Cache thumbnails across reloads

This will speed up sort changes, as well as simple reloads,
at the cost of an extra hash map from URIs to Cairo surface references.

It seems unnecessary to provide an explicit option to flush this cache,
as it may be cleared by changing either the directory or the current
thumbnail size.

fiv-browser.c

@@ -72,6 +72,8 @@ struct _FivBrowser {
 	double drag_begin_x;                ///< Viewport start X coordinate or -1
 	double drag_begin_y;                ///< Viewport start Y coordinate or -1
 
+	GHashTable *thumbnail_cache;        ///< [URI]cairo_surface_t, for item_size
+
 	Thumbnailer *thumbnailers;          ///< Parallelized thumbnailers
 	size_t thumbnailers_len;            ///< Thumbnailers array size
 	GList *thumbnailers_queue;          ///< Queued up Entry pointers
@@ -84,8 +86,12 @@ struct _FivBrowser {
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
+/// The "last modified" timestamp of source images for thumbnails.
+static cairo_user_data_key_t fiv_browser_key_mtime_msec;
+
 struct entry {
 	char *uri;                          ///< GIO URI
+	gint64 mtime_msec;                  ///< Modification time in milliseconds
 	cairo_surface_t *thumbnail;         ///< Prescaled thumbnail
 	GIcon *icon;                        ///< If no thumbnail, use this icon
 };
@@ -427,18 +433,34 @@ entry_add_thumbnail(gpointer data, gpointer user_data)
 	g_clear_pointer(&self->thumbnail, cairo_surface_destroy);
 
 	FivBrowser *browser = FIV_BROWSER(user_data);
-	GFile *file = g_file_new_for_uri(self->uri);
-	self->thumbnail = rescale_thumbnail(
-		fiv_thumbnail_lookup(file, browser->item_size), browser->item_height);
-	if (self->thumbnail)
-		goto out;
+	cairo_surface_t *cached =
+		g_hash_table_lookup(browser->thumbnail_cache, self->uri);
+	if (cached &&
+		(intptr_t) cairo_surface_get_user_data(
+			cached, &fiv_browser_key_mtime_msec) == self->mtime_msec) {
+		self->thumbnail = cairo_surface_reference(cached);
+	} else {
+		cairo_surface_t *found = fiv_thumbnail_lookup(
+			self->uri, self->mtime_msec, browser->item_size);
+		self->thumbnail = rescale_thumbnail(found, browser->item_height);
+	}
+
+	if (self->thumbnail) {
+		// This choice of mtime favours unnecessary thumbnail reloading.
+		cairo_surface_set_user_data(self->thumbnail,
+			&fiv_browser_key_mtime_msec, (void *) (intptr_t) self->mtime_msec,
+			NULL);
+		return;
+	}
 
 	// Fall back to symbolic icons, though there's only so much we can do
 	// in parallel--GTK+ isn't thread-safe.
+	GFile *file = g_file_new_for_uri(self->uri);
 	GFileInfo *info = g_file_query_info(file,
 		G_FILE_ATTRIBUTE_STANDARD_NAME
 		"," G_FILE_ATTRIBUTE_STANDARD_SYMBOLIC_ICON,
 		G_FILE_QUERY_INFO_NONE, NULL, NULL);
+	g_object_unref(file);
 	if (info) {
 		GIcon *icon = g_file_info_get_symbolic_icon(info);
 		if (icon)
@@ -449,8 +471,6 @@ entry_add_thumbnail(gpointer data, gpointer user_data)
 	// The GVfs backend may not be friendly.
 	if (!self->icon)
 		self->icon = g_icon_new_for_string("text-x-generic-symbolic", NULL);
-out:
-	g_object_unref(file);
 }
 
 static void
@@ -506,8 +526,18 @@ reload_thumbnails(FivBrowser *self)
 		g_thread_pool_push(pool, &g_array_index(self->entries, Entry, i), NULL);
 	g_thread_pool_free(pool, FALSE, TRUE);
 
-	for (guint i = 0; i < self->entries->len; i++)
-		materialize_icon(self, &g_array_index(self->entries, Entry, i));
+	// Once a URI disappears from the model, its thumbnail is forgotten.
+	g_hash_table_remove_all(self->thumbnail_cache);
+
+	for (guint i = 0; i < self->entries->len; i++) {
+		Entry *entry = &g_array_index(self->entries, Entry, i);
+		if (entry->thumbnail) {
+			g_hash_table_insert(self->thumbnail_cache, g_strdup(entry->uri),
+				cairo_surface_reference(entry->thumbnail));
+		}
+
+		materialize_icon(self, entry);
+	}
 
 	gtk_widget_queue_resize(GTK_WIDGET(self));
 }
@@ -529,6 +559,11 @@ thumbnailer_reprocess_entry(FivBrowser *self, GBytes *output, Entry *entry)
 			fiv_io_deserialize(output), self->item_height))) {
 		entry_add_thumbnail(entry, self);
 		materialize_icon(self, entry);
+	} else {
+		// This choice of mtime favours unnecessary thumbnail reloading.
+		cairo_surface_set_user_data(entry->thumbnail,
+			&fiv_browser_key_mtime_msec, (void *) (intptr_t) entry->mtime_msec,
+			NULL);
 	}
 
 	gtk_widget_queue_resize(GTK_WIDGET(self));
@@ -914,6 +949,8 @@ fiv_browser_finalize(GObject *gobject)
 		g_clear_object(&self->model);
 	}
 
+	g_hash_table_destroy(self->thumbnail_cache);
+
 	cairo_surface_destroy(self->glow);
 	g_clear_object(&self->pointer);
 
@@ -958,6 +995,8 @@ set_item_size(FivBrowser *self, FivThumbnailSize size)
 	if (size != self->item_size) {
 		self->item_size = size;
 		self->item_height = fiv_thumbnail_sizes[self->item_size].size;
+
+		g_hash_table_remove_all(self->thumbnail_cache);
 		reload_thumbnails(self);
 		thumbnailers_start(self);
 
@@ -1674,6 +1713,9 @@ fiv_browser_init(FivBrowser *self)
 	g_array_set_clear_func(self->layouted_rows, (GDestroyNotify) row_free);
 	abort_button_tracking(self);
 
+	self->thumbnail_cache = g_hash_table_new_full(g_str_hash, g_str_equal,
+		g_free, (GDestroyNotify) cairo_surface_destroy);
+
 	self->thumbnailers_len = g_get_num_processors();
 	self->thumbnailers =
 		g_malloc0_n(self->thumbnailers_len, sizeof *self->thumbnailers);
@@ -1689,6 +1731,7 @@ fiv_browser_init(FivBrowser *self)
 
 // --- Public interface --------------------------------------------------------
 
+// TODO(p): Later implement any arguments of this FivIoModel signal.
 static void
 on_model_files_changed(FivIoModel *model, FivBrowser *self)
 {
@@ -1698,18 +1741,16 @@ on_model_files_changed(FivIoModel *model, FivBrowser *self)
 	if (self->selected)
 		selected_uri = g_strdup(self->selected->uri);
 
-	// TODO(p): Later implement arguments.
 	thumbnailers_abort(self);
 	g_array_set_size(self->entries, 0);
 	g_array_set_size(self->layouted_rows, 0);
 
-	GPtrArray *files = fiv_io_model_get_files(self->model);
-	for (guint i = 0; i < files->len; i++) {
-		g_array_append_val(self->entries,
-			((Entry) {.thumbnail = NULL, .uri = files->pdata[i]}));
-		files->pdata[i] = NULL;
+	gsize len = 0;
+	const FivIoModelEntry *files = fiv_io_model_get_files(self->model, &len);
+	for (gsize i = 0; i < len; i++) {
+		g_array_append_val(self->entries, ((Entry) {.thumbnail = NULL,
+			.uri = g_strdup(files[i].uri), .mtime_msec = files[i].mtime_msec}));
 	}
-	g_ptr_array_free(files, TRUE);
 
 	fiv_browser_select(self, selected_uri);
 	g_free(selected_uri);

fiv-io.c

@@ -2795,14 +2795,8 @@ fiv_io_deserialize(GBytes *bytes)
 
 #include <fnmatch.h>
 
-typedef struct {
-	gchar *uri;                         ///< GIO URI
-	gchar *collate_key;                 ///< Collate key for the filename
-	gint64 mtime_msec;                  ///< Modification time in milliseconds
-} ModelEntry;
-
 static void
-model_entry_finalize(ModelEntry *entry)
+model_entry_finalize(FivIoModelEntry *entry)
 {
 	g_free(entry->uri);
 	g_free(entry->collate_key);
@@ -2867,8 +2861,9 @@ model_supports(FivIoModel *self, const gchar *filename)
 }
 
 static inline int
-model_compare_entries(FivIoModel *self, const ModelEntry *entry1, GFile *file1,
-	const ModelEntry *entry2, GFile *file2)
+model_compare_entries(FivIoModel *self,
+	const FivIoModelEntry *entry1, GFile *file1,
+	const FivIoModelEntry *entry2, GFile *file2)
 {
 	if (g_file_has_prefix(file1, file2))
 		return +1;
@@ -2894,8 +2889,8 @@ model_compare_entries(FivIoModel *self, const ModelEntry *entry1, GFile *file1,
 static gint
 model_compare(gconstpointer a, gconstpointer b, gpointer user_data)
 {
-	const ModelEntry *entry1 = a;
-	const ModelEntry *entry2 = b;
+	const FivIoModelEntry *entry1 = a;
+	const FivIoModelEntry *entry2 = b;
 	GFile *file1 = g_file_new_for_uri(entry1->uri);
 	GFile *file2 = g_file_new_for_uri(entry2->uri);
 	int result = model_compare_entries(user_data, entry1, file1, entry2, file2);
@@ -2939,7 +2934,7 @@ model_reload(FivIoModel *self, GError **error)
 		if (self->filtering && g_file_info_get_is_hidden(info))
 			continue;
 
-		ModelEntry entry = {.uri = g_file_get_uri(child)};
+		FivIoModelEntry entry = {.uri = g_file_get_uri(child)};
 		GDateTime *mtime = g_file_info_get_modification_date_time(info);
 		if (mtime) {
 			entry.mtime_msec = g_date_time_to_unix(mtime) * 1000 +
@@ -3076,8 +3071,8 @@ fiv_io_model_init(FivIoModel *self)
 	self->supported_globs = extract_mime_globs((const char **) types);
 	g_strfreev(types);
 
-	self->files = g_array_new(FALSE, TRUE, sizeof(ModelEntry));
-	self->subdirs = g_array_new(FALSE, TRUE, sizeof(ModelEntry));
+	self->files = g_array_new(FALSE, TRUE, sizeof(FivIoModelEntry));
+	self->subdirs = g_array_new(FALSE, TRUE, sizeof(FivIoModelEntry));
 	g_array_set_clear_func(
 		self->subdirs, (GDestroyNotify) model_entry_finalize);
 	g_array_set_clear_func(
@@ -3107,24 +3102,18 @@ fiv_io_model_get_location(FivIoModel *self)
 	return self->directory;
 }
 
-GPtrArray *
-fiv_io_model_get_files(FivIoModel *self)
+const FivIoModelEntry *
+fiv_io_model_get_files(FivIoModel *self, gsize *len)
 {
-	GPtrArray *a = g_ptr_array_new_full(self->files->len, g_free);
-	for (guint i = 0; i < self->files->len; i++)
-		g_ptr_array_add(
-			a, g_strdup(g_array_index(self->files, ModelEntry, i).uri));
-	return a;
+	*len = self->files->len;
+	return (const FivIoModelEntry *) self->files->data;
 }
 
-GPtrArray *
-fiv_io_model_get_subdirectories(FivIoModel *self)
+const FivIoModelEntry *
+fiv_io_model_get_subdirs(FivIoModel *self, gsize *len)
 {
-	GPtrArray *a = g_ptr_array_new_full(self->subdirs->len, g_free);
-	for (guint i = 0; i < self->subdirs->len; i++)
-		g_ptr_array_add(
-			a, g_strdup(g_array_index(self->subdirs, ModelEntry, i).uri));
-	return a;
+	*len = self->subdirs->len;
+	return (const FivIoModelEntry *) self->subdirs->data;
 }
 
 // --- Export ------------------------------------------------------------------

fiv-io.h

@@ -122,8 +122,14 @@ gboolean fiv_io_model_open(FivIoModel *self, GFile *directory, GError **error);
 /// There is no ownership transfer, and the object may be NULL.
 GFile *fiv_io_model_get_location(FivIoModel *self);
 
-GPtrArray *fiv_io_model_get_files(FivIoModel *self);
-GPtrArray *fiv_io_model_get_subdirectories(FivIoModel *self);
+typedef struct {
+	char *uri;                          ///< GIO URI
+	char *collate_key;                  ///< Collate key for the filename
+	gint64 mtime_msec;                  ///< Modification time in milliseconds
+} FivIoModelEntry;
+
+const FivIoModelEntry *fiv_io_model_get_files(FivIoModel *self, gsize *len);
+const FivIoModelEntry *fiv_io_model_get_subdirs(FivIoModel *self, gsize *len);
 
 // --- Export ------------------------------------------------------------------
 

fiv-sidebar.c

@@ -241,14 +241,15 @@ update_location(FivSidebar *self)
 	if ((row = create_row(self, location, "circle-filled-symbolic")))
 		gtk_container_add(GTK_CONTAINER(self->listbox), row);
 
-	GPtrArray *subdirs = fiv_io_model_get_subdirectories(self->model);
-	for (guint i = 0; i < subdirs->len; i++) {
-		GFile *file = g_file_new_for_uri(subdirs->pdata[i]);
+	gsize len = 0;
+	const FivIoModelEntry *subdirs =
+		fiv_io_model_get_subdirs(self->model, &len);
+	for (gsize i = 0; i < len; i++) {
+		GFile *file = g_file_new_for_uri(subdirs[i].uri);
 		if ((row = create_row(self, file, "go-down-symbolic")))
 			gtk_container_add(GTK_CONTAINER(self->listbox), row);
 		g_object_unref(file);
 	}
-	g_ptr_array_free(subdirs, TRUE);
 }
 
 static void

fiv-thumbnail.c

@@ -579,18 +579,11 @@ fail_init:
 }
 
 cairo_surface_t *
-fiv_thumbnail_lookup(GFile *target, FivThumbnailSize size)
+fiv_thumbnail_lookup(char *uri, gint64 mtime_msec, FivThumbnailSize size)
 {
 	g_return_val_if_fail(size >= FIV_THUMBNAIL_SIZE_MIN &&
 		size <= FIV_THUMBNAIL_SIZE_MAX, NULL);
 
-	// Local files only, at least for now.
-	GStatBuf st = {};
-	const gchar *path = g_file_peek_path(target);
-	if (!path || g_stat(path, &st))
-		return NULL;
-
-	gchar *uri = g_file_get_uri(target);
 	gchar *sum = g_compute_checksum_for_string(G_CHECKSUM_MD5, uri, -1);
 	gchar *thumbnails_dir = fiv_thumbnail_get_root();
 
@@ -605,7 +598,7 @@ fiv_thumbnail_lookup(GFile *target, FivThumbnailSize size)
 		const char *name = fiv_thumbnail_sizes[use].thumbnail_spec_name;
 		gchar *wide =
 			g_strdup_printf("%s/wide-%s/%s.webp", thumbnails_dir, name, sum);
-		result = read_wide_thumbnail(wide, uri, st.st_mtim.tv_sec, &error);
+		result = read_wide_thumbnail(wide, uri, mtime_msec / 1000, &error);
 		if (error) {
 			g_debug("%s: %s", wide, error->message);
 			g_clear_error(&error);
@@ -621,7 +614,7 @@ fiv_thumbnail_lookup(GFile *target, FivThumbnailSize size)
 
 		gchar *path =
 			g_strdup_printf("%s/%s/%s.png", thumbnails_dir, name, sum);
-		result = read_spng_thumbnail(path, uri, st.st_mtim.tv_sec, &error);
+		result = read_spng_thumbnail(path, uri, mtime_msec / 1000, &error);
 		if (error) {
 			g_debug("%s: %s", path, error->message);
 			g_clear_error(&error);
@@ -639,7 +632,6 @@ fiv_thumbnail_lookup(GFile *target, FivThumbnailSize size)
 
 	g_free(thumbnails_dir);
 	g_free(sum);
-	g_free(uri);
 	return result;
 }
 

fiv-thumbnail.h

@@ -62,7 +62,8 @@ gboolean fiv_thumbnail_produce(GFile *target, FivThumbnailSize max_size,
 
 /// Retrieves a thumbnail of the most appropriate quality and resolution
 /// for the target file.
-cairo_surface_t *fiv_thumbnail_lookup(GFile *target, FivThumbnailSize size);
+cairo_surface_t *fiv_thumbnail_lookup(
+	char *uri, gint64 mtime_msec, FivThumbnailSize size);
 
 /// Invalidate the wide thumbnail cache. May write to standard streams.
 void fiv_thumbnail_invalidate(void);

fiv.c

@@ -702,8 +702,13 @@ on_model_files_changed(FivIoModel *model, G_GNUC_UNUSED gpointer user_data)
 {
 	g_return_if_fail(model == g.model);
 
+	gsize len = 0;
+	const FivIoModelEntry *files = fiv_io_model_get_files(g.model, &len);
 	g_ptr_array_free(g.files, TRUE);
-	g.files = fiv_io_model_get_files(g.model);
+	g.files = g_ptr_array_new_full(len, g_free);
+	for (gsize i = 0; i < len; i++)
+		g_ptr_array_add(g.files, g_strdup(files[i].uri));
+
 	update_files_index();
 
 	gtk_widget_set_sensitive(