DXMT: forward D3D10 start instance location

[moreaki]

Summary

Forward the D3D10 DrawIndexedInstanced start-instance argument to the underlying D3D11 context.

MTLD3D10Device::DrawIndexedInstanced currently passes StartIndexLocation as the final DrawIndexedInstanced argument. That final argument is the start-instance/base-instance value, so it should use the incoming StartInstanceLocation parameter instead.

Why

D3D10 indexed instanced draws with a non-zero StartInstanceLocation can currently use the start-index value as the base instance. That can make instance ID based shader inputs and per-instance vertex data selection incorrect.

Validation

• git diff --check
• Applied the same one-line fix on top of the configured macOS/Arm DXMT build branch (DXMT: add LLVM build compatibility fixes #748) and built kmk VBoxDxMt with LLVM 15.0.7.

Closes #760.

Signed-off-by: Roberto Nibali rnibali@gmail.com

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[moreaki]

DXMT v0.80 audit update:

Updating the vendored DXMT tree to v0.80 would not address this. DXMT v0.80 and current DXMT main still pass StartIndexLocation as the final D3D11 DrawIndexedInstanced argument from the D3D10 wrapper.

I opened the equivalent upstream DXMT issue and PR:

• D3D10 DrawIndexedInstanced forwards StartIndexLocation as StartInstanceLocation 3Shain/dxmt#188
• fix(d3d10): forward indexed instanced start instance 3Shain/dxmt#189