xwm: Add icon support to the frame

This fetches the _NET_WM_ICON property of the X11 window, and use the
first image found as the frame icon.

This has been tested with various X11 programs, and improves usability
and user-friendliness a bit.

Changes since v1:
- Changed frame_button_create() to use
  frame_button_create_from_surface() internally.
- Removed a check that should never have been commited.

Changes since v2:
- Request UINT32_MAX items instead of 2048, to avoid cutting valid
  icons.
- Strengthen checks against malformed input.
- Handle XCB_PROPERTY_DELETE to remove the icon.
- Schedule a repaint if the icon changed.

Changes since v3:
- Keep the previous Cairo surface until the new one has been
  successfully loaded.
- Use uint32_t for cardinals.  Unsigned is the same type except on
  16-bit machines, but uint32_t is clearer.
- Declare length as uint32_t too, like in xcb_get_property_reply_t.

Signed-off-by: Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>

clients/window.c

@@ -2546,7 +2546,7 @@ window_frame_create(struct window *window, void *data)
 
 	frame = xzalloc(sizeof *frame);
 	frame->frame = frame_create(window->display->theme, 0, 0,
-				    buttons, window->title);
+	                            buttons, window->title, NULL);
 
 	frame->widget = window_add_widget(window, frame);
 	frame->child = widget_add_widget(frame->widget, data);
@@ -5449,7 +5449,7 @@ create_menu(struct display *display,
 	menu->user_data = user_data;
 	menu->widget = window_add_widget(menu->window, menu);
 	menu->frame = frame_create(window->display->theme, 0, 0,
-				   FRAME_BUTTON_NONE, NULL);
+	                           FRAME_BUTTON_NONE, NULL, NULL);
 	fail_on_null(menu->frame, 0, __FILE__, __LINE__);
 	menu->entries = entries;
 	menu->count = count;

libweston/compositor-wayland.c

@@ -869,7 +869,7 @@ wayland_output_set_windowed(struct wayland_output *output)
 			return -1;
 	}
 	output->frame = frame_create(b->theme, 100, 100,
-				     FRAME_BUTTON_CLOSE, output->title);
+	                             FRAME_BUTTON_CLOSE, output->title, NULL);
 	if (!output->frame)
 		return -1;
 

shared/cairo-util.h

@@ -126,7 +126,7 @@ enum {
 
 struct frame *
 frame_create(struct theme *t, int32_t width, int32_t height, uint32_t buttons,
-	     const char *title);
+             const char *title, cairo_surface_t *icon);
 
 void
 frame_destroy(struct frame *frame);

shared/frame.c

@@ -108,7 +108,7 @@ struct frame {
 };
 
 static struct frame_button *
-frame_button_create(struct frame *frame, const char *icon,
+frame_button_create_from_surface(struct frame *frame, cairo_surface_t *icon,
                                  enum frame_status status_effect,
                                  enum frame_button_flags flags)
 {
@@ -118,12 +118,7 @@ frame_button_create(struct frame *frame, const char *icon,
 	if (!button)
 		return NULL;
 
-	button->icon = cairo_image_surface_create_from_png(icon);
-	if (!button->icon) {
-		free(button);
-		return NULL;
-	}
-
+	button->icon = icon;
 	button->frame = frame;
 	button->flags = flags;
 	button->status_effect = status_effect;
@@ -133,6 +128,30 @@ frame_button_create(struct frame *frame, const char *icon,
 	return button;
 }
 
+static struct frame_button *
+frame_button_create(struct frame *frame, const char *icon_name,
+                    enum frame_status status_effect,
+                    enum frame_button_flags flags)
+{
+	struct frame_button *button;
+	cairo_surface_t *icon;
+
+	icon = cairo_image_surface_create_from_png(icon_name);
+	if (cairo_surface_status(icon) != CAIRO_STATUS_SUCCESS)
+		goto error;
+
+	button = frame_button_create_from_surface(frame, icon, status_effect,
+	                                          flags);
+	if (!button)
+		goto error;
+
+	return button;
+
+error:
+	cairo_surface_destroy(icon);
+	return NULL;
+}
+
 static void
 frame_button_destroy(struct frame_button *button)
 {
@@ -305,7 +324,7 @@ frame_destroy(struct frame *frame)
 
 struct frame *
 frame_create(struct theme *t, int32_t width, int32_t height, uint32_t buttons,
-	     const char *title)
+             const char *title, cairo_surface_t *icon)
 {
 	struct frame *frame;
 	struct frame_button *button;
@@ -332,10 +351,17 @@ frame_create(struct theme *t, int32_t width, int32_t height, uint32_t buttons,
 	}
 
 	if (title) {
+		if (icon) {
+			button = frame_button_create_from_surface(frame,
+			                                          icon,
+			                                          FRAME_STATUS_MENU,
+			                                          FRAME_BUTTON_CLICK_DOWN);
+		} else {
 			button = frame_button_create(frame,
 			                             DATADIR "/weston/icon_window.png",
 			                             FRAME_STATUS_MENU,
 			                             FRAME_BUTTON_CLICK_DOWN);
+		}
 		if (!button)
 			goto free_frame;
 	}

xwayland/window-manager.c

@@ -138,6 +138,8 @@ struct weston_wm_window {
 	xcb_window_t frame_id;
 	struct frame *frame;
 	cairo_surface_t *cairo_surface;
+	int icon;
+	cairo_surface_t *icon_surface;
 	uint32_t surface_id;
 	struct weston_surface *surface;
 	struct weston_desktop_xwayland_surface *shsurf;
@@ -473,6 +475,7 @@ weston_wm_window_read_properties(struct weston_wm_window *window)
 		{ wm->atom.net_wm_state,       TYPE_NET_WM_STATE,          NULL },
 		{ wm->atom.net_wm_window_type, XCB_ATOM_ATOM,              F(type) },
 		{ wm->atom.net_wm_name,        XCB_ATOM_STRING,            F(name) },
+		{ wm->atom.net_wm_icon,        XCB_ATOM_CARDINAL,          F(icon) },
 		{ wm->atom.net_wm_pid,         XCB_ATOM_CARDINAL,          F(pid) },
 		{ wm->atom.motif_wm_hints,     TYPE_MOTIF_WM_HINTS,        NULL },
 		{ wm->atom.wm_client_machine,  XCB_ATOM_WM_CLIENT_MACHINE, F(machine) },
@@ -989,7 +992,8 @@ weston_wm_window_create_frame(struct weston_wm_window *window)
 
 	window->frame = frame_create(window->wm->theme,
 	                             window->width, window->height,
-				     buttons, window->name);
+	                             buttons, window->name,
+	                             window->icon_surface);
 	frame_resize_inside(window->frame, window->width, window->height);
 
 	weston_wm_window_get_frame_size(window, &width, &height);
@@ -1347,6 +1351,53 @@ weston_wm_window_schedule_repaint(struct weston_wm_window *window)
 				       weston_wm_window_do_repaint, window);
 }
 
+static void
+weston_wm_handle_icon(struct weston_wm *wm, struct weston_wm_window *window)
+{
+	xcb_get_property_reply_t *reply;
+	xcb_get_property_cookie_t cookie;
+	uint32_t length;
+	uint32_t *data, width, height;
+	cairo_surface_t *new_surface;
+
+	/* TODO: icons don’t have any specified order, we should pick the
+	 * closest one to the target dimension instead of the first one. */
+
+	cookie = xcb_get_property(wm->conn, 0, window->id,
+	                          wm->atom.net_wm_icon, XCB_ATOM_ANY, 0,
+	                          UINT32_MAX);
+	reply = xcb_get_property_reply(wm->conn, cookie, NULL);
+	length = xcb_get_property_value_length(reply);
+
+	/* This is in 32-bit words, not in bytes. */
+	if (length < 2)
+		return;
+
+	data = xcb_get_property_value(reply);
+	width = *data++;
+	height = *data++;
+
+	/* Some checks against malformed input. */
+	if (width == 0 || height == 0 || length < 2 + width * height)
+		return;
+
+	new_surface =
+		cairo_image_surface_create_for_data((unsigned char *)data,
+		                                    CAIRO_FORMAT_ARGB32,
+		                                    width, height, width * 4);
+
+	/* Bail out in case anything wrong happened during surface creation. */
+	if (cairo_surface_status(new_surface) != CAIRO_STATUS_SUCCESS) {
+		cairo_surface_destroy(new_surface);
+		return;
+	}
+
+	if (window->icon_surface)
+		cairo_surface_destroy(window->icon_surface);
+
+	window->icon_surface = new_surface;
+}
+
 static void
 weston_wm_handle_property_notify(struct weston_wm *wm, xcb_generic_event_t *event)
 {
@@ -1367,6 +1418,16 @@ weston_wm_handle_property_notify(struct weston_wm *wm, xcb_generic_event_t *even
 		read_and_dump_property(wm, property_notify->window,
 				       property_notify->atom);
 
+	if (property_notify->atom == wm->atom.net_wm_icon) {
+		if (property_notify->state != XCB_PROPERTY_DELETE) {
+			weston_wm_handle_icon(wm, window);
+		} else {
+			cairo_surface_destroy(window->icon_surface);
+			window->icon_surface = NULL;
+		}
+		weston_wm_window_schedule_repaint(window);
+	}
+
 	if (property_notify->atom == wm->atom.net_wm_name ||
 	    property_notify->atom == XCB_ATOM_WM_NAME)
 		weston_wm_window_schedule_repaint(window);