[PATCH v3] xwm: Choose icon closest to target size

[Scott Moreau]

Xwayland clients can offer multiple icon sizes in no particular order.
Previously xwm was selecting the first one unconditionally. This patch
selects the icon that matches the size closest to the target size. The
target size is hard coded to 16 since there is only one theme and the
data used to create the theme is hard coded.
---

Changed in v2:

- Fix typo setting width to height

Changed in v3:

- Move checks for malformed input into data handling function

 xwayland/window-manager.c | 74 ++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 67 insertions(+), 7 deletions(-)

diff --git a/xwayland/window-manager.c b/xwayland/window-manager.c
index c307e19..30c4b1c 100644
--- a/xwayland/window-manager.c
+++ b/xwayland/window-manager.c
@@ -1352,6 +1352,70 @@ weston_wm_window_schedule_repaint(struct weston_wm_window *window)
 				       weston_wm_window_do_repaint, window);
 }
 
+static uint32_t *
+get_icon_size_from_data(int target_width, int target_height,
+						uint32_t *width, uint32_t *height,
+						uint32_t length, uint32_t *data)
+{
+	uint32_t *d = data, **img = NULL, *ret = NULL, w, h;
+	int num_sizes = 0, *sizes = NULL, a1, a2, a3;
+
+	*width = *height = 0;
+
+	while (d - data < length / 4) {
+		w = *d++;
+		h = *d++;
+
+		/* Some checks against malformed input. */
+		if (w == 0 || h == 0 || length < 2 + w * h) {
+			free(sizes);
+			free(img);
+			return NULL;
+		}
+
+		sizes = realloc(sizes, 2 * (num_sizes + 1) * sizeof(uint32_t));
+		if (!sizes) {
+			free(img);
+			return NULL;
+		}
+
+		img = realloc(img, (num_sizes + 1) * sizeof(uint32_t *));
+		if (!img) {
+			free(sizes);
+			return NULL;
+		}
+
+		sizes[(num_sizes * 2) + 0] = w;
+		sizes[(num_sizes * 2) + 1] = h;
+		img[num_sizes] = d;
+
+		num_sizes++;
+		d += w * h;
+	}
+
+	/* Choose closest match by comparing icon dimension areas */
+	a1 = target_width * target_height;
+
+	while (num_sizes--) {
+		w = sizes[(num_sizes * 2) + 0];
+		h = sizes[(num_sizes * 2) + 1];
+
+		a2 = w * h;
+		a3 = *width * *height;
+
+		if (a2 != a3 && abs(a2 - a1) < abs(a3 - a1)) {
+			*width = w;
+			*height = h;
+			ret = img[num_sizes];
+		}
+	}
+
+	free(sizes);
+	free(img);
+
+	return ret;
+}
+
 static void
 weston_wm_handle_icon(struct weston_wm *wm, struct weston_wm_window *window)
 {
@@ -1361,9 +1425,6 @@ weston_wm_handle_icon(struct weston_wm *wm, struct weston_wm_window *window)
 	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);
@@ -1375,11 +1436,10 @@ weston_wm_handle_icon(struct weston_wm *wm, struct weston_wm_window *window)
 		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)
+	data = get_icon_size_from_data(16, 16, &width, &height, length, data);
+
+	if (!data)
 		return;
 
 	new_surface =
-- 
2.7.4