From 417962665748b97a09389b1c5c7fbfad0923d140 Mon Sep 17 00:00:00 2001
From: Brandon DeRosier <x@bdero.me>
Date: Mon, 23 Oct 2023 02:44:11 -0700
Subject: [PATCH] [Impeller] OpenGLES: Ensure frag/vert textures are bound with
 unique texture units.

---
 .../backend/gles/buffer_bindings_gles.cc      | 30 +++++++++++--------
 .../backend/gles/buffer_bindings_gles.h       |  7 +++--
 2 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/impeller/renderer/backend/gles/buffer_bindings_gles.cc b/impeller/renderer/backend/gles/buffer_bindings_gles.cc
index 9335f4c0b3b77..cfff3b1740771 100644
--- a/impeller/renderer/backend/gles/buffer_bindings_gles.cc
+++ b/impeller/renderer/backend/gles/buffer_bindings_gles.cc
@@ -155,11 +155,15 @@ bool BufferBindingsGLES::BindUniformData(const ProcTableGLES& gl,
     }
   }
 
-  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;
   }
 
@@ -334,20 +338,22 @@ bool BufferBindingsGLES::BindUniformBuffer(const ProcTableGLES& gl,
   return true;
 }
 
-bool BufferBindingsGLES::BindTextures(const ProcTableGLES& gl,
-                                      const Bindings& bindings,
-                                      ShaderStage stage) {
-  size_t active_index = 0;
+std::optional<size_t> BufferBindingsGLES::BindTextures(
+    const ProcTableGLES& gl,
+    const Bindings& bindings,
+    ShaderStage stage,
+    size_t unit_start_index) {
+  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;
     }
 
     auto location = ComputeTextureLocation(data.second.texture.GetMetadata());
     if (location == -1) {
-      return false;
+      return std::nullopt;
     }
 
     //--------------------------------------------------------------------------
@@ -356,7 +362,7 @@ 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);
 
@@ -364,7 +370,7 @@ bool BufferBindingsGLES::BindTextures(const ProcTableGLES& gl,
     /// Bind the texture.
     ///
     if (!texture_gles.Bind()) {
-      return false;
+      return std::nullopt;
     }
 
     //--------------------------------------------------------------------------
@@ -373,7 +379,7 @@ 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;
     }
 
     //--------------------------------------------------------------------------
@@ -386,7 +392,7 @@ bool BufferBindingsGLES::BindTextures(const ProcTableGLES& gl,
     ///
     active_index++;
   }
-  return true;
+  return active_index;
 }
 
 }  // namespace impeller
diff --git a/impeller/renderer/backend/gles/buffer_bindings_gles.h b/impeller/renderer/backend/gles/buffer_bindings_gles.h
index 39f48ffc911d1..c30e4e631b887 100644
--- a/impeller/renderer/backend/gles/buffer_bindings_gles.h
+++ b/impeller/renderer/backend/gles/buffer_bindings_gles.h
@@ -70,9 +70,10 @@ class BufferBindingsGLES {
                          Allocator& transients_allocator,
                          const BufferResource& buffer);
 
-  bool BindTextures(const ProcTableGLES& gl,
-                    const Bindings& bindings,
-                    ShaderStage stage);
+  std::optional<size_t> BindTextures(const ProcTableGLES& gl,
+                                     const Bindings& bindings,
+                                     ShaderStage stage,
+                                     size_t unit_start_index = 0);
 
   BufferBindingsGLES(const BufferBindingsGLES&) = delete;