allow the caller to specified raster-surface rowbytes

tests/SurfaceTest.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCanvas.h"
 #include "SkData.h"
 #include "SkDevice.h"
@@ skipping 643 matching lines @@
         for (auto& test_func : { &test_no_canvas1, &test_no_canvas2 }) {
             for (auto& mode : modes) {
                 SkAutoTUnref<SkSurface> surface(
                     surface_func(context, kPremul_SkAlphaType, nullptr));
                 test_func(reporter, surface, mode);
             }
         }
     }
 }
 #endif
+
+static void check_rowbytes_remain_consistent(SkSurface* surface, skiatest::Reporter* reporter) {
+    SkImageInfo info;
+    size_t rowBytes;
+    REPORTER_ASSERT(reporter, surface->peekPixels(&info, &rowBytes));
+
+    SkAutoTUnref<SkImage> image(surface->newImageSnapshot());
+    SkImageInfo im_info;
+    size_t im_rowbytes;
+    REPORTER_ASSERT(reporter, image->peekPixels(&im_info, &im_rowbytes));
+
+    REPORTER_ASSERT(reporter, rowBytes == im_rowbytes);
+
+    // trigger a copy-on-write
+    surface->getCanvas()->drawPaint(SkPaint());
+    SkAutoTUnref<SkImage> image2(surface->newImageSnapshot());
+    REPORTER_ASSERT(reporter, image->uniqueID() != image2->uniqueID());
+
+    SkImageInfo im_info2;
+    size_t im_rowbytes2;
+    REPORTER_ASSERT(reporter, image2->peekPixels(&im_info2, &im_rowbytes2));
+
+    REPORTER_ASSERT(reporter, im_rowbytes2 == im_rowbytes);

[bsalomon, 2016/01/29 13:59:25]

Should we doc this behavior with the SkSurface factory method? (images snapped
from a raster surface have the same rowbytes as the surface)?

[reed1, 2016/01/30 00:52:48]

Done.

+}
+
+DEF_TEST(surface_rowbytes, reporter) {
+    const SkImageInfo info = SkImageInfo::MakeN32Premul(100, 100);
+
+    SkAutoTUnref<SkSurface> surf0(SkSurface::NewRaster(info));
+    check_rowbytes_remain_consistent(surf0, reporter);
+
+    // specify a larger rowbytes
+    SkAutoTUnref<SkSurface> surf1(SkSurface::NewRaster(info, 500, nullptr));
+    check_rowbytes_remain_consistent(surf1, reporter);
+
+    // Try some illegal rowByte values
+    SkSurface* s = SkSurface::NewRaster(info, 396, nullptr);    // needs to be at least 400
+    REPORTER_ASSERT(reporter, nullptr == s);
+    s = SkSurface::NewRaster(info, 1 << 30, nullptr); // allocation to large
+    REPORTER_ASSERT(reporter, nullptr == s);
+}