commit c20e080388c45b6f0bd6d55b640960c7cd1d0025
author Derek Sollenberger <djsollen@google.com> Wed May 19 16:20:59 2021 -0400
committer Derek Sollenberger <djsollen@google.com> Tue May 25 11:32:00 2021 +0000
tree 2c454ca934bde14b90d059eaeb71ca0e70074e15
parent 6b38461a39eca271da55cf14682b6dfef764529b

Avoid blur behind for layers that are fully opaque.

This addresses cases where the layer is a solid color or has an
opaque buffer that will result in the blur being completely
overwritten by the layer's contents.

Bug: 188050128
Test: atest librenderengine_test and verfied by mskp capture
Change-Id: I5ef76eca9a3dda21d1faa652da60abb22282925a

libs/renderengine/skia/SkiaGLRenderEngine.cpp

diff --git a/libs/renderengine/skia/SkiaGLRenderEngine.cpp b/libs/renderengine/skia/SkiaGLRenderEngine.cpp
index 9f6ecaa..47c330f 100644
--- a/libs/renderengine/skia/SkiaGLRenderEngine.cpp
+++ b/libs/renderengine/skia/SkiaGLRenderEngine.cpp
@@ -725,6 +725,14 @@
         return BAD_VALUE;
     }
 
+    // setup color filter if necessary
+    sk_sp<SkColorFilter> displayColorTransform;
+    if (display.colorTransform != mat4()) {
+        displayColorTransform = SkColorFilters::Matrix(toSkColorMatrix(display.colorTransform));
+    }
+    const bool ctModifiesAlpha =
+            displayColorTransform && !displayColorTransform->isAlphaUnchanged();
+
     // Find if any layers have requested blur, we'll use that info to decide when to render to an
     // offscreen buffer and when to render to the native buffer.
     sk_sp<SkSurface> activeSurface(dstSurface);
@@ -734,6 +742,10 @@
     if (mBlurFilter) {
         bool requiresCompositionLayer = false;
         for (const auto& layer : layers) {
+            // if the layer doesn't have blur or it is not visible then continue
+            if (!layerHasBlur(layer, ctModifiesAlpha)) {
+                continue;
+            }
             if (layer->backgroundBlurRadius > 0 &&
                 layer->backgroundBlurRadius < BlurFilter::kMaxCrossFadeRadius) {
                 requiresCompositionLayer = true;
@@ -779,12 +791,6 @@
         canvas->drawRegion(clearRegion, paint);
     }
 
-    // setup color filter if necessary
-    sk_sp<SkColorFilter> displayColorTransform;
-    if (display.colorTransform != mat4()) {
-        displayColorTransform = SkColorFilters::Matrix(toSkColorMatrix(display.colorTransform));
-    }
-
     for (const auto& layer : layers) {
         ATRACE_NAME("DrawLayer");
 
@@ -850,7 +856,7 @@
         const auto [bounds, roundRectClip] =
                 getBoundsAndClip(layer->geometry.boundaries, layer->geometry.roundedCornersCrop,
                                  layer->geometry.roundedCornersRadius);
-        if (mBlurFilter && layerHasBlur(layer)) {
+        if (mBlurFilter && layerHasBlur(layer, ctModifiesAlpha)) {
             std::unordered_map<uint32_t, sk_sp<SkImage>> cachedBlurs;
 
             // if multiple layers have blur, then we need to take a snapshot now because
@@ -1188,8 +1194,15 @@
     return {SkRRect::MakeRect(bounds), clip};
 }
 
-inline bool SkiaGLRenderEngine::layerHasBlur(const LayerSettings* layer) {
-    return layer->backgroundBlurRadius > 0 || layer->blurRegions.size();
+inline bool SkiaGLRenderEngine::layerHasBlur(const LayerSettings* layer,
+                                             bool colorTransformModifiesAlpha) {
+    if (layer->backgroundBlurRadius > 0 || layer->blurRegions.size()) {
+        // return false if the content is opaque and would therefore occlude the blur
+        const bool opaqueContent = !layer->source.buffer.buffer || layer->source.buffer.isOpaque;
+        const bool opaqueAlpha = layer->alpha == 1.0f && !colorTransformModifiesAlpha;
+        return layer->skipContentDraw || !(opaqueContent && opaqueAlpha);
+    }
+    return false;
 }
 
 inline SkColor SkiaGLRenderEngine::getSkColor(const vec4& color) {