[gnome-shell] texture-cache: Keep aspect ratio for content images

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 5520bb389024406a4f9f603c4ebf842026ecaf5a
Author: Florian Müllner <fmuellner gnome org>
Date:   Tue Apr 30 20:37:34 2019 +0200

    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

 src/st/st-texture-cache.c | 30 +++++++++++++++++++++++-------
 1 file changed, 23 insertions(+), 7 deletions(-)
---
diff --git a/src/st/st-texture-cache.c b/src/st/st-texture-cache.c
index cbe3afaba..eec28007b 100644
--- 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),