AuroraMiddleware/gtk2
1
0
Fork 0
forked from AuroraMiddleware/gtk
Code Issues Pull Requests Projects Releases Wiki Activity

gsk: Fix angle normalization

Browse Source 
I was getting assertions that normalize_angle() failed the
result < 260 check. Doing some research on this it turns out
to be a precision issue. If the incomming angle is very slightly
below zero, then adding 360 to it may end up with exactly 360.

I simplified the code a bit to avoid division and rounding, because in
practice most angles will be "just outside" the 0-360 degree anyway.
And i also added a workaround for the "result is 360" case by just
setting it to 0.
This commit is contained in:
Alexander Larsson 2020-02-11 10:00:34 +01:00
parent af98c46d04
commit 1f0438e7fe
1 changed files with 15 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
gsk/gsktransform.c
View File

@ -821,20 +821,28 @@ static const GskTransformClass GSK_ROTATE_TRANSFORM_CLASS =
static inline float
normalize_angle (float angle)
{
float f;
if (angle >= 0 && angle < 360)
return angle;
f = angle - (360 * ((int)(angle / 360.0)));
while (angle >= 360)
angle -= 360;
while (angle < 0)
angle += 360;
if (f < 0)
f = 360 + f;
/* Due to precision issues we may end up with a result that is just
* past the allowed range when rounded. For example, something like
* -epsilon + 360 when rounded to a float may end up with 360.
* So, we handle these cases by returning the exact value 0.
*/
g_assert (f < 360.0);
g_assert (f >= 0.0);
if (angle >= 360)
angle = 0;
return f;
g_assert (angle < 360.0);
g_assert (angle >= 0.0);
return angle;
}
/**