *l, int width, struct layout *dest)
{
	hard_assert (l != NULL && l->head != NULL);

	int parts = 0, max_height = 0;
	LIST_FOR_EACH (struct widget, w, l->head)
	{
		max_height = MAX (max_height, w->height);
		if (w->width < 0)
			parts -= w->width;
		else
			width -= w->width;
	}

	int remaining = MAX (width, 0), part_width = parts ? remaining / parts : 0;
	struct widget *last = NULL;
	LIST_FOR_EACH (struct widget, w, l->head)
	{
		w->height = max_height;
		if (w->width < 0)
		{
			remaining -= (w->width *= -part_width);
			last = w;
		}
	}
	if (last)
		last->width += remaining;

	int x = 0;
	LIST_FOR_EACH (struct widget, w, l->head)
	{
		widget_move (w, x - w->x, 0);
		x += w->width;
	}

	app_append_layout (l, dest);
}

static void
app_flush_layout (struct layout *l, struct layout *out)
{
	app_flush_layout_full (l, g_xui.width, out);
}

static struct widget *
app_push (struct layout *l, struct widget *w)
{
	LIST_APPEND_WITH_TAIL (l->head, l->tail, w);
	return w;
}

static struct widget *
app_push_fill (struct layout *l, struct widget *w)
{
	w->width = -1;
	LIST_APPEND_WITH_TAIL (l->head, l->tail, w);
	return w;
}

/// Write the given UTF-8 string padded with spaces.
/// @param[in] attrs  Text attributes for the text, including padding.
static void
app_layout_text (const char *str, chtype attrs, struct layout *out)
{
	struct layout l = {};
	app_push (&l, g.ui->padding (attrs, 0.25, 1));
	app_push_fill (&l, g.ui->label (attrs, str));
	app_push (&l, g.ui->padding (attrs, 0.25, 1));
	app_flush_layout (&l, out);
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

static void
app_layout_song_info (struct layout *out)
{
	compact_map_t map;
	if (!(map = item_list_get (&g.playlist, g.song)))
		return;

	chtype attrs[2] = { APP_ATTR (NORMAL), APP_ATTR (HIGHLIGHT) };

	// Split the path for files lying within MPD's "music_directory".
	const char *file = compact_map_find (map, "file");
	const char *subroot_basename = NULL;
	if (file && *file != '/' && !strstr (file, "://"))
	{
		const char *last_slash = strrchr (file, '/');
		if (last_slash)
			subroot_basename = last_slash + 1;
		else
			subroot_basename = file;
	}

	const char *title = NULL;
	const char *name = compact_map_find (map, "name");
	if ((title = compact_map_find (map, "title"))
	 || (title = name)
	 || (title = subroot_basename)
	 || (title = file))
	{
		struct layout l = {};
		app_push (&l, g.ui->padding (attrs[0], 0.25, 1));
		app_push (&l, g.ui->label (attrs[1], title));
		app_push_fill (&l, g.ui->padding (attrs[0], 0, 1));
		app_push (&l, g.ui->padding (attrs[0], 0.25, 1));
		app_flush_layout (&l, out);
	}

	// Showing a blank line is better than having the controls jump around
	// while switching between files that we do and don't have enough data for.
	struct layout l = {};
	app_push (&l, g.ui->padding (attrs[0], 0.25, 1));

	char *artist = compact_map_find (map, "artist");
	char *album  = compact_map_find (map, "album");
	if (artist || album)
	{
		if (artist)
		{
			app_push (&l, g.ui->label (attrs[0], "by "));
			app_push (&l, g.ui->label (attrs[1], artist));
		}
		if (album)
		{
			app_push (&l, g.ui->label (attrs[0], &" from "[!artist]));
			app_push (&l, g.ui->label (attrs[1], album));
		}
	}
	else if (subroot_basename && subroot_basename != file)
	{
		char *parent = xstrndup (file, subroot_basename - file - 1);
		app_push (&l, g.ui->label (attrs[0], "in "));
		app_push (&l, g.ui->label (attrs[1], parent));
		free (parent);
	}
	else if (file && *file != '/' && strstr (file, "://")
		&& name && name != title)
	{
		// This is likely to contain the name of an Internet radio.
		app_push (&l, g.ui->label (attrs[1], name));
	}

	app_push_fill (&l, g.ui->padding (attrs[0], 0, 1));
	app_push (&l, g.ui->padding (attrs[0], 0.25, 1));
	app_flush_layout (&l, out);
}

static char *
app_time_string (int seconds)
{
	int minutes = seconds / 60; seconds %= 60;
	int hours   = minutes / 60; minutes %= 60;

	struct str s = str_make ();
	if (hours)
		str_append_printf (&s, "%d:%02d:", hours, minutes);
	else
		str_append_printf (&s, "%d:", minutes);

	str_append_printf (&s, "%02d", seconds);
	return str_steal (&s);
}

static void
app_layout_status (struct layout *out)
{
	bool stopped = g.state == PLAYER_STOPPED;
	if (!stopped)
		app_layout_song_info (out);

	chtype attrs[2] = { APP_ATTR (NORMAL), APP_ATTR (HIGHLIGHT) };
	struct layout l = {};

	app_push (&l, g.ui->padding (attrs[0], 0.25, 1));
	app_push (&l, g.ui->button (attrs[!stopped], "<<", ACTION_MPD_PREVIOUS));
	app_push (&l, g.ui->padding (attrs[0], 0.5, 1));
	const char *toggle = g.state == PLAYER_PLAYING ? "||" : "|>";
	app_push (&l, g.ui->button (attrs[1], toggle, ACTION_MPD_TOGGLE));
	app_push (&l, g.ui->padding (attrs[0], 0.5, 1));
	app_push (&l, g.ui->button (attrs[!stopped], "[]", ACTION_MPD_STOP));
	app_push (&l, g.ui->padding (attrs[0], 0.5, 1));
	app_push (&l, g.ui->button (attrs[!stopped], ">>", ACTION_MPD_NEXT));
	app_push (&l, g.ui->padding (attrs[0], 1, 1));

	if (stopped)
		app_push_fill (&l, g.ui->label (attrs[0], "Stopped"));
	else
	{
		if (g.song_elapsed >= 0)
		{
			char *s = app_time_string (g.song_elapsed);
			app_push (&l, g.ui->label (attrs[0], s));
			free (s);
		}
		if (g.song_duration >= 1)
		{
			char *s = app_time_string (g.song_duration);
			app_push (&l, g.ui->label (attrs[0], " / "));
			app_push (&l, g.ui->label (attrs[0], s));
			free (s);
		}

		app_push (&l, g.ui->padding (attrs[0], 1, 1));
	}

	struct str volume = str_make ();
#ifdef WITH_PULSE
	if (g.pulse_control_requested)
	{
		if (pulse_volume_status (&g.pulse, &volume))
		{
			if (g.volume >= 0 && g.volume != 100)
				str_append_printf (&volume, " (%d%%)", g.volume);
		}
		else
		{
			if (g.volume >= 0)
				str_append_printf (&volume, "(%d%%)", g.volume);
		}
	}
	else
#endif  // WITH_PULSE
	if (g.volume >= 0)
		str_append_printf (&volume, "%3d%%", g.volume);

	if (!stopped && g.song_elapsed >= 0 && g.song_duration >= 1)
		app_push (&l, g.ui->gauge (attrs[0]))
			->id = WIDGET_GAUGE;
	else
		app_push_fill (&l, g.ui->padding (attrs[0], 0, 1));

	if (volume.len)
	{
		app_push (&l, g.ui->padding (attrs[0], 1, 1));
		app_push (&l, g.ui->label (attrs[0], volume.str))
			->id = WIDGET_VOLUME;
	}
	str_free (&volume);

	app_push (&l, g.ui->padding (attrs[0], 0.25, 1));
	app_flush_layout (&l, out);
}

static void
app_layout_tabs (struct layout *out)
{
	chtype attrs[2] = { APP_ATTR (TAB_BAR), APP_ATTR (TAB_ACTIVE) };
	struct layout l = {};

	// The help tab is disguised so that it's not too intruding
	app_push (&l, g.ui->padding (attrs[g.active_tab == g.help_tab], 0.25, 1))
		->id = WIDGET_TAB;
	app_push (&l, g.ui->label (attrs[g.active_tab == g.help_tab], APP_TITLE))
		->id = WIDGET_TAB;

	// XXX: attrs[0]?
	app_push (&l, g.ui->padding (attrs[g.active_tab == g.help_tab], 0.5, 1))
		->id = WIDGET_TAB;

	int i = 0;
	LIST_FOR_EACH (struct tab, iter, g.tabs)
	{
		struct widget *w = app_push (&l,
			g.ui->label (attrs[iter == g.active_tab], iter->name));
		w->id = WIDGET_TAB;
		w->userdata = ++i;
	}

	app_push_fill (&l, g.ui->padding (attrs[0], 1, 1));

#ifdef WITH_FFTW
	// This seems like the most reasonable, otherwise unoccupied space
	if (g.spectrum_fd != -1)
	{
		app_push (&l, g.ui->spectrum (attrs[0], g.spectrum.bars))
			->id = WIDGET_SPECTRUM;
	}
#endif  // WITH_FFTW

	app_flush_layout (&l, out);
}

static void
app_layout_padding (chtype attrs, struct layout *out)
{
	struct layout l = {};
	app_push_fill (&l, g.ui->padding (attrs, 0, 0.125));
	app_flush_layout (&l, out);
}

static void
app_layout_header (struct layout *out)
{
	if (g.client.state == MPD_CONNECTED)
	{
		app_layout_padding (APP_ATTR (NORMAL), out);
		app_layout_status (out);
		app_layout_padding (APP_ATTR (NORMAL), out);
	}

	app_layout_tabs (out);

	const char *header = g.active_tab->header;
	if (header)
		app_layout_text (header, APP_ATTR (HEADER), out);
}

/// Figure out scrollbar appearance.  @a s is the minimal slider length as well
/// as the scrollbar resolution per @a visible item.
struct scrollbar { long length, start; }
app_compute_scrollbar (struct tab *tab, long visible, long s)
{
	long top = s * tab->item_top, total = s * tab->item_count;
	if (total < visible)
		return (struct scrollbar) { 0, 0 };
	if (visible == 1)
		return (struct scrollbar) { s, 0 };
	if (visible == 2)
		return (struct scrollbar) { s, top >= total / 2 ? s : 0 };

	// Only be at the top or bottom when the top or bottom item can be seen.
	// The algorithm isn't optimal but it's a bitch to get right.
	double available_length = visible - 2 - s + 1;

	double lenf = s + available_length * visible / total, length = 0.;
	long offset = 1 + available_length * top / total + modf (lenf, &length);

	if (top == 0)
		return (struct scrollbar) { length, 0 };
	if (top + visible >= total)
		return (struct scrollbar) { length, visible - length };

	return (struct scrollbar) { length, offset };
}

static struct layout
app_layout_row (struct tab *tab, int item_index)
{
	int row_attrs = (item_index & 1) ? APP_ATTR (ODD) : APP_ATTR (EVEN);

	bool override_colors = true;
	if (item_index == tab->item_selected)
		row_attrs = g_xui.focused
			? APP_ATTR (SELECTION) : APP_ATTR (DEFOCUSED);
	else if (tab->item_mark > -1 &&
	   ((item_index >= tab->item_mark && item_index <= tab->item_selected)
	 || (item_index >= tab->item_selected && item_index <= tab->item_mark)))
		row_attrs = g_xui.focused
			? APP_ATTR (MULTISELECT) : APP_ATTR (DEFOCUSED);
	else
		override_colors = false;

	// The padding must be added before the recoloring below.
	struct layout l = tab->on_item_layout (item_index);
	struct widget *w = g.ui->padding (0, 0.25, 1);
	LIST_PREPEND (l.head, w);
	app_push (&l, g.ui->padding (0, 0.25, 1));

	// Combine attributes used by the handler with the defaults.
	LIST_FOR_EACH (struct widget, w, l.head)
	{
		chtype *attrs = &w->attrs;
		if (override_colors)
			*attrs = (*attrs & ~(A_COLOR | A_REVERSE)) | row_attrs;
		else if ((*attrs & A_COLOR) && (row_attrs & A_COLOR))
			*attrs |= (row_attrs & ~A_COLOR);
		else
			*attrs |=  row_attrs;
	}
	return l;
}

static void
app_layout_view (struct layout *out, int height)
{
	struct layout l = {};
	struct widget *list = app_push_fill (&l, g.ui->list ());
	list->id = WIDGET_LIST;
	list->height = height;
	list->width = g_xui.width;

	struct tab *tab = g.active_tab;
	if ((int) tab->item_count * g_xui.vunit > list->height)
	{
		struct widget *scrollbar = g.ui->scrollbar (APP_ATTR (SCROLLBAR));
		list->width -= scrollbar->width;
		app_push (&l, scrollbar)->id = WIDGET_SCROLLBAR;
	}

	int to_show = MIN ((int) tab->item_count - tab->item_top,
		ceil ((double) list->height / g_xui.vunit));

	struct layout children = {};
	for (int row = 0; row < to_show; row++)
	{
		int item_index = tab->item_top + row;
		struct layout subl = app_layout_row (tab, item_index);
		// TODO: Change layouting so that we don't need to know list->width.
		app_flush_layout_full (&subl, list->width, &children);
	}
	list->children = children.head;

	app_flush_layout (&l, out);
}

static void
app_layout_mpd_status_playlist (struct layout *l, chtype attrs)
{
	char *songs = (g.playlist.len == 1)
		? xstrdup_printf ("1 song")
		: xstrdup_printf ("%zu songs", g.playlist.len);
	app_push (l, g.ui->label (attrs, songs));
	free (songs);

	int hours   = g.playlist_time / 3600;
	int minutes = g.playlist_time % 3600 / 60;
	if (hours || minutes)
	{
		struct str length = str_make ();
		if (hours == 1)
			str_append_printf (&length, " 1 hour");
		else if (hours)
			str_append_printf (&length, " %d hours", hours);

		if (minutes == 1)
			str_append_printf (&length, " 1 minute");
		else if (minutes)
			str_append_printf (&length, " %d minutes", minutes);

		app_push (l, g.ui->padding (attrs, 1, 1));
		app_push (l, g.ui->label (attrs, length.str + 1));
		str_free (&length);
	}

	const char *task = NULL;
	if (g.poller_curl.registered)
		task = "Downloading...";
	else if (str_map_find (&g.playback_info, "updating_db"))
		task = "Updating database...";

	if (task)
	{
		app_push (l, g.ui->padding (attrs, 1, 1));
		app_push (l, g.ui->label (attrs, task));
	}
}

static void
app_layout_mpd_status (struct layout *out)
{
	struct layout l = {};
	chtype attrs[2] = { APP_ATTR (NORMAL), APP_ATTR (HIGHLIGHT) };
	app_push (&l, g.ui->padding (attrs[0], 0.25, 1));

	if (g.active_tab->item_mark > -1)
	{
		struct tab_range r = tab_selection_range (g.active_tab);
		char *msg = xstrdup_printf (r.from == r.upto
			? "Selected %d item" : "Selected %d items", r.upto - r.from + 1);
		app_push_fill (&l, g.ui->label (attrs[0], msg));
		free (msg);
	}
	else
	{
		app_layout_mpd_status_playlist (&l, attrs[0]);
		l.tail->width = -1;
	}

	const char *s = NULL;
	struct str_map *map = &g.playback_info;
	bool repeat  = (s = str_map_find (map, "repeat"))  && strcmp (s, "0");
	bool random  = (s = str_map_find (map, "random"))  && strcmp (s, "0");
	bool single  = (s = str_map_find (map, "single"))  && strcmp (s, "0");
	bool consume = (s = str_map_find (map, "consume")) && strcmp (s, "0");

	if (g.ui->have_icons || repeat)
	{
		app_push (&l, g.ui->padding (attrs[0], 0.5, 1));
		app_push (&l,
			g.ui->button (attrs[repeat], "repeat", ACTION_MPD_REPEAT));
	}
	if (g.ui->have_icons || random)
	{
		app_push (&l, g.ui->padding (attrs[0], 0.5, 1));
		app_push (&l,
			g.ui->button (attrs[random], "random", ACTION_MPD_RANDOM));
	}
	if (g.ui->have_icons || single)
	{
		app_push (&l, g.ui->padding (attrs[0], 0.5, 1));
		app_push (&l,
			g.ui->button (attrs[single], "single", ACTION_MPD_SINGLE));
	}
	if (g.ui->have_icons || consume)
	{
		app_push (&l, g.ui->padding (attrs[0], 0.5, 1));
		app_push (&l,
			g.ui->button (attrs[consume], "consume", ACTION_MPD_CONSUME));
	}

	app_push (&l, g.ui->padding (attrs[0], 0.25, 1));
	app_flush_layout (&l, out);
}

static void
app_layout_statusbar (struct layout *out)
{
	chtype attrs[2] = { APP_ATTR (NORMAL), APP_ATTR (HIGHLIGHT) };
	app_layout_padding (attrs[0], out);

	struct layout l = {};
	if (g.message)
	{
		app_push (&l, g.ui->padding (attrs[0], 0.25, 1));
		if (!g.message_detail)
			app_push_fill (&l, g.ui->label (attrs[1], g.message));
		else
		{
			app_push (&l, g.ui->label (attrs[1], g.message));
			app_push_fill (&l, g.ui->label (attrs[0], g.message_detail));
		}
		app_push (&l, g.ui->padding (attrs[0], 0.25, 1));

		app_flush_layout (&l, out);
		LIST_FOR_EACH (struct widget, w, l.head)
			w->id = WIDGET_MESSAGE;
	}
	else if (g.editor.line)
	{
		app_push (&l, g.ui->padding (attrs[0], 0.25, 1));
		app_push (&l, g.ui->editor (attrs[1]));
		app_push (&l, g.ui->padding (attrs[0], 0.25, 1));
		app_flush_layout (&l, out);
	}
	else if (g.client.state == MPD_CONNECTED)
		app_layout_mpd_status (out);
	else if (g.client.state == MPD_CONNECTING)
		app_layout_text ("Connecting to MPD...", attrs[0], out);
	else if (g.client.state == MPD_DISCONNECTED)
		app_layout_text ("Disconnected", attrs[0], out);

	app_layout_padding (attrs[0], out);
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

static struct widget *
app_widget_by_id (int id)
{
	LIST_FOR_EACH (struct widget, w, g_xui.widgets)
		if (w->id == id)
			return w;
	return NULL;
}

static int
app_visible_items_height (void)
{
	struct widget *list = app_widget_by_id (WIDGET_LIST);
	hard_assert (list != NULL);

	// The raw number of items that would have fit on the terminal
	return MAX (0, list->height);
}

static int
app_visible_items (void)
{
	return app_visible_items_height () / g_xui.vunit;
}

/// Checks what items are visible and returns if the range was alright
static bool
app_fix_view_range (void)
{
	struct tab *tab = g.active_tab;
	if (tab->item_top < 0)
	{
		tab->item_top = 0;
		return false;
	}

	// If the contents are at least as long as the screen, always fill it
	int max_item_top = (int) tab->item_count - app_visible_items ();
	// But don't let that suggest a negative offset
	max_item_top = MAX (max_item_top, 0);

	if (tab->item_top > max_item_top)
	{
		tab->item_top = max_item_top;
		return false;
	}
	return true;
}

static void
app_layout (void)
{
	struct layout top = {}, bottom = {};
	app_layout_header (&top);
	app_layout_statusbar (&bottom);

	int available_height = g_xui.height;
	if (top.tail)
		available_height -= top.tail->y + top.tail->height;
	if (bottom.tail)
		available_height -= bottom.tail->y + bottom.tail->height;

	struct layout widgets = {};
	app_append_layout (&top, &widgets);
	app_layout_view (&widgets, available_height);
	app_append_layout (&bottom, &widgets);
	g_xui.widgets = widgets.head;

	app_fix_view_range();

	curs_set (0);
}

// --- Actions -----------------------------------------------------------------

/// Scroll down (positive) or up (negative) @a n items
static bool
app_scroll (int n)
{
	g.active_tab->item_top += n;
	xui_invalidate ();
	return app_fix_view_range ();
}

static void
app_ensure_selection_visible (void)
{
	struct tab *tab = g.active_tab;
	if (tab->item_selected < 0 || !tab->item_count)
		return;

	int too_high = tab->item_top - tab->item_selected;
	if (too_high > 0)
		app_scroll (-too_high);

	int too_low = tab->item_selected
		- (tab->item_top + app_visible_items () - 1);
	if (too_low > 0)
		app_scroll (too_low);
}

static bool
app_center_cursor (void)
{
	struct tab *tab = g.active_tab;
	if (tab->item_selected < 0 || !tab->item_count)
		return false;

	int offset = tab->item_selected - tab->item_top;
	int target = app_visible_items () / 2;
	app_scroll (offset - target);
	return true;
}

static bool
app_move_selection (int diff)
{
	struct tab *tab = g.active_tab;
	int fixed = tab->item_selected + diff;
	fixed = MIN (fixed, (int) tab->item_count - 1);
	fixed = MAX (fixed, 0);

	bool result = !diff || tab->item_selected != fixed;
	tab->item_selected = fixed;
	xui_invalidate ();

	app_ensure_selection_visible ();
	return result;
}

static void
app_show_message (char *message, char *detail)
{
	cstr_set (&g.message, message);
	cstr_set (&g.message_detail, detail);
	poller_timer_set (&g.message_timer, 5000);
	xui_invalidate ();
}

static void
app_hide_message (void)
{
	if (!g.message)
		return;

	cstr_set (&g.message, NULL);
	cstr_set (&g.message_detail, NULL);
	poller_timer_reset (&g.message_timer);
	xui_invalidate ();
}

static void
app_on_clipboard_copy (const char *text)
{
	app_show_message (xstrdup ("Text copied to clipboard: "), xstrdup (text));
}

static struct widget *
app_make_label (chtype attrs, const char *label)
{
	return g_xui.ui->label (attrs, 0, label);
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

static void
app_prepend_tab (struct tab *tab)
{
	LIST_PREPEND (g.tabs, tab);
	xui_invalidate ();
}

static void
app_switch_tab (struct tab *tab)
{
	if (tab == g.active_tab)
		return;

	g.last_tab = g.active_tab;
	g.active_tab = tab;
	xui_invalidate ();
}

static bool
app_goto_tab (int tab_index)
{
	int i = 0;
	LIST_FOR_EACH (struct tab, iter, g.tabs)
		if (i++ == tab_index)
		{
			app_switch_tab (iter);
			return true;
		}
	return false;
}

// --- Actions -----------------------------------------------------------------

static int
action_resolve (const char *name)
{
	for (int i = 0; i < ACTION_USER_0; i++)
		if (!strcasecmp_ascii (g_action_names[i], name))
			return i;

	// We could put this lookup first, and accordingly adjust
	// app_init_bindings() to do action_resolve(action_name(action)),
	// however the ability to override internal actions seems pointless.
	for (size_t i = 0; i < g.action_names.len; i++)
		if (!strcasecmp_ascii (g.action_names.vector[i], name))
			return ACTION_USER_0 + i;
	return -1;
}

static const char *
action_name (enum action action)
{
	if (action < ACTION_USER_0)
		return g_action_names[action];

	size_t user_action = action - ACTION_USER_0;
	hard_assert (user_action < g.action_names.len);
	return g.action_names.vector[user_action];
}

static const char *
action_description (enum action action)
{
	if (action < ACTION_USER_0)
		return g_action_descriptions[action];

	size_t user_action = action - ACTION_USER_0;
	hard_assert (user_action < g.action_descriptions.len);
	return g.action_descriptions.vector[user_action];
}

static const char *
action_command (enum action action)
{
	if (action < ACTION_USER_0)
		return NULL;

	size_t user_action = action - ACTION_USER_0;
	hard_assert (user_action < g.action_commands.len);
	return g.action_commands.vector[user_action];
}

// --- User input handling -----------------------------------------------------

static void
mpd_client_vsend_command (struct mpd_client *self, va_list ap)
{
	struct strv v = strv_make ();
	const char *command;
	while ((command = va_arg (ap, const char *)))
		strv_append (&v, command);
	mpd_client_send_commandv (self, v.vector);
	strv_free (&v);
}

/// Send a command to MPD without caring about the response
static bool mpd_client_send_simple (struct mpd_client *self, ...)
	ATTRIBUTE_SENTINEL;

static void
mpd_on_simple_response (const struct mpd_response *response,
	const struct strv *data, void *user_data)
{
	(void) data;
	(void) user_data;

	if (!response->success)
		print_error ("%s: %s", "command failed", response->message_text);
}

static bool
mpd_client_send_simple (struct mpd_client *self, ...)
{
	if (self->state != MPD_CONNECTED)
		return false;

	va_list ap;
	va_start (ap, self);
	mpd_client_vsend_command (self, ap);
	va_end (ap);

	mpd_client_add_task (self, mpd_on_simple_response, NULL);
	mpd_client_idle (self, 0);
	return true;
}

#define MPD_SIMPLE(...) \
	mpd_client_send_simple (&g.client, __VA_ARGS__, NULL)

static bool
app_setvol (int value)
{
	char *volume = xstrdup_printf ("%d", MAX (0, MIN (100, value)));
	bool result = g.volume >= 0 && MPD_SIMPLE ("setvol", volume);
	free (volume);
	return result;
}

static void
app_on_mpd_command_editor_end (bool confirmed)
{
	struct mpd_client *c = &g.client;
	if (!confirmed)
		return;

	size_t len;
	char *u8 = (char *) u32_to_u8 (g.editor.line, g.editor.len + 1, NULL, &len);
	mpd_client_send_command_raw (c, u8);
	free (u8);

	mpd_client_add_task (c, mpd_on_simple_response, NULL);
	mpd_client_idle (c, 0);
}

static size_t
incremental_search_match (const ucs4_t *needle, size_t len,
	const ucs4_t *chars, size_t chars_len)
{
	// XXX: this is slow and simplistic, but unistring is awkward to use
	size_t best = 0;
	for (size_t start = 0; start < chars_len; start++)
	{
		size_t i = 0;
		for (; i < len && start + i < chars_len; i++)
			if (uc_tolower (needle[i]) != uc_tolower (chars[start + i]))
				break;
		best = MAX (best, i);
	}
	return best;
}

static void
incremental_search_on_changed (void)
{
	struct tab *tab = g.active_tab;
	if (!tab->item_count)
		return;

	size_t best = 0, current = 0, index = MAX (tab->item_selected, 0), i = 0;
	while (i++ < tab->item_count)
	{
		struct str s = str_make ();
		LIST_FOR_EACH (struct widget, w, tab->on_item_layout (index).head)
		{
			str_append (&s, w->text);
			widget_destroy (w);
		}

		size_t len;
		ucs4_t *text = u8_to_u32 ((const uint8_t *) s.str, s.len, NULL, &len);
		str_free (&s);
		current = incremental_search_match
			(g.editor.line, g.editor.len, text, len);
		free (text);
		if (best < current)
		{
			best = current;
			tab->item_selected = index;
			app_move_selection (0);
		}
		index = (index + 1) % tab->item_count;
	}
}

static void
incremental_search_on_end (bool confirmed)
{
	(void) confirmed;
	// Required callback, nothing to do here.
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

static bool
run_command (const char *command, struct str *output, struct error **e)
{
	char *adjusted = xstrdup_printf ("2>&1 %s", command);
	print_debug ("running command: %s", adjusted);

	FILE *fp = popen (adjusted, "r");
	free (adjusted);
	if (!fp)
		return error_set (e, "%s", strerror (errno));

	char buf[BUFSIZ];
	size_t len;
	while ((len = fread (buf, 1, sizeof buf, fp)) == sizeof buf)
		str_append_data (output, buf, len);
	str_append_data (output, buf, len);

	int status = pclose (fp);
	if (status < 0)