From 4184a2db90045c10d56faa390042ebf062a285fa 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 9032b61ef..a3e250345 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,
@@ -1220,7 +1218,8 @@ 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;