Add ability to use different thumbnail sizes

4 files changed, 340 insertions, 166 deletions

diff --git a/fastiv-browser.c b/fastiv-browser.c
index feb4ca3..e025d66 100644
--- a/fastiv-browser.c
+++ b/fastiv-browser.c
@@ -41,6 +41,8 @@
 struct _FastivBrowser {
 	GtkWidget parent_instance;
 
+	FastivIoThumbnailSize item_size;    ///< Thumbnail height in pixels
+
 	GArray *entries;                    ///< [Entry]
 	GArray *layouted_rows;              ///< [Row]
 	int selected;
@@ -55,7 +57,6 @@ typedef struct entry Entry;
 typedef struct item Item;
 typedef struct row Row;
 
-static const double g_row_height = 256;
 static const double g_permitted_width_multiplier = 2;
 
 // Could be split out to also-idiomatic row-spacing/column-spacing properties.
@@ -114,7 +115,7 @@ append_row(FastivBrowser *self, int *y, int x, GArray *items_array)
 	}));
 
 	// Not trying to pack them vertically, but this would be the place to do it.
-	*y += g_row_height;
+	*y += (int) self->item_size;
 	*y += self->item_border_y;
 }
 
@@ -199,13 +200,13 @@ draw_outer_border(FastivBrowser *self, cairo_t *cr, int width, int height)
 }
 
 static GdkRectangle
-item_extents(const Item *item, const Row *row)
+item_extents(FastivBrowser *self, const Item *item, const Row *row)
 {
 	int width = cairo_image_surface_get_width(item->entry->thumbnail);
 	int height = cairo_image_surface_get_height(item->entry->thumbnail);
 	return (GdkRectangle) {
 		.x = row->x_offset + item->x_offset,
-		.y = row->y_offset + g_row_height - height,
+		.y = row->y_offset + (int) self->item_size - height,
 		.width = width,
 		.height = height,
 	};
@@ -217,7 +218,7 @@ entry_at(FastivBrowser *self, int x, int y)
 	for (guint i = 0; i < self->layouted_rows->len; i++) {
 		const Row *row = &g_array_index(self->layouted_rows, Row, i);
 		for (Item *item = row->items; item->entry; item++) {
-			GdkRectangle extents = item_extents(item, row);
+			GdkRectangle extents = item_extents(self, item, row);
 			if (x >= extents.x &&
 				y >= extents.y &&
 				x <= extents.x + extents.width &&
@@ -243,7 +244,7 @@ draw_row(FastivBrowser *self, cairo_t *cr, const Row *row)
 	gtk_style_context_get_border(style, state, &border);
 	for (Item *item = row->items; item->entry; item++) {
 		cairo_save(cr);
-		GdkRectangle extents = item_extents(item, row);
+		GdkRectangle extents = item_extents(self, item, row);
 		cairo_translate(cr, extents.x - border.left, extents.y - border.top);
 
 		gtk_style_context_save(style);
@@ -281,6 +282,159 @@ draw_row(FastivBrowser *self, cairo_t *cr, const Row *row)
 	gtk_style_context_restore(style);
 }
 
+// --- Thumbnails --------------------------------------------------------------
+
+// NOTE: "It is important to note that when an image with an alpha channel is
+// scaled, linear encoded, pre-multiplied component values must be used!"
+static cairo_surface_t *
+rescale_thumbnail(cairo_surface_t *thumbnail, double row_height)
+{
+	if (!thumbnail)
+		return thumbnail;
+
+	int width = cairo_image_surface_get_width(thumbnail);
+	int height = cairo_image_surface_get_height(thumbnail);
+
+	double scale_x = 1;
+	double scale_y = 1;
+	if (width > g_permitted_width_multiplier * height) {
+		scale_x = g_permitted_width_multiplier * row_height / width;
+		scale_y = round(scale_x * height) / height;
+	} else {
+		scale_y = row_height / height;
+		scale_x = round(scale_y * width) / width;
+	}
+	if (scale_x == 1 && scale_y == 1)
+		return thumbnail;
+
+	int projected_width = round(scale_x * width);
+	int projected_height = round(scale_y * height);
+	cairo_surface_t *scaled = cairo_image_surface_create(
+		CAIRO_FORMAT_ARGB32, projected_width, projected_height);
+
+	// pixman can take gamma into account when scaling, unlike Cairo.
+	struct pixman_f_transform xform_floating;
+	struct pixman_transform xform;
+
+	// PIXMAN_a8r8g8b8_sRGB can be used for gamma-correct results,
+	// but it's an incredibly slow transformation
+	pixman_format_code_t format = PIXMAN_a8r8g8b8;
+
+	pixman_image_t *src = pixman_image_create_bits(format, width, height,
+		(uint32_t *) cairo_image_surface_get_data(thumbnail),
+		cairo_image_surface_get_stride(thumbnail));
+	pixman_image_t *dest = pixman_image_create_bits(format,
+		cairo_image_surface_get_width(scaled),
+		cairo_image_surface_get_height(scaled),
+		(uint32_t *) cairo_image_surface_get_data(scaled),
+		cairo_image_surface_get_stride(scaled));
+
+	pixman_f_transform_init_scale(&xform_floating, scale_x, scale_y);
+	pixman_f_transform_invert(&xform_floating, &xform_floating);
+	pixman_transform_from_pixman_f_transform(&xform, &xform_floating);
+	pixman_image_set_transform(src, &xform);
+	pixman_image_set_filter(src, PIXMAN_FILTER_BILINEAR, NULL, 0);
+	pixman_image_set_repeat(src, PIXMAN_REPEAT_PAD);
+
+	pixman_image_composite(PIXMAN_OP_SRC, src, NULL, dest, 0, 0, 0, 0, 0, 0,
+		projected_width, projected_height);
+	pixman_image_unref(src);
+	pixman_image_unref(dest);
+
+	cairo_surface_destroy(thumbnail);
+	cairo_surface_mark_dirty(scaled);
+	return scaled;
+}
+
+static void
+entry_add_thumbnail(gpointer data, gpointer user_data)
+{
+	Entry *self = data;
+	g_clear_object(&self->icon);
+	if (self->thumbnail)
+		cairo_surface_destroy(self->thumbnail);
+
+	FastivIoThumbnailSize size = FASTIV_BROWSER(user_data)->item_size;
+	self->thumbnail = rescale_thumbnail(
+		fastiv_io_lookup_thumbnail(self->filename, size), (int) size);
+	if (self->thumbnail)
+		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_path(self->filename);
+	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)
+			self->icon = g_object_ref(icon);
+		g_object_unref(info);
+	}
+}
+
+static void
+materialize_icon(FastivBrowser *self, Entry *entry)
+{
+	if (!entry->icon)
+		return;
+
+	// Fucker will still give us non-symbolic icons, no more playing nice.
+	// TODO(p): Investigate a bit closer. We may want to abandon the idea
+	// of using GLib to look up icons for us, derive a list from a guessed
+	// MIME type, with "-symbolic" prefixes and fallbacks,
+	// and use gtk_icon_theme_choose_icon() instead.
+	// TODO(p): Make sure we have /some/ icon for every entry.
+	// TODO(p): We might want to populate these on an as-needed basis.
+	GtkIconInfo *icon_info = gtk_icon_theme_lookup_by_gicon(
+		gtk_icon_theme_get_default(), entry->icon, (int) self->item_size / 2,
+		GTK_ICON_LOOKUP_FORCE_SYMBOLIC);
+	if (!icon_info)
+		return;
+
+	// Bílá, bílá, bílá, bílá... komu by se nelíbí-lá...
+	// We do not want any highlights, nor do we want to remember the style.
+	const GdkRGBA white = {1, 1, 1, 1};
+	GdkPixbuf *pixbuf = gtk_icon_info_load_symbolic(
+		icon_info, &white, &white, &white, &white, NULL, NULL);
+	if (pixbuf) {
+		int outer_size = (int) self->item_size;
+		entry->thumbnail =
+			cairo_image_surface_create(CAIRO_FORMAT_A8, outer_size, outer_size);
+
+		// "Note that the resulting pixbuf may not be exactly this size;"
+		// though GTK_ICON_LOOKUP_FORCE_SIZE is also an option.
+		int x = (outer_size - gdk_pixbuf_get_width(pixbuf)) / 2;
+		int y = (outer_size - gdk_pixbuf_get_height(pixbuf)) / 2;
+
+		cairo_t *cr = cairo_create(entry->thumbnail);
+		gdk_cairo_set_source_pixbuf(cr, pixbuf, x, y);
+		cairo_paint(cr);
+		cairo_destroy(cr);
+
+		g_object_unref(pixbuf);
+	}
+	g_object_unref(icon_info);
+}
+
+static void
+reload_thumbnails(FastivBrowser *self)
+{
+	GThreadPool *pool = g_thread_pool_new(
+		entry_add_thumbnail, self, g_get_num_processors(), FALSE, NULL);
+	for (guint i = 0; i < self->entries->len; i++)
+		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));
+
+	gtk_widget_queue_resize(GTK_WIDGET(self));
+}
+
 // --- Boilerplate -------------------------------------------------------------
 
 // TODO(p): For proper navigation, we need to implement GtkScrollable.
@@ -289,6 +443,13 @@ G_DEFINE_TYPE_EXTENDED(FastivBrowser, fastiv_browser, GTK_TYPE_WIDGET, 0,
 		fastiv_browser_scrollable_init) */)
 
 enum {
+	PROP_THUMBNAIL_SIZE = 1,
+	N_PROPERTIES
+};
+
+static GParamSpec *browser_properties[N_PROPERTIES];
+
+enum {
 	ITEM_ACTIVATED,
 	LAST_SIGNAL,
 };
@@ -308,6 +469,37 @@ fastiv_browser_finalize(GObject *gobject)
 	G_OBJECT_CLASS(fastiv_browser_parent_class)->finalize(gobject);
 }
 
+static void
+fastiv_browser_get_property(
+	GObject *object, guint property_id, GValue *value, GParamSpec *pspec)
+{
+	FastivBrowser *self = FASTIV_BROWSER(object);
+	switch (property_id) {
+	case PROP_THUMBNAIL_SIZE:
+		g_value_set_enum(value, self->item_size);
+		break;
+	default:
+		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, property_id, pspec);
+	}
+}
+
+static void
+fastiv_browser_set_property(
+	GObject *object, guint property_id, const GValue *value, GParamSpec *pspec)
+{
+	FastivBrowser *self = FASTIV_BROWSER(object);
+	switch (property_id) {
+	case PROP_THUMBNAIL_SIZE:
+		if (g_value_get_enum(value) != (int) self->item_size) {
+			self->item_size = g_value_get_enum(value);
+			reload_thumbnails(self);
+		}
+		break;
+	default:
+		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, property_id, pspec);
+	}
+}
+
 static GtkSizeRequestMode
 fastiv_browser_get_request_mode(G_GNUC_UNUSED GtkWidget *widget)
 {
@@ -323,7 +515,8 @@ fastiv_browser_get_preferred_width(
 
 	GtkBorder padding = {};
 	gtk_style_context_get_padding(style, GTK_STATE_FLAG_NORMAL, &padding);
-	*minimum = *natural = g_permitted_width_multiplier * g_row_height +
+	*minimum = *natural =
+		g_permitted_width_multiplier * (int) self->item_size +
 		padding.left + 2 * self->item_border_x + padding.right;
 }
 
@@ -401,7 +594,7 @@ fastiv_browser_draw(GtkWidget *widget, cairo_t *cr)
 			.x = 0,
 			.y = row->y_offset - self->item_border_y,
 			.width = allocation.width,
-			.height = g_row_height + 2 * self->item_border_y,
+			.height = (int) self->item_size + 2 * self->item_border_y,
 		};
 		if (!have_clip || gdk_rectangle_intersect(&clip, &extents, NULL))
 			draw_row(self, cr, row);
@@ -520,6 +713,19 @@ fastiv_browser_class_init(FastivBrowserClass *klass)
 {
 	GObjectClass *object_class = G_OBJECT_CLASS(klass);
 	object_class->finalize = fastiv_browser_finalize;
+	object_class->get_property = fastiv_browser_get_property;
+	object_class->set_property = fastiv_browser_set_property;
+
+	browser_properties[PROP_THUMBNAIL_SIZE] = g_param_spec_enum(
+		"thumbnail-size", "Thumbnail size", "The thumbnail height to use",
+		FASTIV_TYPE_IO_THUMBNAIL_SIZE, FASTIV_IO_THUMBNAIL_SIZE_NORMAL,
+		G_PARAM_READWRITE);
+	g_object_class_install_properties(
+		object_class, N_PROPERTIES, browser_properties);
+
+	browser_signals[ITEM_ACTIVATED] = g_signal_new("item-activated",
+		G_TYPE_FROM_CLASS(klass), 0, 0, NULL, NULL, NULL,
+		G_TYPE_NONE, 2, G_TYPE_STRING, GTK_TYPE_PLACES_OPEN_FLAGS);
 
 	GtkWidgetClass *widget_class = GTK_WIDGET_CLASS(klass);
 	widget_class->get_request_mode = fastiv_browser_get_request_mode;
@@ -533,10 +739,6 @@ fastiv_browser_class_init(FastivBrowserClass *klass)
 	widget_class->motion_notify_event = fastiv_browser_motion_notify_event;
 	widget_class->style_updated = fastiv_browser_style_updated;
 
-	browser_signals[ITEM_ACTIVATED] = g_signal_new("item-activated",
-		G_TYPE_FROM_CLASS(klass), 0, 0, NULL, NULL, NULL,
-		G_TYPE_NONE, 2, G_TYPE_STRING, GTK_TYPE_PLACES_OPEN_FLAGS);
-
 	// TODO(p): Later override "screen_changed", recreate Pango layouts there,
 	// if we get to have any, or otherwise reflect DPI changes.
 	gtk_widget_class_set_css_name(widget_class, "fastiv-browser");
@@ -552,96 +754,15 @@ fastiv_browser_init(FastivBrowser *self)
 	self->layouted_rows = g_array_new(FALSE, TRUE, sizeof(Row));
 	g_array_set_clear_func(self->layouted_rows, (GDestroyNotify) row_free);
 
+	self->item_size = FASTIV_IO_THUMBNAIL_SIZE_NORMAL;
 	self->selected = -1;
 	self->glow = cairo_image_surface_create(CAIRO_FORMAT_A1, 0, 0);
-}
-
-// NOTE: "It is important to note that when an image with an alpha channel is
-// scaled, linear encoded, pre-multiplied component values must be used!"
-static cairo_surface_t *
-rescale_thumbnail(cairo_surface_t *thumbnail)
-{
-	if (!thumbnail)
-		return thumbnail;
-
-	int width = cairo_image_surface_get_width(thumbnail);
-	int height = cairo_image_surface_get_height(thumbnail);
-
-	double scale_x = 1;
-	double scale_y = 1;
-	if (width > g_permitted_width_multiplier * height) {
-		scale_x = g_permitted_width_multiplier * g_row_height / width;
-		scale_y = round(scale_x * height) / height;
-	} else {
-		scale_y = g_row_height / height;
-		scale_x = round(scale_y * width) / width;
-	}
-	if (scale_x == 1 && scale_y == 1)
-		return thumbnail;
-
-	int projected_width = round(scale_x * width);
-	int projected_height = round(scale_y * height);
-	cairo_surface_t *scaled = cairo_image_surface_create(
-		CAIRO_FORMAT_ARGB32, projected_width, projected_height);
-
-	// pixman can take gamma into account when scaling, unlike Cairo.
-	struct pixman_f_transform xform_floating;
-	struct pixman_transform xform;
-
-	// PIXMAN_a8r8g8b8_sRGB can be used for gamma-correct results,
-	// but it's an incredibly slow transformation
-	pixman_format_code_t format = PIXMAN_a8r8g8b8;
-
-	pixman_image_t *src = pixman_image_create_bits(format, width, height,
-		(uint32_t *) cairo_image_surface_get_data(thumbnail),
-		cairo_image_surface_get_stride(thumbnail));
-	pixman_image_t *dest = pixman_image_create_bits(format,
-		cairo_image_surface_get_width(scaled),
-		cairo_image_surface_get_height(scaled),
-		(uint32_t *) cairo_image_surface_get_data(scaled),
-		cairo_image_surface_get_stride(scaled));
 
-	pixman_f_transform_init_scale(&xform_floating, scale_x, scale_y);
-	pixman_f_transform_invert(&xform_floating, &xform_floating);
-	pixman_transform_from_pixman_f_transform(&xform, &xform_floating);
-	pixman_image_set_transform(src, &xform);
-	pixman_image_set_filter(src, PIXMAN_FILTER_BILINEAR, NULL, 0);
-	pixman_image_set_repeat(src, PIXMAN_REPEAT_PAD);
-
-	pixman_image_composite(PIXMAN_OP_SRC, src, NULL, dest, 0, 0, 0, 0, 0, 0,
-		projected_width, projected_height);
-	pixman_image_unref(src);
-	pixman_image_unref(dest);
-
-	cairo_surface_destroy(thumbnail);
-	cairo_surface_mark_dirty(scaled);
-	return scaled;
+	g_signal_connect_swapped(gtk_settings_get_default(),
+		"notify::gtk-icon-theme-name", G_CALLBACK(reload_thumbnails), self);
 }
 
-static void
-entry_add_thumbnail(gpointer data, G_GNUC_UNUSED gpointer user_data)
-{
-	Entry *self = data;
-	self->thumbnail =
-		rescale_thumbnail(fastiv_io_lookup_thumbnail(self->filename));
-	if (self->thumbnail)
-		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_path(self->filename);
-	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)
-			self->icon = g_object_ref(icon);
-		g_object_unref(info);
-	}
-}
+// --- Public interface --------------------------------------------------------
 
 void
 fastiv_browser_load(
@@ -676,56 +797,6 @@ fastiv_browser_load(
 	}
 	g_object_unref(enumerator);
 
-	GThreadPool *pool = g_thread_pool_new(
-		entry_add_thumbnail, NULL, g_get_num_processors(), FALSE, NULL);
-	for (guint i = 0; i < self->entries->len; i++)
-		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++) {
-		Entry *entry = &g_array_index(self->entries, Entry, i);
-		if (!entry->icon)
-			continue;
-
-		// Fucker will still give us non-symbolic icons, no more playing nice.
-		// TODO(p): Investigate a bit closer. We may want to abandon the idea
-		// of using GLib to look up icons for us, derive a list from a guessed
-		// MIME type, with "-symbolic" prefixes and fallbacks,
-		// and use gtk_icon_theme_choose_icon() instead.
-		// TODO(p): Make sure we have /some/ icon for every entry.
-		// TODO(p): GtkSettings -> notify::gtk-icon-theme-name?
-		// TODO(p): We might want to populate these on an as-needed basis.
-		GtkIconInfo *icon_info =
-			gtk_icon_theme_lookup_by_gicon(gtk_icon_theme_get_default(),
-				entry->icon, g_row_height / 2, GTK_ICON_LOOKUP_FORCE_SYMBOLIC);
-		if (!icon_info)
-			continue;
-
-		// Bílá, bílá, bílá, bílá... komu by se nelíbí-lá...
-		// We do not want any highlights, nor do we want to remember the style.
-		const GdkRGBA white = {1, 1, 1, 1};
-		GdkPixbuf *pixbuf = gtk_icon_info_load_symbolic(
-			icon_info, &white, &white, &white, &white, NULL, NULL);
-		if (pixbuf) {
-			int outer_size = g_row_height;
-			entry->thumbnail = cairo_image_surface_create(
-				CAIRO_FORMAT_A8, outer_size, outer_size);
-
-			// "Note that the resulting pixbuf may not be exactly this size;"
-			// though GTK_ICON_LOOKUP_FORCE_SIZE is also an option.
-			int x = (outer_size - gdk_pixbuf_get_width(pixbuf)) / 2;
-			int y = (outer_size - gdk_pixbuf_get_height(pixbuf)) / 2;
-
-			cairo_t *cr = cairo_create(entry->thumbnail);
-			gdk_cairo_set_source_pixbuf(cr, pixbuf, x, y);
-			cairo_paint(cr);
-			cairo_destroy(cr);
-
-			g_object_unref(pixbuf);
-		}
-		g_object_unref(icon_info);
-	}
-
-	// TODO(p): Sort and filter the entries.
-	gtk_widget_queue_resize(GTK_WIDGET(self));
+	// TODO(p): Sort the entries before.
+	reload_thumbnails(self);
 }
diff --git a/fastiv-io.c b/fastiv-io.c
index e1bb60a..60c0292 100644
--- a/fastiv-io.c
+++ b/fastiv-io.c
@@ -102,6 +102,29 @@ fastiv_io_all_supported_media_types(void)
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
+GType
+fastiv_io_thumbnail_size_get_type(void)
+{
+	static gsize guard;
+	if (g_once_init_enter(&guard)) {
+#define XX(name, value, dir) {FASTIV_IO_THUMBNAIL_SIZE_ ## name, \
+	"FASTIV_IO_THUMBNAIL_SIZE_" #name, #name},
+		static const GEnumValue values[] = {FASTIV_IO_THUMBNAIL_SIZES(XX) {}};
+#undef XX
+		GType type = g_enum_register_static(
+			g_intern_static_string("FastivIoThumbnailSize"), values);
+		g_once_init_leave(&guard, type);
+	}
+	return guard;
+}
+
+#define XX(name, value, dir) {FASTIV_IO_THUMBNAIL_SIZE_ ## name, dir},
+FastivIoThumbnailSizeInfo fastiv_io_thumbnail_sizes[] = {
+	FASTIV_IO_THUMBNAIL_SIZES(XX) {}};
+#undef XX
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
 #define FASTIV_IO_ERROR fastiv_io_error_quark()
 
 G_DEFINE_QUARK(fastiv-io-error-quark, fastiv_io_error)
@@ -981,8 +1004,20 @@ fail_init:
 }
 
 cairo_surface_t *
-fastiv_io_lookup_thumbnail(const gchar *target)
+fastiv_io_lookup_thumbnail(const gchar *target, FastivIoThumbnailSize size)
 {
+	// TODO(p): Consider having linear enum constants,
+	// and using a trivial lookup table. This is ridiculous.
+	int size_index = 0;
+	while (fastiv_io_thumbnail_sizes[size_index].size &&
+		fastiv_io_thumbnail_sizes[size_index].size < size)
+		size_index++;
+	int size_count = size_index;
+	while (fastiv_io_thumbnail_sizes[size_count].size)
+		size_count++;
+
+	g_return_val_if_fail(fastiv_io_thumbnail_sizes[size_index].size, NULL);
+
 	GStatBuf st;
 	if (g_stat(target, &st))
 		return NULL;
@@ -997,17 +1032,22 @@ fastiv_io_lookup_thumbnail(const gchar *target)
 	gchar *cache_dir = get_xdg_home_dir("XDG_CACHE_HOME", ".cache");
 
 	cairo_surface_t *result = NULL;
-	const gchar *sizes[] = {"large", "x-large", "xx-large", "normal"};
 	GError *error = NULL;
-	for (gsize i = 0; !result && i < G_N_ELEMENTS(sizes); i++) {
-		gchar *path = g_strdup_printf(
-			"%s/thumbnails/%s/%s.png", cache_dir, sizes[i], sum);
+	for (int i = 0; i < size_count; i++) {
+		int size_use = size_index + i;
+		if (size_use >= size_count)
+			size_use = size_count - i - 1;
+
+		gchar *path = g_strdup_printf("%s/thumbnails/%s/%s.png", cache_dir,
+			fastiv_io_thumbnail_sizes[size_use].directory_name, sum);
 		result = read_spng_thumbnail(path, uri, st.st_mtim.tv_sec, &error);
 		if (error) {
 			g_debug("%s: %s", path, error->message);
 			g_clear_error(&error);
 		}
 		g_free(path);
+		if (result)
+			break;
 	}
 
 	g_free(cache_dir);
diff --git a/fastiv-io.h b/fastiv-io.h
index 5a90e91..101db6c 100644
--- a/fastiv-io.h
+++ b/fastiv-io.h
@@ -19,12 +19,39 @@
 
 #include <cairo.h>
 #include <glib.h>
+#include <gio/gio.h>
 
 extern const char *fastiv_io_supported_media_types[];
 
 char **fastiv_io_all_supported_media_types(void);
 
+// And this is how you avoid glib-mkenums.
+typedef enum _FastivIoThumbnailSize {
+#define FASTIV_IO_THUMBNAIL_SIZES(XX) \
+	XX(SMALL,  128, "normal") \
+	XX(NORMAL, 256, "large") \
+	XX(LARGE,  512, "x-large") \
+	XX(HUGE,  1024, "xx-large")
+#define XX(name, value, dir) FASTIV_IO_THUMBNAIL_SIZE_ ## name = value,
+	FASTIV_IO_THUMBNAIL_SIZES(XX)
+#undef XX
+	FASTIV_IO_THUMBNAIL_SIZE_MIN = FASTIV_IO_THUMBNAIL_SIZE_SMALL,
+	FASTIV_IO_THUMBNAIL_SIZE_MAX = FASTIV_IO_THUMBNAIL_SIZE_HUGE
+} FastivIoThumbnailSize;
+
+GType fastiv_io_thumbnail_size_get_type(void) G_GNUC_CONST;
+#define FASTIV_TYPE_IO_THUMBNAIL_SIZE (fastiv_io_thumbnail_size_get_type())
+
+typedef struct _FastivIoThumbnailSizeInfo {
+	FastivIoThumbnailSize size;         ///< Nominal size in pixels
+	const char *directory_name;         ///< thumbnail-spec directory name
+} FastivIoThumbnailSizeInfo;
+
+// The array is null-terminated.
+extern FastivIoThumbnailSizeInfo fastiv_io_thumbnail_sizes[];
+
 cairo_surface_t *fastiv_io_open(const gchar *path, GError **error);
 cairo_surface_t *fastiv_io_open_from_data(
 	const char *data, size_t len, const gchar *path, GError **error);
-cairo_surface_t *fastiv_io_lookup_thumbnail(const gchar *target);
+cairo_surface_t *fastiv_io_lookup_thumbnail(
+	const gchar *target, FastivIoThumbnailSize size);
diff --git a/fastiv.c b/fastiv.c
index aa6e3e7..bfc8432 100644
--- a/fastiv.c
+++ b/fastiv.c
@@ -71,6 +71,8 @@ struct {
 	GtkWidget *browser_scroller;
 	GtkWidget *browser_paned;
 	GtkWidget *browser_sidebar;
+	GtkWidget *plus;
+	GtkWidget *minus;
 } g;
 
 static gboolean
@@ -330,6 +332,35 @@ on_open_location(G_GNUC_UNUSED GtkPlacesSidebar *sidebar, GFile *location,
 	}
 }
 
+static void
+on_toolbar_zoom(G_GNUC_UNUSED GtkButton *button, gpointer user_data)
+{
+	FastivIoThumbnailSize size = FASTIV_IO_THUMBNAIL_SIZE_MIN;
+	g_object_get(g.browser, "thumbnail-size", &size, NULL);
+
+	gintptr position = -1, count = 0, adjustment = (gintptr) user_data;
+	while (fastiv_io_thumbnail_sizes[count].size) {
+		if (fastiv_io_thumbnail_sizes[count].size == size)
+			position = count;
+		count++;
+	}
+
+	position += adjustment;
+	g_return_if_fail(position >= 0 && position < count);
+	g_object_set(g.browser, "thumbnail-size",
+		fastiv_io_thumbnail_sizes[position].size, NULL);
+}
+
+static void
+on_notify_thumbnail_size(
+	GObject *object, GParamSpec *param_spec, G_GNUC_UNUSED gpointer user_data)
+{
+	FastivIoThumbnailSize size = 0;
+	g_object_get(object, g_param_spec_get_name(param_spec), &size, NULL);
+	gtk_widget_set_sensitive(g.plus, size < FASTIV_IO_THUMBNAIL_SIZE_MAX);
+	gtk_widget_set_sensitive(g.minus, size > FASTIV_IO_THUMBNAIL_SIZE_MIN);
+}
+
 // Cursor keys, e.g., simply cannot be bound through accelerators
 // (and GtkWidget::keynav-failed would arguably be an awful solution).
 //
@@ -559,27 +590,30 @@ main(int argc, char *argv[])
 	g_signal_connect(g.browser_sidebar, "open-location",
 		G_CALLBACK(on_open_location), NULL);
 
-	GtkWidget *plus = gtk_button_new_from_icon_name("zoom-in-symbolic",
+	g.plus = gtk_button_new_from_icon_name("zoom-in-symbolic",
 		GTK_ICON_SIZE_BUTTON);
-	gtk_widget_set_tooltip_text(plus, "Larger thumbnails");
-	GtkWidget *minus = gtk_button_new_from_icon_name("zoom-out-symbolic",
+	gtk_widget_set_tooltip_text(g.plus, "Larger thumbnails");
+	g_signal_connect(g.plus, "clicked",
+		G_CALLBACK(on_toolbar_zoom), (gpointer) +1);
+
+	g.minus = gtk_button_new_from_icon_name("zoom-out-symbolic",
 		GTK_ICON_SIZE_BUTTON);
-	gtk_widget_set_tooltip_text(minus, "Smaller thumbnails");
+	gtk_widget_set_tooltip_text(g.minus, "Smaller thumbnails");
+	g_signal_connect(g.minus, "clicked",
+		G_CALLBACK(on_toolbar_zoom), (gpointer) -1);
 
 	GtkWidget *zoom_group = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 0);
 	gtk_style_context_add_class(
 		gtk_widget_get_style_context(zoom_group), GTK_STYLE_CLASS_LINKED);
-	gtk_box_pack_start(GTK_BOX(zoom_group), plus, FALSE, FALSE, 0);
-	gtk_box_pack_start(GTK_BOX(zoom_group), minus, FALSE, FALSE, 0);
+	gtk_box_pack_start(GTK_BOX(zoom_group), g.plus, FALSE, FALSE, 0);
+	gtk_box_pack_start(GTK_BOX(zoom_group), g.minus, FALSE, FALSE, 0);
 
 	GtkWidget *funnel = gtk_toggle_button_new();
 	gtk_container_add(GTK_CONTAINER(funnel),
 		gtk_image_new_from_icon_name("funnel-symbolic", GTK_ICON_SIZE_BUTTON));
 	gtk_widget_set_tooltip_text(funnel, "Hide unsupported files");
-
-	// TODO(p): Implement these as well.
-	gtk_widget_set_sensitive(plus, FALSE);
-	gtk_widget_set_sensitive(minus, FALSE);
+	g_signal_connect(funnel, "toggled",
+		G_CALLBACK(on_filtering_toggled), NULL);
 
 	GtkBox *toolbar =
 		fastiv_sidebar_get_toolbar(FASTIV_SIDEBAR(g.browser_sidebar));
@@ -611,7 +645,9 @@ main(int argc, char *argv[])
 	g.supported_globs = extract_mime_globs((const char **) types);
 	g_strfreev(types);
 
-	g_signal_connect(funnel, "toggled", G_CALLBACK(on_filtering_toggled), NULL);
+	g_signal_connect(g.browser, "notify::thumbnail-size",
+		G_CALLBACK(on_notify_thumbnail_size), NULL);
+	on_toolbar_zoom(NULL, (gpointer) 0);
 	gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(funnel), TRUE);
 
 	g.files = g_ptr_array_new_full(16, g_free);