Re-enable RE test ..._premultipliesAlpha on Graphite w/ tolerance 1

Ganesh rounds this more consistently than Graphite, but Graphite's
approach is technically more correct. See egdaniel@'s description at
b/331446496#comment5

Bug: b/331446496
Change-Id: Ib1fd7975f36ccc114cef3b0cdd60ac173df62a69
Test: librenderengine_test

1 files changed, 6 insertions, 6 deletions

diff --git a/libs/renderengine/tests/RenderEngineTest.cpp b/libs/renderengine/tests/RenderEngineTest.cpp
index 4bd0852b05..4e5440f5ae 100644
--- a/libs/renderengine/tests/RenderEngineTest.cpp
+++ b/libs/renderengine/tests/RenderEngineTest.cpp
@@ -1265,7 +1265,12 @@ void RenderEngineTest::fillRedBufferWithPremultiplyAlpha() {
 
 void RenderEngineTest::fillBufferWithPremultiplyAlpha() {
     fillRedBufferWithPremultiplyAlpha();
-    expectBufferColor(fullscreenRect(), 128, 0, 0, 128);
+    // Different backends and GPUs may round 255 * 0.5 = 127.5 differently, but
+    // either 127 or 128 are acceptable. Checking both 127 and 128 with a
+    // tolerance of 1 allows either 127 or 128 to pass, while preventing 126 or
+    // 129 from erroneously passing.
+    expectBufferColor(fullscreenRect(), 127, 0, 0, 127, 1);
+    expectBufferColor(fullscreenRect(), 128, 0, 0, 128, 1);
 }
 
 void RenderEngineTest::fillRedBufferWithoutPremultiplyAlpha() {
@@ -2061,11 +2066,6 @@ TEST_P(RenderEngineTest, drawLayers_fillBufferTextureTransform) {
 }
 
 TEST_P(RenderEngineTest, drawLayers_fillBuffer_premultipliesAlpha) {
-    // TODO: b/331446496 - Fix in Graphite and re-enable.
-    if (GetParam()->skiaBackend() == renderengine::RenderEngine::SkiaBackend::GRAPHITE) {
-        GTEST_SKIP();
-    }
-
     if (!GetParam()->apiSupported()) {
         GTEST_SKIP();
     }