Bug 57609

Summary: i915 driver reports too large maximum viewport
Product: Mesa Reporter: karaluh <karaluh>
Component: Drivers/DRI/i915Assignee: Ian Romanick <idr>
Status: RESOLVED WONTFIX QA Contact:
Severity: normal    
Priority: medium CC: karaluh
Version: 9.0   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: i915 features:
Bug Depends on:    
Bug Blocks: 67224    

Description karaluh 2012-11-27 12:09:12 UTC
As in summary, glxinfo -l reports GL_MAX_VIEWPORT_DIMS = 16384, 16384 which results in too slow to be unusable dual screen composited setup. Original bug report here:
https://bugs.kde.org/show_bug.cgi?id=308439
Comment 1 Ian Romanick 2013-07-23 17:02:41 UTC
I suspect KDE is using the advertised maximum viewport incorrectly.  The OpenGL spec requires the value be fairly large.  Section 2.12.1 (Controlling the Viewport) says:

    The maximum viewport dimensions must be greater than or equal to
    the larger of the visible dimensions of the display being rendered
    to (if a display exists), and the largest renderbuffer image which
    can be successfully created and attached to a framebuffer object
    (see chapter 4).

X allows the user to create very large windows and pixmaps... even larger than the display itself.  As a result, we can't advertise a small value here and still comply with the spec.

If KDE wants to know sizes that will be "fast," GL_MAX_RENDERBUFFER_SIZE is likely a better metric.

Unless there is additional feedback, I'm going to close this as WONTFIX.
Comment 2 Ian Romanick 2013-07-23 18:02:42 UTC
Looking at the patch in the upstream bug, it looks like they've found the correct solution.  Closing.

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