Improve performance of unclipped save layers.

Instead of allocating a separate renderTarget and switching
between them on each draw the new implementation follows the same
pattern that the old HWUI renderer used. The area of the layer is
now copied to a buffer on the GPU, the area is then cleared, rendered
as normal, and finally the texture is redrawn using dst_over blending.

This results in no render target switches and is considerably faster
on some hardware.

Test: CtsGraphicsTestCases, CtsUiRenderingTestCases
Bug: 119222339
Change-Id: I716aac1fc31e4c7a171373d37dee82034c01cf18

core/jni/android_graphics_Canvas.cpp

@@ -102,6 +102,10 @@ static jint saveLayerAlpha(jlong canvasHandle, jfloat l, jfloat t,
     return static_cast<jint>(get_canvas(canvasHandle)->saveLayerAlpha(l, t, r, b, alpha, flags));
 }
 
+static jint saveUnclippedLayer(jlong canvasHandle, jint l, jint t, jint r, jint b) {
+    return reinterpret_cast<jint>(get_canvas(canvasHandle)->saveUnclippedLayer(l, t, r, b));
+}
+
 static bool restore(jlong canvasHandle) {
     Canvas* canvas = get_canvas(canvasHandle);
     if (canvas->getSaveCount() <= 1) {
@@ -651,6 +655,7 @@ static const JNINativeMethod gMethods[] = {
     {"nSave","(JI)I", (void*) CanvasJNI::save},
     {"nSaveLayer","(JFFFFJI)I", (void*) CanvasJNI::saveLayer},
     {"nSaveLayerAlpha","(JFFFFII)I", (void*) CanvasJNI::saveLayerAlpha},
+    {"nSaveUnclippedLayer","(JIIII)I", (void*) CanvasJNI::saveUnclippedLayer},
     {"nGetSaveCount","(J)I", (void*) CanvasJNI::getSaveCount},
     {"nRestore","(J)Z", (void*) CanvasJNI::restore},
     {"nRestoreToCount","(JI)V", (void*) CanvasJNI::restoreToCount},

graphics/java/android/graphics/Canvas.java

@@ -556,7 +556,7 @@ public class Canvas extends BaseCanvas {
      * @hide
      */
     public int saveUnclippedLayer(int left, int top, int right, int bottom) {
-        return nSaveLayer(mNativeCanvasWrapper, left, top, right, bottom, 0, 0);
+        return nSaveUnclippedLayer(mNativeCanvasWrapper, left, top, right, bottom);
     }
 
     /**
@@ -1395,6 +1395,8 @@ public class Canvas extends BaseCanvas {
     private static native int nSaveLayerAlpha(long nativeCanvas, float l, float t, float r, float b,
             int alpha, int layerFlags);
     @CriticalNative
+    private static native int nSaveUnclippedLayer(long nativeCanvas, int l, int t, int r, int b);
+    @CriticalNative
     private static native boolean nRestore(long canvasHandle);
     @CriticalNative
     private static native void nRestoreToCount(long canvasHandle, int saveCount);

libs/hwui/DisplayListOps.in

@@ -18,6 +18,7 @@ X(Flush)
 X(Save) 
 X(Restore) 
 X(SaveLayer)
+X(SaveBehind)
 X(Concat) 
 X(SetMatrix) 
 X(Translate)

libs/hwui/RecordingCanvas.cpp

@@ -18,6 +18,7 @@
 
 #include "VectorDrawable.h"
 
+#include "SkAndroidFrameworkUtils.h"
 #include "SkCanvas.h"
 #include "SkData.h"
 #include "SkDrawShadowInfo.h"
@@ -116,6 +117,16 @@ struct SaveLayer final : Op {
                       clipMatrix.isIdentity() ? nullptr : &clipMatrix, flags});
     }
 };
+struct SaveBehind final : Op {
+    static const auto kType = Type::SaveBehind;
+    SaveBehind(const SkRect* subset) {
+        if (subset) { this->subset = *subset; }
+    }
+    SkRect  subset = kUnset;
+    void draw(SkCanvas* c, const SkMatrix&) const {
+        SkAndroidFrameworkUtils::SaveBehind(c, &subset);
+    }
+};
 
 struct Concat final : Op {
     static const auto kType = Type::Concat;
@@ -579,6 +590,10 @@ void DisplayListData::saveLayer(const SkRect* bounds, const SkPaint* paint,
     this->push<SaveLayer>(0, bounds, paint, backdrop, clipMask, clipMatrix, flags);
 }
 
+void DisplayListData::saveBehind(const SkRect* subset) {
+    this->push<SaveBehind>(0, subset);
+}
+
 void DisplayListData::concat(const SkMatrix& matrix) {
     this->push<Concat>(0, matrix);
 }
@@ -848,6 +863,11 @@ void RecordingCanvas::willRestore() {
     fDL->restore();
 }
 
+bool RecordingCanvas::onDoSaveBehind(const SkRect* subset) {
+    fDL->saveBehind(subset);
+    return false;
+}
+
 void RecordingCanvas::didConcat(const SkMatrix& matrix) {
     fDL->concat(matrix);
 }

libs/hwui/RecordingCanvas.h

@@ -75,6 +75,7 @@ private:
     void save();
     void saveLayer(const SkRect*, const SkPaint*, const SkImageFilter*, const SkImage*,
                    const SkMatrix*, SkCanvas::SaveLayerFlags);
+    void saveBehind(const SkRect*);
     void restore();
 
     void concat(const SkMatrix&);
@@ -146,6 +147,7 @@ public:
     void willSave() override;
     SaveLayerStrategy getSaveLayerStrategy(const SaveLayerRec&) override;
     void willRestore() override;
+    bool onDoSaveBehind(const SkRect*) override;
 
     void onFlush() override;
 

libs/hwui/SkiaCanvas.cpp

@@ -24,6 +24,7 @@
 #include "hwui/PaintFilter.h"
 #include "pipeline/skia/AnimatedDrawables.h"
 
+#include <SkAndroidFrameworkUtils.h>
 #include <SkAnimatedImage.h>
 #include <SkCanvasStateUtils.h>
 #include <SkColorFilter.h>
@@ -185,6 +186,11 @@ int SkiaCanvas::saveLayerAlpha(float left, float top, float right, float bottom,
     return this->saveLayer(left, top, right, bottom, nullptr, flags);
 }
 
+int SkiaCanvas::saveUnclippedLayer(int left, int top, int right, int bottom) {
+    SkRect bounds = SkRect::MakeLTRB(left, top, right, bottom);
+    return SkAndroidFrameworkUtils::SaveBehind(mCanvas, &bounds);
+}
+
 class SkiaCanvas::Clip {
 public:
     Clip(const SkRect& rect, SkClipOp op, const SkMatrix& m)

libs/hwui/SkiaCanvas.h

@@ -74,6 +74,7 @@ public:
                           SaveFlags::Flags flags) override;
     virtual int saveLayerAlpha(float left, float top, float right, float bottom, int alpha,
                                SaveFlags::Flags flags) override;
+    virtual int saveUnclippedLayer(int left, int top, int right, int bottom) override;
 
     virtual void getMatrix(SkMatrix* outMatrix) const override;
     virtual void setMatrix(const SkMatrix& matrix) override;

libs/hwui/hwui/Canvas.h

@@ -196,6 +196,7 @@ public:
                           SaveFlags::Flags flags) = 0;
     virtual int saveLayerAlpha(float left, float top, float right, float bottom, int alpha,
                                SaveFlags::Flags flags) = 0;
+    virtual int saveUnclippedLayer(int, int, int, int) = 0;
 
     // Matrix
     virtual void getMatrix(SkMatrix* outMatrix) const = 0;