[mutter] background: Use monitor scale to generate the texture at real monitor size

[Jonas Ådahl <jadahl src gnome org>]

commit 3512647419f006602c237f3eeff768578876c055
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Thu Aug 3 15:48:51 2017 +0200

    background: Use monitor scale to generate the texture at real monitor size
    
    We need to use pixel size of the monitor in order to generate a valid
    texture with full quality for current monitor
    
    In spanned case the background should cover all the differently scaled monitors
    thus we scale the texture up to the maximum scaling level and then we resample
    it drawing only each side in the monitor it should occupy using the proper
    scaling level.
    
    In wallpaper mode (or color mode) for example we don't need to scale the area,
    also the texture size we return should be unscaled, not to confuse
    MetaBackgroundActor making it use more space than needed.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=765011

 src/compositor/meta-background.c | 36 +++++++++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 11 deletions(-)
---
diff --git a/src/compositor/meta-background.c b/src/compositor/meta-background.c
index f06d54245..6dd4242d2 100644
--- a/src/compositor/meta-background.c
+++ b/src/compositor/meta-background.c
@@ -370,6 +370,7 @@ set_texture_area_from_monitor_area (cairo_rectangle_int_t *monitor_area,
 static void
 get_texture_area (MetaBackground          *self,
                   cairo_rectangle_int_t   *monitor_rect,
+                  float                    monitor_scale,
                   CoglTexture             *texture,
                   cairo_rectangle_int_t   *texture_area)
 {
@@ -394,7 +395,7 @@ get_texture_area (MetaBackground          *self,
       meta_display_get_size (self->display, &screen_width, &screen_height);
 
       /* Start off by centering a tile in the middle of the
-       * total screen area.
+       * total screen area taking care of the monitor scaling.
        */
       image_area.x = (screen_width - texture_width) / 2.0;
       image_area.y = (screen_height - texture_height) / 2.0;
@@ -462,9 +463,9 @@ get_texture_area (MetaBackground          *self,
          */
         meta_display_get_size (self->display, &screen_width, &screen_height);
 
-        /* unclipped texture area is whole screen */
-        image_area.width = screen_width;
-        image_area.height = screen_height;
+        /* unclipped texture area is whole screen, scaled depending on monitor */
+        image_area.width = screen_width * monitor_scale;
+        image_area.height = screen_height * monitor_scale;
 
         /* But make (0,0) line up with the appropriate monitor */
         image_area.x = -monitor_rect->x;
@@ -481,12 +482,13 @@ draw_texture (MetaBackground        *self,
               CoglFramebuffer       *framebuffer,
               CoglPipeline          *pipeline,
               CoglTexture           *texture,
-              cairo_rectangle_int_t *monitor_area)
+              cairo_rectangle_int_t *monitor_area,
+              float                  monitor_scale)
 {
   cairo_rectangle_int_t texture_area;
   gboolean bare_region_visible;
 
-  get_texture_area (self, monitor_area, texture, &texture_area);
+  get_texture_area (self, monitor_area, monitor_scale, texture, &texture_area);
 
   switch (self->style)
     {
@@ -728,6 +730,7 @@ meta_background_get_texture (MetaBackground         *self,
   MetaRectangle geometry;
   cairo_rectangle_int_t monitor_area;
   CoglTexture *texture1, *texture2;
+  float monitor_scale;
 
   g_return_val_if_fail (META_IS_BACKGROUND (self), NULL);
   g_return_val_if_fail (monitor_index >= 0 && monitor_index < self->n_monitors, NULL);
@@ -735,6 +738,7 @@ meta_background_get_texture (MetaBackground         *self,
   monitor = &self->monitors[monitor_index];
 
   meta_display_get_monitor_geometry (self->display, monitor_index, &geometry);
+  monitor_scale = meta_display_get_monitor_scale (self->display, monitor_index);
   monitor_area.x = geometry.x;
   monitor_area.y = geometry.y;
   monitor_area.width = geometry.width;
@@ -758,8 +762,8 @@ meta_background_get_texture (MetaBackground         *self,
       ensure_wallpaper_texture (self, texture1))
     {
       if (texture_area)
-        get_texture_area (self, &monitor_area, self->wallpaper_texture,
-                          texture_area);
+        get_texture_area (self, &monitor_area, monitor_scale,
+                          self->wallpaper_texture, texture_area);
       if (wrap_mode)
         *wrap_mode = COGL_PIPELINE_WRAP_MODE_REPEAT;
       return self->wallpaper_texture;
@@ -770,6 +774,14 @@ meta_background_get_texture (MetaBackground         *self,
       CoglError *catch_error = NULL;
       gboolean bare_region_visible = FALSE;
 
+      if (self->style != G_DESKTOP_BACKGROUND_STYLE_WALLPAPER)
+        {
+          monitor_area.x *= monitor_scale;
+          monitor_area.y *= monitor_scale;
+          monitor_area.width *= monitor_scale;
+          monitor_area.height *= monitor_scale;
+        }
+
       if (monitor->texture == NULL)
         {
           CoglOffscreen *offscreen;
@@ -809,7 +821,8 @@ meta_background_get_texture (MetaBackground         *self,
 
           bare_region_visible = draw_texture (self,
                                               monitor->fbo, pipeline,
-                                              texture2, &monitor_area);
+                                              texture2, &monitor_area,
+                                              monitor_scale);
 
           cogl_object_unref (pipeline);
         }
@@ -833,7 +846,8 @@ meta_background_get_texture (MetaBackground         *self,
 
           bare_region_visible = bare_region_visible || draw_texture (self,
                                                                      monitor->fbo, pipeline,
-                                                                     texture1, &monitor_area);
+                                                                     texture1, &monitor_area,
+                                                                     monitor_scale);
 
           cogl_object_unref (pipeline);
         }
@@ -855,7 +869,7 @@ meta_background_get_texture (MetaBackground         *self,
     }
 
   if (texture_area)
-    set_texture_area_from_monitor_area (&monitor_area, texture_area);
+    set_texture_area_from_monitor_area (&geometry, texture_area);
 
   if (wrap_mode)
     *wrap_mode = COGL_PIPELINE_WRAP_MODE_CLAMP_TO_EDGE;