Fix crash that occurred when scaling a clipped object, as reported in lp:811819

Fixed bugs:
  - https://launchpad.net/bugs/811819

(bzr r10464)

1 files changed, 8 insertions, 4 deletions

diff --git a/src/sp-item-transform.cpp b/src/sp-item-transform.cpp
index eb4b81a61..0fbce27f9 100644
--- a/src/sp-item-transform.cpp
+++ b/src/sp-item-transform.cpp
@@ -248,10 +248,6 @@ get_scale_transform_with_unequal_stroke (Geom::Rect const &bbox_visual, Geom::Re
     gdouble r0w = w0 - bbox_geom.width(); // r0w is the average strokewidth of the left and right edges, i.e. 0.5*(r0l + r0r)
     gdouble r0h = h0 - bbox_geom.height(); // r0h is the average strokewidth of the top and bottom edges, i.e. 0.5*(r0t + r0b)
 
-    // Check whether the stroke is not negative; should not be possible, but just in case:
-    g_assert(r0w >= 0);
-    g_assert(r0h >= 0);
-
     if (bbox_visual.hasZeroArea()) { // Obviously we cannot scale from empty visual bounding boxes at all, so we will only translate in such a case
         Geom::Affine move = Geom::Translate(x0 - bbox_visual.min()[Geom::X], y0 - bbox_visual.min()[Geom::Y]);
         return (move);
@@ -266,6 +262,14 @@ get_scale_transform_with_unequal_stroke (Geom::Rect const &bbox_visual, Geom::Re
         return (p2o * direct * o2n);
     }
 
+    // Check whether the stroke is negative; i.e. the geometric bounding box is larger than the visual bounding box, which
+    // occurs for example for clipped objects (see launchpad bug #811819)
+    if (r0w < 0 || r0w < 0) {
+        // How should we handle the stroke width scaling of clipped object? I don't know if we can/should handle this,
+        // so for now we simply return the direct scaling
+        return (p2o * direct * o2n);
+    }
+
     // Here starts the calculation you've been waiting for; first do some preparation
     int flip_x = (w1 > 0) ? 1 : -1;
     int flip_y = (h1 > 0) ? 1 : -1;