ANGLE SwapChain11 fails with EGL_BAD_ALLOC (Steam CEF black window)

[cyyever]

Environment

• DXMT v0.74 (builtin)
• Wine 11.5 (upstream, x86_64 via Rosetta 2)
• macOS 26.4 (Tahoe), Apple M2
• Steam client (steamwebhelper using Chromium CEF with ANGLE D3D11 backend)

Problem

Steam's CEF uses ANGLE to translate OpenGL ES to D3D11. With DXMT, ANGLE's SwapChain11::reset() fails:

SwapChain11.cpp:636 (virtual rx::SwapChain11::reset): Could not create additional swap chains or offscreen surfaces, HRESULT: 0x80004005
EGL Driver message (Critical) eglCreateWindowSurface: Bad allocation.
eglCreateWindowSurface failed with error EGL_BAD_ALLOC

The GPU process crashes repeatedly and Steam shows a black window.

Steps to reproduce

1. Build Wine 11.5 from source on macOS (x86_64 via Rosetta)
2. Install DXMT v0.74 builtin DLLs
3. Create a Wine prefix and install Steam
4. Launch Steam — observe black window
5. Check Steam/logs/cef_log.txt for the SwapChain11 errors

Related

Issue #79 (ANGLE D3D11 Backend dEQP tests)

[3Shain]

Do you get any log from DXMT? CEF does cross-process rendering (not shared resource, but creating swapchain for HWND of a remote process) without cli argument tweaks, which DXMT doesn't support (and can't support at the moment, due to upstream Wine limitation) and returns E_FAIL (0x80004005).

[cyyever]

Thanks for the quick response. Here are the DXMT logs (DXMT_LOG_LEVEL=3):

info:  Failed to set Metal cache path, fallback to system default
info:  Failed to set Metal cache path, fallback to system default
info:  Maximum supported feature level: D3D_FEATURE_LEVEL_11_1
info:  Using feature level D3D_FEATURE_LEVEL_11_1
warn:  D3D11Resource(tex2d): Unknown interface query f8fb5c27-c6b3-4f75-a4c8-439af2ef564c
err:   CreateSwapChain: cross-process swapchain not supported yet

As you suspected, the issue is the cross-process swapchain. Steam's CEF GPU process creates a swap chain for an HWND owned by the main Steam process.

[YupItzAfi]

Umm, idk if there's more nuance to this, but here I go...
So you can get Steam running via DXMT, here you need to set --in-process-gpu. First in C:/Program Files (x86)/Steam/bin/cef/cef.win7x64, change steamwebhelper.exe to steamwebhelper_real.exe and then you can use my helper program, which is to be placed in that folder. Then DXMT should work.
Basically you can't execute steam.exe with --in-process-gpu, but flags must go directly to steamwebhelper.exe. That helper program does exactly that and has been working for me since.