[Impeller] OpenGLES: Ensure frag/vert textures are bound with unique texture units.

Author: bdero

impeller/renderer/backend/gles/buffer_bindings_gles.cc

@@ -155,11 +155,15 @@ bool BufferBindingsGLES::BindUniformData(
     }
   }
 
-  if (!BindTextures(gl, vertex_bindings, ShaderStage::kVertex)) {
+  std::optional<size_t> next_unit_index =
+      BindTextures(gl, vertex_bindings, ShaderStage::kVertex);
+  if (!next_unit_index.has_value()) {
     return false;
   }
 
-  if (!BindTextures(gl, fragment_bindings, ShaderStage::kFragment)) {
+  if (!BindTextures(gl, fragment_bindings, ShaderStage::kFragment,
+                    *next_unit_index)
+           .has_value()) {
     return false;
   }
 
@@ -295,23 +299,25 @@ bool BufferBindingsGLES::BindUniformBuffer(const ProcTableGLES& gl,
   return true;
 }
 
-bool BufferBindingsGLES::BindTextures(const ProcTableGLES& gl,
-                                      const Bindings& bindings,
-                                      ShaderStage stage) const {
-  size_t active_index = 0;
+std::optional<size_t> BufferBindingsGLES::BindTextures(
+    const ProcTableGLES& gl,
+    const Bindings& bindings,
+    ShaderStage stage,
+    size_t unit_start_index) const {
+  size_t active_index = unit_start_index;
   for (const auto& data : bindings.sampled_images) {
     const auto& texture_gles = TextureGLES::Cast(*data.second.texture.resource);
     if (data.second.texture.GetMetadata() == nullptr) {
       VALIDATION_LOG << "No metadata found for texture binding.";
-      return false;
+      return std::nullopt;
     }
 
     const auto uniform_key =
         CreateUniformMemberKey(data.second.texture.GetMetadata()->name);
     auto uniform = uniform_locations_.find(uniform_key);
     if (uniform == uniform_locations_.end()) {
       VALIDATION_LOG << "Could not find uniform for key: " << uniform_key;
-      return false;
+      return std::nullopt;
     }
 
     //--------------------------------------------------------------------------
@@ -320,15 +326,15 @@ bool BufferBindingsGLES::BindTextures(const ProcTableGLES& gl,
     if (active_index >= gl.GetCapabilities()->GetMaxTextureUnits(stage)) {
       VALIDATION_LOG << "Texture units specified exceed the capabilities for "
                         "this shader stage.";
-      return false;
+      return std::nullopt;
     }
     gl.ActiveTexture(GL_TEXTURE0 + active_index);
 
     //--------------------------------------------------------------------------
     /// Bind the texture.
     ///
     if (!texture_gles.Bind()) {
-      return false;
+      return std::nullopt;
     }
 
     //--------------------------------------------------------------------------
@@ -337,7 +343,7 @@ bool BufferBindingsGLES::BindTextures(const ProcTableGLES& gl,
     ///
     const auto& sampler_gles = SamplerGLES::Cast(*data.second.sampler.resource);
     if (!sampler_gles.ConfigureBoundTexture(texture_gles, gl)) {
-      return false;
+      return std::nullopt;
     }
 
     //--------------------------------------------------------------------------
@@ -350,7 +356,7 @@ bool BufferBindingsGLES::BindTextures(const ProcTableGLES& gl,
     ///
     active_index++;
   }
-  return true;
+  return active_index;
 }
 
 }  // namespace impeller

impeller/renderer/backend/gles/buffer_bindings_gles.h

@@ -61,9 +61,10 @@ class BufferBindingsGLES {
                          Allocator& transients_allocator,
                          const BufferResource& buffer) const;
 
-  bool BindTextures(const ProcTableGLES& gl,
-                    const Bindings& bindings,
-                    ShaderStage stage) const;
+  std::optional<size_t> BindTextures(const ProcTableGLES& gl,
+                                     const Bindings& bindings,
+                                     ShaderStage stage,
+                                     size_t unit_start_index = 0) const;
 
   FML_DISALLOW_COPY_AND_ASSIGN(BufferBindingsGLES);
 };