Drawable Renderer (#1570), Move generic shader lookup to context virtual

src/mbgl/gfx/context.hpp

@@ -24,6 +24,7 @@ class DrawableBuilder;
 class DrawableTweaker;
 class OffscreenTexture;
 class ShaderProgramBase;
+class ShaderRegistry;
 
 using DrawablePtr = std::shared_ptr<Drawable>;
 using UniqueDrawableBuilder = std::unique_ptr<DrawableBuilder>;
@@ -106,6 +107,9 @@ public:
     
     /// Create a new drawable tweaker
     virtual DrawableTweakerPtr createDrawableTweaker() = 0;
+    
+    /// Get the generic shader with the specified name
+    virtual gfx::ShaderProgramBasePtr getGenericShader(gfx::ShaderRegistry&, const std::string& name) = 0;
 };
 
 } // namespace gfx

src/mbgl/gl/context.cpp

@@ -1,4 +1,6 @@
 #include <mbgl/gl/context.hpp>
+
+#include <mbgl/gfx/shader_registry.hpp>
 #include <mbgl/gl/command_encoder.hpp>
 #include <mbgl/gl/defines.hpp>
 #include <mbgl/gl/drawable_gl.hpp>
@@ -487,6 +489,10 @@ gfx::DrawableTweakerPtr Context::createDrawableTweaker() {
     return std::make_shared<gl::DrawableGLTweaker>();
 }
 
+gfx::ShaderProgramBasePtr Context::getGenericShader(gfx::ShaderRegistry& shaders, const std::string& name) {
+    return shaders.get<gl::ShaderProgramGL>(name);
+}
+
 void Context::clear(std::optional<mbgl::Color> color,
                     std::optional<float> depth,
                     std::optional<int32_t> stencil) {

src/mbgl/gl/context.hpp

@@ -107,6 +107,8 @@ public:
     gfx::UniqueDrawableBuilder createDrawableBuilder(std::string name) override;
     gfx::DrawableTweakerPtr createDrawableTweaker() override;
 
+    gfx::ShaderProgramBasePtr getGenericShader(gfx::ShaderRegistry&, const std::string& name) override;
+
 private:
     RendererBackend& backend;
     bool cleanupOnDestruction = true;

src/mbgl/style/layers/background_layer_impl.cpp

@@ -31,25 +31,15 @@ bool BackgroundLayer::Impl::hasLayoutDifference(const Layer::Impl&) const {
 
 constexpr auto shaderName = "background_generic";
 
-struct ShaderHack final : public gfx::ShaderProgramBase {
-    static constexpr std::string_view Name{"GenericGLShader"};
-    const std::string_view typeName() const noexcept override { return Name; }
-    const gfx::VertexAttributeArray& getUniforms() const override { return *dummy; }
-    const gfx::VertexAttributeArray& getVertexAttributes() const override { return *dummy; }
-    gfx::VertexAttributeArray& mutableUniforms() override { return *dummy; }
-    gfx::VertexAttributeArray& mutableVertexAttributes() override { return *dummy; }
-    gfx::VertexAttributeArray* dummy = nullptr;
-};
-
 void BackgroundLayer::Impl::layerAdded(gfx::ShaderRegistry& shaders,
-                                       gfx::Context&,
+                                       gfx::Context& context,
                                        const TransformState&,
                                        const PropertyEvaluationParameters&,
                                        UniqueChangeRequestVec&) const {
     {
         std::unique_lock<std::mutex> guard(mutex);
         if (!shader) {
-            shader = shaders.get<ShaderHack>(shaderName);
+            shader = context.getGenericShader(shaders, shaderName);
         }
     }
 }