Simple cleanups related to SkFixed.

src/core/SkPaint.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkPaint.h"
 #include "SkAnnotation.h"
 #include "SkAutoKern.h"
@@ skipping 1010 matching lines @@
     if (scale) {
         maxWidth /= scale;
     }
 
     SkAutoGlyphCache    autoCache(paint, nullptr, nullptr);
     SkGlyphCache*       cache = autoCache.getCache();
 
     SkMeasureCacheProc glyphCacheProc = paint.getMeasureCacheProc(false);
     const int        xyIndex = paint.isVerticalText() ? 1 : 0;
     // use 64bits for our accumulator, to avoid overflowing 16.16
-    Sk48Dot16        max = SkScalarToFixed(maxWidth);
+    Sk48Dot16        max = SkScalarTo48Dot16(maxWidth);

[reed1, 2016/02/11 21:43:44]

Wow, this seems like a bug bug. Is/was there a test that showed this bug?

[dogben, 2016/02/11 21:53:13]

The previous code was actually fine, assuming maxWidth is within the range of
SkFixed. Casting from SkFixed (aka Sk16Dot16) to Sk48Dot16 is just adding zeros
(or ones) on the left.

[reed1, 2016/02/11 22:22:59]

So we could write a test that measures a big string (e.g. at a large
point-size), and see it overflow the SkFixed?

[dogben, 2016/02/12 02:35:24]

Oh! For some reason I was thinking that was the width of one glyph.

Large point-size is handled by scaling down the font and the maxWidth, so that's
not a problem.

However, this method previously could only handle ~5kB of text at the default
size. The fix allows it to handle more than 1GB.

     Sk48Dot16        width = 0;
 
     SkAutoKern  autokern;
 
     if (this->isDevKernText()) {
         int rsb = 0;
         while (text < stop) {
             const char* curr = text;
             const SkGlyph& g = glyphCacheProc(cache, &text);
             SkFixed x = SkAutoKern_AdjustF(rsb, g.fLsbDelta) + advance(g, xyIndex);
@@ skipping 1488 matching lines @@
 }
 
 uint32_t SkPaint::getHash() const {
     // We're going to hash 10 pointers and 7 32-bit values, finishing up with fBitfields,
     // so fBitfields should be 10 pointers and 6 32-bit values from the start.
     static_assert(offsetof(SkPaint, fBitfields) == 10 * sizeof(void*) + 6 * sizeof(uint32_t),
                   "SkPaint_notPackedTightly");
     return SkChecksum::Murmur3(reinterpret_cast<const uint32_t*>(this),
                                offsetof(SkPaint, fBitfields) + sizeof(fBitfields));
 }