Glyph positions maintain 32 bit integer part.

include/core/SkFixed.h

 /*
  * 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.
  */
 
 #ifndef SkFixed_DEFINED
 #define SkFixed_DEFINED
 
@@ skipping 132 matching lines @@
 typedef int64_t SkFixed3232;   // 32.32
 
 #define SkIntToFixed3232(x)       ((SkFixed3232)(x) << 32)
 #define SkFixed3232ToInt(x)       ((int)((x) >> 32))
 #define SkFixedToFixed3232(x)     ((SkFixed3232)(x) << 16)
 #define SkFixed3232ToFixed(x)     ((SkFixed)((x) >> 16))
 #define SkFloatToFixed3232(x)     ((SkFixed3232)((x) * (65536.0f * 65536.0f)))
 
 #define SkScalarToFixed3232(x)    SkFloatToFixed3232(x)
 
+///////////////////////////////////////////////////////////////////////////////
+
+// 64bits wide, with a 16bit bias. Useful when accumulating lots of 16.16 so
+// we don't overflow along the way
+typedef int64_t Sk48Dot16;

[mtklein, 2015/03/05 21:00:03]

Let's harmonize the names of SkFixed3232 and Sk48Dot16.  Either way seems fine.

Can we not just use SkFixed3232?  There are ops up there to convert to and from
SkFixed.

[bungeman-skia, 2015/03/05 21:17:56]

As seen here, I pulled Sk48Dot16 out of SkPaint because measureText was using it
for exactly the reasons I want to use it here. The really nice thing about using
48.16 is that you don't have to keep shifting back a forth to work with SkFixed
(with SkFixed3232 there are a bunch of extra shifts, and we don't even want the
extra bits on the low end).

Note that we currently have SkFixed, SkFixed3232, Sk48Dot16, FDot8, and SkFDot6.
Making any two of these consistent seems inconsistent.

+
+static inline float Sk48Dot16ToScalar(Sk48Dot16 x) {
+    return (float) (x * 1.5258789e-5);   // x * (1 / 65536.0f)
+}
+#define SkFloatTo48Dot16(x)   ((Sk48Dot16)((x) * SK_Fixed1))

[reed1, 2015/03/09 16:33:56]

I know the value is correct, but it might read clearer if this was 65536, to
match the comment above in the toscalar version.

[bungeman-skia, 2015/03/09 17:49:12]

Made things line up in a more sane way.

+
+#define SkScalarTo48Dot16(x)    SkFloatTo48Dot16(x)
+
 #endif