Fix 4444 on Vulkan devices who don't support RGBA_4444

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

Committed: https://skia.googlesource.com/skia/+/637b3bf2b9c10398d823bd015a722842d4f2f971
Review-Url: https://codereview.chromium.org/2238563002

4 files changed, 23 insertions, 4 deletions

diff --git a/src/gpu/GrGpu.cpp b/src/gpu/GrGpu.cpp
index 7199b4d976..e14e8929b0 100644
--- a/src/gpu/GrGpu.cpp
+++ b/src/gpu/GrGpu.cpp
@@ -277,6 +277,12 @@ bool GrGpu::getReadPixelsInfo(GrSurface* srcSurface, int width, int height, size
         return false;
     }
 
+    // We currently do not support reading into the packed formats 565 or 4444 as they are not
+    // required to have read back support on all devices and backends.
+    if (kRGB_565_GrPixelConfig == readConfig || kRGBA_4444_GrPixelConfig == readConfig) {
+        return false;
+    }
+
     if (!this->onGetReadPixelsInfo(srcSurface, width, height, rowBytes, readConfig, drawPreference,
                                    tempDrawInfo)) {
         return false;
diff --git a/src/gpu/vk/GrVkCaps.cpp b/src/gpu/vk/GrVkCaps.cpp
index cf9f4f025e..9027f68815 100644
--- a/src/gpu/vk/GrVkCaps.cpp
+++ b/src/gpu/vk/GrVkCaps.cpp
@@ -137,7 +137,16 @@ void GrVkCaps::initGLSLCaps(const VkPhysicalDeviceProperties& properties,
             glslCaps->fConfigTextureSwizzle[i] = GrSwizzle::RRRR();
             glslCaps->fConfigOutputSwizzle[i] = GrSwizzle::AAAA();
         } else {
-            glslCaps->fConfigTextureSwizzle[i] = GrSwizzle::RGBA();
+            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();
+            }
         }
     }
 
diff --git a/src/gpu/vk/GrVkCaps.h b/src/gpu/vk/GrVkCaps.h
index ca92e59cae..3733f2c1d6 100644
--- a/src/gpu/vk/GrVkCaps.h
+++ b/src/gpu/vk/GrVkCaps.h
@@ -101,7 +101,7 @@ private:
         uint16_t fLinearFlags;
     };
     ConfigInfo fConfigTable[kGrPixelConfigCnt];
-    
+
     StencilFormat fPreferedStencilFormat;
 
     // Tells of if we can pass in straight GLSL string into vkCreateShaderModule
diff --git a/src/gpu/vk/GrVkUtil.cpp b/src/gpu/vk/GrVkUtil.cpp
index 760b20b458..ffbad25fd9 100644
--- a/src/gpu/vk/GrVkUtil.cpp
+++ b/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: