[PATCH 14/19] present: Add window flip mode

Keith Packard keithp at keithp.com
Mon Feb 5 19:09:00 UTC 2018

Michel Dänzer <michel at daenzer.net> writes:

> Ignoring the Security extension, the client has the same control over
> the contents of another application's window *using* the X protocol,
> doesn't it?

Yeah, good point -- it could easily call DRI3BufferFromPixmap for the
window pixmap and have exactly the same access.

> If this is a concern, Present could try allocating a new window pixmap
> to unflip to, and just leave the last flip pixmap as the window pixmap
> if that fails (which it "never" will, in basically any scenario where
> the X server can otherwise continue working normally).

Given your point above, I can't think of any reason to not just use the
provided pixmap as the window pixmap. It does mean we'll be trusting
that the application doesn't accidentally re-use the buffer at some
later time, but as you say, there's no actual security benefit.

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