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[matrix] Avoid error correction overhead for translation matrices.

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We can only correct rounding errors between cairo and pixman matrices for
scaled matrices - so skip the inversion and point transformation overhead
for simple translation matrices.
This commit is contained in:
Chris Wilson 2008-10-22 18:17:49 +01:00
parent 57a1d932f3
commit 2c277ddbea
1 changed files with 8 additions and 3 deletions
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11
src/cairo-matrix.c
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@ -813,8 +813,8 @@ _cairo_matrix_to_pixman_matrix (const cairo_matrix_t *matrix,
*pixman_transform = pixman_identity_transform;
}
else {
cairo_matrix_t inv = *matrix;
double x = 0, y = 0;
cairo_matrix_t inv;
double x,y;
pixman_vector_t vector;
pixman_transform->matrix[0][0] = _cairo_fixed_16_16_from_double (matrix->xx);
@ -839,11 +839,16 @@ _cairo_matrix_to_pixman_matrix (const cairo_matrix_t *matrix,
* space and adjust pixman's transform to agree with cairo's at
* that point. */
if (_cairo_matrix_is_translation (matrix))
return;
/* Note: If we can't invert the transformation, skip the adjustment. */
inv = *matrix;
if (cairo_matrix_invert (&inv) != CAIRO_STATUS_SUCCESS)
return;
/* find the device space coordinate that maps to (0, 0) */
x = 0, y = 0;
cairo_matrix_transform_point (&inv, &x, &y);
/* transform the resulting device space coordinate back
@ -852,7 +857,7 @@ _cairo_matrix_to_pixman_matrix (const cairo_matrix_t *matrix,
vector.vector[1] = _cairo_fixed_16_16_from_double (y);
vector.vector[2] = 1 << 16;
if (!pixman_transform_point_3d (pixman_transform, &vector))
if (! pixman_transform_point_3d (pixman_transform, &vector))
return;
/* Ideally, the vector should now be (0, 0). We can now compensate