Update RenderEngine blur to snap an image of the full surface.

Snapping a subregion of a surface causes Skia's GPU surfaces to make
a copy of the pixels into a new buffer so that the dimensions of the
buffer match the requested size. By requesting a basic snapshot this
CL avoids any uncessary framebuffer copies.

Also refactor the code to start consolidating where blurs are used.

Test: tracing SysUI blurs
Bug: 176903027
Change-Id: I72a9e442e50bc6d945c601efca1fdd2ce7cdfcd1
diff --git a/libs/renderengine/skia/SkiaGLRenderEngine.cpp b/libs/renderengine/skia/SkiaGLRenderEngine.cpp
index 1eb8da9..fcb3196 100644
--- a/libs/renderengine/skia/SkiaGLRenderEngine.cpp
+++ b/libs/renderengine/skia/SkiaGLRenderEngine.cpp
@@ -661,30 +661,33 @@
         // Layers have a local transform that should be applied to them
         canvas->concat(getSkM44(layer->geometry.positionTransform).asM33());
 
-        SkPaint paint;
-        const auto& bounds = layer->geometry.boundaries;
-        const auto dest = getSkRect(bounds);
-        const auto layerRect = canvas->getTotalMatrix().mapRect(dest);
-        std::unordered_map<uint32_t, sk_sp<SkImage>> cachedBlurs;
-        if (mBlurFilter) {
+        const auto bounds = getSkRect(layer->geometry.boundaries);
+        if (mBlurFilter && layerHasBlur(layer)) {
+            std::unordered_map<uint32_t, sk_sp<SkImage>> cachedBlurs;
+
+            // image to be blurred
+            sk_sp<SkImage> blurInput = surface->makeImageSnapshot();
+            // rect to be blurred in the coordinate space of blurInput
+            const auto blurRect = canvas->getTotalMatrix().mapRect(bounds);
+
             if (layer->backgroundBlurRadius > 0) {
                 ATRACE_NAME("BackgroundBlur");
-                auto blurredSurface = mBlurFilter->generate(canvas, surface,
-                                                            layer->backgroundBlurRadius, layerRect);
-                cachedBlurs[layer->backgroundBlurRadius] = blurredSurface;
+                auto blurredImage =
+                        mBlurFilter->generate(grContext.get(), layer->backgroundBlurRadius,
+                                              blurInput, blurRect);
 
-                drawBlurRegion(canvas, getBlurRegion(layer), layerRect, blurredSurface);
+                cachedBlurs[layer->backgroundBlurRadius] = blurredImage;
+
+                drawBlurRegion(canvas, getBlurRegion(layer), blurRect, blurredImage);
             }
-            if (layer->blurRegions.size() > 0) {
-                for (auto region : layer->blurRegions) {
-                    if (cachedBlurs[region.blurRadius]) {
-                        continue;
-                    }
+            for (auto region : layer->blurRegions) {
+                if (cachedBlurs[region.blurRadius] != nullptr) {
                     ATRACE_NAME("BlurRegion");
-                    auto blurredSurface =
-                            mBlurFilter->generate(canvas, surface, region.blurRadius, layerRect);
-                    cachedBlurs[region.blurRadius] = blurredSurface;
+                    cachedBlurs[region.blurRadius] =
+                            mBlurFilter->generate(grContext.get(), region.blurRadius, blurInput,
+                                                  blurRect);
                 }
+                drawBlurRegion(canvas, region, blurRect, cachedBlurs[region.blurRadius]);
             }
         }
 
@@ -698,6 +701,7 @@
                            : layer->sourceDataspace)
                 : ui::Dataspace::UNKNOWN;
 
+        SkPaint paint;
         if (layer->source.buffer.buffer) {
             ATRACE_NAME("DrawImage");
             const auto& item = layer->source.buffer;
@@ -724,7 +728,7 @@
             // textureTansform was intended to be passed directly into a shader, so when
             // building the total matrix with the textureTransform we need to first
             // normalize it, then apply the textureTransform, then scale back up.
-            texMatrix.preScale(1.0f / bounds.getWidth(), 1.0f / bounds.getHeight());
+            texMatrix.preScale(1.0f / bounds.width(), 1.0f / bounds.height());
             texMatrix.postScale(image->width(), image->height());
 
             SkMatrix matrix;
@@ -794,14 +798,10 @@
 
         paint.setColorFilter(filter);
 
-        for (const auto effectRegion : layer->blurRegions) {
-            drawBlurRegion(canvas, effectRegion, layerRect, cachedBlurs[effectRegion.blurRadius]);
-        }
-
         if (layer->shadow.length > 0) {
             const auto rect = layer->geometry.roundedCornersRadius > 0
                     ? getSkRect(layer->geometry.roundedCornersCrop)
-                    : dest;
+                    : bounds;
             drawShadow(canvas, rect, layer->geometry.roundedCornersRadius, layer->shadow);
         } else {
             // Shadows are assumed to live only on their own layer - it's not valid
@@ -812,7 +812,7 @@
             if (layer->geometry.roundedCornersRadius > 0) {
                 canvas->clipRRect(getRoundedRect(layer), true);
             }
-            canvas->drawRect(dest, paint);
+            canvas->drawRect(bounds, paint);
         }
         canvas->restore();
     }
@@ -877,6 +877,10 @@
                       .bottom = static_cast<int>(rect.fBottom)};
 }
 
+inline bool SkiaGLRenderEngine::layerHasBlur(const LayerSettings* layer) {
+    return layer->backgroundBlurRadius > 0 || layer->blurRegions.size();
+}
+
 inline SkColor SkiaGLRenderEngine::getSkColor(const vec4& color) {
     return SkColorSetARGB(color.a * 255, color.r * 255, color.g * 255, color.b * 255);
 }
diff --git a/libs/renderengine/skia/SkiaGLRenderEngine.h b/libs/renderengine/skia/SkiaGLRenderEngine.h
index 810fc2a..4f4a9d4 100644
--- a/libs/renderengine/skia/SkiaGLRenderEngine.h
+++ b/libs/renderengine/skia/SkiaGLRenderEngine.h
@@ -81,6 +81,7 @@
     inline SkRect getSkRect(const Rect& layer);
     inline SkRRect getRoundedRect(const LayerSettings* layer);
     inline BlurRegion getBlurRegion(const LayerSettings* layer);
+    inline bool layerHasBlur(const LayerSettings* layer);
     inline SkColor getSkColor(const vec4& color);
     inline SkM44 getSkM44(const mat4& matrix);
     inline SkPoint3 getSkPoint3(const vec3& vector);
diff --git a/libs/renderengine/skia/filters/BlurFilter.cpp b/libs/renderengine/skia/filters/BlurFilter.cpp
index 87b1a7c..0d123c7 100644
--- a/libs/renderengine/skia/filters/BlurFilter.cpp
+++ b/libs/renderengine/skia/filters/BlurFilter.cpp
@@ -34,17 +34,14 @@
 BlurFilter::BlurFilter() {
     SkString blurString(R"(
         in shader input;
-        uniform float in_inverseScale;
         uniform float2 in_blurOffset;
 
         half4 main(float2 xy) {
-            float2 scaled_xy = float2(xy.x * in_inverseScale, xy.y * in_inverseScale);
-
-            half4 c = sample(input, scaled_xy);
-            c += sample(input, scaled_xy + float2( in_blurOffset.x,  in_blurOffset.y));
-            c += sample(input, scaled_xy + float2( in_blurOffset.x, -in_blurOffset.y));
-            c += sample(input, scaled_xy + float2(-in_blurOffset.x,  in_blurOffset.y));
-            c += sample(input, scaled_xy + float2(-in_blurOffset.x, -in_blurOffset.y));
+            half4 c = sample(input, xy);
+            c += sample(input, xy + float2( in_blurOffset.x,  in_blurOffset.y));
+            c += sample(input, xy + float2( in_blurOffset.x, -in_blurOffset.y));
+            c += sample(input, xy + float2(-in_blurOffset.x,  in_blurOffset.y));
+            c += sample(input, xy + float2(-in_blurOffset.x, -in_blurOffset.y));
 
             return half4(c.rgb * 0.2, 1.0);
         }
@@ -57,8 +54,8 @@
     mBlurEffect = std::move(blurEffect);
 }
 
-sk_sp<SkImage> BlurFilter::generate(SkCanvas* canvas, const sk_sp<SkSurface> input,
-                                    const uint32_t blurRadius, SkRect rect) const {
+sk_sp<SkImage> BlurFilter::generate(GrRecordingContext* context, const uint32_t blurRadius,
+                                    const sk_sp<SkImage> input, const SkRect& blurRect) const {
     // Kawase is an approximation of Gaussian, but it behaves differently from it.
     // A radius transformation is required for approximating them, and also to introduce
     // non-integer steps, necessary to smoothly interpolate large radii.
@@ -66,33 +63,35 @@
     float numberOfPasses = std::min(kMaxPasses, (uint32_t)ceil(tmpRadius));
     float radiusByPasses = tmpRadius / (float)numberOfPasses;
 
-    SkImageInfo scaledInfo = SkImageInfo::MakeN32Premul((float)rect.width() * kInputScale,
-                                                        (float)rect.height() * kInputScale);
+    // create blur surface with the bit depth and colorspace of the original surface
+    SkImageInfo scaledInfo = input->imageInfo().makeWH(blurRect.width() * kInputScale,
+                                                       blurRect.height() * kInputScale);
 
     const float stepX = radiusByPasses;
     const float stepY = radiusByPasses;
 
-    // start by drawing and downscaling and doing the first blur pass
+    // For sampling Skia's API expects the inverse of what logically seems appropriate. In this
+    // case you might expect Translate(blurRect.fLeft, blurRect.fTop) X Scale(kInverseInputScale)
+    // but instead we must do the inverse.
+    SkMatrix blurMatrix = SkMatrix::Translate(-blurRect.fLeft, -blurRect.fTop);
+    blurMatrix.postScale(kInputScale, kInputScale);
+
+    // start by downscaling and doing the first blur pass
     SkSamplingOptions linear(SkFilterMode::kLinear, SkMipmapMode::kNone);
     SkRuntimeShaderBuilder blurBuilder(mBlurEffect);
     blurBuilder.child("input") =
-            input->makeImageSnapshot(rect.round())
-                    ->makeShader(SkTileMode::kClamp, SkTileMode::kClamp, linear);
-    blurBuilder.uniform("in_inverseScale") = kInverseInputScale;
-    blurBuilder.uniform("in_blurOffset") =
-            SkV2{stepX * kInverseInputScale, stepY * kInverseInputScale};
+            input->makeShader(SkTileMode::kClamp, SkTileMode::kClamp, linear, blurMatrix);
+    blurBuilder.uniform("in_blurOffset") = SkV2{stepX * kInputScale, stepY * kInputScale};
 
-    sk_sp<SkImage> tmpBlur(
-            blurBuilder.makeImage(canvas->recordingContext(), nullptr, scaledInfo, false));
+    sk_sp<SkImage> tmpBlur(blurBuilder.makeImage(context, nullptr, scaledInfo, false));
 
     // And now we'll build our chain of scaled blur stages
-    blurBuilder.uniform("in_inverseScale") = 1.0f;
     for (auto i = 1; i < numberOfPasses; i++) {
         const float stepScale = (float)i * kInputScale;
         blurBuilder.child("input") =
                 tmpBlur->makeShader(SkTileMode::kClamp, SkTileMode::kClamp, linear);
         blurBuilder.uniform("in_blurOffset") = SkV2{stepX * stepScale, stepY * stepScale};
-        tmpBlur = blurBuilder.makeImage(canvas->recordingContext(), nullptr, scaledInfo, false);
+        tmpBlur = blurBuilder.makeImage(context, nullptr, scaledInfo, false);
     }
 
     return tmpBlur;
diff --git a/libs/renderengine/skia/filters/BlurFilter.h b/libs/renderengine/skia/filters/BlurFilter.h
index 08641c9..e9a5dee 100644
--- a/libs/renderengine/skia/filters/BlurFilter.h
+++ b/libs/renderengine/skia/filters/BlurFilter.h
@@ -48,8 +48,8 @@
     virtual ~BlurFilter(){};
 
     // Execute blur, saving it to a texture
-    sk_sp<SkImage> generate(SkCanvas* canvas, const sk_sp<SkSurface> input, const uint32_t radius,
-                            SkRect rect) const;
+    sk_sp<SkImage> generate(GrRecordingContext* context, const uint32_t radius,
+                            const sk_sp<SkImage> blurInput, const SkRect& blurRect) const;
     // Returns a matrix that should be applied to the blur shader
     SkMatrix getShaderMatrix() const;
 
diff --git a/libs/renderengine/tests/RenderEngineTest.cpp b/libs/renderengine/tests/RenderEngineTest.cpp
index 58afe6e..886c9da 100644
--- a/libs/renderengine/tests/RenderEngineTest.cpp
+++ b/libs/renderengine/tests/RenderEngineTest.cpp
@@ -950,15 +950,18 @@
     blurLayer.sourceDataspace = ui::Dataspace::V0_SRGB_LINEAR;
     blurLayer.geometry.boundaries = fullscreenRect().toFloatRect();
     blurLayer.backgroundBlurRadius = blurRadius;
+    SourceVariant::fillColor(blurLayer, 0.0f, 0.0f, 1.0f, this);
     blurLayer.alpha = 0;
     layers.push_back(&blurLayer);
 
     invokeDraw(settings, layers);
 
-    expectBufferColor(Rect(center - 1, center - 5, center, center + 5), 150, 150, 0, 255,
-                      50 /* tolerance */);
-    expectBufferColor(Rect(center, center - 5, center + 1, center + 5), 150, 150, 0, 255,
-                      50 /* tolerance */);
+    // solid color
+    expectBufferColor(Rect(0, 0, 1, 1), 255, 0, 0, 255, 0 /* tolerance */);
+
+    // blurred color (downsampling should result in the center color being close to 128)
+    expectBufferColor(Rect(center - 1, center - 5, center + 1, center + 5), 128, 128, 0, 255,
+                      10 /* tolerance */);
 }
 
 template <typename SourceVariant>