texture-cache: Keep aspect ratio for content images

Images are loaded either with a supplied fixed size, or using the "native"
dimensions of the file. When creating a content image from the loaded data,
we currently simply apply this directly to the preferred size.

This works usually fine: GdkPixbuf will always keep the aspect ratio, so
if only one dimension is provided, the other will be adjusted accordingly:

Loading a 200x200 image with a requested size of (100, -1) will result in
a 100x100 content image.

There is a catch though: GdkPixbuf will only scale *down* to the requested
size, no up. That is, loading a 100x100 image with a requested size of
(200, -1) will result in a 100x100 pixbuf. But as we assume that the pixbuf
size matches the requested size, the image content ends up with 200x100.

Fix this by explicitly handling the case where only one size was supplied,
and make the other dimension take the aspect ratio into account

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/525

diff --git a/src/st/st-texture-cache.c b/src/st/st-texture-cache.c
index cbe3afaba13f1c2924dd61aec3fb7e1bd82a7102..eec28007b34bd2152b204dc0f06be4978b74df26 100644 (file)
--- a/src/st/st-texture-cache.c
+++ b/src/st/st-texture-cache.c
@@ -496,15 +496,31 @@ pixbuf_to_st_content_image (GdkPixbuf *pixbuf,
   ClutterContent *image;
   g_autoptr(GError) error = NULL;
 
-  if (width < 0)
-    width = ceilf (gdk_pixbuf_get_width (pixbuf) / resource_scale);
-  else
-    width *= paint_scale;
+  float native_width, native_height;
+
+  native_width = ceilf (gdk_pixbuf_get_width (pixbuf) / resource_scale);
+  native_height = ceilf (gdk_pixbuf_get_height (pixbuf) / resource_scale);
 
-  if (height < 0)
-    height = ceilf (gdk_pixbuf_get_height (pixbuf) / resource_scale);
+  if (width < 0 && height < 0)
+    {
+      width = native_width;
+      height = native_height;
+    }
+  else if (width < 0)
+    {
+      height *= paint_scale;
+      width = native_width * (height / native_height);
+    }
+  else if (height < 0)
+    {
+      width *= paint_scale;
+      height = native_height * (width / native_width);
+    }
   else
-    height *= paint_scale;
+    {
+      width *= paint_scale;
+      height *= paint_scale;
+    }
 
   image = st_image_content_new_with_preferred_size (width, height);
   clutter_image_set_data (CLUTTER_IMAGE (image),