icon-loader: load SVG icons at max scale of any usable output

- Add a new function to get the maximum scale of all usable outputs
- Pass the maximum output scale through to img_svg_load(), which
  ultimately calls cairo_surface_set_device_scale() before rendering

include/icon-loader.h

@@ -7,6 +7,6 @@ struct server;
 void icon_loader_init(struct server *server);
 void icon_loader_finish(struct server *server);
 struct lab_data_buffer *icon_loader_lookup(struct server *server,
-	const char *app_id, int size, int scale);
+	const char *app_id, int size, float scale);
 
 #endif /* LABWC_ICON_LOADER_H */

include/img/img-svg.h

@@ -5,6 +5,6 @@
 struct lab_data_buffer;
 
 void img_svg_load(const char *filename, struct lab_data_buffer **buffer,
-	int size);
+	int size, float scale);
 
 #endif /* LABWC_IMG_SVG_H */

include/labwc.h

@@ -546,6 +546,14 @@ struct wlr_box output_usable_area_scaled(struct output *output);
 void handle_output_power_manager_set_mode(struct wl_listener *listener,
 	void *data);
 void output_enable_adaptive_sync(struct wlr_output *output, bool enabled);
+
+/**
+ * output_max_scale() - get maximum scale factor of all usable outputs.
+ * Used when loading/rendering resources (e.g. icons) that may be
+ * displayed on any output.
+ */
+float output_max_scale(struct server *server);
+
 void new_tearing_hint(struct wl_listener *listener, void *data);
 
 void server_init(struct server *server);

src/icon-loader.c

@@ -5,6 +5,7 @@
 #include <string.h>
 #include <strings.h>
 #include <wlr/util/log.h>
+#include "common/macros.h"
 #include "common/mem.h"
 #include "common/string-helpers.h"
 #include "config.h"
@@ -219,7 +220,8 @@ get_db_entry_by_id_fuzzy(struct sfdo_desktop_db *db, const char *app_id)
 }
 
 struct lab_data_buffer *
-icon_loader_lookup(struct server *server, const char *app_id, int size, int scale)
+icon_loader_lookup(struct server *server, const char *app_id, int size,
+		float scale)
 {
 	struct icon_loader *loader = server->icon_loader;
 	if (!loader) {
@@ -236,16 +238,23 @@ icon_loader_lookup(struct server *server, const char *app_id, int size, int scal
 		icon_name = sfdo_desktop_entry_get_icon(entry, NULL);
 	}
 
+	/*
+	 * libsfdo doesn't support loading icons for fractional scales,
+	 * so round down and increase the icon size to compensate.
+	 */
+	int lookup_scale = MAX((int)scale, 1);
+	int lookup_size = lroundf(size * scale / lookup_scale);
+
 	struct icon_ctx ctx = {0};
 	int ret;
 	if (!icon_name) {
 		/* fall back to app id */
-		ret = process_rel_name(&ctx, app_id, loader, size, scale);
+		ret = process_rel_name(&ctx, app_id, loader, lookup_size, lookup_scale);
 	} else if (icon_name[0] == '/') {
 		ret = process_abs_name(&ctx, icon_name);
 	} else {
 		/* this should be the case for most icons */
-		ret = process_rel_name(&ctx, icon_name, loader, size, scale);
+		ret = process_rel_name(&ctx, icon_name, loader, lookup_size, lookup_scale);
 	}
 	if (ret < 0) {
 		return NULL;
@@ -261,7 +270,7 @@ icon_loader_lookup(struct server *server, const char *app_id, int size, int scal
 		break;
 	case SFDO_ICON_FILE_FORMAT_SVG:
 #if HAVE_RSVG
-		img_svg_load(ctx.path, &icon_buffer, size * scale);
+		img_svg_load(ctx.path, &icon_buffer, size, scale);
 #endif
 		break;
 	case SFDO_ICON_FILE_FORMAT_XPM:

src/img/img-svg.c

@@ -15,8 +15,8 @@
 #include "labwc.h"
 
 void
-img_svg_load(const char *filename, struct lab_data_buffer **buffer,
-		int size)
+img_svg_load(const char *filename, struct lab_data_buffer **buffer, int size,
+		float scale)
 {
 	if (*buffer) {
 		wlr_buffer_drop(&(*buffer)->base);
@@ -39,7 +39,7 @@ img_svg_load(const char *filename, struct lab_data_buffer **buffer,
 		return;
 	}
 
-	*buffer = buffer_create_cairo(size, size, 1.0);
+	*buffer = buffer_create_cairo(size, size, scale);
 	cairo_surface_t *image = (*buffer)->surface;
 	cairo_t *cr = (*buffer)->cairo;
 

src/output.c

@@ -1067,3 +1067,17 @@ output_enable_adaptive_sync(struct wlr_output *output, bool enabled)
 			enabled ? "en" : "dis", output->name);
 	}
 }
+
+float
+output_max_scale(struct server *server)
+{
+	/* Never return less than 1, in case outputs are disabled */
+	float scale = 1;
+	struct output *output;
+	wl_list_for_each(output, &server->outputs, link) {
+		if (output_is_usable(output)) {
+			scale = MAX(scale, output->wlr_output->scale);
+		}
+	}
+	return scale;
+}

src/ssd/ssd-titlebar.c

@@ -604,8 +604,16 @@ ssd_update_window_icon(struct ssd *ssd)
 	int hpad = theme->window_button_width / 10;
 	int icon_size = MIN(theme->window_button_width - 2 * hpad,
 		theme->title_height - 2 * theme->padding_height);
-	/* TODO: take into account output scales */
-	int icon_scale = 1;
+
+	/*
+	 * Load/render icons at the max scale of any usable output (at
+	 * this point in time). We don't want to be constantly reloading
+	 * icons as views are moved between outputs.
+	 *
+	 * TODO: currently there's no signal to reload/render icons if
+	 * outputs are reconfigured and the max scale changes.
+	 */
+	float icon_scale = output_max_scale(ssd->view->server);
 
 	struct lab_data_buffer *icon_buffer = icon_loader_lookup(
 		ssd->view->server, app_id, icon_size, icon_scale);

src/theme.c

@@ -257,7 +257,8 @@ load_button(struct theme *theme, struct button *b, int active)
 		int size = theme->title_height - 2 * theme->padding_height;
 		get_button_filename(filename, sizeof(filename), b->name,
 			active ? "-active.svg" : "-inactive.svg");
-		img_svg_load(filename, buffer, size);
+		/* TODO: account for output scale */
+		img_svg_load(filename, buffer, size, 1);
 	}
 #endif