618765 - unbind VBO required in order to share GL context with toolkit

Status: RESOLVED FIXED

(Core :: Graphics, defect)

Description

[Oleg Romashin (:romaxa)]

Attachment: Unbind Quad VBO

On attempt to render mozilla layout with OGL Manager togeter with Qt/Meego toolkit items (statusbar, FPS renderer, and other possible items on QGraphicsScene) I see this error:
PVR:Aborting: Offset to VBO out of bounds. Likely an app bug in glVertexAttribPointer!

Comment from internal bugzilla:

**************
The error message you're getting indicates that the app is trying use geometry
from a vertex buffer object (VBO) with an offset that goes beyond the end of
the buffer. The most common cause for this is forgetting to unbind a VBO before
using a client-side vertex attribute array. For example:

    glVertexAttribPointer(attr, 3, GL_FLOAT, GL_FALSE, 0, &someArray[0]);

should be

    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glVertexAttribPointer(attr, 3, GL_FLOAT, GL_FALSE, 0, &someArray[0]);

This is because if a vertex buffer object is bound when glVertexAttribPointer
is called, the last parameter is interpreted as an offset into the VBO instead
of an absolute memory pointer.
**************

Comment 1

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

Comment on attachment 497211 [details] [diff] [review]
Unbind Quad VBO

ugh.  this is a Qt bug, but we have to work around it (if it depends on GL state, it should set that state!).

No need for an UnbindQuadVBO function, it's got nothing to do with the Quad VBO.

We should bind buffer 0 again at the end of Initialize (like you have), and also at the end of Render.  No need to bind it at the end of every quad draw, and in fact that'll be pretty expensive.  (We actually want to do even fewer state changes in there, but at some point we'll want to add state tracking to GLContext to do that).  We shouldn't ever have Qt GL rendering in the middle of our own rendering, so as long as we return a GL state back to Qt, we should be fine.

Comment 2

[Florian Hänel [:heeen]]

This longer happens, so I assume it got fixed through returning consistent state.

Comment 3

[Oleg Romashin (:romaxa)]

Attachment: Another version of patch, frontend only

Problem still exists, and I see it from time to time.
Also this API needed for native Embedding, right after EndTransaction we must unbind vbo in order to get it working in embedding context

Comment 4

[Oleg Romashin (:romaxa)]

Attachment: Unbind VBO, Addressed vlad comments

Comment 5

[Jeff Muizelaar [:jrmuizel]]

Comment on attachment 574977 [details] [diff] [review]
Unbind VBO, Addressed vlad comments

mwoodrow says this is fine.

Comment 6

[Dão Gottwald [:dao]]

http://hg.mozilla.org/integration/mozilla-inbound/rev/e52370a94c8d

Comment 7

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/e52370a94c8d

Comment 8

[Oleg Romashin (:romaxa)]

Attachment: Missing returns that also need unbind VBO

Forgot about earlier returns which also needs UnbindVBO

Comment 9

[Oleg Romashin (:romaxa)]

Need to land additional patch

Comment 10

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/5ebeef1eabcb