Add helper function to calculate the area of the intersection of two rectangles.

1 files changed, 13 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/common/utils.c b/src/mesa/drivers/dri/common/utils.c
index 74ed299a628..6a189e72858 100644
--- a/src/mesa/drivers/dri/common/utils.c
+++ b/src/mesa/drivers/dri/common/utils.c
@@ -421,6 +421,19 @@ driCheckDriDdxDrmVersions2(const char * driver_name,
 
 
 
+GLint
+driIntersectArea( drm_clip_rect_t rect1, drm_clip_rect_t rect2 )
+{
+   if (rect2.x1 > rect1.x1) rect1.x1 = rect2.x1;
+   if (rect2.x2 < rect1.x2) rect1.x2 = rect2.x2;
+   if (rect2.y1 > rect1.y1) rect1.y1 = rect2.y1;
+   if (rect2.y2 < rect1.y2) rect1.y2 = rect2.y2;
+
+   if (rect1.x1 > rect1.x2 || rect1.y1 > rect1.y2) return 0;
+
+   return (rect1.x2 - rect1.x1) * (rect1.y2 - rect1.y1);
+}
+
 GLboolean driClipRectToFramebuffer( const GLframebuffer *buffer,
 				    GLint *x, GLint *y,
 				    GLsizei *width, GLsizei *height )