Bug 33616

Summary: Transformed image is incorrectly offset when source is a window
Product: xorg Reporter: Keith Kriewall <keith.kriewall>
Component: Server/GeneralAssignee: Xorg Project Team <xorg-team>
Status: RESOLVED FIXED QA Contact: Xorg Project Team <xorg-team>
Severity: normal    
Priority: medium    
Version: unspecified   
Hardware: x86 (IA32)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:

Description Keith Kriewall 2011-01-27 12:14:23 UTC 
An Xrender composite operation involving a scaling or rotating transform and a source picture that is a window results in a mis-aligned transformed image.  If the source picture is a pixmap, the transform works correctly.

An X client that does the following will exhibit the problem:

CreateWindow (57x77) as source
CreateWindow (775x550) as destination
RenderCreatePicture for each of the above drawables
RenderSetPictureFilter (source,"nearest")
RenderSetPictureTransform (source, matrix = 
  [ 1.4615326, 0,        -1069.8418 ]
  [ 0,         1.222229, -587.89215 ]
  [ 0,         0,        1          ] )
RenderComposite(Src operator, srcX/Y=(732,481), dstX/Y=(732,481), for 39x63)

If you substitute a pixmap instead of a window for the source, the transformed (scaled down) source image will be correctly positioned on the destination window.

Found in: X11R7.4 (server versions 1.5.2 and 1.6.4)
Works in: X11R7.1 and earlier

It almost appears that the composite operation is using the center point of the transformed image as the origin, rather than (0,0).

Reporting this against pixman because the only relevant difference between Xrender 7.1 and 7.4 source is the conversion to pixman.
Comment 1 Søren Sandmann Pedersen 2011-01-28 11:31:43 UTC 
There are still issues with windows used as sources in current X servers, but I believe transformations are handled mostly correctly since server version 1.7.4.

Moving to the X server component, and closing as FIXED, but feel free to reopen if you can reproduce with a current server.

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