unom/punktfunk
1
0
Fork 0
Code Issues Pull Requests Actions 1 Packages Projects Releases 4 Wiki Activity

fix(windows-host): force EXTEND topology so a new IddCx display isn't cloned

Browse Source 
A freshly-added IddCx virtual display lands in CLONE/duplicate mode when a
physical display is already active (a laptop panel, an attached monitor): the
cloned output shares that display's source, so the OS never commits a distinct
path for it, never calls ASSIGN_SWAPCHAIN, and capture sees no frames - the
session fails "not an active display path / needs a WDDM GPU to activate" and
tears down with 0 frames (seen live on an Intel-iGPU + NVIDIA-Optimus laptop).

force_extend_topology() applies the EXTEND preset (the programmatic Win+P
"Extend") right after ADD so the IDD comes up as its own active path; the
existing resolve_gdi_name -> set_active_mode -> isolate_displays_ccd bring-up
then proceeds. Idempotent / no-op on a sole-display (headless single-GPU) box,
so it's safe on the path that already worked.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Enrico Bühler
2026-06-26 14:33:15 +00:00
parent 5bf787eb2b
commit 8e87e617df
2 changed files with 35 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files
crates/punktfunk-host/src/windows/win_display.rs
+24 -1
View File
@@ -21,7 +21,7 @@ use windows::Win32::Devices::Display::{
DISPLAYCONFIG_GET_ADVANCED_COLOR_INFO, DISPLAYCONFIG_MODE_INFO, DISPLAYCONFIG_PATH_INFO,
DISPLAYCONFIG_SET_ADVANCED_COLOR_STATE, DISPLAYCONFIG_SOURCE_DEVICE_NAME,
QDC_ONLY_ACTIVE_PATHS, SDC_ALLOW_CHANGES, SDC_APPLY, SDC_FORCE_MODE_ENUMERATION,
SDC_SAVE_TO_DATABASE, SDC_USE_SUPPLIED_DISPLAY_CONFIG,
SDC_SAVE_TO_DATABASE, SDC_TOPOLOGY_EXTEND, SDC_USE_SUPPLIED_DISPLAY_CONFIG,
};
use windows::Win32::Graphics::Gdi::{
ChangeDisplaySettingsExW, EnumDisplaySettingsW, CDS_TEST, CDS_UPDATEREGISTRY, DEVMODEW,
@@ -31,6 +31,29 @@ use windows::Win32::Graphics::Gdi::{
use crate::vdisplay::Mode;
/// Force the desktop into EXTEND topology - the programmatic equivalent of the Win+P / DisplaySwitch
/// "Extend" shortcut. Windows defaults a FRESHLY-ADDED monitor into CLONE/duplicate mode when a
/// physical display is already active (e.g. a laptop panel): a cloned IddCx output shares the panel's
/// source, so the OS never commits a distinct path for it, never calls ASSIGN_SWAPCHAIN, and capture
/// sees no frames (`resolve_gdi_name` stays `None` and the session fails "not an active display path").
/// Applying the EXTEND preset across the live set of connected displays makes the new IddCx monitor its
/// OWN active path, so the rest of bring-up (`resolve_gdi_name` -> `set_active_mode` ->
/// `isolate_displays_ccd`) proceeds. Best-effort + idempotent: a no-op on a single-display (already
/// sole/extended) box, so it is safe to call unconditionally. `rc == 0` is success.
pub(crate) unsafe fn force_extend_topology() {
// A topology flag with no supplied path/mode arrays tells the OS to recompute + apply that preset
// for the currently-connected displays (the same code path DisplaySwitch.exe drives).
let rc = SetDisplayConfig(None, None, SDC_APPLY | SDC_TOPOLOGY_EXTEND);
if rc == 0 {
tracing::info!(
"display topology forced to EXTEND (a new IddCx monitor would otherwise be CLONED onto the \
existing panel -> no distinct source -> no frames)"
);
} else {
tracing::warn!("display force-EXTEND topology: SetDisplayConfig rc={rc:#x}");
}
}
/// Resolve the `\\.\DisplayN` GDI name for a SudoVDA target id via the CCD API. Returns `None`
/// until the OS activates the target into the desktop topology (needs a real WDDM GPU; on a
/// GPU-less box this stays `None` even though ADD succeeded).