Fix texture errors on iOS Metal

Change-Id: I027b5e4a8ab737047e9fcd16be8b7597644c7dd6
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/307569
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>

src/core/SkCompressedDataUtils.cpp

@@ -277,6 +277,19 @@ size_t SkCompressedDataSize(SkImage::CompressionType type, SkISize dimensions,
     return totalSize;
 }
 
+size_t SkCompressedBlockSize(SkImage::CompressionType type) {
+    switch (type) {
+        case SkImage::CompressionType::kNone:
+            return 0;
+        case SkImage::CompressionType::kETC2_RGB8_UNORM:
+            return sizeof(ETC1Block);
+        case SkImage::CompressionType::kBC1_RGB8_UNORM:
+        case SkImage::CompressionType::kBC1_RGBA8_UNORM:
+            return sizeof(BC1Block);
+    }
+    SkUNREACHABLE;
+}
+
 size_t SkCompressedFormatDataSize(SkImage::CompressionType compressionType,
                                   SkISize dimensions, bool mipMapped) {
     return SkCompressedDataSize(compressionType, dimensions, nullptr, mipMapped);

src/core/SkCompressedDataUtils.h

@@ -29,7 +29,7 @@ static constexpr bool SkCompressionTypeIsOpaque(SkImage::CompressionType compres
 
 size_t SkCompressedDataSize(SkImage::CompressionType, SkISize baseDimensions,
                             SkTArray<size_t>* individualMipOffsets, bool mipMapped);
-
+size_t SkCompressedBlockSize(SkImage::CompressionType type);
 
 /**
  * Returns the data size for the given SkImage::CompressionType

src/gpu/mtl/GrMtlGpu.mm

@@ -337,13 +337,16 @@ bool GrMtlGpu::uploadToTexture(GrMtlTexture* tex, int left, int top, int width,
             bpp, {width, height}, &individualMipOffsets, mipLevelCount);
     SkASSERT(combinedBufferSize);
 
+
+    // offset value must be a multiple of the destination texture's pixel size in bytes
 #ifdef SK_BUILD_FOR_MAC
-    static const int kAlignment = 4;
+    static const size_t kMinAlignment = 4;
 #else
-    static const int kAlignment = 1;
+    static const size_t kMinAlignment = 1;
 #endif
+    size_t alignment = std::max(bpp, kMinAlignment);
     GrStagingBufferManager::Slice slice = fStagingBufferManager.allocateStagingBufferSlice(
-            combinedBufferSize, kAlignment);
+            combinedBufferSize, alignment);
     if (!slice.fBuffer) {
         return false;
     }
@@ -627,13 +630,11 @@ sk_sp<GrTexture> GrMtlGpu::onCreateCompressedTexture(SkISize dimensions,
     SkASSERT(individualMipOffsets.count() == numMipLevels);
     SkASSERT(dataSize == combinedBufferSize);
 
-#ifdef SK_BUILD_FOR_MAC
-    static const int kAlignment = 4;
-#else
-    static const int kAlignment = 1;
-#endif
+    // offset value must be a multiple of the destination texture's pixel size in bytes
+    // for compressed textures, this is the block size
+    size_t alignment = SkCompressedBlockSize(compressionType);
     GrStagingBufferManager::Slice slice = fStagingBufferManager.allocateStagingBufferSlice(
-            dataSize, kAlignment);
+            dataSize, alignment);
     if (!slice.fBuffer) {
         return nullptr;
     }