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GskTransform: Compute sin/deg of 90deg rotations manually

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Otherwise we might end up with inaccuracies, e.g. when
gsk_transform_transform_bounds()'ing bounds.
This commit is contained in:
Timm Bäder 2019-12-19 12:30:08 +01:00
parent e62f135c6a
commit 766d4dff76
1 changed files with 36 additions and 8 deletions
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44
gsk/gsktransform.c
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@ -685,16 +685,46 @@ gsk_rotate_transform_finalize (GskTransform *self)
{
}
static inline void
_sincos (float deg,
float *out_s,
float *out_c)
{
if (deg == 90.0)
{
*out_c = 0.0;
*out_s = 1.0;
}
else if (deg == 180.0)
{
*out_c = -1.0;
*out_s = 0.0;
}
else if (deg == 270.0)
{
*out_c = 0.0;
*out_s = -1.0;
}
else if (deg == 0.0)
{
*out_c = 1.0;
*out_s = 0.0;
}
else
{
sincosf (deg * M_PI / 180.0, out_s, out_c);
}
}
static void
gsk_rotate_transform_to_matrix (GskTransform *transform,
graphene_matrix_t *out_matrix)
{
GskRotateTransform *self = (GskRotateTransform *) transform;
float rad, c, s;
float c, s;
_sincos (self->angle, &s, &c);
rad = self->angle * M_PI / 180.f;
c = cosf (rad);
s = sinf (rad);
graphene_matrix_init_from_2d (out_matrix,
c, s,
-s, c,
@ -711,14 +741,12 @@ gsk_rotate_transform_apply_2d (GskTransform *transform,
float *out_dy)
{
GskRotateTransform *self = (GskRotateTransform *) transform;
float s, c, rad, xx, xy, yx, yy;
float s, c, xx, xy, yx, yy;
if (fmodf (self->angle, 360.0f) == 0.0)
return;
rad = self->angle * G_PI / 180.0f;
s = sinf (rad);
c = cosf (rad);
_sincos (self->angle, &s, &c);
xx = c * *out_xx + s * *out_xy;
yx = c * *out_yx + s * *out_yy;