Refactor trimming logic for read/writePixels()

(1) Move trimming logic into Bitmap/Pixmap level for
    raster.  Everything goes through here, so we'll
    only do the work once.
(2) This means it also goes to GPU level.
(3) Always use SkReadPixelsRec rather than inlining
    the logic.
(4) Create an SkWritePixelsRec to encapsulate write
    trimming.
(5) Disabled kIndex8 as a dst - always.

BUG=skia:6021

Change-Id: I748f50c3b726f7c6de5462e2b1ccb54bc387a510
Reviewed-on: https://skia-review.googlesource.com/7326
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Matt Sarett <msarett@google.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/src/core/SkWritePixelsRec.h b/src/core/SkWritePixelsRec.h
new file mode 100644
index 0000000000..652a13a822
--- /dev/null
+++ b/src/core/SkWritePixelsRec.h
@@ -0,0 +1,41 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkWritePixelsRec_DEFINED
+#define SkWritePixelsRec_DEFINED
+
+#include "SkImageInfo.h"
+
+/**
+ *  Helper class to package and trim the parameters passed to writePixels()
+ */
+struct SkWritePixelsRec {
+    SkWritePixelsRec(const SkImageInfo& info, const void* pixels, size_t rowBytes, int x, int y)
+        : fPixels(pixels)
+        , fRowBytes(rowBytes)
+        , fInfo(info)
+        , fX(x)
+        , fY(y)
+    {}
+
+    const void* fPixels;
+    size_t      fRowBytes;
+    SkImageInfo fInfo;
+    int         fX;
+    int         fY;
+
+    /*
+     *  On true, may have modified its fields (except fRowBytes) to make it a legal subset
+     *  of the specified dst width/height.
+     *
+     *  On false, leaves self unchanged, but indicates that it does not overlap dst, or
+     *  is not valid (e.g. bad fInfo) for writePixels().
+     */
+    bool trim(int dstWidth, int dstHeight);
+};
+
+#endif