Fix 4444 on Vulkan devices who don't support RGBA_4444

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2238563002

Review-Url: https://codereview.chromium.org/2238563002

src/gpu/vk/GrVkCaps.cpp

@@ -136,10 +136,19 @@ void GrVkCaps::initGLSLCaps(const VkPhysicalDeviceProperties& properties,
         if (GrPixelConfigIsAlphaOnly(config)) {
             glslCaps->fConfigTextureSwizzle[i] = GrSwizzle::RRRR();
             glslCaps->fConfigOutputSwizzle[i] = GrSwizzle::AAAA();
+        } else {
+            if (kRGBA_4444_GrPixelConfig == config) {
+                // The vulkan spec does not require R4G4B4A4 to be supported for texturing so we
+                // store the data in a B4G4R4A4 texture and then swizzle it when doing texture reads
+                // or writing to outputs. Since we're not actually changing the data at all, the
+                // only extra work is the swizzle in the shader for all operations.
+                glslCaps->fConfigTextureSwizzle[i] = GrSwizzle::BGRA();
+                glslCaps->fConfigOutputSwizzle[i] = GrSwizzle::BGRA();
             } else {
                 glslCaps->fConfigTextureSwizzle[i] = GrSwizzle::RGBA();
             }
         }
+    }
 
     // Vulkan is based off ES 3.0 so the following should all be supported
     glslCaps->fUsesPrecisionModifiers = true;

src/gpu/vk/GrVkUtil.cpp

@@ -30,7 +30,9 @@ bool GrPixelConfigToVkFormat(GrPixelConfig config, VkFormat* format) {
             *format = VK_FORMAT_R5G6B5_UNORM_PACK16;
             break;
         case kRGBA_4444_GrPixelConfig:
-            *format = VK_FORMAT_R4G4B4A4_UNORM_PACK16;
+            // R4G4B4A4 is not required to be supported so we actually
+            // store the data is if it was B4G4R4A4 and swizzle in shaders
+            *format = VK_FORMAT_B4G4R4A4_UNORM_PACK16;
             break;
         case kIndex_8_GrPixelConfig:
             // No current vulkan support for this config
@@ -88,7 +90,9 @@ bool GrVkFormatToPixelConfig(VkFormat format, GrPixelConfig* config) {
         case VK_FORMAT_R5G6B5_UNORM_PACK16:
             *config = kRGB_565_GrPixelConfig;
             break;
-        case VK_FORMAT_R4G4B4A4_UNORM_PACK16:
+        case VK_FORMAT_B4G4R4A4_UNORM_PACK16:
+            // R4G4B4A4 is not required to be supported so we actually
+            // store RGBA_4444 data as B4G4R4A4.
             *config = kRGBA_4444_GrPixelConfig;
             break;
         case VK_FORMAT_R8_UNORM:

tests/PackedConfigsTextureTest.cpp

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/*
+ * This is a straightforward test of using packed pixel configs (4444, 565).
+ * This test will make sure that these RGBA_4444 and RGB_565 are always supported
+ * as valid texturing configs.
+ */
+
+#include "Test.h"
+
+#if SK_SUPPORT_GPU
+#include "GrContext.h"
+#include "GrTexture.h"
+
+static const int DEV_W = 100, DEV_H = 100;
+static const SkIRect DEV_RECT = SkIRect::MakeWH(DEV_W, DEV_H);
+
+template <typename T>
+void runTest(skiatest::Reporter* reporter, GrContext* context,
+             T val1, T val2, int arraySize, GrPixelConfig config) {
+    SkTDArray<T> controlPixelData, readBuffer;
+    controlPixelData.setCount(arraySize);
+    readBuffer.setCount(arraySize);
+
+    for (int i = 0; i < arraySize; i += 2) {
+        controlPixelData[i] = val1;
+        controlPixelData[i + 1] = val2;
+    }
+
+    for (int origin = 0; origin < 2; ++origin) {
+        GrSurfaceDesc desc;
+        desc.fFlags = kNone_GrSurfaceFlags;
+        desc.fWidth = DEV_W;
+        desc.fHeight = DEV_H;
+        desc.fConfig = config;
+        desc.fOrigin = 0 == origin ?
+            kTopLeft_GrSurfaceOrigin : kBottomLeft_GrSurfaceOrigin;
+        SkAutoTUnref<GrTexture> fpTexture(context->textureProvider()->createTexture(
+            desc, SkBudgeted::kNo, controlPixelData.begin(), 0));
+        SkASSERT(fpTexture);
+        fpTexture->readPixels(0, 0, DEV_W, DEV_H, desc.fConfig, readBuffer.begin(), 0);
+        REPORTER_ASSERT(reporter,
+                        0 == memcmp(readBuffer.begin(), controlPixelData.begin(),
+                                    readBuffer.bytes()));
+    }
+}
+
+static const int CONTROL_ARRAY_SIZE = DEV_W * DEV_H;
+
+DEF_GPUTEST_FOR_RENDERING_CONTEXTS(RGBA4444TextureTest, reporter, ctxInfo) {
+    runTest<uint16_t>(reporter, ctxInfo.grContext(), 0xFF00, 0xFA62,
+                      CONTROL_ARRAY_SIZE, kRGBA_4444_GrPixelConfig);
+}
+
+DEF_GPUTEST_FOR_RENDERING_CONTEXTS(RGB565TextureTest, reporter, ctxInfo) {
+    runTest<uint16_t>(reporter, ctxInfo.grContext(), 0xFF00, 0xFA62,
+                      CONTROL_ARRAY_SIZE, kRGB_565_GrPixelConfig);
+}
+
+#endif