[Impeller] Add validation for mipmap generation enforced at binding time

impeller/renderer/backend/gles/blit_command_gles.cc

@@ -163,7 +163,7 @@ std::string BlitGenerateMipmapCommandGLES::GetLabel() const {
 
 bool BlitGenerateMipmapCommandGLES::Encode(const ReactorGLES& reactor) const {
   auto texture_gles = TextureGLES::Cast(texture.get());
-  if (!texture_gles->GenerateMipmaps()) {
+  if (!texture_gles->GenerateMipmap()) {
     return false;
   }
 

impeller/renderer/backend/gles/sampler_gles.cc

@@ -3,8 +3,10 @@
 // found in the LICENSE file.
 
 #include "impeller/renderer/backend/gles/sampler_gles.h"
+
 #include <iostream>
 
+#include "impeller/base/validation.h"
 #include "impeller/renderer/backend/gles/formats_gles.h"
 #include "impeller/renderer/backend/gles/proc_table_gles.h"
 #include "impeller/renderer/backend/gles/texture_gles.h"
@@ -69,6 +71,13 @@ bool SamplerGLES::ConfigureBoundTexture(const TextureGLES& texture,
     return false;
   }
 
+  if (texture.NeedsMipmapGeneration()) {
+    VALIDATION_LOG
+        << "Texture mip count is > 1, but the mipmap has not been generated. "
+           "Texture can not be sampled safely.";
+    return false;
+  }
+
   auto target = ToTextureTarget(texture.GetTextureDescriptor().type);
 
   if (!target.has_value()) {

impeller/renderer/backend/gles/texture_gles.cc

@@ -425,7 +425,7 @@ bool TextureGLES::Bind() const {
   return true;
 }
 
-bool TextureGLES::GenerateMipmaps() const {
+bool TextureGLES::GenerateMipmap() {
   if (!IsValid()) {
     return false;
   }
@@ -453,6 +453,7 @@ bool TextureGLES::GenerateMipmaps() const {
 
   const auto& gl = reactor_->GetProcTable();
   gl.GenerateMipmap(ToTextureType(type));
+  mipmap_generated_ = true;
   return true;
 }
 

impeller/renderer/backend/gles/texture_gles.h

@@ -37,7 +37,7 @@ class TextureGLES final : public Texture,
 
   [[nodiscard]] bool Bind() const;
 
-  [[nodiscard]] bool GenerateMipmaps() const;
+  [[nodiscard]] bool GenerateMipmap();
 
   enum class AttachmentPoint {
     kColor0,

impeller/renderer/backend/metal/blit_command_mtl.mm

@@ -147,14 +147,7 @@
 
 bool BlitGenerateMipmapCommandMTL::Encode(
     id<MTLBlitCommandEncoder> encoder) const {
-  auto texture_mtl = TextureMTL::Cast(*texture).GetMTLTexture();
-  if (!texture_mtl) {
-    return false;
-  }
-
-  [encoder generateMipmapsForTexture:texture_mtl];
-
-  return true;
+  return TextureMTL::Cast(*texture).GenerateMipmap(encoder);
 };
 
 }  // namespace impeller

impeller/renderer/backend/metal/render_pass_mtl.mm

@@ -382,6 +382,13 @@ static bool Bind(PassBindingsCache& pass,
     return false;
   }
 
+  if (texture.NeedsMipmapGeneration()) {
+    VALIDATION_LOG
+        << "Texture at binding index " << bind_index
+        << " has a mip count > 1, but the mipmap has not been generated.";
+    return false;
+  }
+
   return pass.SetTexture(stage, bind_index,
                          TextureMTL::Cast(texture).GetMTLTexture());
 }

impeller/renderer/backend/metal/texture_mtl.h

@@ -29,6 +29,8 @@ class TextureMTL final : public Texture,
 
   bool IsWrapped() const;
 
+  bool GenerateMipmap(id<MTLBlitCommandEncoder> encoder);
+
  private:
   id<MTLTexture> texture_ = nullptr;
   bool is_valid_ = false;

impeller/renderer/backend/metal/texture_mtl.mm

@@ -92,4 +92,15 @@
   return is_wrapped_;
 }
 
+bool TextureMTL::GenerateMipmap(id<MTLBlitCommandEncoder> encoder) {
+  if (!texture_) {
+    return false;
+  }
+
+  [encoder generateMipmapsForTexture:texture_];
+  mipmap_generated_ = true;
+
+  return true;
+}
+
 }  // namespace impeller

impeller/renderer/backend/vulkan/blit_command_vk.cc

@@ -148,7 +148,7 @@ static void InsertImageMemoryBarrier(const vk::CommandBuffer& cmd,
 }
 
 bool BlitGenerateMipmapCommandVK::Encode(CommandEncoderVK& encoder) const {
-  const auto& src = TextureVK::Cast(*texture);
+  auto& src = TextureVK::Cast(*texture);
 
   const auto size = src.GetTextureDescriptor().size;
   uint32_t mip_count = src.GetTextureDescriptor().mip_count;
@@ -249,6 +249,7 @@ bool BlitGenerateMipmapCommandVK::Encode(CommandEncoderVK& encoder) const {
   // state so it doesn't try to perform redundant transitions under the hood.
   src.SetLayoutWithoutEncoding(vk::ImageLayout::eShaderReadOnlyOptimal);
 
+  src.SetMipmapGenerated();
   return true;
 }
 

impeller/renderer/backend/vulkan/render_pass_vk.cc

@@ -351,6 +351,12 @@ static bool UpdateDescriptorSets(vk::Device device,
     }
 
     auto texture = bindings.textures.at(index).resource;
+    if (texture->NeedsMipmapGeneration()) {
+      VALIDATION_LOG
+          << "Texture at binding index " << index
+          << " has a mip count > 1, but the mipmap has not been generated.";
+      return false;
+    }
     const auto& texture_vk = TextureVK::Cast(*texture);
     const SamplerVK& sampler = SamplerVK::Cast(*sampler_handle.resource);
 

impeller/renderer/backend/vulkan/texture_vk.cc

@@ -85,6 +85,10 @@ vk::ImageLayout TextureVK::GetLayout() const {
   return layout_;
 }
 
+void TextureVK::SetMipmapGenerated() {
+  mipmap_generated_ = true;
+}
+
 vk::ImageLayout TextureVK::SetLayoutWithoutEncoding(
     vk::ImageLayout layout) const {
   WriterLock lock(layout_mutex_);

impeller/renderer/backend/vulkan/texture_vk.h

@@ -36,6 +36,8 @@ class TextureVK final : public Texture, public BackendCast<TextureVK, Texture> {
 
   vk::ImageLayout GetLayout() const;
 
+  void SetMipmapGenerated();
+
  private:
   std::weak_ptr<Context> context_;
   std::shared_ptr<TextureSourceVK> source_;

impeller/renderer/texture.cc

@@ -73,4 +73,8 @@ Scalar Texture::GetYCoordScale() const {
   return 1.0;
 }
 
+bool Texture::NeedsMipmapGeneration() const {
+  return !mipmap_generated_ && desc_.mip_count > 1;
+}
+
 }  // namespace impeller

impeller/renderer/texture.h

@@ -41,6 +41,8 @@ class Texture {
 
   virtual Scalar GetYCoordScale() const;
 
+  bool NeedsMipmapGeneration() const;
+
  protected:
   explicit Texture(TextureDescriptor desc);
 
@@ -52,6 +54,8 @@ class Texture {
       std::shared_ptr<const fml::Mapping> mapping,
       size_t slice) = 0;
 
+  bool mipmap_generated_ = false;
+
  private:
   TextureIntent intent_ = TextureIntent::kRenderToTexture;
   const TextureDescriptor desc_;