[bug] [cef] Black screen when running CEF app with transparency

[aervxa]

Describe the bug

when running a cef app with transparent:true
I get these errors:

[7542:7542:0715/104252.353262:ERROR:content/browser/gpu/gpu_process_host.cc:1089] GPU process exited unexpectedly: exit_code=139
[7542:7542:0715/104256.038834:ERROR:content/browser/gpu/gpu_process_host.cc:1089] GPU process exited unexpectedly: exit_code=139
[7542:7542:0715/104259.525112:ERROR:content/browser/gpu/gpu_process_host.cc:1089] GPU process exited unexpectedly: exit_code=139
[8363:8372:0715/104259.543699:ERROR:ui/base/x/x11_software_bitmap_presenter.cc:147] XGetWindowAttributes failed for window 52428804

If i pass --disable-gpu I still get:

[8363:8372:0715/104259.543699:ERROR:ui/base/x/x11_software_bitmap_presenter.cc:147] XGetWindowAttributes failed for window 52428804

in both cases, a constant black screen stays.

temp fix

setting transparent:false has it working with no errors

Reproduction

Set transparent: true and run cef app

Expected behavior

Transparency works
and the app not crashing/staying black

Full tauri info output

[✔] Environment
    - OS: Arch Linux Rolling Release x86_64 (X64) (KDE on wayland)
    ✔ webkit2gtk-4.1: 2.52.4
    ✔ rsvg2: 2.62.3
    ✔ rustc: 1.96.0 (ac68faa20 2026-05-25)
    ✔ cargo: 1.96.0 (30a34c682 2026-05-25)
    ✔ rustup: 1.29.0 (28d1352db 2026-03-05)
    ✔ Rust toolchain: 1.96.0-x86_64-unknown-linux-gnu (overridden by environment variable RUSTUP_TOOLCHAIN)
    - node: 24.18.0
    - npm: 11.16.0

[-] Packages
    - tauri 🦀: git+https://github.com/tauri-apps/tauri?branch=feat/cef#771228574cbef93324f362c757bb769581b3c66b (2.11.3), (outdated, latest: 2.11.5)
    - tauri-build 🦀: git+https://github.com/tauri-apps/tauri?branch=feat/cef#771228574cbef93324f362c757bb769581b3c66b (2.6.3)
    - wry 🦀: 0.55.1
    - tao 🦀: 0.35.2, (outdated, latest: 0.35.3)
    - @tauri-apps/api  ⱼₛ: 2.11.0 (outdated, latest: 2.11.1)
    - @tauri-apps/cli  ⱼₛ: 2.11.1 (outdated, latest: 2.11.4)

[-] Plugins
    - tauri-plugin-store 🦀: 2.4.3
    - @tauri-apps/plugin-store  ⱼₛ: 2.4.3
    - tauri-plugin-log 🦀: 2.8.0, (outdated, latest: 2.9.0)
    - @tauri-apps/plugin-log  ⱼₛ: not installed!
    - tauri-plugin-os 🦀: 2.3.2
    - @tauri-apps/plugin-os  ⱼₛ: 2.3.2

[-] App
    - build-type: bundle
    - CSP: unset
    - frontendDist: ../.output/public
    - devUrl: http://localhost:3000/
    - framework: Vue.js (Nuxt)
    - bundler: Vite

Stack trace

Additional context

This did not exist in prior versions of either cef or tauri-runtime-cef, I have run the same app with transparency before (around a few days back before 1.50)

[Q1zin]

Yes! I have the same problem. Moreover, on macos there is a white background, and on windows it is black.

[CarltonHere]

With transparent: true, PR #15105 (d99624b, CEF 145) works correctly. Starting with CEF 148 and the new runtime architecture, the window displays an opaque white background.

This may be caused by PR #15588 replacing CEF Views with winit + set_as_child. The CEF child HWND covers the parent window’s Mica backdrop, while transparent CSS and background_color: 0 cannot make that HWND participate in alpha compositing.

[amrbashir]

transparency on macOS and Windows require a special build of CEF that we patched ourselves https://web.crabnebula.cloud/crabnebula/cef-patched/releases . We used to have it enabled by default but reverted that for now. Linux has not been a priority and I can't confirm whether transparency works there or not.

You can use that by setting CEF_DOWNLOAD_URL env var to https://cdn.crabnebula.app/download/crabnebula/cef-patched/latest

If still doesn't work, please let me know and I will investigate, but ensure your build is not using an old downloaded CEF runtime.

[Q1zin]

Wow, it worked, I tested it on macos. Tell me exactly what changes you've made, we're just developing our own version of chromium/cef, which we're bringing up to tauri. If you have a repository/patches/environment for fix transparency, could you share it?)

[amrbashir]

https://github.com/crabnebula-dev/cef/commit/d215e82d5bbd61c71efcc3954fc4b8832fd09bda

[CarltonHere]

transparency on macOS and Windows require a special build of CEF that we patched ourselves https://web.crabnebula.cloud/crabnebula/cef-patched/releases . We used to have it enabled by default but reverted that for now. Linux has not been a priority and I can't confirm whether transparency works there or not.

You can use that by setting CEF_DOWNLOAD_URL env var to https://cdn.crabnebula.app/download/crabnebula/cef-patched/latest

If still doesn't work, please let me know and I will investigate, but ensure your build is not using an old downloaded CEF runtime.

Verified with patched CEF on the official feat/cef single-window path (WebviewWindow + Alloy + transparent background + Mica). Background transparency still fails(https://github.com/CarltonHere/cef-transparency-repro).

Suspected cause: on Windows, Tauri embeds via set_as_child (native child HWND), not the Views path (unlike macOS). The patch only sets kTranslucent for Views frameless windows in window_view.cc. This may be the missing piece:

File: libcef/browser/native/native_widget_delegate.cc
Function: CefNativeWidgetDelegate::Init

// current
params.opacity = kOpaque;

// suggested (same logic as window_view.cc)
params.opacity = background_color_ == SK_ColorTRANSPARENT
                     ? kTranslucent : kOpaque;

macOS works because it does not go through this Widget path. The change above is unverified — hope this helps.

[amrbashir]

On Windows, we embed using set_as_child on all 3 platforms, this is not the problem.

The problem could be related to frameless because when we were using CEF views framework, setting kTranslucent removed decorations (aka title bar) for the window as well, so I guarded kTranslucent usage on Windows behind is_frameless && is_transparent unlike other platforms which only use is_transparent.

However we are no longer using CEF Views framework to create or embed the webview, and so this shouldn't really block the window from being transparent.

[aervxa]

the cef patched mirror on crabnebula doesn't provide a build for linux, so i cannot confirm if it works or not in the patched cef (on linux)

[Q1zin]

I've tested everything again.:
Everything works perfectly on macOS.
On Windows, no, and no matter what window modes I set, there is no result, always a black screen.
If you tell me that everything should work, I'll write a small demo project and send it to you for tests

[CarltonHere]

I applied a second patch on top of your transparency work and rebuilt CEF to verify — luckily, it works!
Release Branch

[Q1zin]

Yes, it works on Windows as well. However, note that cef_runtime_style_t::CEF_RUNTIME_STYLE_DEFAULT = Chrome Runtime, and transparency only works in Alloy, so don't forget to reassign

[rufreakde]

I applied a second patch on top of your transparency work and rebuilt CEF to verify — luckily, it works! Release Branch

any idea if this patch fix is also already released to: https://github.com/energye/energy ?