Reverts "[Impeller] support GLES 3.0 MSAA without extension. (#56705)" (flutter/engine#56741)

Reverts: flutter/engine#56705
Initiated by: jonahwilliams
Reason for reverting: goldens occassionally fail to render anything.
Original PR Author: jonahwilliams

Reviewed By: {gaaclarke}

This change reverts the following previous change:
Adds multisampling support for GLES devices without GL_EXT_multisampled_render_to_texture provided they are at least GLES 3.0 to support mutlisampled render buffers.

Fixes https://github.com/flutter/flutter/issues/158360
Fixes https://github.com/flutter/flutter/issues/157951

TBD: should we prefer renderbuffer 3.0 approach over multisample_render_to_texture?

engine/src/flutter/impeller/display_list/canvas.cc

@@ -1667,15 +1667,10 @@ bool Canvas::BlitToOnscreen() {
   auto offscreen_target = render_passes_.back()
                               .inline_pass_context->GetPassTarget()
                               .GetRenderTarget();
-  // Unlike other backends the blit to restore the onscreen fails for GLES
+
-  // if the src is a multisample framebuffer, even if we specifically target
-  // the non-multisampled resolve of the dst.
-  bool is_gles_and_must_skip_blit = renderer_.GetContext()->GetBackendType() ==
-                                    Context::BackendType::kOpenGLES;
   if (renderer_.GetContext()
           ->GetCapabilities()
-          ->SupportsTextureToTextureBlits() &&
+          ->SupportsTextureToTextureBlits()) {
-      !is_gles_and_must_skip_blit) {
     auto blit_pass = command_buffer->CreateBlitPass();
     blit_pass->AddCopy(offscreen_target.GetRenderTargetTexture(),
                        render_target_.GetRenderTargetTexture());

engine/src/flutter/impeller/renderer/backend/gles/capabilities_gles.cc

@@ -125,11 +125,7 @@ CapabilitiesGLES::CapabilitiesGLES(const ProcTableGLES& gl) {
 
     // We hard-code 4x MSAA, so let's make sure it's supported.
     GLint value = 0;
-    gl.GetIntegerv(GL_MAX_SAMPLES, &value);
+    gl.GetIntegerv(GL_MAX_SAMPLES_EXT, &value);
-    supports_offscreen_msaa_ = value >= 4;
-  } else if (desc->GetGlVersion().major_version >= 3 && desc->IsES()) {
-    GLint value = 0;
-    gl.GetIntegerv(GL_MAX_SAMPLES, &value);
     supports_offscreen_msaa_ = value >= 4;
   }
   is_es_ = desc->IsES();

engine/src/flutter/impeller/renderer/backend/gles/proc_table_gles.h

@@ -242,7 +242,6 @@ void(glDepthRange)(GLdouble n, GLdouble f);
   PROC(FenceSync);                         \
   PROC(DeleteSync);                        \
   PROC(WaitSync);                          \
-  PROC(RenderbufferStorageMultisample)     \
   PROC(BlitFramebuffer);
 
 #define FOR_EACH_IMPELLER_EXT_PROC(PROC)    \

engine/src/flutter/impeller/renderer/backend/gles/render_pass_gles.cc

@@ -7,6 +7,7 @@
 #include <cstdint>
 
 #include "GLES3/gl3.h"
+#include "flutter/fml/trace_event.h"
 #include "fml/closure.h"
 #include "fml/logging.h"
 #include "impeller/base/validation.h"
@@ -126,7 +127,6 @@ struct RenderPassData {
   Scalar clear_depth = 1.0;
 
   std::shared_ptr<Texture> color_attachment;
-  std::shared_ptr<Texture> resolve_attachment;
   std::shared_ptr<Texture> depth_attachment;
   std::shared_ptr<Texture> stencil_attachment;
 
@@ -191,6 +191,8 @@ void RenderPassGLES::ResetGLState(const ProcTableGLES& gl) {
     const ReactorGLES& reactor,
     const std::vector<Command>& commands,
     const std::shared_ptr<GPUTracerGLES>& tracer) {
+  TRACE_EVENT0("impeller", "RenderPassGLES::EncodeCommandsInReactor");
+
   const auto& gl = reactor.GetProcTable();
 #ifdef IMPELLER_DEBUG
   tracer->MarkFrameStart(gl);
@@ -488,55 +490,6 @@ void RenderPassGLES::ResetGLState(const ProcTableGLES& gl) {
     }
   }
 
-  if (pass_data.resolve_attachment &&
-      !gl.GetCapabilities()->SupportsImplicitResolvingMSAA() &&
-      !is_default_fbo) {
-    FML_DCHECK(pass_data.resolve_attachment != pass_data.color_attachment);
-    // Perform multisample resolve via blit.
-    // Create and bind a resolve FBO.
-    GLuint resolve_fbo;
-    gl.GenFramebuffers(1u, &resolve_fbo);
-    gl.BindFramebuffer(GL_FRAMEBUFFER, resolve_fbo);
-
-    if (!TextureGLES::Cast(*pass_data.resolve_attachment)
-             .SetAsFramebufferAttachment(
-                 GL_FRAMEBUFFER, TextureGLES::AttachmentType::kColor0)) {
-      return false;
-    }
-
-    auto status = gl.CheckFramebufferStatus(GL_FRAMEBUFFER);
-    if (gl.CheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
-      VALIDATION_LOG << "Could not create a complete frambuffer: "
-                     << DebugToFramebufferError(status);
-      return false;
-    }
-
-    // Bind MSAA renderbuffer to read framebuffer.
-    gl.BindFramebuffer(GL_READ_FRAMEBUFFER, fbo);
-    gl.BindFramebuffer(GL_DRAW_FRAMEBUFFER, resolve_fbo);
-
-    RenderPassGLES::ResetGLState(gl);
-    auto size = pass_data.color_attachment->GetSize();
-
-    gl.BlitFramebuffer(0,                    // srcX0
-                       0,                    // srcY0
-                       size.width,           // srcX1
-                       size.height,          // srcY1
-                       0,                    // dstX0
-                       0,                    // dstY0
-                       size.width,           // dstX1
-                       size.height,          // dstY1
-                       GL_COLOR_BUFFER_BIT,  // mask
-                       GL_NEAREST            // filter
-    );
-
-    gl.BindFramebuffer(GL_DRAW_FRAMEBUFFER, GL_NONE);
-    gl.BindFramebuffer(GL_READ_FRAMEBUFFER, GL_NONE);
-    gl.DeleteFramebuffers(1u, &resolve_fbo);
-    // Rebind the original FBO so that we can discard it below.
-    gl.BindFramebuffer(GL_FRAMEBUFFER, fbo);
-  }
-
   if (gl.DiscardFramebufferEXT.IsAvailable()) {
     std::vector<GLenum> attachments;
 
@@ -594,7 +547,6 @@ bool RenderPassGLES::OnEncodeCommands(const Context& context) const {
   /// Setup color data.
   ///
   pass_data->color_attachment = color0.texture;
-  pass_data->resolve_attachment = color0.resolve_texture;
   pass_data->clear_color = color0.clear_color;
   pass_data->clear_color_attachment = CanClearAttachment(color0.load_action);
   pass_data->discard_color_attachment =
@@ -604,9 +556,8 @@ bool RenderPassGLES::OnEncodeCommands(const Context& context) const {
   // resolved when we bind the texture to the framebuffer. We don't need to
   // discard the attachment when we are done.
   if (color0.resolve_texture) {
-    pass_data->discard_color_attachment =
+    FML_DCHECK(context.GetCapabilities()->SupportsImplicitResolvingMSAA());
-        pass_data->discard_color_attachment &&
+    pass_data->discard_color_attachment = false;
-        !context.GetCapabilities()->SupportsImplicitResolvingMSAA();
   }
 
   //----------------------------------------------------------------------------

engine/src/flutter/impeller/renderer/backend/gles/texture_gles.cc

@@ -45,8 +45,7 @@ static bool IsDepthStencilFormat(PixelFormat format) {
 }
 
 static TextureGLES::Type GetTextureTypeFromDescriptor(
-    const TextureDescriptor& desc,
+    const TextureDescriptor& desc) {
-    bool supports_implict_msaa) {
   const auto usage = static_cast<TextureUsageMask>(desc.usage);
   const auto render_target = TextureUsage::kRenderTarget;
   const auto is_msaa = desc.sample_count == SampleCount::kCount4;
@@ -54,9 +53,7 @@ static TextureGLES::Type GetTextureTypeFromDescriptor(
     return is_msaa ? TextureGLES::Type::kRenderBufferMultisampled
                    : TextureGLES::Type::kRenderBuffer;
   }
-  return is_msaa ? (supports_implict_msaa
+  return is_msaa ? TextureGLES::Type::kTextureMultisampled
-                        ? TextureGLES::Type::kTextureMultisampled
-                        : TextureGLES::Type::kRenderBufferMultisampled)
                  : TextureGLES::Type::kTexture;
 }
 
@@ -193,11 +190,7 @@ TextureGLES::TextureGLES(std::shared_ptr<ReactorGLES> reactor,
                          std::optional<HandleGLES> external_handle)
     : Texture(desc),
       reactor_(std::move(reactor)),
-      type_(
+      type_(GetTextureTypeFromDescriptor(GetTextureDescriptor())),
-          GetTextureTypeFromDescriptor(GetTextureDescriptor(),
-                                       reactor_->GetProcTable()
-                                           .GetCapabilities()
-                                           ->SupportsImplicitResolvingMSAA())),
       handle_(external_handle.has_value()
                   ? external_handle.value()
                   : reactor_->CreateHandle(ToHandleType(type_))),
@@ -369,7 +362,7 @@ static std::optional<GLenum> ToRenderBufferFormat(PixelFormat format) {
   switch (format) {
     case PixelFormat::kB8G8R8A8UNormInt:
     case PixelFormat::kR8G8B8A8UNormInt:
-      return GL_RGBA8;
+      return GL_RGBA4;
     case PixelFormat::kR32G32B32A32Float:
       return GL_RGBA32F;
     case PixelFormat::kR16G16B16A16Float:
@@ -452,32 +445,19 @@ void TextureGLES::InitializeContentsIfNecessary() const {
       {
         TRACE_EVENT0("impeller", "RenderBufferStorageInitialization");
         if (type_ == Type::kRenderBufferMultisampled) {
-          // BEWARE: these functions are not at all equivalent! the extensions
+          gl.RenderbufferStorageMultisampleEXT(
-          // are from EXT_multisampled_render_to_texture and cannot be used
+              GL_RENDERBUFFER,               // target
-          // with regular GLES 3.0 multisampled renderbuffers/textures.
+              4,                             // samples
-          if (gl.GetCapabilities()->SupportsImplicitResolvingMSAA()) {
+              render_buffer_format.value(),  // internal format
-            gl.RenderbufferStorageMultisampleEXT(
+              size.width,                    // width
-                /*target=*/GL_RENDERBUFFER,                        //
+              size.height                    // height
-                /*samples=*/4,                                     //
+          );
-                /*internal_format=*/render_buffer_format.value(),  //
-                /*width=*/size.width,                              //
-                /*height=*/size.height                             //
-            );
-          } else {
-            gl.RenderbufferStorageMultisample(
-                /*target=*/GL_RENDERBUFFER,                        //
-                /*samples=*/4,                                     //
-                /*internal_format=*/render_buffer_format.value(),  //
-                /*width=*/size.width,                              //
-                /*height=*/size.height                             //
-            );
-          }
         } else {
           gl.RenderbufferStorage(
-              /*target=*/GL_RENDERBUFFER,                        //
+              GL_RENDERBUFFER,               // target
-              /*internal_format=*/render_buffer_format.value(),  //
+              render_buffer_format.value(),  // internal format
-              /*width=*/size.width,                              //
+              size.width,                    // width
-              /*height=*/size.height                             //
+              size.height                    // height
           );
         }
       }