| // Copyright 2017 The Chromium Authors |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef CC_PAINT_IMAGE_ANIMATION_COUNT_H_ |
| #define CC_PAINT_IMAGE_ANIMATION_COUNT_H_ |
| |
| namespace cc { |
| |
| // GIF and WebP support animation. The explanation below is in terms of GIF, |
| // but the same constants are used for WebP, too. |
| // GIFs have an optional 16-bit unsigned loop count that describes how an |
| // animated GIF should be cycled. If the loop count is absent, the animation |
| // cycles once; if it is 0, the animation cycles infinitely; otherwise the |
| // animation plays n + 1 cycles (where n is the specified loop count). If the |
| // GIF decoder defaults to kAnimationLoopOnce in the absence of any loop count |
| // and translates an explicit "0" loop count to kAnimationLoopInfinite, then we |
| // get a couple of nice side effects: |
| // * By making kAnimationLoopOnce be 0, we allow the animation cycling code in |
| // BitmapImage.cpp to avoid special-casing it, and simply treat all |
| // non-negative loop counts identically. |
| // * By making the other two constants negative, we avoid conflicts with any |
| // real loop count values. |
| const int kAnimationLoopOnce = 0; |
| const int kAnimationLoopInfinite = -1; |
| const int kAnimationNone = -2; |
| |
| } // namespace cc |
| |
| #endif // CC_PAINT_IMAGE_ANIMATION_COUNT_H_ |