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fix(host/windows): rebuild the output fresh on every WGC↔DDA source switch

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Key insight (from the user): a fresh RECONNECT shows the secure desktop but the
live transition does not — so the difference is what a fresh session does that
the live switch skipped. A reconnect runs build() = REMOVE + fresh ADD of the
SudoVDA monitor + re-isolate + a fresh capturer; the live transition instead
reused the session-start output (created while on the NORMAL desktop), which goes
born-lost (ACCESS_LOST storm → black) on the secure desktop.

Fix: virtual_stream_relay now calls build() on EVERY source switch (both WGC→DDA
and DDA→WGC), then opens DDA on the new target for secure / uses the fresh helper
for normal. This makes each transition equivalent to the reconnect that works —
fixing both the WGC→DDA cutover (secure desktop now in the clean output state DDA
can duplicate) and the DDA→WGC cutover (a fresh helper's first frame is its
opening IDR, so await_idr clears immediately instead of waiting on a wedged
helper). Costs a ~1-2s rebuild per transition, acceptable for UAC/lock events.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Enrico Bühler
2026-06-16 10:40:55 +00:00
parent ef4786387e
commit 3f191ba2ea
2 changed files with 62 additions and 27 deletions
Download Patch File Download Diff File Expand all files Collapse all files
crates/punktfunk-host/src/capture/composed_flip.rs
+33 -12
View File
@@ -17,19 +17,21 @@
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::Arc;
use windows::core::{w, PCWSTR};
use windows::core::w;
use windows::Win32::Foundation::{HWND, LPARAM, LRESULT, WPARAM};
use windows::Win32::Graphics::Gdi::{GetStockObject, BLACK_BRUSH, HBRUSH};
use windows::Win32::System::LibraryLoader::GetModuleHandleW;
use windows::Win32::System::StationsAndDesktops::{
CloseDesktop, GetUserObjectInformationW, OpenInputDesktop, SetThreadDesktop,
DESKTOP_ACCESS_FLAGS, DESKTOP_CONTROL_FLAGS, UOI_NAME,
};
use windows::Win32::UI::WindowsAndMessaging::{
CreateWindowExW, DefWindowProcW, DestroyWindow, DispatchMessageW, PeekMessageW, RegisterClassW,
SetLayeredWindowAttributes, SetWindowPos, ShowWindow, TranslateMessage, HWND_TOPMOST,
LWA_ALPHA, MSG, PM_REMOVE, SWP_NOACTIVATE, SWP_NOMOVE, SWP_NOSIZE, SW_SHOWNOACTIVATE,
WNDCLASSW, WS_EX_LAYERED, WS_EX_NOACTIVATE, WS_EX_TOOLWINDOW, WS_EX_TOPMOST, WS_EX_TRANSPARENT,
WS_POPUP,
CreateWindowExW, DefWindowProcW, DestroyWindow, DispatchMessageW, GetSystemMetrics,
PeekMessageW, RegisterClassW, SetLayeredWindowAttributes, SetWindowPos, ShowWindow,
TranslateMessage, HWND_TOPMOST, LWA_COLORKEY, MSG, PM_REMOVE, SM_CXVIRTUALSCREEN,
SM_CYVIRTUALSCREEN, SM_XVIRTUALSCREEN, SM_YVIRTUALSCREEN, SWP_NOACTIVATE, SWP_NOMOVE,
SWP_NOSIZE, SW_SHOWNOACTIVATE, WNDCLASSW, WS_EX_LAYERED, WS_EX_NOACTIVATE, WS_EX_TOOLWINDOW,
WS_EX_TOPMOST, WS_EX_TRANSPARENT, WS_POPUP,
};
/// A running force-composed-flip overlay. Drop signals the thread to tear down its window + exit.
@@ -105,6 +107,8 @@ unsafe fn make_overlay() -> Option<HWND> {
lpfnWndProc: Some(wndproc),
hInstance: hinst.into(),
lpszClassName: class,
// Paint the window black so LWA_COLORKEY(black) keys it out → visually invisible.
hbrBackground: HBRUSH(GetStockObject(BLACK_BRUSH).0),
..Default::default()
};
let atom = RegisterClassW(&wc);
@@ -115,15 +119,24 @@ unsafe fn make_overlay() -> Option<HWND> {
tracing::warn!(err = e.0, "force-composed-flip: RegisterClassW failed");
}
}
// Cover the WHOLE virtual screen (all outputs incl. the SudoVDA): a 1x1 corner window may not even
// sit on the captured output's rect, and independent-flip is per-output. A window overlapping the
// output is what disqualifies its flip.
let (vx, vy, vw, vh) = (
GetSystemMetrics(SM_XVIRTUALSCREEN),
GetSystemMetrics(SM_YVIRTUALSCREEN),
GetSystemMetrics(SM_CXVIRTUALSCREEN).max(1),
GetSystemMetrics(SM_CYVIRTUALSCREEN).max(1),
);
let hwnd = match CreateWindowExW(
WS_EX_LAYERED | WS_EX_TRANSPARENT | WS_EX_TOPMOST | WS_EX_NOACTIVATE | WS_EX_TOOLWINDOW,
class,
w!(""),
WS_POPUP,
0,
0,
1,
1,
vx,
vy,
vw,
vh,
None,
None,
Some(hinst.into()),
@@ -137,8 +150,16 @@ unsafe fn make_overlay() -> Option<HWND> {
return None;
}
};
// alpha=1: technically visible (so it disqualifies independent-flip) but imperceptible.
let _ = SetLayeredWindowAttributes(hwnd, windows::Win32::Foundation::COLORREF(0), 1, LWA_ALPHA);
// Color-key on black: the window is painted black (its WNDCLASS background brush) and black is keyed
// out, so it's visually invisible — but DWM counts it as a real opaque window covering the output,
// which is what disqualifies the fullscreen independent-flip (a near-zero ALPHA layered window is
// often ignored by the flip-eligibility check; a color-keyed one is not).
let _ = SetLayeredWindowAttributes(
hwnd,
windows::Win32::Foundation::COLORREF(0x0000_0000),
0,
LWA_COLORKEY,
);
let _ = ShowWindow(hwnd, SW_SHOWNOACTIVATE);
let _ = SetWindowPos(
hwnd,