[lasem] svg_view: avoid cairo errors when gradient matrix is not invertible.

[Emmanuel Pacaud <emmanuel src gnome org>]

commit 2af1dcb18d3bc06867ad2a6bfdfcd6378711e214
Author: Emmanuel Pacaud <emmanuel gnome org>
Date:   Tue Jun 12 20:03:28 2012 +0200

    svg_view: avoid cairo errors when gradient matrix is not invertible.

 src/lsmsvggradientelement.c |   16 ++++++++--------
 src/lsmsvgview.c            |   20 ++++++++++++++++----
 src/lsmsvgview.h            |    6 ++++--
 3 files changed, 28 insertions(+), 14 deletions(-)
---
diff --git a/src/lsmsvggradientelement.c b/src/lsmsvggradientelement.c
index 4820567..3671e05 100644
--- a/src/lsmsvggradientelement.c
+++ b/src/lsmsvggradientelement.c
@@ -72,14 +72,14 @@ lsm_svg_gradient_element_render (LsmSvgElement *self, LsmSvgView *view)
 		   gradient->transform.matrix.e,
 		   gradient->transform.matrix.f);
 
-	lsm_svg_view_set_gradient_properties (view,
-					      gradient->spread_method.value,
-					      gradient->units.value,
-					      &gradient->transform.matrix);
-
-	for (node = LSM_DOM_NODE (referenced_gradient)->first_child; node != NULL; node = node->next_sibling)
-		if (LSM_IS_SVG_ELEMENT (node))
-		    lsm_svg_element_render (LSM_SVG_ELEMENT (node), view);
+	if (lsm_svg_view_set_gradient_properties (view,
+						  gradient->spread_method.value,
+						  gradient->units.value,
+						  &gradient->transform.matrix)) {
+		for (node = LSM_DOM_NODE (referenced_gradient)->first_child; node != NULL; node = node->next_sibling)
+			if (LSM_IS_SVG_ELEMENT (node))
+				lsm_svg_element_render (LSM_SVG_ELEMENT (node), view);
+	}
 }
 
 static void
diff --git a/src/lsmsvgview.c b/src/lsmsvgview.c
index 2029f55..1ed54fd 100644
--- a/src/lsmsvgview.c
+++ b/src/lsmsvgview.c
@@ -194,17 +194,19 @@ lsm_svg_view_add_gradient_color_stop (LsmSvgView *view, double offset)
 					   style->stop_opacity->value * view->pattern_data->opacity);
 }
 
-void
+gboolean
 lsm_svg_view_set_gradient_properties (LsmSvgView *view,
 				      LsmSvgSpreadMethod method,
 				      LsmSvgPatternUnits units,
 				      const LsmSvgMatrix *gradient_matrix)
 {
 	cairo_matrix_t matrix;
+	cairo_matrix_t inv_matrix;
+	cairo_status_t status;
 
-	g_return_if_fail (LSM_IS_SVG_VIEW (view));
-	g_return_if_fail (view->pattern_data != NULL);
-	g_return_if_fail (view->pattern_data->pattern != NULL);
+	g_return_val_if_fail (LSM_IS_SVG_VIEW (view), FALSE);
+	g_return_val_if_fail (view->pattern_data != NULL, FALSE);
+	g_return_val_if_fail (view->pattern_data->pattern != NULL, FALSE);
 
 	switch (method) {
 		case LSM_SVG_SPREAD_METHOD_REFLECT:
@@ -238,7 +240,17 @@ lsm_svg_view_set_gradient_properties (LsmSvgView *view,
 
 	}
 
+	inv_matrix = matrix;
+	status = cairo_matrix_invert (&inv_matrix);
+
+	if (status != CAIRO_STATUS_SUCCESS) {
+		lsm_debug_render ("SvgView::set_gradient_properties] Not invertible matrix");
+		return FALSE;
+	}
+
 	cairo_pattern_set_matrix (view->pattern_data->pattern, &matrix);
+
+	return TRUE;
 }
 
 gboolean
diff --git a/src/lsmsvgview.h b/src/lsmsvgview.h
index 0bb7140..58187b0 100644
--- a/src/lsmsvgview.h
+++ b/src/lsmsvgview.h
@@ -99,12 +99,14 @@ void 		lsm_svg_view_create_radial_gradient 	(LsmSvgView *view, double cx, double
 void 		lsm_svg_view_create_linear_gradient 	(LsmSvgView *view, double x1, double y1,
 							                   double x2, double y2);
 void 		lsm_svg_view_add_gradient_color_stop	(LsmSvgView *view, double offset);
-void 		lsm_svg_view_set_gradient_properties	(LsmSvgView *view,
+G_GNUC_WARN_UNUSED_RESULT gboolean 	
+		lsm_svg_view_set_gradient_properties	(LsmSvgView *view,
 							 LsmSvgSpreadMethod method,
 							 LsmSvgPatternUnits units,
 							 const LsmSvgMatrix *matrix);
 
-gboolean	lsm_svg_view_create_surface_pattern	(LsmSvgView *view, const LsmBox *viewport,
+G_GNUC_WARN_UNUSED_RESULT gboolean
+		lsm_svg_view_create_surface_pattern	(LsmSvgView *view, const LsmBox *viewport,
 							 const LsmSvgMatrix *matrix,
 							 LsmSvgViewSurfaceType surface_type) G_GNUC_WARN_UNUSED_RESULT;