Bump version, update NEWS

The updater assumed the terminal cursor was invisible.

.clang-format

@@ -0,0 +1,32 @@
+# clang-format is fairly limited, and these rules are approximate:
+#  - array initializers can get terribly mangled with clang-format 12.0,
+#  - sometimes it still aligns with space characters,
+#  - struct name NL { NL ... NL } NL name; is unachievable.
+BasedOnStyle: GNU
+ColumnLimit: 80
+IndentWidth: 4
+TabWidth: 4
+UseTab: ForContinuationAndIndentation
+BreakBeforeBraces: Allman
+SpaceAfterCStyleCast: true
+AlignAfterOpenBracket: DontAlign
+AlignOperands: DontAlign
+AlignConsecutiveMacros: Consecutive
+AllowAllArgumentsOnNextLine: false
+AllowAllParametersOfDeclarationOnNextLine: false
+IndentGotoLabels: false
+
+# IncludeCategories has some potential, but it may also break the build.
+# Note that the documentation says the value should be "Never".
+SortIncludes: false
+
+# This is a compromise, it generally works out aesthetically better.
+BinPackArguments: false
+
+# Unfortunately, this can't be told to align to column 40 or so.
+SpacesBeforeTrailingComments: 2
+
+# liberty-specific macro body wrappers.
+MacroBlockBegin: "BLOCK_START"
+MacroBlockEnd: "BLOCK_END"
+ForEachMacros: ["LIST_FOR_EACH"]

.gitignore

@@ -7,3 +7,5 @@
 /nncmpp.files
 /nncmpp.creator*
 /nncmpp.includes
+/nncmpp.cflags
+/nncmpp.cxxflags

CMakeLists.txt

@@ -1,5 +1,5 @@
 cmake_minimum_required (VERSION 3.0)
-project (nncmpp VERSION 0.9.0 LANGUAGES C)
+project (nncmpp VERSION 1.1.1 LANGUAGES C)
 
 # Moar warnings
 if ("${CMAKE_C_COMPILER_ID}" MATCHES "GNU" OR CMAKE_COMPILER_IS_GNUCC)
@@ -21,38 +21,59 @@ include (AddThreads)
 find_package (Termo QUIET NO_MODULE)
 option (USE_SYSTEM_TERMO
 	"Don't compile our own termo library, use the system one" ${Termo_FOUND})
-
 if (USE_SYSTEM_TERMO)
 	if (NOT Termo_FOUND)
 		message (FATAL_ERROR "System termo library not found")
-	endif (NOT Termo_FOUND)
+	endif ()
 else ()
+	# We don't want the library to install, but EXCLUDE_FROM_ALL ignores tests
 	add_subdirectory (termo EXCLUDE_FROM_ALL)
-	# We don't have many good choices when we don't want to install it and want
-	# to support older versions of CMake; this is a relatively clean approach
-	# (other possibilities: setting a variable in the parent scope, using a
-	# cache variable, writing a special config file with build paths in it and
-	# including it here, or setting a custom property on the targets).
+	file (WRITE ${PROJECT_BINARY_DIR}/CTestCustom.cmake
+		"execute_process (COMMAND ${CMAKE_COMMAND} --build termo)")
+
+	# We don't have many good choices; this is a relatively clean approach
+	# (other possibilities: setting a variable in the parent scope, using
+	# a cache variable, writing a special config file with build paths in it
+	# and including it here, or setting a custom property on the targets)
 	get_directory_property (Termo_INCLUDE_DIRS
 		DIRECTORY termo INCLUDE_DIRECTORIES)
 	set (Termo_LIBRARIES termo-static)
 endif ()
 
+pkg_check_modules (fftw fftw3 fftw3f)
+option (WITH_FFTW "Use FFTW to enable spectrum visualisation" ${fftw_FOUND})
+if (WITH_FFTW)
+	if (NOT fftw_FOUND)
+		message (FATAL_ERROR "FFTW not found")
+	endif ()
+endif ()
+
 include_directories (${Unistring_INCLUDE_DIRS}
-	${Ncursesw_INCLUDE_DIRS} ${Termo_INCLUDE_DIRS} ${curl_INCLUDE_DIRS})
-link_directories (${curl_LIBRARY_DIRS})
+	${Ncursesw_INCLUDE_DIRS} ${Termo_INCLUDE_DIRS} ${curl_INCLUDE_DIRS}
+	${fftw_INCLUDE_DIRS})
+link_directories (${curl_LIBRARY_DIRS} ${fftw_LIBRARY_DIRS})
 
 # Configuration
-include (CheckFunctionExists)
-set (CMAKE_REQUIRED_LIBRARIES ${Ncursesw_LIBRARIES})
-CHECK_FUNCTION_EXISTS ("resizeterm" HAVE_RESIZETERM)
-
 if ("${CMAKE_SYSTEM_NAME}" MATCHES "BSD")
 	# Need this for SIGWINCH in FreeBSD and OpenBSD respectively;
 	# our POSIX version macros make it undefined
 	add_definitions (-D__BSD_VISIBLE=1 -D_BSD_SOURCE=1)
+elseif (APPLE)
+	add_definitions (-D_DARWIN_C_SOURCE)
 endif ()
 
+include (CheckFunctionExists)
+set (CMAKE_REQUIRED_LIBRARIES ${Ncursesw_LIBRARIES})
+CHECK_FUNCTION_EXISTS ("resizeterm" HAVE_RESIZETERM)
+
+# -lm may or may not be a part of libc
+foreach (extra m)
+	find_library (extra_lib_${extra} ${extra})
+	if (extra_lib_${extra})
+		list (APPEND extra_libraries ${extra_lib_${extra}})
+	endif ()
+endforeach ()
+
 # Generate a configuration file
 configure_file (${PROJECT_SOURCE_DIR}/config.h.in
 	${PROJECT_BINARY_DIR}/config.h)
@@ -61,27 +82,31 @@ include_directories (${PROJECT_SOURCE_DIR} ${PROJECT_BINARY_DIR})
 # Build the main executable and link it
 add_executable (${PROJECT_NAME} ${PROJECT_NAME}.c)
 target_link_libraries (${PROJECT_NAME} ${Unistring_LIBRARIES}
-	${Ncursesw_LIBRARIES} termo-static ${curl_LIBRARIES})
+	${Ncursesw_LIBRARIES} termo-static ${curl_LIBRARIES}
+	${fftw_LIBRARIES} ${extra_libraries})
 add_threads (${PROJECT_NAME})
 
 # Installation
 include (GNUInstallDirs)
 install (TARGETS ${PROJECT_NAME} DESTINATION ${CMAKE_INSTALL_BINDIR})
 install (FILES LICENSE DESTINATION ${CMAKE_INSTALL_DOCDIR})
+install (DIRECTORY contrib DESTINATION ${CMAKE_INSTALL_DATADIR}/${PROJECT_NAME})
 
-# Generate documentation from program help
-find_program (HELP2MAN_EXECUTABLE help2man)
-if (NOT HELP2MAN_EXECUTABLE)
-	message (FATAL_ERROR "help2man not found")
+# Generate documentation from text markup
+find_program (ASCIIDOCTOR_EXECUTABLE asciidoctor)
+if (NOT ASCIIDOCTOR_EXECUTABLE)
+	message (FATAL_ERROR "asciidoctor not found")
 endif ()
 
 foreach (page ${PROJECT_NAME})
 	set (page_output "${PROJECT_BINARY_DIR}/${page}.1")
 	list (APPEND project_MAN_PAGES "${page_output}")
 	add_custom_command (OUTPUT ${page_output}
-		COMMAND ${HELP2MAN_EXECUTABLE} -N
-			"${PROJECT_BINARY_DIR}/${page}" -o ${page_output}
-		DEPENDS ${page}
+		COMMAND ${ASCIIDOCTOR_EXECUTABLE} -b manpage
+			-a release-version=${PROJECT_VERSION}
+			"${PROJECT_SOURCE_DIR}/${page}.adoc"
+			-o "${page_output}"
+		DEPENDS ${page}.adoc
 		COMMENT "Generating man page for ${page}" VERBATIM)
 endforeach ()
 

LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2016 - 2020, Přemysl Eric Janouch <p@janouch.name>
+Copyright (c) 2016 - 2021, 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.

NEWS

@@ -1,3 +1,42 @@
+1.1.1 (2021-11-04)
+
+ * Terminal focus in/out events no longer ring the terminall bell
+
+ * Made mouse work in non-rxvt terminals with recent xterm terminfo
+
+
+1.1.0 (2021-10-21)
+
+ * Now requesting and processing terminal de/focus events,
+   using a new "defocused" attribute for selected rows
+
+ * Made it possible to show a spectrum visualiser when built against FFTW
+
+ * Any program arguments are now added to MPD's current playlist
+
+
+1.0.0 (2020-11-05)
+
+ * Coming with a real manual page instead of a help2man-generated stub
+
+ * Added a mode to poll MPD for the elapsed time, enabled by default,
+   fixing two cases of improper tracking
+
+ * Started showing song duration in the library
+
+ * Added C-PgUp/PgDown and C-Left/Right bindings to iterate tabs
+
+ * Added VIM-like C-y and C-e bindings for scrolling
+
+ * Added Windows Explorer-like M-Up binding to go up a directory
+
+ * Worked around a cURL bug crashing the application
+
+ * Fixed handling of direct SHOUTcast streams
+
+ * Miscellaneous little fixes
+
+
 0.9.0 (2018-11-02)
 
  * Initial release

README.adoc

@@ -22,11 +22,16 @@ Packages
 Regular releases are sporadic.  git master should be stable enough.  You can get
 a package with the latest development version from Archlinux's AUR.
 
-Building and Running
---------------------
-Build dependencies: CMake, pkg-config, help2man, liberty (included),
+Documentation
+-------------
+See the link:nncmpp.adoc[man page] for information about usage.
+The rest of this README will concern itself with externalities.
+
+Building
+--------
+Build dependencies: CMake, pkg-config, asciidoctor, liberty (included),
                     termo (included) +
-Runtime dependencies: ncursesw, libunistring, cURL
+Runtime dependencies: ncursesw, libunistring, cURL, fftw3 (optional)
 
  $ git clone --recursive https://git.janouch.name/p/nncmpp.git
  $ mkdir nncmpp/build
@@ -43,37 +48,6 @@ Or you can try telling CMake to make a package for you.  For Debian it is:
  $ cpack -G DEB
  # dpkg -i nncmpp-*.deb
 
-Having the program installed, create a configuration file and run it.
-
-Configuration
--------------
-Create _~/.config/nncmpp/nncmpp.conf_ with contents like the following:
-
-....
-settings = {
-	address    = "localhost:6600"
-	password   = "<your password>"
-	root       = "~/Music"
-}
-colors = {
-	normal      = ""
-	highlight   = "bold"
-	elapsed     = "reverse"
-	remains     = "ul"
-	tab_bar     = "reverse"
-	tab_active  = "ul"
-	even        = ""
-	odd         = ""
-	selection   = "reverse"
-	multiselect = "-1 6"
-	scrollbar   = ""
-}
-streams = {
-	"dnbradio.com" = "http://www.dnbradio.com/hi.m3u"
-	"BassDrive.com" = "http://bassdrive.com/v2/streams/BassDrive.pls"
-}
-....
-
 Terminal caveats
 ----------------
 This application aspires to be as close to a GUI as possible.  It expects you

config.h.in

@@ -5,6 +5,7 @@
 #define PROGRAM_VERSION "${PROJECT_VERSION}"
 
 #cmakedefine HAVE_RESIZETERM
+#cmakedefine WITH_FFTW
 
 #endif  // ! CONFIG_H
 

contrib/light-theme-256.conf

@@ -12,6 +12,7 @@ colors = {
 
 	selection = "231 202"
 	multiselect = "231 88"
+	defocused = "231 250"
 	directory = "16 231 bold"
 
 	incoming = "28"

nncmpp.adoc

@@ -0,0 +1,113 @@
+nncmpp(1)
+=========
+:doctype: manpage
+:manmanual: nncmpp Manual
+:mansource: nncmpp {release-version}
+
+Name
+----
+nncmpp - terminal-based MPD client
+
+Synopsis
+--------
+*nncmpp* [_OPTION_]... [_URL_ | _PATH_]...
+
+Description
+-----------
+*nncmpp* is a terminal-based GUI-like MPD client.  On start up it will welcome
+you with an overview of all key bindings and the actions they're assigned to.
+Individual tabs can be switched to either using the mouse or by pressing *M-1*
+through *M-9*, corresponding to the order they appear in.
+
+As a convenience utility, any program arguments are added to the MPD queue.
+Note that to add files outside the database, you need to connect to MPD using
+a socket file.
+
+Options
+-------
+*-d*, *--debug*::
+	Adds a "Debug" tab showing all MPD communication and other information
+	that help debug various issues.
+
+*-h*, *--help*::
+	Display a help message and exit.
+
+*-V*, *--version*::
+	Output version information and exit.
+
+Configuration
+-------------
+Unless you run MPD on a remote machine, on an unusual port, or protected by
+a password, the client doesn't need a configuration file to work.  It is,
+however, likely that you'll want to customize the looks or add some streams.
+You can start off with the following snippet:
+
+....
+settings = {
+	address    = "localhost:6600"
+	password   = "<your password>"
+	root       = "~/Music"
+}
+colors = {
+	normal      = ""
+	highlight   = "bold"
+	elapsed     = "reverse"
+	remains     = "ul"
+	tab_bar     = "reverse"
+	tab_active  = "ul"
+	even        = ""
+	odd         = ""
+	selection   = "reverse"
+	multiselect = "-1 6"
+	defocused   = "ul"
+	scrollbar   = ""
+}
+streams = {
+	"dnbradio.com" = "http://www.dnbradio.com/hi.m3u"
+	"BassDrive.com" = "http://bassdrive.com/v2/streams/BassDrive.pls"
+}
+....
+
+Terminal attributes are accepted in a format similar to that of *git-config*(1),
+only named colours aren't supported.  The distribution contains example colour
+schemes in the _contrib_ directory.
+
+// TODO: it seems like liberty should contain an includable snippet about
+//   the format, which could form a part of nncmpp.conf(5).
+
+Spectrum visualiser
+-------------------
+When built against the FFTW library, *nncmpp* can make use of MPD's "fifo"
+output plugin to show the audio spectrum.  This has some caveats, namely that
+it may not be properly synchronized, only one instance of a client can read from
+a given named pipe at a time, it will cost you some CPU time, and finally you'll
+need to set it up manually to match your MPD configuration, e.g.:
+
+....
+settings = {
+	...
+	spectrum_path = "~/.mpd/mpd.fifo"  # "path"
+	spectrum_format = "44100:16:2"     # "format" (samplerate:bits:channels)
+	spectrum_bars = 8                  # beware of exponential complexity
+	...
+}
+....
+
+The sample rate should be greater than 40 kHz, the number of bits 8 or 16,
+and the number of channels doesn't matter, as they're simply averaged together.
+
+Files
+-----
+*nncmpp* follows the XDG Base Directory Specification.
+
+_~/.config/nncmpp/nncmpp.conf_::
+	The configuration file.
+
+Reporting bugs
+--------------
+Use https://git.janouch.name/p/nncmpp to report bugs, request features,
+or submit pull requests.
+
+See also
+--------
+*mpd*(1)

nncmpp.c

@@ -1,7 +1,7 @@
 /*
  * nncmpp -- the MPD client you never knew you needed
  *
- * Copyright (c) 2016 - 2020, Přemysl Eric Janouch <p@janouch.name>
+ * Copyright (c) 2016 - 2021, 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.
@@ -39,6 +39,8 @@
 	 * 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           ) \
@@ -76,15 +78,13 @@ enum
 #include <math.h>
 #include <locale.h>
 #include <termios.h>
-#ifndef TIOCGWINSZ
 #include <sys/ioctl.h>
-#endif  // ! TIOCGWINSZ
 
 // ncurses is notoriously retarded for input handling, we need something
 // different if only to receive mouse events reliably.
 //
-// 2020 update: ncurses is mostly reliable now but rxvt-unicode needs to start
-// supporting 1006, or ncurses needs to start supporting the 1015 mode.
+// 2021 update: ncurses is mostly reliable now, though rxvt-unicode only
+// supports the 1006 mode that ncurses also supports mode starting with 9.25.
 
 #include "termo.h"
 
@@ -93,6 +93,13 @@ enum
 
 #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
+
 #define APP_TITLE  PROGRAM_NAME         ///< Left top corner
 
 // --- Utilities ---------------------------------------------------------------
@@ -101,7 +108,7 @@ enum
 static void
 update_curses_terminal_size (void)
 {
-#if defined (HAVE_RESIZETERM) && defined (TIOCGWINSZ)
+#if defined HAVE_RESIZETERM && defined TIOCGWINSZ
 	struct winsize size;
 	if (!ioctl (STDOUT_FILENO, TIOCGWINSZ, (char *) &size))
 	{
@@ -558,6 +565,301 @@ item_list_resize (struct item_list *self, size_t len)
 	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 *spectrum;                     ///< String buffer for the "render"
+
+	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->spectrum;
+	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: 9 * 7 = 63 dB of range.
+		int height = N_ELEMENTS (spectrum_bars) - 1 + (int) (db / 7);
+		p += strlen (strcpy (p, spectrum_bars[MAX (height, 0)]));
+	}
+}
+
+static bool
+spectrum_init (struct spectrum *s, char *format, int bars, 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->spectrum = xcalloc (sizeof *s->spectrum, s->bars * 3 + 1);
+	s->top_bins = xcalloc (sizeof *s->top_bins, s->bars);
+	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);
+	}
+
+	// Limit updates to 30 times per second to limit CPU load
+	s->samples = s->sampling_rate / s->bins * 2 / 30;
+	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 (sizeof *s->window, s->bins);
+	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 (sizeof *s->data, s->bins);
+	s->windowed = fftw_malloc (sizeof *s->windowed * s->bins);
+	s->out = fftw_malloc (sizeof *s->out * (s->useful_bins + 1));
+	s->p = fftwf_plan_dft_r2c_1d (s->bins, s->windowed, s->out, FFTW_MEASURE);
+	s->accumulator = xcalloc (sizeof *s->accumulator, s->useful_bins);
+	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);
+
+	free (s->spectrum);
+	free (s->top_bins);
+	free (s->buffer);
+
+	memset (s, 0, sizeof *s);
+}
+
+#endif  // WITH_FFTW
+
 // --- Application -------------------------------------------------------------
 
 // Function names are prefixed mostly because of curses which clutters the
@@ -658,6 +960,7 @@ static struct app_context
 
 	struct config config;               ///< Program configuration
 	struct strv streams;                ///< List of "name NUL URI NUL"
+	struct strv enqueue;                ///< Items to enqueue once connected
 
 	struct tab *help_tab;               ///< Special help tab
 	struct tab *tabs;                   ///< All other tabs
@@ -673,6 +976,13 @@ static struct app_context
 	int gauge_offset;                   ///< Offset to the gauge or -1
 	int gauge_width;                    ///< Width of the gauge, if present
 
+#ifdef WITH_FFTW
+	struct spectrum spectrum;           ///< Spectrum analyser
+	int spectrum_fd;                    ///< FIFO file descriptor (non-blocking)
+	int spectrum_column, spectrum_row;  ///< Position for fast refresh
+	struct poller_fd spectrum_event;    ///< FIFO watcher
+#endif  // WITH_FFTW
+
 	struct line_editor editor;          ///< Line editor
 	struct poller_idle refresh_event;   ///< Refresh the screen
 
@@ -682,6 +992,7 @@ static struct app_context
 	struct poller_timer tk_timer;       ///< termo timeout timer
 	bool locale_is_utf8;                ///< The locale is Unicode
 	bool use_partial_boxes;             ///< Use Unicode box drawing chars
+	bool focused;                       ///< Whether the terminal has focus
 
 	struct attrs attrs[ATTRIBUTE_COUNT];
 }
@@ -741,10 +1052,28 @@ static struct config_schema g_config_settings[] =
 	{ .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
 	{ .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" },
+#endif  // WITH_FFTW
+
 	// 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
@@ -894,11 +1223,17 @@ app_init_context (void)
 	g.client = mpd_client_make (&g.poller);
 	g.config = config_make ();
 	g.streams = strv_make ();
+	g.enqueue = strv_make ();
 	g.playlist = item_list_make ();
 
 	g.playback_info = str_map_make (free);
 	g.playback_info.key_xfrm = tolower_ascii_strxfrm;
 
+#ifdef WITH_FFTW
+	g.spectrum_fd = -1;
+	g.spectrum_row = g.spectrum_column = -1;
+#endif  // WITH_FFTW
+
 	// This is also approximately what libunistring does internally,
 	// since the locale name is canonicalized by locale_charset().
 	// Note that non-Unicode locales are handled pretty inefficiently.
@@ -908,6 +1243,9 @@ app_init_context (void)
 	// TODO: make this configurable
 	g.use_partial_boxes = g.locale_is_utf8;
 
+	// Presumably, although not necessarily; unsure if queryable at all
+	g.focused = true;
+
 	app_init_attributes ();
 }
 
@@ -916,9 +1254,9 @@ app_init_terminal (void)
 {
 	TERMO_CHECK_VERSION;
 	if (!(g.tk = termo_new (STDIN_FILENO, NULL, 0)))
-		abort ();
+		exit_fatal ("failed to set up the terminal");
 	if (!initscr () || nonl () == ERR)
-		abort ();
+		exit_fatal ("failed to set up the terminal");
 
 	// By default we don't use any colors so they're not required...
 	if (start_color () == ERR
@@ -947,8 +1285,18 @@ app_free_context (void)
 	mpd_client_free (&g.client);
 	str_map_free (&g.playback_info);
 	strv_free (&g.streams);
+	strv_free (&g.enqueue);
 	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
+
 	line_editor_free (&g.editor);
 
 	config_free (&g.config);
@@ -1210,6 +1558,21 @@ app_draw_header (void)
 	g.tabs_offset = g.header_height;
 	LIST_FOR_EACH (struct tab, iter, g.tabs)
 		row_buffer_append (&buf, iter->name, attrs[iter == g.active_tab]);
+
+#ifdef WITH_FFTW
+	// This seems like the most reasonable, otherwise unoccupied space
+	if (g.spectrum_fd != -1)
+	{
+		// Find some space and remember where it was, for fast refreshes
+		row_buffer_ellipsis (&buf, COLS - g.spectrum.bars - 1);
+		row_buffer_align (&buf, COLS - g.spectrum.bars, attrs[false]);
+		g.spectrum_row = g.header_height;
+		g.spectrum_column = buf.total_width;
+
+		row_buffer_append (&buf, g.spectrum.spectrum, attrs[false]);
+	}
+#endif  // WITH_FFTW
+
 	app_flush_header (&buf, attrs[false]);
 
 	const char *header = g.active_tab->header;
@@ -1336,11 +1699,13 @@ app_draw_view (void)
 
 		bool override_colors = true;
 		if (item_index == tab->item_selected)
-			row_attrs = APP_ATTR (SELECTION);
+			row_attrs = g.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 = APP_ATTR (MULTISELECT);
+			row_attrs = g.focused
+				? APP_ATTR (MULTISELECT) : APP_ATTR (DEFOCUSED);
 		else
 			override_colors = false;
 
@@ -2221,6 +2586,14 @@ app_init_bindings (const char *keymap,
 static bool
 app_process_termo_event (termo_key_t *event)
 {
+	bool handled = false;
+	if ((handled = event->type == TERMO_TYPE_FOCUS))
+	{
+		g.focused = !!event->code.focused;
+		app_invalidate ();
+		// Senseless fall-through
+	}
+
 	struct binding dummy = { *event, 0, 0 }, *binding;
 	if (g.editor.line)
 	{
@@ -2228,7 +2601,7 @@ app_process_termo_event (termo_key_t *event)
 			sizeof *binding, app_binding_cmp)))
 			return app_editor_process_action (binding->action);
 		if (event->type != TERMO_TYPE_KEY || event->modifiers != 0)
-			return false;
+			return handled;
 
 		line_editor_insert (&g.editor, event->code.codepoint);
 		app_invalidate ();
@@ -2247,7 +2620,7 @@ app_process_termo_event (termo_key_t *event)
 		if (app_goto_tab ((n == 0 ? 10 : n) - 1))
 			return true;
 	}
-	return false;
+	return handled;
 }
 
 // --- Current tab -------------------------------------------------------------
@@ -3405,6 +3778,143 @@ debug_tab_init (void)
 	return super;
 }
 
+// --- Spectrum analyser -------------------------------------------------------
+
+#ifdef WITH_FFTW
+
+static void
+spectrum_redraw (void)
+{
+	// A full refresh would be too computationally expensive,
+	// let's hack around it in this case
+	if (g.spectrum_row != -1)
+	{
+		// Don't mess up the line editor caret, when it's shown
+		int last_x, last_y;
+		getyx (stdscr, last_y, last_x);
+
+		attrset (APP_ATTR (TAB_BAR));
+		mvaddstr (g.spectrum_row, g.spectrum_column, g.spectrum.spectrum);
+		attrset (0);
+
+		move (last_y, last_x);
+		refresh ();
+	}
+	else
+		app_invalidate ();
+}
+
+// When any problem occurs with the FIFO, we'll just give up on it completely
+static void
+spectrum_discard_fifo (void)
+{
+	if (g.spectrum_fd != -1)
+	{
+		poller_fd_reset (&g.spectrum_event);
+		xclose (g.spectrum_fd);
+		g.spectrum_fd = -1;
+
+		spectrum_free (&g.spectrum);
+		g.spectrum_row = g.spectrum_column = -1;
+		app_invalidate ();
+	}
+}
+
+static void
+spectrum_on_fifo_readable (const struct pollfd *pfd, void *user_data)
+{
+	(void) user_data;
+	struct spectrum *s = &g.spectrum;
+
+	bool update = false;
+	ssize_t n;
+restart:
+	while ((n = read (pfd->fd,
+		s->buffer + s->buffer_len, s->buffer_size - s->buffer_len)) > 0)
+		if ((s->buffer_len += n) == s->buffer_size)
+		{
+			update = true;
+			spectrum_sample (s);
+			s->buffer_len = 0;
+		}
+
+	if (!n)
+		spectrum_discard_fifo ();
+	else if (errno == EINTR)
+		goto restart;
+	else if (errno != EAGAIN)
+	{
+		print_error ("spectrum: %s", strerror (errno));
+		spectrum_discard_fifo ();
+	}
+	else if (update)
+		spectrum_redraw ();
+}
+
+// When playback is stopped, we need to feed the analyser some zeroes ourselves.
+// We could also just hide it.  Hard to say which is simpler or better.
+static void
+spectrum_clear (void)
+{
+	if (g.spectrum_fd != -1)
+	{
+		struct spectrum *s = &g.spectrum;
+		memset (s->buffer, 0, s->buffer_size);
+		spectrum_sample (s);
+		spectrum_sample (s);
+		s->buffer_len = 0;
+
+		spectrum_redraw ();
+	}
+}
+
+static void
+spectrum_setup_fifo (void)
+{
+	const char *spectrum_path =
+		get_config_string (g.config.root, "settings.spectrum_path");
+	const char *spectrum_format =
+		get_config_string (g.config.root, "settings.spectrum_format");
+	struct config_item *spectrum_bars =
+		config_item_get (g.config.root, "settings.spectrum_bars", NULL);
+	if (!spectrum_path)
+		return;
+
+	struct error *e = NULL;
+	char *path = resolve_filename
+		(spectrum_path, resolve_relative_config_filename);
+
+	if (!path)
+		print_error ("spectrum: %s", "FIFO path could not be resolved");
+	else if (!g.locale_is_utf8)
+		print_error ("spectrum: %s", "UTF-8 locale required");
+	else if (!spectrum_init (&g.spectrum,
+		(char *) spectrum_format, spectrum_bars->value.integer, &e))
+	{
+		print_error ("spectrum: %s", e->message);
+		error_free (e);
+	}
+	else if ((g.spectrum_fd = open (path, O_RDONLY | O_NONBLOCK)) == -1)
+	{
+		print_error ("spectrum: %s: %s", path, strerror (errno));
+		spectrum_free (&g.spectrum);
+	}
+	else
+	{
+		g.spectrum_event = poller_fd_make (&g.poller, g.spectrum_fd);
+		g.spectrum_event.dispatcher = spectrum_on_fifo_readable;
+		poller_fd_set (&g.spectrum_event, POLLIN);
+	}
+
+	free (path);
+}
+
+#else  // ! WITH_FFTW
+#define spectrum_setup_fifo()
+#define spectrum_clear()
+#define spectrum_discard_fifo()
+#endif  // ! WITH_FFTW
+
 // --- MPD interface -----------------------------------------------------------
 
 static void
@@ -3465,6 +3975,10 @@ mpd_update_playback_state (void)
 		if (!strcmp (state, "play"))   g.state = PLAYER_PLAYING;
 		if (!strcmp (state, "pause"))  g.state = PLAYER_PAUSED;
 	}
+	if (g.state == PLAYER_STOPPED)
+	{
+		spectrum_clear ();
+	}
 
 	// Values in "time" are always rounded.  "elapsed", introduced in MPD 0.16,
 	// is in millisecond precision and "duration" as well, starting with 0.20.
@@ -3681,6 +4195,57 @@ mpd_queue_reconnect (void)
 	poller_timer_set (&g.connect_event, 5 * 1000);
 }
 
+// On an error, MPD discards the rest of our enqueuing commands--work it around
+static void mpd_enqueue_step (size_t start_offset);
+
+static void
+mpd_on_enqueue_response (const struct mpd_response *response,
+	const struct strv *data, void *user_data)
+{
+	(void) data;
+	intptr_t start_offset = (intptr_t) user_data;
+
+	if (response->success)
+		strv_reset (&g.enqueue);
+	else
+	{
+		// Their addition may also overflow, but YOLO
+		hard_assert (start_offset >= 0 && response->list_offset >= 0);
+
+		print_error ("%s: %s", response->message_text,
+			g.enqueue.vector[start_offset + response->list_offset]);
+		mpd_enqueue_step (start_offset + response->list_offset + 1);
+	}
+}
+
+static void
+mpd_enqueue_step (size_t start_offset)
+{
+	struct mpd_client *c = &g.client;
+	if (start_offset >= g.enqueue.len)
+	{
+		strv_reset (&g.enqueue);
+		return;
+	}
+
+	// TODO: might want to consider using addid and autoplaying
+	mpd_client_list_begin (c);
+	for (size_t i = start_offset; i < g.enqueue.len; i++)
+		mpd_client_send_command (c, "add", g.enqueue.vector[i], NULL);
+	mpd_client_list_end (c);
+	mpd_client_add_task (c, mpd_on_enqueue_response, (void *) start_offset);
+	mpd_client_idle (c, 0);
+}
+
+static void
+mpd_on_ready (void)
+{
+	mpd_request_info ();
+	library_tab_reload (NULL);
+	spectrum_setup_fifo ();
+	mpd_enqueue_step (0);
+}
+
 static void
 mpd_on_password_response (const struct mpd_response *response,
 	const struct strv *data, void *user_data)
@@ -3690,10 +4255,7 @@ mpd_on_password_response (const struct mpd_response *response,
 	struct mpd_client *c = &g.client;
 
 	if (response->success)
-	{
-		mpd_request_info ();
-		library_tab_reload (NULL);
-	}
+		mpd_on_ready ();
 	else
 	{
 		print_error ("%s: %s",
@@ -3716,10 +4278,7 @@ mpd_on_connected (void *user_data)
 		mpd_client_add_task (c, mpd_on_password_response, NULL);
 	}
 	else
-	{
-		mpd_request_info ();
-		library_tab_reload (NULL);
-	}
+		mpd_on_ready ();
 }
 
 static void
@@ -3736,6 +4295,8 @@ mpd_on_failure (void *user_data)
 	mpd_update_playback_state ();
 	current_tab_update ();
 	info_tab_update ();
+
+	spectrum_discard_fifo ();
 }
 
 static void
@@ -4016,6 +4577,28 @@ app_init_poller_events (void)
 	g.refresh_event.dispatcher = app_on_refresh;
 }
 
+static void
+app_init_enqueue (char *argv[], int argc)
+{
+	// TODO: MPD is unwilling to play directories, so perhaps recurse ourselves
+	char cwd[4096] = "";
+	for (int i = 0; i < argc; i++)
+	{
+		// This is a super-trivial method of URL detection, however anything
+		// contaning the scheme and authority delimiters in a sequence is most
+		// certainly not a filesystem path, and thus it will work as expected.
+		// Error handling may be done by MPD.
+		const char *path_or_URL = argv[i];
+		if (*path_or_URL == '/' || strstr (path_or_URL, "://"))
+			strv_append (&g.enqueue, path_or_URL);
+		else if (!*cwd && !getcwd (cwd, sizeof cwd))
+			exit_fatal ("getcwd: %s", strerror (errno));
+		else
+			strv_append_owned (&g.enqueue,
+				xstrdup_printf ("%s/%s", cwd, path_or_URL));
+	}
+}
+
 int
 main (int argc, char *argv[])
 {
@@ -4028,7 +4611,8 @@ main (int argc, char *argv[])
 	};
 
 	struct opt_handler oh =
-		opt_handler_make (argc, argv, opts, NULL, "MPD client.");
+		opt_handler_make (argc, argv, opts,
+			"[URL | PATH]...", "Terminal-based MPD client.");
 
 	int c;
 	while ((c = opt_handler_get (&oh)) != -1)
@@ -4051,12 +4635,6 @@ main (int argc, char *argv[])
 
 	argc -= optind;
 	argv += optind;
-
-	if (argc)
-	{
-		opt_handler_usage (&oh, stderr);
-		exit (EXIT_FAILURE);
-	}
 	opt_handler_free (&oh);
 
 	// We only need to convert to and from the terminal encoding
@@ -4064,10 +4642,11 @@ main (int argc, char *argv[])
 		print_warning ("failed to set the locale");
 
 	app_init_context ();
+	app_init_enqueue (argv, argc);
 	app_load_configuration ();
-	app_init_terminal ();
 	signals_setup_handlers ();
 	app_init_poller_events ();
+	app_init_terminal ();
 
 	g_normal_keys = app_init_bindings ("normal",
 		g_normal_defaults, N_ELEMENTS (g_normal_defaults), &g_normal_keys_len);
@@ -4087,6 +4666,11 @@ main (int argc, char *argv[])
 	app_prepend_tab (current_tab_init ());
 	app_switch_tab ((g.help_tab = help_tab_init ()));
 
+	// TODO: the help tab should be the default for new users only,
+	//   so provide a configuration option to flip this
+	if (argc)
+		app_switch_tab (&g_current_tab);
+
 	g.polling = true;
 	while (g.polling)
 		poller_run (&g.poller);