gdkglcontext-wayland: Fallback to GLES 2.0 after legacy failed

This lets the NGL backend be selected instead of the Cairo backend on
devices which expose both GL and GLES, but have better support of GLES.

Tested on a PinePhone.

1 files changed, 40 insertions, 6 deletions

diff --git a/gdk/wayland/gdkglcontext-wayland.c b/gdk/wayland/gdkglcontext-wayland.c
index 1667117e7f..9e2572f5be 100644
--- a/gdk/wayland/gdkglcontext-wayland.c
+++ b/gdk/wayland/gdkglcontext-wayland.c
@@ -126,14 +126,48 @@ gdk_wayland_gl_context_realize (GdkGLContext *context,
                                                   : EGL_NO_CONTEXT,
                           context_attribs);
 
+  /* If context creation failed without the ES bit, let's try again with it */
+  if (ctx == NULL)
+    {
+      i = 0;
+      context_attribs[i++] = EGL_CONTEXT_MAJOR_VERSION;
+      context_attribs[i++] = 2;
+      context_attribs[i++] = EGL_CONTEXT_MINOR_VERSION;
+      context_attribs[i++] = 0;
+      context_attribs[i++] = EGL_CONTEXT_FLAGS_KHR;
+      context_attribs[i++] = flags & ~EGL_CONTEXT_OPENGL_FORWARD_COMPATIBLE_BIT_KHR;
+      context_attribs[i++] = EGL_NONE;
+      g_assert (i < N_EGL_ATTRS);
+
+      eglBindAPI (EGL_OPENGL_ES_API);
+
+      legacy_bit = FALSE;
+      use_es = TRUE;
+
+      GDK_DISPLAY_NOTE (display, OPENGL,
+                g_message ("eglCreateContext failed, switching to OpenGL ES"));
+      ctx = eglCreateContext (display_wayland->egl_display,
+                              context_wayland->egl_config,
+                              share != NULL ? GDK_WAYLAND_GL_CONTEXT (share)->egl_context
+                                 : shared_data_context != NULL ? GDK_WAYLAND_GL_CONTEXT (shared_data_context)->egl_context
+                                    : EGL_NO_CONTEXT,
+                              context_attribs);
+    }
+
   /* If context creation failed without the legacy bit, let's try again with it */
-  if (ctx == NULL && !legacy_bit)
+  if (ctx == NULL)
     {
-      /* Ensure that re-ordering does not break the offsets */
-      g_assert (context_attribs[0] == EGL_CONTEXT_OPENGL_PROFILE_MASK_KHR);
-      context_attribs[1] = EGL_CONTEXT_OPENGL_COMPATIBILITY_PROFILE_BIT_KHR;
-      context_attribs[3] = 3;
-      context_attribs[5] = 0;
+      i = 0;
+      context_attribs[i++] = EGL_CONTEXT_OPENGL_PROFILE_MASK_KHR;
+      context_attribs[i++] = EGL_CONTEXT_OPENGL_COMPATIBILITY_PROFILE_BIT_KHR;
+      context_attribs[i++] = EGL_CONTEXT_MAJOR_VERSION;
+      context_attribs[i++] = 3;
+      context_attribs[i++] = EGL_CONTEXT_MINOR_VERSION;
+      context_attribs[i++] = 0;
+      context_attribs[i++] = EGL_CONTEXT_FLAGS_KHR;
+      context_attribs[i++] = flags & ~EGL_CONTEXT_OPENGL_FORWARD_COMPATIBLE_BIT_KHR;
+      context_attribs[i++] = EGL_NONE;
+      g_assert (i < N_EGL_ATTRS);
 
       eglBindAPI (EGL_OPENGL_API);