rhi: gl: Reset tracked state upon a buffer update or readback

...encountered in the command list.

Move all, previously local, tracking variables into a struct. This
allows creating helper functions to reduce error-prone repetition in the
executeCommandBuffer() function body.

The only real change in the patch is in the handling of
Command::BufferSubData and Command::GetBufferSubData: here, instead of
calling glBindBuffer directly, use a helper function that also resets
the relevant state tracking variables. A subsequent
Command::BindVertexBuffer or BindIndexBuffer will therefore correctly
rebind the appropriate buffers.

This is particularly relevant with certain command stream patterns
exercised by some Qt Quick 3D scenes:

- A View3D renders a mesh,
- another View3D has some 2D Qt Quick content, as well as a model with
  the same mesh.

When both View3Ds use the default Offscreen render mode, the resulting
command list consists of segments along the lines of:

1. prepare resources for first View3D

2. render content for first View3D - this binds the vertex and index
   buffers for the mesh (state is tracked; all 1-4 steps are within
   the same command list, processed by a single call to
   executeCommandBuffer())

3. prepare the content for the "inline" 2D Qt Quick scene - this may
   update vertex and index buffers, that may lead to adding
   BufferSubData commands to the list (tracked state (last
   vertex/index buffer) may need invalidation/updating - and that's
   where our problem lies)

4. the second View3Ds 3D content is rendered: a model with the same
   mesh as the last (Quick)3D draw call, so same vertex and index
   buffers. If #3 did not invalidate and/or update the tracked state,
   the glBindBuffer calls are (incorrectly) skipped.

Fixes: QTBUG-89780
Pick-to: 6.0
Change-Id: Icc933252f3993b8727d192e7ba4aa0f842bab51e
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

0 files changed, 0 insertions, 0 deletions