Properly support the opaque flag in Skia RenderEngine
When the opaque flag is present, the alpha channel from the image is not
used for compositing. But, a layer-wide alpha bit can still be used for
blending, which means the src blending mode can't be used. Other
solutions like lying about the pixel format don't map cleanly to formats
other than RGBA8888 as well. So, we apply a color filter that is adding
a solid black with the input image, which on the vast majority of
formats floods the alpha channel to 1.0 as desired. The one exception
may be FP16 since color values are allowed to be beyond 1.0, but we
don't support FP16 destination buffers anyways.
Bug: 173419151
Test: SurfaceFlinger_test:LayerTypeAndRenderTypeTransactionTests/LayerTypeAndRenderTypeTransactionTest#SetFlagsOpaque
Change-Id: Iec26706bc304df97b55eb2900bbacf13865708ea
diff --git a/libs/renderengine/skia/SkiaGLRenderEngine.cpp b/libs/renderengine/skia/SkiaGLRenderEngine.cpp
index 46ae18c..5cde369 100644
--- a/libs/renderengine/skia/SkiaGLRenderEngine.cpp
+++ b/libs/renderengine/skia/SkiaGLRenderEngine.cpp
@@ -19,25 +19,10 @@
#define LOG_TAG "RenderEngine"
#define ATRACE_TAG ATRACE_TAG_GRAPHICS
-#include <cstdint>
-#include <memory>
-
-#include "SkImageInfo.h"
-#include "log/log_main.h"
-#include "system/graphics-base-v1.0.h"
+#include "SkiaGLRenderEngine.h"
#include <EGL/egl.h>
#include <EGL/eglext.h>
-#include <sync/sync.h>
-#include <ui/BlurRegion.h>
-#include <ui/GraphicBuffer.h>
-#include <utils/Trace.h>
-#include "../gl/GLExtensions.h"
-#include "SkiaGLRenderEngine.h"
-#include "filters/BlurFilter.h"
-#include "filters/LinearEffect.h"
-#include "skia/debug/SkiaCapture.h"
-
#include <GrContextOptions.h>
#include <SkCanvas.h>
#include <SkColorFilter.h>
@@ -48,8 +33,23 @@
#include <SkShadowUtils.h>
#include <SkSurface.h>
#include <gl/GrGLInterface.h>
+#include <sync/sync.h>
+#include <ui/BlurRegion.h>
+#include <ui/GraphicBuffer.h>
+#include <utils/Trace.h>
#include <cmath>
+#include <cstdint>
+#include <memory>
+
+#include "../gl/GLExtensions.h"
+#include "SkBlendMode.h"
+#include "SkImageInfo.h"
+#include "filters/BlurFilter.h"
+#include "filters/LinearEffect.h"
+#include "log/log_main.h"
+#include "skia/debug/SkiaCapture.h"
+#include "system/graphics-base-v1.0.h"
bool checkGlError(const char* op, int lineNumber);
@@ -661,7 +661,35 @@
nullptr));
}
- paint.setColorFilter(SkColorFilters::Matrix(toSkColorMatrix(display.colorTransform)));
+ sk_sp<SkColorFilter> filter =
+ SkColorFilters::Matrix(toSkColorMatrix(display.colorTransform));
+
+ // Handle opaque images - it's a little nonstandard how we do this.
+ // Fundamentally we need to support SurfaceControl.Builder#setOpaque:
+ // https://developer.android.com/reference/android/view/SurfaceControl.Builder#setOpaque(boolean)
+ // The important language is that when isOpaque is set, opacity is not sampled from the
+ // alpha channel, but blending may still be supported on a transaction via setAlpha. So,
+ // here's the conundrum:
+ // 1. We can't force the SkImage alpha type to kOpaque_SkAlphaType, because it's treated as
+ // an internal hint - composition is undefined when there are alpha bits present.
+ // 2. We can try to lie about the pixel layout, but that only works for RGBA8888 buffers,
+ // i.e., treating them as RGBx8888 instead. But we can't do the same for RGBA1010102 because
+ // RGBx1010102 is not supported as a pixel layout for SkImages. It's also not clear what to
+ // use for F16 either, and lying about the pixel layout is a bit of a hack anyways.
+ // 3. We can't change the blendmode to src, because while this satisfies the requirement for
+ // ignoring the alpha channel, it doesn't quite satisfy the blending requirement because
+ // src always clobbers the destination content.
+ //
+ // So, what we do here instead is an additive blend mode where we compose the input image
+ // with a solid black. This might need to be reassess if this does not support FP16
+ // incredibly well, but FP16 end-to-end isn't well supported anyway at the moment.
+ if (layer->source.buffer.buffer && layer->source.buffer.isOpaque) {
+ filter = SkColorFilters::Compose(filter,
+ SkColorFilters::Blend(SK_ColorBLACK,
+ SkBlendMode::kPlus));
+ }
+
+ paint.setColorFilter(filter);
for (const auto effectRegion : layer->blurRegions) {
drawBlurRegion(canvas, effectRegion, layerRect, cachedBlurs[effectRegion.blurRadius]);