[GTK+3] re-add ability to show alt-tab thumbnails when compositor is on

adapted from:
https://git.gnome.org/browse/metacity/commit/?id=e6828a3ee2cab1ec1acbdd5a444dc1cb98215a75
https://git.gnome.org/browse/metacity/commit/?id=758902aef22629943738241cea1f597b6db4b18e
https://git.gnome.org/browse/metacity/commit/?id=c6ba6dc7f458720d9f8666881f45a830580468cb
https://git.gnome.org/browse/metacity/commit/?id=68bdf1ab9de815e07f5cd75b2e1fa24ba92ae319
https://git.gnome.org/browse/metacity/commit/?id=78bbf4423f72797a05bfaddd4121d70db30de9a3

7 files changed, 114 insertions, 11 deletions

diff --git a/src/compositor/compositor-private.h b/src/compositor/compositor-private.h
index 61e7ffb0..1eef9633 100644
--- a/src/compositor/compositor-private.h
+++ b/src/compositor/compositor-private.h
@@ -44,8 +44,13 @@ struct _MetaCompositor
   void (*process_event) (MetaCompositor *compositor,
                          XEvent         *event,
                          MetaWindow     *window);
+#if GTK_CHECK_VERSION (3, 0, 0)
+  cairo_surface_t *(* get_window_surface) (MetaCompositor *compositor,
+                                           MetaWindow     *window);
+#else
   Pixmap (*get_window_pixmap) (MetaCompositor *compositor,
                                MetaWindow     *window);
+#endif
   void (*set_active_window) (MetaCompositor *compositor,
                              MetaScreen     *screen,
                              MetaWindow     *window);
diff --git a/src/compositor/compositor-xrender.c b/src/compositor/compositor-xrender.c
index 5080f80d..1da598c5 100644
--- a/src/compositor/compositor-xrender.c
+++ b/src/compositor/compositor-xrender.c
@@ -34,6 +34,11 @@
 #include <unistd.h>
 
 #include <gdk/gdk.h>
+#include <gtk/gtk.h>
+
+#if GTK_CHECK_VERSION (3, 0, 0)
+#include <cairo/cairo-xlib.h>
+#endif
 
 #include "display.h"
 #include "screen.h"
@@ -2797,6 +2802,46 @@ xrender_process_event (MetaCompositor *compositor,
 #endif
 }
 
+#if GTK_CHECK_VERSION (3, 0, 0)
+static cairo_surface_t *
+xrender_get_window_surface (MetaCompositor *compositor,
+                            MetaWindow     *window)
+{
+#ifdef HAVE_COMPOSITE_EXTENSIONS
+  MetaFrame *frame;
+  Window xwindow;
+  MetaScreen *screen;
+  MetaCompWindow *cw;
+  MetaCompositorXRender *xrc;
+  Display *display;
+  Pixmap pixmap;
+
+  frame = meta_window_get_frame (window);
+
+  if (frame)
+    xwindow = meta_frame_get_xwindow (frame);
+  else
+    xwindow = meta_window_get_xwindow (window);
+
+  screen = meta_window_get_screen (window);
+  cw = find_window_for_screen (screen, xwindow);
+
+  if (cw == NULL)
+    return NULL;
+
+  xrc = (MetaCompositorXRender *) compositor;
+  display = meta_display_get_xdisplay (xrc->display);
+
+  if (meta_window_is_shaded (window))
+    pixmap = cw->shaded_back_pixmap;
+  else
+    pixmap = cw->back_pixmap;
+
+  return cairo_xlib_surface_create (display, pixmap, cw->attrs.visual,
+                                    cw->attrs.width, cw->attrs.height);
+#endif
+}
+#else
 static Pixmap
 xrender_get_window_pixmap (MetaCompositor *compositor,
                            MetaWindow     *window)
@@ -2817,6 +2862,7 @@ xrender_get_window_pixmap (MetaCompositor *compositor,
     return cw->back_pixmap;
 #endif
 }
+#endif  /* GTK_CHECK_VERSION */
 
 static void
 xrender_set_active_window (MetaCompositor *compositor,
@@ -3000,7 +3046,11 @@ static MetaCompositor comp_info = {
   xrender_remove_window,
   xrender_set_updates,
   xrender_process_event,
+#if GTK_CHECK_VERSION (3, 0, 0)
+  xrender_get_window_surface,
+#else
   xrender_get_window_pixmap,
+#endif
   xrender_set_active_window,
   xrender_free_window,
   xrender_maximize_window,
diff --git a/src/compositor/compositor.c b/src/compositor/compositor.c
index f7a28261..4d3f370b 100644
--- a/src/compositor/compositor.c
+++ b/src/compositor/compositor.c
@@ -107,6 +107,21 @@ meta_compositor_process_event (MetaCompositor *compositor,
 #endif
 }
 
+#if GTK_CHECK_VERSION (3, 0, 0)
+cairo_surface_t *
+meta_compositor_get_window_surface (MetaCompositor *compositor,
+                                    MetaWindow     *window)
+{
+#ifdef HAVE_COMPOSITE_EXTENSIONS
+  if (compositor && compositor->get_window_surface)
+    return compositor->get_window_surface (compositor, window);
+  else
+    return NULL;
+#else
+  return NULL;
+#endif
+}
+#else
 Pixmap
 meta_compositor_get_window_pixmap (MetaCompositor *compositor,
                                    MetaWindow     *window)
@@ -120,6 +135,7 @@ meta_compositor_get_window_pixmap (MetaCompositor *compositor,
   return None;
 #endif
 }
+#endif  /* GTK_CHECK_VERSION */
 
 void
 meta_compositor_set_active_window (MetaCompositor *compositor,
diff --git a/src/core/screen.c b/src/core/screen.c
index 14fa9953..b4cb5ef7 100644
--- a/src/core/screen.c
+++ b/src/core/screen.c
@@ -1213,7 +1213,6 @@ meta_screen_update_cursor (MetaScreen *screen)
   XFreeCursor (screen->display->xdisplay, xcursor);
 }
 
-#if !GTK_CHECK_VERSION (3, 0, 0)
 #define MAX_PREVIEW_SIZE 150.0
 
 static GdkPixbuf *
@@ -1221,16 +1220,38 @@ get_window_pixbuf (MetaWindow *window,
                    int        *width,
                    int        *height)
 {
+#if GTK_CHECK_VERSION (3, 0, 0)
+  cairo_surface_t *surface;
+#else
   Pixmap pmap;
+#endif
   GdkPixbuf *pixbuf, *scaled;
   double ratio;
 
+#if GTK_CHECK_VERSION (3, 0, 0)
+  surface = meta_compositor_get_window_surface (window->display->compositor,
+                                                window);
+  if (surface == None)
+    return NULL;
+#else
   pmap = meta_compositor_get_window_pixmap (window->display->compositor,
                                             window);
   if (pmap == None)
     return NULL;
+#endif
+
+  meta_error_trap_push (NULL);
 
+#if GTK_CHECK_VERSION (3, 0, 0)
+  pixbuf = meta_ui_get_pixbuf_from_surface (surface);
+  cairo_surface_destroy (surface);
+#else
   pixbuf = meta_ui_get_pixbuf_from_pixmap (pmap);
+#endif
+
+  if (meta_error_trap_pop_with_return (NULL, FALSE) != Success)
+    g_clear_object (&pixbuf);
+
   if (pixbuf == NULL)
     return NULL;
 
@@ -1256,7 +1277,6 @@ get_window_pixbuf (MetaWindow *window,
   g_object_unref (pixbuf);
   return scaled;
 }
-#endif
 
 void
 meta_screen_ensure_tab_popup (MetaScreen      *screen,
@@ -1290,17 +1310,14 @@ meta_screen_ensure_tab_popup (MetaScreen      *screen,
     {
       MetaWindow *window;
       MetaRectangle r;
-#if !GTK_CHECK_VERSION (3, 0, 0)
       GdkPixbuf *win_pixbuf = NULL;
       int width = 0, height = 0;
-#endif
 
       window = tmp->data;
 
       entries[i].key = (MetaTabEntryKey) window->xwindow;
       entries[i].title = window->title;
 
-#if !GTK_CHECK_VERSION (3, 0, 0)
       /* Only get the pixbuf if the user does NOT have
          compositing-fast-alt-tab-set to true
          in GSettings. There is an obvious lag when the pixbuf is
@@ -1333,10 +1350,6 @@ meta_screen_ensure_tab_popup (MetaScreen      *screen,
                                 t_width - icon_width, t_height - icon_height,
                                 1.0, 1.0, GDK_INTERP_BILINEAR, 255);
         }
-#else
-      /* at the moment, thumbnails are disabled for GTK3 */
-      entries[i].icon = g_object_ref (window->icon);
-#endif
 
       entries[i].blank = FALSE;
       entries[i].hidden = !meta_window_showing_on_its_workspace (window);
diff --git a/src/include/compositor.h b/src/include/compositor.h
index 5c238890..0eebe569 100644
--- a/src/include/compositor.h
+++ b/src/include/compositor.h
@@ -23,6 +23,7 @@
 #define META_COMPOSITOR_H
 
 #include <glib.h>
+#include <gtk/gtk.h>
 #include <X11/Xlib.h>
 
 #include "types.h"
@@ -50,8 +51,13 @@ void meta_compositor_set_updates (MetaCompositor *compositor,
 void meta_compositor_process_event (MetaCompositor *compositor,
                                     XEvent         *event,
                                     MetaWindow     *window);
+#if GTK_CHECK_VERSION (3, 0, 0)
+cairo_surface_t *meta_compositor_get_window_surface (MetaCompositor *compositor,
+                                                     MetaWindow *window);
+#else
 Pixmap meta_compositor_get_window_pixmap (MetaCompositor *compositor,
                                           MetaWindow     *window);
+#endif
 void meta_compositor_set_active_window (MetaCompositor *compositor,
                                         MetaScreen     *screen,
                                         MetaWindow     *window);
diff --git a/src/include/ui.h b/src/include/ui.h
index 70987d33..4705eda2 100644
--- a/src/include/ui.h
+++ b/src/include/ui.h
@@ -177,7 +177,9 @@ int      meta_ui_get_drag_threshold       (MetaUI *ui);
 
 MetaUIDirection meta_ui_get_direction (void);
 
-#if !GTK_CHECK_VERSION (3, 0, 0)
+#if GTK_CHECK_VERSION (3, 0, 0)
+GdkPixbuf *meta_ui_get_pixbuf_from_surface (cairo_surface_t *surface);
+#else
 GdkPixbuf *meta_ui_get_pixbuf_from_pixmap (Pixmap   pmap);
 #endif
 
diff --git a/src/ui/ui.c b/src/ui/ui.c
index 731c615b..130a671f 100644
--- a/src/ui/ui.c
+++ b/src/ui/ui.c
@@ -1104,7 +1104,18 @@ MetaUIDirection meta_ui_get_direction(void)
 	return META_UI_DIRECTION_LTR;
 }
 
-#if !GTK_CHECK_VERSION (3, 0, 0)
+#if GTK_CHECK_VERSION (3, 0, 0)
+GdkPixbuf *meta_ui_get_pixbuf_from_surface (cairo_surface_t *surface)
+{
+	gint width;
+	gint height;
+
+	width = cairo_xlib_surface_get_width (surface);
+	height = cairo_xlib_surface_get_height (surface);
+
+	return gdk_pixbuf_get_from_surface (surface, 0, 0, width, height);
+}
+#else
 GdkPixbuf* meta_ui_get_pixbuf_from_pixmap(Pixmap pmap)
 {
 	GdkPixmap* gpmap;