gpu: Disable the ubershader when shaders aren't nonuniform

If shaders don't support nonuniform indexing, we emulate it via if/else
ladders (or switch ladders) which get inlined by the GLSL compiles and
massively blow up the code.

And that makes compilation of the shaders take minutes and results in
shader code that isn't necessarily faster.

So we disable it on GL entirely and on Vulkan if the required features
aren't available.

As it's only an optimization and does not fall back to Cairo anymore,
this should be fine.

gdk/gdkdisplay.c

@@ -1307,6 +1307,17 @@ gdk_display_create_vulkan_context (GdkDisplay  *self,
                          NULL);
 }
 
+gboolean
+gdk_display_has_vulkan_feature (GdkDisplay        *self,
+                                GdkVulkanFeatures  feature)
+{
+#ifdef GDK_RENDERING_VULKAN
+  return !!(self->vulkan_features & feature);
+#else
+  return FALSE;
+#endif
+}
+
 static void
 gdk_display_init_gl (GdkDisplay *self)
 {

gdk/gdkdisplayprivate.h

@@ -233,6 +233,8 @@ void                _gdk_display_unpause_events       (GdkDisplay       *display
 
 void                gdk_display_init_dmabuf           (GdkDisplay       *self);
 
+gboolean            gdk_display_has_vulkan_feature    (GdkDisplay       *self,
+                                                       GdkVulkanFeatures feature);
 GdkVulkanContext *  gdk_display_create_vulkan_context (GdkDisplay       *self,
                                                        GError          **error);
 

gsk/gpu/gsknglrenderer.c

@@ -54,6 +54,13 @@ gsk_ngl_renderer_create_context (GskGpuRenderer       *renderer,
   gdk_gl_context_make_current (context);
 
   *supported = -1;
+
+  /* Shader compilation takes too long when texture() and get_float() calls
+   * use if/else ladders to avoid non-uniform indexing.
+   * And that is always true with GL.
+   */
+  *supported &= ~GSK_GPU_OPTIMIZE_UBER;
+
   if (!gdk_gl_context_check_version (context, "4.2", "9.9") &&
       !epoxy_has_gl_extension ("GL_EXT_base_instance") &&
       !epoxy_has_gl_extension ("GL_ARB_base_instance"))

gsk/gpu/gskvulkanrenderer.c

@@ -98,6 +98,15 @@ gsk_vulkan_renderer_create_context (GskGpuRenderer       *renderer,
 
   *supported = -1;
 
+  /* Shader compilation takes too long when texture() and get_float() calls
+   * use if/else ladders to avoid non-uniform indexing.
+   * This is true when we use the Vulkan 1.0 shaders, but works with the Vulkan 1.2
+   * shaders.
+   */
+  if (!gdk_display_has_vulkan_feature (display, GDK_VULKAN_FEATURE_DYNAMIC_INDEXING) ||
+      !gdk_display_has_vulkan_feature (display, GDK_VULKAN_FEATURE_NONUNIFORM_INDEXING))
+    *supported &= ~GSK_GPU_OPTIMIZE_UBER;
+
   return GDK_DRAW_CONTEXT (context);
 }