Enable partial repaint for Android/OpenGL (flutter/engine#29591)

engine/src/flutter/shell/common/shell_test_platform_view_gl.cc

@@ -63,7 +63,9 @@ bool ShellTestPlatformViewGL::GLContextClearCurrent() {
 }
 
 // |GPUSurfaceGLDelegate|
-bool ShellTestPlatformViewGL::GLContextPresent(uint32_t fbo_id) {
+bool ShellTestPlatformViewGL::GLContextPresent(
+    uint32_t fbo_id,
+    const std::optional<SkIRect>& damage) {
   return gl_surface_.Present();
 }
 

engine/src/flutter/shell/common/shell_test_platform_view_gl.h

@@ -58,7 +58,8 @@ class ShellTestPlatformViewGL : public ShellTestPlatformView,
   bool GLContextClearCurrent() override;
 
   // |GPUSurfaceGLDelegate|
-  bool GLContextPresent(uint32_t fbo_id) override;
+  bool GLContextPresent(uint32_t fbo_id,
+                        const std::optional<SkIRect>& damage) override;
 
   // |GPUSurfaceGLDelegate|
   intptr_t GLContextFBO(GLFrameInfo frame_info) const override;

engine/src/flutter/shell/gpu/gpu_surface_gl.cc

@@ -242,7 +242,7 @@ std::unique_ptr<SurfaceFrame> GPUSurfaceGL::AcquireFrame(const SkISize& size) {
   SurfaceFrame::SubmitCallback submit_callback =
       [weak = weak_factory_.GetWeakPtr()](const SurfaceFrame& surface_frame,
                                           SkCanvas* canvas) {
-        return weak ? weak->PresentSurface(canvas) : false;
+        return weak ? weak->PresentSurface(surface_frame, canvas) : false;
       };
 
   framebuffer_info = delegate_->GLContextFramebufferInfo();
@@ -251,17 +251,19 @@ std::unique_ptr<SurfaceFrame> GPUSurfaceGL::AcquireFrame(const SkISize& size) {
                                         std::move(context_switch));
 }
 
-bool GPUSurfaceGL::PresentSurface(SkCanvas* canvas) {
+bool GPUSurfaceGL::PresentSurface(const SurfaceFrame& frame, SkCanvas* canvas) {
   if (delegate_ == nullptr || canvas == nullptr || context_ == nullptr) {
     return false;
   }
 
+  delegate_->GLContextSetDamageRegion(frame.submit_info().buffer_damage);
+
   {
     TRACE_EVENT0("flutter", "SkCanvas::Flush");
     onscreen_surface_->getCanvas()->flush();
   }
 
-  if (!delegate_->GLContextPresent(fbo_id_)) {
+  if (!delegate_->GLContextPresent(fbo_id_, frame.submit_info().frame_damage)) {
     return false;
   }
 

engine/src/flutter/shell/gpu/gpu_surface_gl.h

@@ -60,7 +60,7 @@ class GPUSurfaceGL : public Surface {
       const SkISize& untransformed_size,
       const SkMatrix& root_surface_transformation);
 
-  bool PresentSurface(SkCanvas* canvas);
+  bool PresentSurface(const SurfaceFrame& frame, SkCanvas* canvas);
 
   GPUSurfaceGLDelegate* delegate_;
   sk_sp<GrDirectContext> context_;

engine/src/flutter/shell/gpu/gpu_surface_gl_delegate.h

@@ -5,6 +5,8 @@
 #ifndef FLUTTER_SHELL_GPU_GPU_SURFACE_GL_DELEGATE_H_
 #define FLUTTER_SHELL_GPU_GPU_SURFACE_GL_DELEGATE_H_
 
+#include <optional>
+
 #include "flutter/common/graphics/gl_context_switch.h"
 #include "flutter/flow/embedded_views.h"
 #include "flutter/fml/macros.h"
@@ -31,9 +33,17 @@ class GPUSurfaceGLDelegate {
   // either the GPU or IO threads.
   virtual bool GLContextClearCurrent() = 0;
 
+  // Inform the GL Context that there's going to be no writing beyond
+  // the specified region
+  virtual void GLContextSetDamageRegion(const std::optional<SkIRect>& region) {}
+
   // Called to present the main GL surface. This is only called for the main GL
   // context and not any of the contexts dedicated for IO.
-  virtual bool GLContextPresent(uint32_t fbo_id) = 0;
+  //
+  // Damage is a hint to compositor telling it which parts of front buffer
+  // need to be updated
+  virtual bool GLContextPresent(uint32_t fbo_id,
+                                const std::optional<SkIRect>& damage) = 0;
 
   // The ID of the main window bound framebuffer. Typically FBO0.
   virtual intptr_t GLContextFBO(GLFrameInfo frame_info) const = 0;

engine/src/flutter/shell/platform/android/android_context_gl.cc

@@ -6,8 +6,12 @@
 
 #include <EGL/eglext.h>
 
+#include <list>
 #include <utility>
 
+// required to get API level
+#include <sys/system_properties.h>
+
 #include "flutter/fml/trace_event.h"
 
 namespace flutter {
@@ -105,10 +109,135 @@ static bool TeardownContext(EGLDisplay display, EGLContext context) {
   return true;
 }
 
+class AndroidEGLSurfaceDamage {
+ public:
+  void init(EGLDisplay display, EGLContext context) {
+    if (GetAPILevel() < 28) {
+      // Disable partial repaint for devices older than Android 9. There
+      // are old devices that have extensions below available but the
+      // implementation causes glitches (i.e. Xperia Z3 with Android 6).
+      partial_redraw_supported_ = false;
+      return;
+    }
+
+    const char* extensions = eglQueryString(display, EGL_EXTENSIONS);
+
+    if (HasExtension(extensions, "EGL_KHR_partial_update")) {
+      set_damage_region_ = reinterpret_cast<PFNEGLSETDAMAGEREGIONKHRPROC>(
+          eglGetProcAddress("eglSetDamageRegionKHR"));
+    }
+
+    if (HasExtension(extensions, "EGL_EXT_swap_buffers_with_damage")) {
+      swap_buffers_with_damage_ =
+          reinterpret_cast<PFNEGLSWAPBUFFERSWITHDAMAGEEXTPROC>(
+              eglGetProcAddress("eglSwapBuffersWithDamageEXT"));
+    } else if (HasExtension(extensions, "EGL_KHR_swap_buffers_with_damage")) {
+      swap_buffers_with_damage_ =
+          reinterpret_cast<PFNEGLSWAPBUFFERSWITHDAMAGEEXTPROC>(
+              eglGetProcAddress("eglSwapBuffersWithDamageKHR"));
+    }
+
+    partial_redraw_supported_ =
+        set_damage_region_ != nullptr && swap_buffers_with_damage_ != nullptr;
+  }
+
+  static int GetAPILevel() {
+    char sdk_version_string[PROP_VALUE_MAX];
+    if (__system_property_get("ro.build.version.sdk", sdk_version_string)) {
+      return atoi(sdk_version_string);
+    } else {
+      return -1;
+    }
+  }
+
+  void SetDamageRegion(EGLDisplay display,
+                       EGLSurface surface,
+                       const std::optional<SkIRect>& region) {
+    if (set_damage_region_ && region) {
+      auto rects = RectToInts(display, surface, *region);
+      set_damage_region_(display, surface, rects.data(), 1);
+    }
+  }
+
+  // Maximum damage history - for triple buffering we need to store damage for
+  // last two frames; Some Android devices (Pixel 4) use quad buffering.
+  static const int kMaxHistorySize = 10;
+
+  bool SupportsPartialRepaint() const { return partial_redraw_supported_; }
+
+  std::optional<SkIRect> InitialDamage(EGLDisplay display, EGLSurface surface) {
+    if (!partial_redraw_supported_) {
+      return std::nullopt;
+    }
+
+    EGLint age;
+    eglQuerySurface(display, surface, EGL_BUFFER_AGE_EXT, &age);
+
+    if (age == 0) {  // full repaint
+      return std::nullopt;
+    } else {
+      // join up to (age - 1) last rects from damage history
+      --age;
+      auto res = SkIRect::MakeEmpty();
+      for (auto i = damage_history_.rbegin();
+           i != damage_history_.rend() && age > 0; ++i, --age) {
+        res.join(*i);
+      }
+      return res;
+    }
+  }
+
+  bool SwapBuffersWithDamage(EGLDisplay display,
+                             EGLSurface surface,
+                             const std::optional<SkIRect>& damage) {
+    if (swap_buffers_with_damage_ && damage) {
+      damage_history_.push_back(*damage);
+      if (damage_history_.size() > kMaxHistorySize) {
+        damage_history_.pop_front();
+      }
+      auto rects = RectToInts(display, surface, *damage);
+      return swap_buffers_with_damage_(display, surface, rects.data(), 1);
+    } else {
+      return eglSwapBuffers(display, surface);
+    }
+  }
+
+ private:
+  std::array<EGLint, 4> static RectToInts(EGLDisplay display,
+                                          EGLSurface surface,
+                                          const SkIRect& rect) {
+    EGLint height;
+    eglQuerySurface(display, surface, EGL_HEIGHT, &height);
+
+    std::array<EGLint, 4> res{rect.left(), height - rect.bottom(), rect.width(),
+                              rect.height()};
+    return res;
+  }
+
+  PFNEGLSETDAMAGEREGIONKHRPROC set_damage_region_ = nullptr;
+  PFNEGLSWAPBUFFERSWITHDAMAGEEXTPROC swap_buffers_with_damage_ = nullptr;
+
+  bool partial_redraw_supported_;
+
+  bool HasExtension(const char* extensions, const char* name) {
+    const char* r = strstr(extensions, name);
+    auto len = strlen(name);
+    // check that the extension name is terminated by space or null terminator
+    return r != nullptr && (r[len] == ' ' || r[len] == 0);
+  }
+
+  std::list<SkIRect> damage_history_;
+};
+
 AndroidEGLSurface::AndroidEGLSurface(EGLSurface surface,
                                      EGLDisplay display,
                                      EGLContext context)
-    : surface_(surface), display_(display), context_(context) {}
+    : surface_(surface),
+      display_(display),
+      context_(context),
+      damage_(std::make_unique<AndroidEGLSurfaceDamage>()) {
+  damage_->init(display_, context);
+}
 
 AndroidEGLSurface::~AndroidEGLSurface() {
   auto result = eglDestroySurface(display_, surface_);
@@ -128,9 +257,23 @@ bool AndroidEGLSurface::MakeCurrent() const {
   return true;
 }
 
-bool AndroidEGLSurface::SwapBuffers() {
+void AndroidEGLSurface::SetDamageRegion(
+    const std::optional<SkIRect>& buffer_damage) {
+  damage_->SetDamageRegion(display_, surface_, buffer_damage);
+}
+
+bool AndroidEGLSurface::SwapBuffers(
+    const std::optional<SkIRect>& surface_damage) {
   TRACE_EVENT0("flutter", "AndroidContextGL::SwapBuffers");
-  return eglSwapBuffers(display_, surface_);
+  return damage_->SwapBuffersWithDamage(display_, surface_, surface_damage);
+}
+
+bool AndroidEGLSurface::SupportsPartialRepaint() const {
+  return damage_->SupportsPartialRepaint();
+}
+
+std::optional<SkIRect> AndroidEGLSurface::InitialDamage() {
+  return damage_->InitialDamage(display_, surface_);
 }
 
 SkISize AndroidEGLSurface::GetSize() const {

engine/src/flutter/shell/platform/android/android_context_gl.h

@@ -23,6 +23,8 @@ namespace flutter {
 /// This can be used in conjunction to unique_ptr to provide better guarantees
 /// about the lifespan of the `EGLSurface` object.
 ///
+class AndroidEGLSurfaceDamage;
+
 class AndroidEGLSurface {
  public:
   AndroidEGLSurface(EGLSurface surface, EGLDisplay display, EGLContext context);
@@ -43,13 +45,35 @@ class AndroidEGLSurface {
   ///
   bool MakeCurrent() const;
 
+  //----------------------------------------------------------------------------
+  ///
+  /// @return     Whether target surface supports partial repaint.
+  ///
+  bool SupportsPartialRepaint() const;
+
+  //----------------------------------------------------------------------------
+  /// @brief      This is the minimal area that needs to be repainted to get
+  ///             correct result.
+  ///
+  /// With double or triple buffering this buffer content may lag behind
+  /// current front buffer and the rect accounts for accumulated damage.
+  ///
+  /// @return     The area of current surface where it is behind front buffer.
+  ///
+  std::optional<SkIRect> InitialDamage();
+
+  //----------------------------------------------------------------------------
+  /// @brief      Sets the damage region for current surface. Corresponds to
+  //              eglSetDamageRegionKHR
+  void SetDamageRegion(const std::optional<SkIRect>& buffer_damage);
+
   //----------------------------------------------------------------------------
   /// @brief      This only applies to on-screen surfaces such as those created
   ///             by `AndroidContextGL::CreateOnscreenSurface`.
   ///
   /// @return     Whether the EGL surface color buffer was swapped.
   ///
-  bool SwapBuffers();
+  bool SwapBuffers(const std::optional<SkIRect>& surface_damage);
 
   //----------------------------------------------------------------------------
   /// @return     The size of an `EGLSurface`.
@@ -60,6 +84,7 @@ class AndroidEGLSurface {
   const EGLSurface surface_;
   const EGLDisplay display_;
   const EGLContext context_;
+  std::unique_ptr<AndroidEGLSurfaceDamage> damage_;
 };
 
 //------------------------------------------------------------------------------

engine/src/flutter/shell/platform/android/android_surface_gl.cc

@@ -126,10 +126,27 @@ bool AndroidSurfaceGL::GLContextClearCurrent() {
   return GLContextPtr()->ClearCurrent();
 }
 
-bool AndroidSurfaceGL::GLContextPresent(uint32_t fbo_id) {
+SurfaceFrame::FramebufferInfo AndroidSurfaceGL::GLContextFramebufferInfo()
+    const {
+  FML_DCHECK(IsValid());
+  SurfaceFrame::FramebufferInfo res;
+  res.supports_readback = true;
+  res.supports_partial_repaint = onscreen_surface_->SupportsPartialRepaint();
+  res.existing_damage = onscreen_surface_->InitialDamage();
+  return res;
+}
+
+void AndroidSurfaceGL::GLContextSetDamageRegion(
+    const std::optional<SkIRect>& region) {
+  FML_DCHECK(IsValid());
+  onscreen_surface_->SetDamageRegion(region);
+}
+
+bool AndroidSurfaceGL::GLContextPresent(uint32_t fbo_id,
+                                        const std::optional<SkIRect>& damage) {
   FML_DCHECK(IsValid());
   FML_DCHECK(onscreen_surface_);
-  return onscreen_surface_->SwapBuffers();
+  return onscreen_surface_->SwapBuffers(damage);
 }
 
 intptr_t AndroidSurfaceGL::GLContextFBO(GLFrameInfo frame_info) const {

engine/src/flutter/shell/platform/android/android_surface_gl.h

@@ -58,7 +58,14 @@ class AndroidSurfaceGL final : public GPUSurfaceGLDelegate,
   bool GLContextClearCurrent() override;
 
   // |GPUSurfaceGLDelegate|
-  bool GLContextPresent(uint32_t fbo_id) override;
+  SurfaceFrame::FramebufferInfo GLContextFramebufferInfo() const override;
+
+  // |GPUSurfaceGLDelegate|
+  void GLContextSetDamageRegion(const std::optional<SkIRect>& region) override;
+
+  // |GPUSurfaceGLDelegate|
+  bool GLContextPresent(uint32_t fbo_id,
+                        const std::optional<SkIRect>& damage) override;
 
   // |GPUSurfaceGLDelegate|
   intptr_t GLContextFBO(GLFrameInfo frame_info) const override;

engine/src/flutter/shell/platform/android/surface/android_surface_mock.cc

@@ -18,7 +18,9 @@ bool AndroidSurfaceMock::GLContextClearCurrent() {
   return true;
 }
 
-bool AndroidSurfaceMock::GLContextPresent(uint32_t fbo_id) {
+bool AndroidSurfaceMock::GLContextPresent(
+    uint32_t fbo_id,
+    const std::optional<SkIRect>& damage) {
   return true;
 }
 

engine/src/flutter/shell/platform/android/surface/android_surface_mock.h

@@ -48,7 +48,8 @@ class AndroidSurfaceMock final : public GPUSurfaceGLDelegate,
   bool GLContextClearCurrent() override;
 
   // |GPUSurfaceGLDelegate|
-  bool GLContextPresent(uint32_t fbo_id) override;
+  bool GLContextPresent(uint32_t fbo_id,
+                        const std::optional<SkIRect>& damage) override;
 
   // |GPUSurfaceGLDelegate|
   intptr_t GLContextFBO(GLFrameInfo frame_info) const override;

engine/src/flutter/shell/platform/darwin/ios/ios_surface_gl.h

@@ -38,7 +38,7 @@ class IOSSurfaceGL final : public IOSSurface, public GPUSurfaceGLDelegate {
   bool GLContextClearCurrent() override;
 
   // |GPUSurfaceGLDelegate|
-  bool GLContextPresent(uint32_t fbo_id) override;
+  bool GLContextPresent(uint32_t fbo_id, const std::optional<SkIRect>& damage) override;
 
   // |GPUSurfaceGLDelegate|
   intptr_t GLContextFBO(GLFrameInfo frame_info) const override;

engine/src/flutter/shell/platform/darwin/ios/ios_surface_gl.mm

@@ -86,7 +86,7 @@ bool IOSSurfaceGL::GLContextClearCurrent() {
 }
 
 // |GPUSurfaceGLDelegate|
-bool IOSSurfaceGL::GLContextPresent(uint32_t fbo_id) {
+bool IOSSurfaceGL::GLContextPresent(uint32_t fbo_id, const std::optional<SkIRect>& damage) {
   TRACE_EVENT0("flutter", "IOSSurfaceGL::GLContextPresent");
   return IsValid() && render_target_->PresentRenderBuffer();
 }

engine/src/flutter/shell/platform/embedder/embedder_surface_gl.cc

@@ -45,7 +45,8 @@ bool EmbedderSurfaceGL::GLContextClearCurrent() {
 }
 
 // |GPUSurfaceGLDelegate|
-bool EmbedderSurfaceGL::GLContextPresent(uint32_t fbo_id) {
+bool EmbedderSurfaceGL::GLContextPresent(uint32_t fbo_id,
+                                         const std::optional<SkIRect>& damage) {
   return gl_dispatch_table_.gl_present_callback(fbo_id);
 }
 

engine/src/flutter/shell/platform/embedder/embedder_surface_gl.h

@@ -56,7 +56,8 @@ class EmbedderSurfaceGL final : public EmbedderSurface,
   bool GLContextClearCurrent() override;
 
   // |GPUSurfaceGLDelegate|
-  bool GLContextPresent(uint32_t fbo_id) override;
+  bool GLContextPresent(uint32_t fbo_id,
+                        const std::optional<SkIRect>& damage) override;
 
   // |GPUSurfaceGLDelegate|
   intptr_t GLContextFBO(GLFrameInfo frame_info) const override;