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actor: Fix transforming stage point when scale is less than 1

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The commit 6cd24faaa5 (actor: Clean up
transform_stage_point()) changed the validation of the transformation
matrix to ignore the fraction part of the determinant. This caused
clutter_actor_transform_stage_point() to fail and return FALSE for
actors which scale was less than 1.

Previously the validation was ('det' being a float):
	det = (RQ[0][0] * ST[0][0])
	    + (RQ[0][1] * ST[0][1])
	    + (RQ[0][2] * ST[0][2]);
	if (!det)
		return FALSE;

Semantically, the if statement expression '!det' is equivalent to
'det == 0', i.e. 'det == 0.0f'. Post cleanup patches, 'det' was turned
into a double, and the if statement was changed to:

	if (CLUTTER_NEARBYINT (det) == 0)
		return FALSE;

which, different from before, rounds the determinant to the nearest
integer value, meaning determinant in the range (-0.5, 0.5) would be
considered invalid.

This patch reverts this part to the old behavior, while, because of the
inexact nature of floating point arithmetics, allowing a bit more liberal
meaning of "equals to 0" than '== 0.0'.

https://bugzilla.gnome.org/show_bug.cgi?id=754766
This commit is contained in:
Jonas Ådahl 2015-09-10 16:12:51 +08:00
parent 63813ad398
commit 5d83260b19
1 changed files with 3 additions and 3 deletions
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4
clutter/clutter-actor.c
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@ -15190,7 +15190,7 @@ clutter_actor_transform_stage_point (ClutterActor *self,
dy2 = v[2].y - v[3].y;
det = DET (dx1, dx2, dy1, dy2);
if (CLUTTER_NEARBYINT (det) == 0)
if (fabs (det) <= DBL_EPSILON)
return FALSE;
RQ[0][2] = DET (px, dx2, py, dy2) / det;
@ -15236,7 +15236,7 @@ clutter_actor_transform_stage_point (ClutterActor *self,
det = (RQ[0][0] * ST[0][0])
+ (RQ[0][1] * ST[0][1])
+ (RQ[0][2] * ST[0][2]);
if (CLUTTER_NEARBYINT (det) == 0)
if (fabs (det) <= DBL_EPSILON)
return FALSE;
/*