Fix "out of memory" when using linear gradient

Steps to reproduce

1. Save the SVG example below as example.svg and run the following command to open it by Eye of GNOME.

   $ eog ./example.svg

2. Resize the window of Eye of GNOME to a smaller size
3. The following messages are printed in the terminal and the behavior becomes strange.

   (eog:755506): Gtk-WARNING **: 22:23:43.421: drawing failure for widget 'EogWindow': out of memory
   
   (eog:755506): Gtk-WARNING **: 22:23:43.504: drawing failure for widget 'EogWindow': out of memory
   
   (eog:755506): Gtk-WARNING **: 22:23:43.530: drawing failure for widget 'EogWindow': out of memory
   
   (eog:755506): Gtk-WARNING **: 22:23:43.563: drawing failure for widget 'EogWindow': out of memory

Why this problem occurs?

This is because Cairo returns an error if the value of matrix elements that the gradient pattern has exceeds PIXMAN_MAX_INT.

In the attached patch, this problem can be avoided by modifying the _cairo_gradient_pattern_fit_to_range() function to check the matrix element values and modify the scale factor.

Materials

Example SVG:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<svg version="1.1" width="1219" height="794" viewBox="0 0 1219 794" xmlns="http://www.w3.org/2000/svg" xmlns:svg="http://www.w3.org/2000/svg">
  <defs>
    <linearGradient
       x1="8146"
       y1="-16306"
       x2="8146"
       y2="0"
       gradientUnits="userSpaceOnUse"
       gradientTransform="matrix(2.355e-5,6.6e-6,-6.6e-6,2.355e-5,250.10396,425.55418)"
       spreadMethod="pad"
       id="lineargradient1">
      <stop style="stop-opacity:1;stop-color:#e3e0df" offset="0" id="stop1" />
      <stop style="stop-opacity:1;stop-color:#64656c" offset="1" id="stop2" />
    </linearGradient>
  </defs>
  <g id="g10" transform="matrix(1.3333333,0,0,1.3333333,0,12.645333)">
    <path
       d="m 250.051,425.746 c -0.031,0.106 0.031,0.215 0.14,0.246 0.102,0.028"
       style="fill:url(#lineargradient1);stroke:none" />
  </g>
</svg>

Patch file

diff --git a/src/cairo-pattern.c b/src/cairo-pattern.c
index 2c0ba31f8..f74046c96 100644
--- a/src/cairo-pattern.c
+++ b/src/cairo-pattern.c
@@ -2767,6 +2767,12 @@ _cairo_gradient_pattern_fit_to_range (const cairo_gradient_pattern_t *gradient,
        dim = MAX (dim, fabs (radial->cd1.center.y - radial->cd2.center.y));
        dim = MAX (dim, fabs (radial->cd1.radius   - radial->cd2.radius));
     }
+    dim = MAX (dim, fabs (gradient->base.matrix.xx));
+    dim = MAX (dim, fabs (gradient->base.matrix.xy));
+    dim = MAX (dim, fabs (gradient->base.matrix.x0));
+    dim = MAX (dim, fabs (gradient->base.matrix.yx));
+    dim = MAX (dim, fabs (gradient->base.matrix.yy));
+    dim = MAX (dim, fabs (gradient->base.matrix.y0));
 
     if (unlikely (dim > max_value)) {
        cairo_matrix_t scale;

Related issues

• https://gitlab.gnome.org/GNOME/librsvg/-/issues/683