[Impeller] Continue enabling MSAA for OpenGLES Backend

impeller/renderer/backend/gles/blit_command_gles.cc

@@ -41,7 +41,7 @@ static std::optional<GLuint> ConfigureFBO(
   gl.BindFramebuffer(fbo_type, fbo);
 
   if (!TextureGLES::Cast(*texture).SetAsFramebufferAttachment(
-          fbo_type, fbo, TextureGLES::AttachmentPoint::kColor0)) {
+          fbo_type, TextureGLES::AttachmentPoint::kColor0)) {
     VALIDATION_LOG << "Could not attach texture to framebuffer.";
     DeleteFBO(gl, fbo, fbo_type);
     return std::nullopt;

impeller/renderer/backend/gles/capabilities_gles.cc

@@ -106,6 +106,17 @@ CapabilitiesGLES::CapabilitiesGLES(const ProcTableGLES& gl) {
       gl.GetDescription()->HasExtension(kOESTextureBorderClampExt)) {
     supports_decal_sampler_address_mode_ = true;
   }
+
+  if (gl.GetDescription()->HasExtension(
+          "GL_EXT_multisampled_render_to_texture")) {
+    supports_offscreen_msaa_ = true;
+
+    // We hard-code 4x MSAA for now, so let's make sure it's supported.
+    GLint value = 0;
+    gl.GetIntegerv(GL_MAX_SAMPLES, &value);
+    FML_DCHECK(value == 4) << "Unexpected max samples: " << value << ". "
+                           << "Only 4x MSAA is currently supported.";
+  }
 }
 
 size_t CapabilitiesGLES::GetMaxTextureUnits(ShaderStage stage) const {
@@ -124,7 +135,7 @@ size_t CapabilitiesGLES::GetMaxTextureUnits(ShaderStage stage) const {
 }
 
 bool CapabilitiesGLES::SupportsOffscreenMSAA() const {
-  return false;
+  return supports_offscreen_msaa_;
 }
 
 bool CapabilitiesGLES::SupportsSSBO() const {

impeller/renderer/backend/gles/capabilities_gles.h

@@ -118,6 +118,7 @@ class CapabilitiesGLES final
  private:
   bool supports_framebuffer_fetch_ = false;
   bool supports_decal_sampler_address_mode_ = false;
+  bool supports_offscreen_msaa_ = false;
 };
 
 }  // namespace impeller

impeller/renderer/backend/gles/render_pass_gles.cc

@@ -176,19 +176,19 @@ struct RenderPassData {
 
     if (auto color = TextureGLES::Cast(pass_data.color_attachment.get())) {
       if (!color->SetAsFramebufferAttachment(
-              GL_FRAMEBUFFER, fbo, TextureGLES::AttachmentPoint::kColor0)) {
+              GL_FRAMEBUFFER, TextureGLES::AttachmentPoint::kColor0)) {
         return false;
       }
     }
     if (auto depth = TextureGLES::Cast(pass_data.depth_attachment.get())) {
       if (!depth->SetAsFramebufferAttachment(
-              GL_FRAMEBUFFER, fbo, TextureGLES::AttachmentPoint::kDepth)) {
+              GL_FRAMEBUFFER, TextureGLES::AttachmentPoint::kDepth)) {
         return false;
       }
     }
     if (auto stencil = TextureGLES::Cast(pass_data.stencil_attachment.get())) {
       if (!stencil->SetAsFramebufferAttachment(
-              GL_FRAMEBUFFER, fbo, TextureGLES::AttachmentPoint::kStencil)) {
+              GL_FRAMEBUFFER, TextureGLES::AttachmentPoint::kStencil)) {
         return false;
       }
     }

impeller/renderer/backend/gles/texture_gles.cc

@@ -22,7 +22,11 @@ static TextureGLES::Type GetTextureTypeFromDescriptor(
   const auto render_target =
       static_cast<TextureUsageMask>(TextureUsage::kRenderTarget);
   if (usage == render_target) {
-    return TextureGLES::Type::kRenderBuffer;
+    if (desc.sample_count == SampleCount::kCount1) {
+      return TextureGLES::Type::kRenderBuffer;
+    } else {
+      return TextureGLES::Type::kRenderBufferMultisampled;
+    }
   }
   return TextureGLES::Type::kTexture;
 }
@@ -382,7 +386,6 @@ void TextureGLES::InitializeContentsIfNecessary() const {
                       nullptr                    // data
         );
       }
-
     } break;
     case Type::kRenderBuffer: {
       auto render_buffer_format =
@@ -402,6 +405,27 @@ void TextureGLES::InitializeContentsIfNecessary() const {
       }
     } break;
     case Type::kRenderBufferMultisampled: {
+      gl.BindTexture(GL_TEXTURE_2D, handle.value());
+      {
+        TRACE_EVENT0("impeller", "TexImage2DInitialization");
+        TexImage2DData tex_data(GetTextureDescriptor().format);
+        // TODO: Remove this before submitting.
+        FML_LOG(ERROR) << "*** " << __PRETTY_FUNCTION__
+                       << " size_w=" << size.width << " h=" << size.height
+                       << " iformat=" << tex_data.internal_format
+                       << " eformat=" << tex_data.external_format;
+        // https://github.com/flutter/engine/blob/main/impeller/renderer/backend/gles/texture_gles.cc#L96
+        gl.TexImage2D(GL_TEXTURE_2D,  // target
+                      0u,             // LOD level (base mip level size checked)
+                      tex_data.internal_format,  // internal format
+                      size.width,                // width
+                      size.height,               // height
+                      0u,                        // border
+                      tex_data.external_format,  // format
+                      tex_data.type,             // type
+                      nullptr                    // data
+        );
+      }
       auto render_buffer_msaa =
           ToRenderBufferFormat(GetTextureDescriptor().format);
       if (!render_buffer_msaa.has_value()) {
@@ -506,7 +530,6 @@ static GLenum ToAttachmentPoint(TextureGLES::AttachmentPoint point) {
 }
 
 bool TextureGLES::SetAsFramebufferAttachment(GLenum target,
-                                             GLuint fbo,
                                              AttachmentPoint point) const {
   if (!IsValid()) {
     return false;

impeller/renderer/backend/gles/texture_gles.h

@@ -46,7 +46,6 @@ class TextureGLES final : public Texture,
     kStencil,
   };
   [[nodiscard]] bool SetAsFramebufferAttachment(GLenum target,
-                                                GLuint fbo,
                                                 AttachmentPoint point) const;
 
   Type GetType() const;