[mutter] clutter: Remove support for transparent windows

[Jonas Ådahl <jadahl src gnome org>]

commit d857edf09c0fbff3d6314f97ce1e5a36ec72dbbd
Author: Jonas Ådahl <jadahl gmail com>
Date:   Thu Jul 9 20:58:20 2020 +0200

    clutter: Remove support for transparent windows
    
    We're only ever a compositor, so we're never asking to be transparent.
    Thus remove support for requesting to paint to GLX or EGL displays with
    an alpha channel.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1364

 clutter/clutter/x11/clutter-backend-x11.c          | 89 ++--------------------
 clutter/clutter/x11/clutter-x11.h                  |  5 --
 cogl/cogl/cogl-swap-chain-private.h                |  2 -
 cogl/cogl/cogl-swap-chain.c                        |  7 --
 cogl/cogl/winsys/cogl-glx-display-private.h        |  1 -
 cogl/cogl/winsys/cogl-winsys-egl.c                 |  2 +-
 cogl/cogl/winsys/cogl-winsys-glx.c                 | 41 +---------
 src/tests/clutter/interactive/test-paint-wrapper.c |  4 -
 8 files changed, 12 insertions(+), 139 deletions(-)
---
diff --git a/clutter/clutter/x11/clutter-backend-x11.c b/clutter/clutter/x11/clutter-backend-x11.c
index 697334b9a8..e4bc3b8df3 100644
--- a/clutter/clutter/x11/clutter-backend-x11.c
+++ b/clutter/clutter/x11/clutter-backend-x11.c
@@ -98,7 +98,6 @@ static const gchar *atom_names[] = {
 
 /* various flags corresponding to pre init setup calls */
 static gboolean clutter_enable_xinput = TRUE;
-static gboolean clutter_enable_argb = FALSE;
 static gboolean clutter_enable_stereo = FALSE;
 static Display  *_foreign_dpy = NULL;
 
@@ -240,13 +239,6 @@ clutter_backend_x11_pre_parse (ClutterBackend  *backend,
       env_string = NULL;
     }
 
-  env_string = g_getenv ("CLUTTER_DISABLE_ARGB_VISUAL");
-  if (env_string)
-    {
-      clutter_enable_argb = FALSE;
-      env_string = NULL;
-    }
-
   env_string = g_getenv ("CLUTTER_DISABLE_XINPUT");
   if (env_string)
     {
@@ -550,15 +542,12 @@ clutter_backend_x11_get_renderer (ClutterBackend  *backend,
 
 static gboolean
 check_onscreen_template (CoglRenderer         *renderer,
-                         CoglSwapChain        *swap_chain,
                          CoglOnscreenTemplate *onscreen_template,
-                         gboolean              enable_argb,
                          gboolean              enable_stereo,
                          GError              **error)
 {
   GError *internal_error = NULL;
 
-  cogl_swap_chain_set_has_alpha (swap_chain, enable_argb);
   cogl_onscreen_template_set_stereo_enabled (onscreen_template,
                                             clutter_enable_stereo);
 
@@ -573,17 +562,15 @@ check_onscreen_template (CoglRenderer         *renderer,
    */
   if (cogl_renderer_check_onscreen_template (renderer, onscreen_template, &internal_error))
     {
-      clutter_enable_argb = enable_argb;
       clutter_enable_stereo = enable_stereo;
 
       return TRUE;
     }
   else
     {
-      if (enable_argb || enable_stereo) /* More possibilities to try */
+      if (enable_stereo) /* More possibilities to try */
         CLUTTER_NOTE (BACKEND,
-                      "Creation of a CoglDisplay with alpha=%s, stereo=%s failed: %s",
-                      enable_argb ? "enabled" : "disabled",
+                      "Creation of a CoglDisplay with, stereo=%s failed: %s",
                       enable_stereo ? "enabled" : "disabled",
                       internal_error != NULL
                         ?  internal_error->message
@@ -611,8 +598,7 @@ clutter_backend_x11_get_display (ClutterBackend  *backend,
   CoglDisplay *display = NULL;
   gboolean res = FALSE;
 
-  CLUTTER_NOTE (BACKEND, "Creating CoglDisplay, alpha=%s, stereo=%s",
-                clutter_enable_argb ? "enabled" : "disabled",
+  CLUTTER_NOTE (BACKEND, "Creating CoglDisplay, stereo=%s",
                 clutter_enable_stereo ? "enabled" : "disabled");
 
   onscreen_template = cogl_onscreen_template_new (swap_chain);
@@ -620,22 +606,13 @@ clutter_backend_x11_get_display (ClutterBackend  *backend,
   /* It's possible that the current renderer doesn't support transparency
    * or doesn't support stereo, so we try the different combinations.
    */
-  if (clutter_enable_argb && clutter_enable_stereo)
-    res = check_onscreen_template (renderer, swap_chain, onscreen_template,
-                                  TRUE, TRUE, error);
-
-  /* Prioritize stereo over alpha */
-  if (!res && clutter_enable_stereo)
-    res = check_onscreen_template (renderer, swap_chain, onscreen_template,
-                                  FALSE, TRUE, error);
-
-  if (!res && clutter_enable_argb)
-    res = check_onscreen_template (renderer, swap_chain, onscreen_template,
-                                  TRUE, FALSE, error);
+  if (clutter_enable_stereo)
+    res = check_onscreen_template (renderer, onscreen_template,
+                                   TRUE, error);
 
   if (!res)
-    res = check_onscreen_template (renderer, swap_chain, onscreen_template,
-                                  FALSE, FALSE, error);
+    res = check_onscreen_template (renderer, onscreen_template,
+                                   FALSE, error);
 
   if (res)
     display = cogl_display_new (renderer, onscreen_template);
@@ -972,56 +949,6 @@ clutter_x11_has_composite_extension (void)
   return have_composite;
 }
 
-/**
- * clutter_x11_set_use_argb_visual:
- * @use_argb: %TRUE if ARGB visuals should be requested by default
- *
- * Sets whether the Clutter X11 backend should request ARGB visuals by default
- * or not.
- *
- * By default, Clutter requests RGB visuals.
- *
- * If no ARGB visuals are found, the X11 backend will fall back to
- * requesting a RGB visual instead.
- *
- * ARGB visuals are required for the #ClutterStage:use-alpha property to work.
- *
- * This function can only be called once, and before clutter_init() is
- * called.
- *
- * Since: 1.2
- */
-void
-clutter_x11_set_use_argb_visual (gboolean use_argb)
-{
-  if (_clutter_context_is_initialized ())
-    {
-      g_warning ("%s() can only be used before calling clutter_init()",
-                 G_STRFUNC);
-      return;
-    }
-
-  CLUTTER_NOTE (BACKEND, "ARGB visuals are %s",
-                use_argb ? "enabled" : "disabled");
-
-  clutter_enable_argb = use_argb;
-}
-
-/**
- * clutter_x11_get_use_argb_visual:
- *
- * Retrieves whether the Clutter X11 backend is using ARGB visuals by default
- *
- * Return value: %TRUE if ARGB visuals are queried by default
- *
- * Since: 1.2
- */
-gboolean
-clutter_x11_get_use_argb_visual (void)
-{
-  return clutter_enable_argb;
-}
-
 /**
  * clutter_x11_set_use_stereo_stage:
  * @use_stereo: %TRUE if the stereo stages should be used if possible.
diff --git a/clutter/clutter/x11/clutter-x11.h b/clutter/clutter/x11/clutter-x11.h
index bf58e6f568..a257360c7a 100644
--- a/clutter/clutter/x11/clutter-x11.h
+++ b/clutter/clutter/x11/clutter-x11.h
@@ -112,11 +112,6 @@ void         clutter_x11_remove_filter (ClutterX11FilterFunc func,
 CLUTTER_EXPORT
 gboolean clutter_x11_has_composite_extension (void);
 
-CLUTTER_EXPORT
-void     clutter_x11_set_use_argb_visual (gboolean use_argb);
-CLUTTER_EXPORT
-gboolean clutter_x11_get_use_argb_visual (void);
-
 CLUTTER_EXPORT
 void     clutter_x11_set_use_stereo_stage (gboolean use_stereo);
 CLUTTER_EXPORT
diff --git a/cogl/cogl/cogl-swap-chain-private.h b/cogl/cogl/cogl-swap-chain-private.h
index 34c2e21200..3e14c2932c 100644
--- a/cogl/cogl/cogl-swap-chain-private.h
+++ b/cogl/cogl/cogl-swap-chain-private.h
@@ -37,8 +37,6 @@ struct _CoglSwapChain
 {
   CoglObject _parent;
 
-  gboolean has_alpha;
-
   int length;
 };
 
diff --git a/cogl/cogl/cogl-swap-chain.c b/cogl/cogl/cogl-swap-chain.c
index 89bab0049c..a01f2d4db3 100644
--- a/cogl/cogl/cogl-swap-chain.c
+++ b/cogl/cogl/cogl-swap-chain.c
@@ -59,13 +59,6 @@ cogl_swap_chain_new (void)
   return _cogl_swap_chain_object_new (swap_chain);
 }
 
-void
-cogl_swap_chain_set_has_alpha (CoglSwapChain *swap_chain,
-                               gboolean has_alpha)
-{
-  swap_chain->has_alpha = has_alpha;
-}
-
 void
 cogl_swap_chain_set_length (CoglSwapChain *swap_chain,
                             int length)
diff --git a/cogl/cogl/winsys/cogl-glx-display-private.h b/cogl/cogl/winsys/cogl-glx-display-private.h
index 265868c408..f931b17644 100644
--- a/cogl/cogl/winsys/cogl-glx-display-private.h
+++ b/cogl/cogl/winsys/cogl-glx-display-private.h
@@ -50,7 +50,6 @@ typedef struct _CoglGLXDisplay
   CoglGLXCachedConfig glx_cached_configs[COGL_GLX_N_CACHED_CONFIGS];
 
   gboolean found_fbconfig;
-  gboolean fbconfig_has_rgba_visual;
   gboolean is_direct;
   gboolean have_vblank_counter;
   gboolean can_vblank_wait;
diff --git a/cogl/cogl/winsys/cogl-winsys-egl.c b/cogl/cogl/winsys/cogl-winsys-egl.c
index 8c999c52bb..6aaac8ef87 100644
--- a/cogl/cogl/winsys/cogl-winsys-egl.c
+++ b/cogl/cogl/winsys/cogl-winsys-egl.c
@@ -223,7 +223,7 @@ egl_attributes_from_framebuffer_config (CoglDisplay *display,
   attributes[i++] = 1;
 
   attributes[i++] = EGL_ALPHA_SIZE;
-  attributes[i++] = config->swap_chain->has_alpha ? 1 : EGL_DONT_CARE;
+  attributes[i++] = EGL_DONT_CARE;
 
   attributes[i++] = EGL_DEPTH_SIZE;
   attributes[i++] = 1;
diff --git a/cogl/cogl/winsys/cogl-winsys-glx.c b/cogl/cogl/winsys/cogl-winsys-glx.c
index 0b1c1eac22..452a88060c 100644
--- a/cogl/cogl/winsys/cogl-winsys-glx.c
+++ b/cogl/cogl/winsys/cogl-winsys-glx.c
@@ -885,7 +885,7 @@ glx_attributes_from_framebuffer_config (CoglDisplay *display,
   attributes[i++] = GLX_BLUE_SIZE;
   attributes[i++] = 1;
   attributes[i++] = GLX_ALPHA_SIZE;
-  attributes[i++] = config->swap_chain->has_alpha ? 1 : GLX_DONT_CARE;
+  attributes[i++] = GLX_DONT_CARE;
   attributes[i++] = GLX_DEPTH_SIZE;
   attributes[i++] = 1;
   attributes[i++] = GLX_STENCIL_SIZE;
@@ -944,40 +944,8 @@ find_fbconfig (CoglDisplay *display,
       goto done;
     }
 
-  if (config->swap_chain->has_alpha)
-    {
-      int i;
-
-      for (i = 0; i < n_configs; i++)
-        {
-          XVisualInfo *vinfo;
-
-          vinfo = glx_renderer->glXGetVisualFromFBConfig (xlib_renderer->xdpy,
-                                                          configs[i]);
-          if (vinfo == NULL)
-            continue;
-
-          if (vinfo->depth == 32 &&
-              (vinfo->red_mask | vinfo->green_mask | vinfo->blue_mask)
-              != 0xffffffff)
-            {
-              COGL_NOTE (WINSYS, "Found an ARGB FBConfig [index:%d]", i);
-              *config_ret = configs[i];
-              goto done;
-            }
-        }
-
-      g_set_error_literal (error, COGL_WINSYS_ERROR,
-                           COGL_WINSYS_ERROR_CREATE_CONTEXT,
-                           "Unable to find fbconfig with rgba visual");
-      ret = FALSE;
-      goto done;
-    }
-  else
-    {
-      COGL_NOTE (WINSYS, "Using the first available FBConfig");
-      *config_ret = configs[0];
-    }
+  COGL_NOTE (WINSYS, "Using the first available FBConfig");
+  *config_ret = configs[0];
 
 done:
   XFree (configs);
@@ -1059,8 +1027,6 @@ create_context (CoglDisplay *display, GError **error)
   CoglXlibRenderer *xlib_renderer =
     _cogl_xlib_renderer_get_data (display->renderer);
   CoglGLXRenderer *glx_renderer = display->renderer->winsys;
-  gboolean support_transparent_windows =
-    display->onscreen_template->config.swap_chain->has_alpha;
   GLXFBConfig config;
   GError *fbconfig_error = NULL;
   XSetWindowAttributes attrs;
@@ -1084,7 +1050,6 @@ create_context (CoglDisplay *display, GError **error)
     }
 
   glx_display->fbconfig = config;
-  glx_display->fbconfig_has_rgba_visual = support_transparent_windows;
 
   COGL_NOTE (WINSYS, "Creating GLX Context (display: %p)",
              xlib_renderer->xdpy);
diff --git a/src/tests/clutter/interactive/test-paint-wrapper.c 
b/src/tests/clutter/interactive/test-paint-wrapper.c
index f66f794337..038226d079 100644
--- a/src/tests/clutter/interactive/test-paint-wrapper.c
+++ b/src/tests/clutter/interactive/test-paint-wrapper.c
@@ -212,10 +212,6 @@ test_paint_wrapper_main (int argc, char *argv[])
 
   error = NULL;
 
-#ifdef CLUTTER_WINDOWING_X11
-  clutter_x11_set_use_argb_visual (TRUE);
-#endif
-
   if (clutter_init_with_args (&argc, &argv,
                               NULL,
                               super_oh_entries,