Fix issue where scale-animating text would jump temporarily a few pixels
Some logic in the native matrix code would determine that a matrix was
'pureTranslate' based on the scale values of a matrix being close-enough to 1,
which was within a very small epsilon. This works in general, because screen space
coordinates make that epsilon value irrelevant, so close-enough really is close-enough.
However, TextView, when centering text, works in a coordinate system that is quite
huge, with left/right values about 500,000. These numbers multiplied times that small
epsilon value would give a result that was significant, and would cause a miscalculation
of up to 4-5 pixels, causing the snap that we'd see for a couple of frames as the
scale got "close enough" to 1.
The fix is to remove the optimization of "close enough". What we really need the matrix to
do is to identify itself as being translate-only when no scale as been set (which is the
default). For the purposes of that check, it is good enough to simply check the values against
1 directly. Similarly, the bounds-check logic needs to check against 0 and 1 directly.
Issue #6452687: Glitch when changing scale of a view containing text
Change-Id: I167fb45d02201fb879deea0e5a7ca95e38128e17
2 files changed