[gtk/wip/otte/gleanup: 33/53] x11: Redo choice between EGL and GLX

[Benjamin Otte <otte src gnome org>]

commit 631b72e91e955285dcf513839ef8cef5e9c601da
Author: Benjamin Otte <otte redhat com>
Date:   Fri Jul 2 03:37:32 2021 +0200

    x11: Redo choice between EGL and GLX
    
    We try EGL first, but are very picky about what we accept.
    If that fails, we try to go with GLX instead.
    And if that also fails, we try EGL again, but this time accept anything.
    
    The idea here is that EGL is the preferred method going forward, but GLX is
    the tried and tested method that we know works. So if we detect issues with
    EGL, we want to avoid using it in favor of GLX.
    
    Also add a GDK_DEBUG=gl-egl option to force EGL at all costs and not try
    GLX.

 gdk/gdk.c                  |  1 +
 gdk/gdkdebug.h             |  9 +++++----
 gdk/x11/gdkglcontext-egl.c | 11 ++++++++++-
 gdk/x11/gdkglcontext-x11.c | 49 +++++++++++++++++++++++-----------------------
 gdk/x11/gdkglcontext-x11.h |  1 +
 5 files changed, 42 insertions(+), 29 deletions(-)
---
diff --git a/gdk/gdk.c b/gdk/gdk.c
index b3a569d34d..c6b5b7b8ce 100644
--- a/gdk/gdk.c
+++ b/gdk/gdk.c
@@ -127,6 +127,7 @@ static const GdkDebugKey gdk_debug_keys[] = {
   { "gl-legacy",       GDK_DEBUG_GL_LEGACY, "Use a legacy OpenGL context" },
   { "gl-gles",         GDK_DEBUG_GL_GLES, "Use a GLES OpenGL context" },
   { "gl-debug",        GDK_DEBUG_GL_DEBUG, "Insert debugging information in OpenGL" },
+  { "gl-egl",          GDK_DEBUG_GL_EGL, "Use EGL on X11" },
   { "gl-glx",          GDK_DEBUG_GL_GLX, "Use GLX on X11" },
   { "vulkan-disable",  GDK_DEBUG_VULKAN_DISABLE, "Disable Vulkan support" },
   { "vulkan-validate", GDK_DEBUG_VULKAN_VALIDATE, "Load the Vulkan validation layer" },
diff --git a/gdk/gdkdebug.h b/gdk/gdkdebug.h
index e03b904ce4..111cc2f28a 100644
--- a/gdk/gdkdebug.h
+++ b/gdk/gdkdebug.h
@@ -41,10 +41,11 @@ typedef enum {
   GDK_DEBUG_GL_LEGACY       = 1 << 15,
   GDK_DEBUG_GL_GLES         = 1 << 16,
   GDK_DEBUG_GL_DEBUG        = 1 << 17,
-  GDK_DEBUG_GL_GLX          = 1 << 18,
-  GDK_DEBUG_VULKAN_DISABLE  = 1 << 19,
-  GDK_DEBUG_VULKAN_VALIDATE = 1 << 20,
-  GDK_DEBUG_DEFAULT_SETTINGS= 1 << 21
+  GDK_DEBUG_GL_EGL          = 1 << 18,
+  GDK_DEBUG_GL_GLX          = 1 << 19,
+  GDK_DEBUG_VULKAN_DISABLE  = 1 << 20,
+  GDK_DEBUG_VULKAN_VALIDATE = 1 << 21,
+  GDK_DEBUG_DEFAULT_SETTINGS= 1 << 22
 } GdkDebugFlags;
 
 extern guint _gdk_debug_flags;
diff --git a/gdk/x11/gdkglcontext-egl.c b/gdk/x11/gdkglcontext-egl.c
index 3df0919738..56a17168b1 100644
--- a/gdk/x11/gdkglcontext-egl.c
+++ b/gdk/x11/gdkglcontext-egl.c
@@ -134,6 +134,7 @@ visual_is_rgba (XVisualInfo *visinfo)
 
 static gboolean
 gdk_x11_display_create_egl_config (GdkX11Display  *display,
+                                   gboolean        force,
                                    Visual        **out_visual,
                                    int            *out_depth,
                                    GError        **error)
@@ -263,6 +264,13 @@ gdk_x11_display_create_egl_config (GdkX11Display  *display,
                            _("No EGL configuration with required features found"));
       return FALSE;
     }
+  else if (!force && best_features != PERFECT)
+    {
+      g_set_error_literal (error, GDK_GL_ERROR,
+                           GDK_GL_ERROR_NOT_AVAILABLE,
+                           _("No perfect EGL configuration found"));
+      return FALSE;
+    }
 
   return TRUE;
 }
@@ -589,6 +597,7 @@ gdk_x11_gl_context_egl_init (GdkX11GLContextEGL *self)
 
 gboolean
 gdk_x11_display_init_egl (GdkX11Display  *self,
+                          gboolean        force,
                           Visual        **out_visual,
                           int            *out_depth,
                           GError        **error)
@@ -625,7 +634,7 @@ gdk_x11_display_init_egl (GdkX11Display  *self,
       return FALSE;
     }
 
-  if (!gdk_x11_display_create_egl_config (self, out_visual, out_depth, error))
+  if (!gdk_x11_display_create_egl_config (self, force, out_visual, out_depth, error))
     {
       eglTerminate (self->egl_display);
       self->egl_display = NULL;
diff --git a/gdk/x11/gdkglcontext-x11.c b/gdk/x11/gdkglcontext-x11.c
index 389faf6292..c74a994c70 100644
--- a/gdk/x11/gdkglcontext-x11.c
+++ b/gdk/x11/gdkglcontext-x11.c
@@ -109,8 +109,6 @@ gdk_x11_display_init_gl (GdkX11Display  *self,
                          GError        **error)
 {
   GdkDisplay *display G_GNUC_UNUSED = GDK_DISPLAY (self);
-  GError *egl_error = NULL;
-  GError *glx_error = NULL;
 
   if (GDK_DISPLAY_DEBUG_CHECK (display, GL_DISABLE))
     {
@@ -120,27 +118,30 @@ gdk_x11_display_init_gl (GdkX11Display  *self,
       return FALSE;
     }
 
-  if (!GDK_DISPLAY_DEBUG_CHECK (display, GL_GLX))
-    {
-      /* We favour EGL */
-      if (gdk_x11_display_init_egl (self, out_visual, out_depth, &egl_error))
-        return TRUE;
-    }
-
-  if (gdk_x11_display_init_glx (self, out_visual, out_depth, &glx_error))
-    {
-      g_clear_error (&egl_error);
-      return TRUE;
-    }
-
-  if (egl_error)
-    {
-      *error = egl_error;
-      g_clear_error (&glx_error);
-    }
-  else
-    *error = glx_error;
-
-  return FALSE;
+  if (GDK_DISPLAY_DEBUG_CHECK (display, GL_EGL))
+    return gdk_x11_display_init_egl (self, TRUE, out_visual, out_depth, error);
+  if (GDK_DISPLAY_DEBUG_CHECK (display, GL_GLX))
+    return gdk_x11_display_init_glx (self, out_visual, out_depth, error);
+
+  /* No env vars set, do the regular GL initialization.
+   * 
+   * We try EGL first, but are very picky about what we accept.
+   * If that fails, we try to go with GLX instead.
+   * And if that also fails, we try EGL again, but this time accept anything.
+   *
+   * The idea here is that EGL is the preferred method going forward, but GLX is
+   * the tried and tested method that we know works. So if we detect issues with
+   * EGL, we want to avoid using it in favor of GLX.
+   */
+
+  if (gdk_x11_display_init_egl (self, FALSE, out_visual, out_depth, error))
+    return TRUE;
+  g_clear_error (error);
+
+  if (gdk_x11_display_init_glx (self, out_visual, out_depth, error))
+    return TRUE;
+  g_clear_error (error);
+
+  return gdk_x11_display_init_egl (self, TRUE, out_visual, out_depth, error);
 }
 
diff --git a/gdk/x11/gdkglcontext-x11.h b/gdk/x11/gdkglcontext-x11.h
index 1aa7fbe545..5cc2ebf5d6 100644
--- a/gdk/x11/gdkglcontext-x11.h
+++ b/gdk/x11/gdkglcontext-x11.h
@@ -101,6 +101,7 @@ gboolean                gdk_x11_gl_context_glx_make_current     (GdkDisplay    *
 typedef struct _GdkX11GLContextEGL      GdkX11GLContextEGL;
 
 gboolean                gdk_x11_display_init_egl                (GdkX11Display *display_x11,
+                                                                 gboolean       force,
                                                                  Visual       **out_visual,
                                                                  int           *out_depth,
                                                                  GError       **error);