Viewer: cover full-screen transition stale frames (#86)

Full-screen enter/exit can expose one stale DWM composition frame while the frame style, menu, and placement are changing. Instead of hiding the app or using LockWindowUpdate, capture the monitor contents before the structural change and show that snapshot as a temporary topmost cover until the final Viewer frame has been repainted and flushed.

This removes the old LockWindowUpdate/DWM-transition timer workaround, which could produce classic-theme flashes, and keeps the placement/copy-bits safeguards from the partial mitigation.

Closes #86

Author: chammoru

Viewer/ViewerView.cpp

@@ -41,8 +41,6 @@ const bool printPlaySpeed = false;
 
 #define WM_VIEWER_PLAY_TIMER (WM_APP + 1)
 
-static const UINT_PTR VIEWER_FULLSCREEN_DWM_TIMER = 0x5100;
-static const UINT VIEWER_FULLSCREEN_DWM_DELAY_MS = 250;
 
 enum QMouseMenuID
 {
@@ -61,6 +59,80 @@ static const QMouseMenuInfo QMouseMenu[] = {
 	{ "Sync Input", QMouseMenuSyncInput },
 };
 
+class CTransitionSnapshotCover {
+public:
+	CTransitionSnapshotCover() : mHwnd(NULL), mBitmap(NULL) {}
+
+	~CTransitionSnapshotCover()
+	{
+		Destroy();
+	}
+
+	bool Create(const RECT &rc)
+	{
+		Destroy();
+
+		const int w = rc.right - rc.left;
+		const int h = rc.bottom - rc.top;
+		if (w <= 0 || h <= 0)
+			return false;
+
+		HDC screenDC = ::GetDC(NULL);
+		if (screenDC == NULL)
+			return false;
+
+		HDC memDC = ::CreateCompatibleDC(screenDC);
+		if (memDC == NULL) {
+			::ReleaseDC(NULL, screenDC);
+			return false;
+		}
+
+		mBitmap = ::CreateCompatibleBitmap(screenDC, w, h);
+		if (mBitmap != NULL) {
+			HGDIOBJ oldBitmap = ::SelectObject(memDC, mBitmap);
+			::BitBlt(memDC, 0, 0, w, h, screenDC, rc.left, rc.top, SRCCOPY);
+			::SelectObject(memDC, oldBitmap);
+		}
+
+		::DeleteDC(memDC);
+		::ReleaseDC(NULL, screenDC);
+
+		if (mBitmap == NULL)
+			return false;
+
+		mHwnd = ::CreateWindowEx(WS_EX_TOOLWINDOW | WS_EX_TOPMOST | WS_EX_NOACTIVATE,
+			_T("STATIC"), NULL, WS_POPUP | SS_BITMAP,
+			rc.left, rc.top, w, h, NULL, NULL, AfxGetInstanceHandle(), NULL);
+		if (mHwnd == NULL) {
+			::DeleteObject(mBitmap);
+			mBitmap = NULL;
+			return false;
+		}
+
+		::SendMessage(mHwnd, STM_SETIMAGE, IMAGE_BITMAP, (LPARAM)mBitmap);
+		::ShowWindow(mHwnd, SW_SHOWNOACTIVATE);
+		::UpdateWindow(mHwnd);
+		::DwmFlush();
+		return true;
+	}
+
+	void Destroy()
+	{
+		if (mHwnd != NULL) {
+			::DestroyWindow(mHwnd);
+			mHwnd = NULL;
+		}
+		if (mBitmap != NULL) {
+			::DeleteObject(mBitmap);
+			mBitmap = NULL;
+		}
+	}
+
+private:
+	HWND mHwnd;
+	HBITMAP mBitmap;
+};
+
 using namespace std;
 
 // CViewerView
@@ -1713,38 +1785,47 @@ void CViewerView::ToggleFullScreen()
 	CMainFrame *pMainFrm = static_cast<CMainFrame *>(AfxGetMainWnd());
 	if (pMainFrm == NULL)
 		return;
+	HWND hFrame = pMainFrm->GetSafeHwnd();
 
 	const bool entering = !mFullMode;
+	MONITORINFO monitorInfo = {};
+	monitorInfo.cbSize = sizeof(monitorInfo);
+	HMONITOR hMonitor = ::MonitorFromWindow(hFrame, MONITOR_DEFAULTTONEAREST);
+	const bool haveMonitorInfo = ::GetMonitorInfo(hMonitor, &monitorInfo) != FALSE;
+
+	CTransitionSnapshotCover transitionCover;
+	if (haveMonitorInfo)
+		transitionCover.Create(monitorInfo.rcMonitor);
+
+	// Batch the structural full-screen change without LockWindowUpdate. That API
+	// can make themed non-client areas flash as classic controls during the frame
+	// swap. The snapshot cover keeps DWM's one-frame stale surface out of view
+	// without flashing through to the desktop or a black placeholder.
 	pMainFrm->SetRedraw(FALSE);
 	SetRedraw(FALSE);
-	::LockWindowUpdate(pMainFrm->GetSafeHwnd());
-	KillTimer(VIEWER_FULLSCREEN_DWM_TIMER);
-	BOOL disableDwmTransitions = TRUE;
-	::DwmSetWindowAttribute(pMainFrm->GetSafeHwnd(),
-		DWMWA_TRANSITIONS_FORCEDISABLED,
-		&disableDwmTransitions,
-		sizeof(disableDwmTransitions));
 
 	if (entering) {
 		mPreFullPlacement.length = sizeof(mPreFullPlacement);
 		mHavePreFullPlacement = pMainFrm->GetWindowPlacement(&mPreFullPlacement) != FALSE;
-		if (mPreFullPlacement.showCmd == SW_SHOWMINIMIZED)
+		if (mPreFullPlacement.showCmd == SW_SHOWMINIMIZED || !pMainFrm->IsZoomed())
 			mPreFullPlacement.showCmd = SW_SHOWNORMAL;
 
 		mFullMode = true;
 
 		MONITORINFO mi = {};
 		mi.cbSize = sizeof(mi);
 		HMONITOR hmon = ::MonitorFromWindow(pMainFrm->GetSafeHwnd(), MONITOR_DEFAULTTONEAREST);
-		if (::GetMonitorInfo(hmon, &mi)) {
+		if (haveMonitorInfo || ::GetMonitorInfo(hmon, &mi)) {
+			if (haveMonitorInfo)
+				mi = monitorInfo;
 			CRect rc(mi.rcMonitor);
 			pMainFrm->SetMenu(NULL);
 			pMainFrm->ModifyStyle(
 				WS_CAPTION | WS_SYSMENU | WS_THICKFRAME | WS_MINIMIZEBOX | WS_MAXIMIZEBOX,
 				WS_POPUP, 0);
 			pMainFrm->SetWindowPos(&CWnd::wndTop, rc.left, rc.top,
 				rc.Width(), rc.Height(),
-				SWP_NOOWNERZORDER | SWP_FRAMECHANGED | SWP_NOREDRAW);
+				SWP_NOOWNERZORDER | SWP_FRAMECHANGED | SWP_NOREDRAW | SWP_NOCOPYBITS);
 		}
 	} else {
 		mFullMode = false;
@@ -1756,24 +1837,32 @@ void CViewerView::ToggleFullScreen()
 			0);
 		pMainFrm->AddMainMenu();
 		GetDocument()->UpdateMenu();
-		if (mHavePreFullPlacement)
+		if (mHavePreFullPlacement && mPreFullPlacement.showCmd != SW_SHOWMAXIMIZED) {
+			const CRect rc(mPreFullPlacement.rcNormalPosition);
+			pMainFrm->SetWindowPos(NULL, rc.left, rc.top,
+				rc.Width(), rc.Height(),
+				SWP_NOZORDER | SWP_NOOWNERZORDER | SWP_FRAMECHANGED |
+				SWP_NOREDRAW | SWP_NOCOPYBITS);
+		} else if (mHavePreFullPlacement) {
 			pMainFrm->SetWindowPlacement(&mPreFullPlacement);
-		else
+		} else {
 			pMainFrm->ShowWindow(SW_RESTORE);
+		}
 		pMainFrm->SetWindowPos(NULL, 0, 0, 0, 0,
 			SWP_NOMOVE | SWP_NOSIZE | SWP_NOZORDER |
-			SWP_NOOWNERZORDER | SWP_FRAMECHANGED | SWP_NOREDRAW);
+			SWP_NOOWNERZORDER | SWP_FRAMECHANGED | SWP_NOREDRAW | SWP_NOCOPYBITS);
 	}
 
 	pMainFrm->RecalcLayout(TRUE);
 	FitToWindow();
 	pMainFrm->SetRedraw(TRUE);
 	SetRedraw(TRUE);
-	::LockWindowUpdate(NULL);
 	pMainFrm->SetForegroundWindow();
 	pMainFrm->RedrawWindow(NULL, NULL,
 		RDW_INVALIDATE | RDW_UPDATENOW | RDW_ALLCHILDREN | RDW_FRAME | RDW_ERASE);
-	SetTimer(VIEWER_FULLSCREEN_DWM_TIMER, VIEWER_FULLSCREEN_DWM_DELAY_MS, NULL);
+	::DwmFlush();
+	transitionCover.Destroy();
+	::DwmFlush();
 }
 
 void CViewerView::ToggleHelp()
@@ -2101,16 +2190,6 @@ void CViewerView::OnDestroy()
 {
 	CView::OnDestroy();
 
-	KillTimer(VIEWER_FULLSCREEN_DWM_TIMER);
-	CMainFrame *pMainFrm = static_cast<CMainFrame *>(AfxGetMainWnd());
-	if (pMainFrm != NULL) {
-		BOOL disableDwmTransitions = FALSE;
-		::DwmSetWindowAttribute(pMainFrm->GetSafeHwnd(),
-			DWMWA_TRANSITIONS_FORCEDISABLED,
-			&disableDwmTransitions,
-			sizeof(disableDwmTransitions));
-	}
-
 	mBufferPool->disable();
 	mBufferQueue->destroy();
 	KillPlayTimer();
@@ -2154,19 +2233,6 @@ void CViewerView::OnSize(UINT nType, int cx, int cy)
 
 void CViewerView::OnTimer(UINT_PTR nIDEvent)
 {
-	if (nIDEvent == VIEWER_FULLSCREEN_DWM_TIMER) {
-		KillTimer(VIEWER_FULLSCREEN_DWM_TIMER);
-		CMainFrame *pMainFrm = static_cast<CMainFrame *>(AfxGetMainWnd());
-		if (pMainFrm != NULL) {
-			BOOL disableDwmTransitions = FALSE;
-			::DwmSetWindowAttribute(pMainFrm->GetSafeHwnd(),
-				DWMWA_TRANSITIONS_FORCEDISABLED,
-				&disableDwmTransitions,
-				sizeof(disableDwmTransitions));
-		}
-		return;
-	}
-
 	CView::OnTimer(nIDEvent);
 }