Reland: [Impeller] Use a device buffer for SkBitmap allocation, use Linear texture on Metal backend. (#41538)

Original PR: #41374

This was reverted because it broke on simulators as they do not support linear textures. To fix this, I've ifdef'd out the DeviceBufferMTL implementation of AsTexture so that it falls back to the slow path copy. Also updated the capabilities check so that the glyph atlas updates the texture contents when it changes.

Author: Jonah Williams

impeller/renderer/backend/metal/context_mtl.mm

@@ -45,6 +45,14 @@ static bool DeviceSupportsComputeSubgroups(id<MTLDevice> device) {
   return supports_subgroups;
 }
 
+static constexpr bool SupportsLinearTexture() {
+#ifdef FML_OS_IOS_SIMULATOR
+  return false;
+#else
+  return true;
+#endif  // FML_OS_IOS_SIMULATOR
+}
+
 static std::unique_ptr<Capabilities> InferMetalCapabilities(
     id<MTLDevice> device,
     PixelFormat color_format) {
@@ -55,6 +63,7 @@ static bool DeviceSupportsComputeSubgroups(id<MTLDevice> device) {
       .SetSupportsBufferToTextureBlits(true)
       .SetSupportsTextureToTextureBlits(true)
       .SetSupportsDecalTileMode(true)
+      .SetSupportsSharedDeviceBufferTextureMemory(SupportsLinearTexture())
       .SetSupportsFramebufferFetch(DeviceSupportsFramebufferFetch(device))
       .SetDefaultColorFormat(color_format)
       .SetDefaultStencilFormat(PixelFormat::kS8UInt)

impeller/renderer/backend/metal/device_buffer_mtl.h

@@ -35,10 +35,12 @@ class DeviceBufferMTL final : public DeviceBuffer,
   // |DeviceBuffer|
   uint8_t* OnGetContents() const override;
 
+#ifndef FML_OS_IOS_SIMULATOR
   // |DeviceBuffer|
   std::shared_ptr<Texture> AsTexture(Allocator& allocator,
                                      const TextureDescriptor& descriptor,
                                      uint16_t row_bytes) const override;
+#endif  // FML_OS_IOS_SIMULATOR
 
   // |DeviceBuffer|
   bool OnCopyHostBuffer(const uint8_t* source,

impeller/renderer/backend/metal/device_buffer_mtl.mm

@@ -29,6 +29,7 @@
   return reinterpret_cast<uint8_t*>(buffer_.contents);
 }
 
+#ifndef FML_OS_IOS_SIMULATOR
 std::shared_ptr<Texture> DeviceBufferMTL::AsTexture(
     Allocator& allocator,
     const TextureDescriptor& descriptor,
@@ -52,6 +53,7 @@
   }
   return std::make_shared<TextureMTL>(descriptor, texture);
 }
+#endif  // FML_OS_IOS_SIMULATOR
 
 [[nodiscard]] bool DeviceBufferMTL::OnCopyHostBuffer(const uint8_t* source,
                                                      Range source_range,

impeller/renderer/backend/vulkan/capabilities_vk.cc

@@ -348,10 +348,16 @@ bool CapabilitiesVK::SupportsReadFromOnscreenTexture() const {
   return false;
 }
 
+// |Capabilities|
 bool CapabilitiesVK::SupportsDecalTileMode() const {
   return true;
 }
 
+// |Capabilities|
+bool CapabilitiesVK::SupportsSharedDeviceBufferTextureMemory() const {
+  return false;
+}
+
 // |Capabilities|
 PixelFormat CapabilitiesVK::GetDefaultColorFormat() const {
   return color_format_;

impeller/renderer/backend/vulkan/capabilities_vk.h

@@ -79,6 +79,9 @@ class CapabilitiesVK final : public Capabilities,
   // |Capabilities|
   bool SupportsDecalTileMode() const override;
 
+  // |Capabilities|
+  bool SupportsSharedDeviceBufferTextureMemory() const override;
+
   // |Capabilities|
   PixelFormat GetDefaultColorFormat() const override;
 

impeller/renderer/capabilities.cc

@@ -66,6 +66,11 @@ class StandardCapabilities final : public Capabilities {
     return supports_decal_tile_mode_;
   }
 
+  // |Capabilities|
+  bool SupportsSharedDeviceBufferTextureMemory() const override {
+    return supports_shared_device_buffer_texture_memory_;
+  }
+
   // |Capabilities|
   PixelFormat GetDefaultColorFormat() const override {
     return default_color_format_;
@@ -88,6 +93,7 @@ class StandardCapabilities final : public Capabilities {
                        bool supports_read_from_onscreen_texture,
                        bool supports_read_from_resolve,
                        bool supports_decal_tile_mode,
+                       bool supports_shared_device_buffer_texture_memory,
                        PixelFormat default_color_format,
                        PixelFormat default_stencil_format)
       : has_threading_restrictions_(has_threading_restrictions),
@@ -102,6 +108,8 @@ class StandardCapabilities final : public Capabilities {
             supports_read_from_onscreen_texture),
         supports_read_from_resolve_(supports_read_from_resolve),
         supports_decal_tile_mode_(supports_decal_tile_mode),
+        supports_shared_device_buffer_texture_memory_(
+            supports_shared_device_buffer_texture_memory),
         default_color_format_(default_color_format),
         default_stencil_format_(default_stencil_format) {}
 
@@ -118,6 +126,7 @@ class StandardCapabilities final : public Capabilities {
   bool supports_read_from_onscreen_texture_ = false;
   bool supports_read_from_resolve_ = false;
   bool supports_decal_tile_mode_ = false;
+  bool supports_shared_device_buffer_texture_memory_ = false;
   PixelFormat default_color_format_ = PixelFormat::kUnknown;
   PixelFormat default_stencil_format_ = PixelFormat::kUnknown;
 
@@ -202,6 +211,12 @@ CapabilitiesBuilder& CapabilitiesBuilder::SetSupportsDecalTileMode(bool value) {
   return *this;
 }
 
+CapabilitiesBuilder&
+CapabilitiesBuilder::SetSupportsSharedDeviceBufferTextureMemory(bool value) {
+  supports_shared_device_buffer_texture_memory_ = value;
+  return *this;
+}
+
 std::unique_ptr<Capabilities> CapabilitiesBuilder::Build() {
   return std::unique_ptr<StandardCapabilities>(new StandardCapabilities(  //
       has_threading_restrictions_,                                        //
@@ -215,6 +230,7 @@ std::unique_ptr<Capabilities> CapabilitiesBuilder::Build() {
       supports_read_from_onscreen_texture_,                               //
       supports_read_from_resolve_,                                        //
       supports_decal_tile_mode_,                                          //
+      supports_shared_device_buffer_texture_memory_,                      //
       *default_color_format_,                                             //
       *default_stencil_format_                                            //
       ));

impeller/renderer/capabilities.h

@@ -37,6 +37,8 @@ class Capabilities {
 
   virtual bool SupportsDecalTileMode() const = 0;
 
+  virtual bool SupportsSharedDeviceBufferTextureMemory() const = 0;
+
   virtual PixelFormat GetDefaultColorFormat() const = 0;
 
   virtual PixelFormat GetDefaultStencilFormat() const = 0;
@@ -79,6 +81,8 @@ class CapabilitiesBuilder {
 
   CapabilitiesBuilder& SetSupportsDecalTileMode(bool value);
 
+  CapabilitiesBuilder& SetSupportsSharedDeviceBufferTextureMemory(bool value);
+
   std::unique_ptr<Capabilities> Build();
 
  private:
@@ -93,6 +97,7 @@ class CapabilitiesBuilder {
   bool supports_read_from_onscreen_texture_ = false;
   bool supports_read_from_resolve_ = false;
   bool supports_decal_tile_mode_ = false;
+  bool supports_shared_device_buffer_texture_memory_ = false;
   std::optional<PixelFormat> default_color_format_ = std::nullopt;
   std::optional<PixelFormat> default_stencil_format_ = std::nullopt;
 

impeller/renderer/capabilities_unittests.cc

@@ -29,6 +29,7 @@ CAPABILITY_TEST(SupportsComputeSubgroups, false);
 CAPABILITY_TEST(SupportsReadFromOnscreenTexture, false);
 CAPABILITY_TEST(SupportsReadFromResolve, false);
 CAPABILITY_TEST(SupportsDecalTileMode, false);
+CAPABILITY_TEST(SupportsSharedDeviceBufferTextureMemory, false);
 
 }  // namespace testing
 }  // namespace impeller