Attachment 19284 Details for Bug 9148 – Cheat and avoid range overflow in the pixman_matrix_t for this particular case

[patch] Cheat and avoid range overflow in the pixman_matrix_t for this particular case

0002--image-Increase-range-of-translate-vector-in-pixman.patch (text/plain), 2.05 KB, created by Chris Wilson on 2008-09-29 08:37:32 UTC

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Creator: Chris Wilson

Created: 2008-09-29 08:37:32 UTC

Size: 2.05 KB

patch

obsolete

>From 4570f8c1fb31c0bad399ca4e8adecba7a5193a02 Mon Sep 17 00:00:00 2001
>From: Chris Wilson <chris@chris-wilson.co.uk>
>Date: Mon, 29 Sep 2008 16:22:48 +0100
>Subject: [PATCH] [image] Increase range of translate vector in pixman_matrix
>
>Exploit the auxiliary offset vector in the attributes to reduce
>likelihood of range overflow in the translation components when converting
>the pattern matrix to fixed-point pixman_matrix_t.
>
>This can probably move higher into acquire_surface_for_surface() after
>being cleaned up.
>---
> src/cairo-image-surface.c |   28 ++++++++++++++++++++++++++--
> 1 files changed, 26 insertions(+), 2 deletions(-)
>
>diff --git a/src/cairo-image-surface.c b/src/cairo-image-surface.c
>index daae8d1..ad0f31a 100644
>--- a/src/cairo-image-surface.c
>+++ b/src/cairo-image-surface.c
>@@ -797,9 +797,33 @@ _cairo_image_surface_clone_similar (void		*abstract_surface,
> 
> static cairo_status_t
> _cairo_image_surface_set_matrix (cairo_image_surface_t	*surface,
>-				 const cairo_matrix_t	*matrix)
>+			         cairo_surface_attributes_t *attributes)
> {
>+    cairo_matrix_t	*matrix;
>     pixman_transform_t pixman_transform;
>+    double tx, ty;
>+
>+    matrix = &attributes->matrix;
>+    tx = ty = 0.;
>+    cairo_matrix_transform_point (matrix, &tx, &ty);
>+    /* reduce likelihood of range overflow with large downscaling */
>+    if (tx != 0. || ty != 0.) {
>+	int ix = (int) tx;
>+	int iy = (int) ty;
>+	cairo_matrix_t m;
>+
>+	m = *matrix;
>+	cairo_matrix_invert (&m);
>+	tx = ix;
>+	ty = iy;
>+	cairo_matrix_transform_distance (&m, &tx, &ty);
>+
>+	attributes->x_offset += tx;
>+	attributes->y_offset += ty;
>+
>+	cairo_matrix_init_translate (&m, -ix, -iy);
>+	cairo_matrix_multiply (matrix, matrix, &m);
>+    }
> 
>     _cairo_matrix_to_pixman_matrix (matrix, &pixman_transform);
> 
>@@ -857,7 +881,7 @@ _cairo_image_surface_set_attributes (cairo_image_surface_t      *surface,
> {
>     cairo_int_status_t status;
> 
>-    status = _cairo_image_surface_set_matrix (surface, &attributes->matrix);
>+    status = _cairo_image_surface_set_matrix (surface, attributes);
>     if (status)
> 	return status;
> 
>-- 
>1.5.6.3
>

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