From 6d3a9e40a4b9ec455af11cce31e4aa616c93db32 Mon Sep 17 00:00:00 2001
From: Keith Packard <keithp@keithp.com>
Date: Mon, 17 Mar 2008 23:04:49 -0700
Subject: [PATCH] Compute matrix inversion instead of using wire version in
 RRCrtcTransformSet

It doesn't make sense to have the client invert this matrix when the server
can do so reasonably efficiently. This avoids weird fixed point rounding
errors when testing the transform against its inverse. Now to fix the
protocol.
---
 randr/rrcrtc.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/randr/rrcrtc.c b/randr/rrcrtc.c
index b71588402..b8b9ec03a 100644
--- a/randr/rrcrtc.c
+++ b/randr/rrcrtc.c
@@ -608,8 +608,6 @@ RRCrtcTransformSet (RRCrtcPtr		crtc,
     PictFilterPtr   filter = NULL;
     int		    width = 0, height = 0;
 
-    if (!PictureTransformIsInverse (transform, inverse))
-	return BadMatch;
     if (filter_len)
     {
 	filter = PictureFindFilter (crtc->pScreen,
@@ -1229,7 +1227,8 @@ ProcRRSetCrtcTransform (ClientPtr client)
 	return RRErrorBase + BadRRCrtc;
 
     PictTransform_from_xRenderTransform (&transform, &stuff->transform);
-    PictTransform_from_xRenderTransform (&inverse, &stuff->inverse);
+    if (!PictureTransformInvert (&inverse, &transform))
+	return BadMatch;
 
     filter = (char *) (stuff + 1);
     nbytes = stuff->nbytesFilter;