app_server: clear background immediately on expose

Reduce stamping artifacts when application slowly responds to redraw requests.

This fixes and reintroduces logic previously removed in hrev53711.
Previous logic was incorrect as it didn't take the possibility of multiple
invalidations of different kinds (expose, update request) into account.
Now separate update and expose regions are maintained and only expose region
is cleared immediately.

Change-Id: I0fd98cb1b45ccec285154e8c0d8e3a1400d156d7
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6067
Reviewed-by: Jérôme Duval <[email protected]>
Tested-by: Commit checker robot <[email protected]>

src/servers/app/Desktop.cpp

@@ -1558,12 +1558,14 @@ Desktop::ResizeWindowBy(Window* window, float x, float y)
 		return;
 	}
 
-	// the dirty region for the inside of the window is
-	// constructed by the window itself in ResizeBy()
+	// The dirty region for the inside of the window is constructed by the window itself in
+	// ResizeBy()
 	BRegion newDirtyRegion;
-	// track the dirty region outside the window in case
-	// it is shrunk in "previouslyOccupiedRegion"
+	// Track the dirty region outside the window in case it is shrunk in "previouslyOccupiedRegion"
 	BRegion previouslyOccupiedRegion(window->VisibleRegion());
+	// Track the region that was drawn in previous update sessions, so we can compute the newly
+	// exposed areas by excluding this from the update region.
+	BRegion previousVisibleContentRegion(window->VisibleContentRegion());
 
 	// stop direct frame buffer access
 	bool direct = false;
@@ -1586,7 +1588,15 @@ Desktop::ResizeWindowBy(Window* window, float x, float y)
 	// ...because we do this ourselves
 	newDirtyRegion.Include(&previouslyOccupiedRegion);
 
-	MarkDirty(newDirtyRegion);
+	// calculate old expose region as window visible region difference
+	BRegion exposeRegion(previouslyOccupiedRegion);
+	exposeRegion.Exclude(&window->VisibleRegion());
+	// ...and new expose region as window content visible region difference
+	BRegion tmp(window->VisibleContentRegion());
+	tmp.Exclude(&previousVisibleContentRegion);
+	exposeRegion.Include(&tmp);
+
+	MarkDirty(newDirtyRegion, exposeRegion);
 	_SetBackground(background);
 	_WindowChanged(window);
 
@@ -2166,14 +2176,14 @@ Desktop::FindTarget(BMessenger& messenger)
 
 
 void
-Desktop::MarkDirty(BRegion& region)
+Desktop::MarkDirty(BRegion& dirtyRegion, BRegion& exposeRegion)
 {
-	if (region.CountRects() == 0)
+	if (dirtyRegion.CountRects() == 0)
 		return;
 
 	if (LockAllWindows()) {
 		// send redraw messages to all windows intersecting the dirty region
-		_TriggerWindowRedrawing(region);
+		_TriggerWindowRedrawing(dirtyRegion, exposeRegion);
 
 		UnlockAllWindows();
 	}
@@ -3455,14 +3465,14 @@ Desktop::_RebuildClippingForAllWindows(BRegion& stillAvailableOnScreen)
 
 
 void
-Desktop::_TriggerWindowRedrawing(BRegion& newDirtyRegion)
+Desktop::_TriggerWindowRedrawing(BRegion& dirtyRegion, BRegion& exposeRegion)
 {
 	// send redraw messages to all windows intersecting the dirty region
 	for (Window* window = CurrentWindows().LastWindow(); window != NULL;
 			window = window->PreviousWindow(fCurrentWorkspace)) {
 		if (!window->IsHidden()
-			&& newDirtyRegion.Intersects(window->VisibleRegion().Frame()))
-			window->ProcessDirtyRegion(newDirtyRegion);
+			&& dirtyRegion.Intersects(window->VisibleRegion().Frame()))
+			window->ProcessDirtyRegion(dirtyRegion, exposeRegion);
 	}
 }
 
@@ -3531,7 +3541,7 @@ Desktop::RebuildAndRedrawAfterWindowChange(Window* changedWindow,
 	_SetBackground(stillAvailableOnScreen);
 	_WindowChanged(changedWindow);
 
-	_TriggerWindowRedrawing(dirty);
+	_TriggerWindowRedrawing(dirty, dirty);
 }
 
 
@@ -3603,7 +3613,7 @@ Desktop::_ScreenChanged(Screen* screen)
 
 	// figure out dirty region
 	dirty.Exclude(&background);
-	_TriggerWindowRedrawing(dirty);
+	_TriggerWindowRedrawing(dirty, dirty);
 
 	// send B_SCREEN_CHANGED to windows on that screen
 	BMessage update(B_SCREEN_CHANGED);

src/servers/app/Desktop.h

@@ -240,7 +240,9 @@ public:
 									team_id teamID);
 			EventTarget*		FindTarget(BMessenger& messenger);
 
-			void				MarkDirty(BRegion& region);
+			void				MarkDirty(BRegion& dirtyRegion, BRegion& exposeRegion);
+			void				MarkDirty(BRegion& region)
+									{ return MarkDirty(region, region); }
 			void				Redraw();
 			void				RedrawBackground();
 
@@ -312,7 +314,7 @@ private:
 			void				_RebuildClippingForAllWindows(
 									BRegion& stillAvailableOnScreen);
 			void				_TriggerWindowRedrawing(
-									BRegion& newDirtyRegion);
+									BRegion& dirtyRegion, BRegion& exposeRegion);
 			void				_SetBackground(BRegion& background);
 
 			status_t			_ActivateApp(team_id team);

src/servers/app/ServerWindow.cpp

@@ -1378,7 +1378,7 @@ fDesktop->LockSingleWindow();
 			float offsetX = x - fCurrentView->Frame().left;
 			float offsetY = y - fCurrentView->Frame().top;
 
-			BRegion dirty;
+			BRegion dirty, expose;
 			fCurrentView->MoveBy(offsetX, offsetY, &dirty);
 
 			// TODO: think about how to avoid this hack:
@@ -1389,7 +1389,7 @@ fDesktop->LockSingleWindow();
 			if (View* parent = fCurrentView->Parent())
 				parent->RebuildClipping(false);
 
-			fWindow->MarkContentDirty(dirty);
+			fWindow->MarkContentDirty(dirty, expose);
 			break;
 		}
 		case AS_VIEW_RESIZE_TO:
@@ -1406,14 +1406,14 @@ fDesktop->LockSingleWindow();
 			float deltaWidth = newWidth - fCurrentView->Frame().Width();
 			float deltaHeight = newHeight - fCurrentView->Frame().Height();
 
-			BRegion dirty;
+			BRegion dirty, expose;
 			fCurrentView->ResizeBy(deltaWidth, deltaHeight, &dirty);
 
 			// TODO: see above
 			if (View* parent = fCurrentView->Parent())
 				parent->RebuildClipping(false);
 
-			fWindow->MarkContentDirty(dirty);
+			fWindow->MarkContentDirty(dirty, expose);
 			break;
 		}
 		case AS_VIEW_GET_COORD:

src/servers/app/View.cpp

@@ -905,7 +905,7 @@ View::CopyBits(IntRect src, IntRect dst, BRegion& windowContentClipping)
 	dirty->Exclude(copyRegion);
 
 	dirty->IntersectWith(screenAndUserClipping);
-	fWindow->MarkContentDirty(*dirty);
+	fWindow->MarkContentDirty(*dirty, *dirty);
 
 	fWindow->RecycleRegion(dirty);
 	fWindow->RecycleRegion(copyRegion);
@@ -1045,8 +1045,8 @@ View::BlendAllLayers()
 
 
 void
-View::Draw(DrawingEngine* drawingEngine, BRegion* effectiveClipping,
-	BRegion* windowContentClipping, bool deep)
+View::Draw(DrawingEngine* drawingEngine, const BRegion* effectiveClipping,
+	const BRegion* windowContentClipping, bool deep)
 {
 	if (!fVisible) {
 		// child views cannot be visible either
@@ -1245,9 +1245,9 @@ View::SetHidden(bool hidden)
 				IntRect clippedBounds = Bounds();
 				ConvertToVisibleInTopView(&clippedBounds);
 
-				BRegion dirty;
+				BRegion dirty, expose;
 				dirty.Set((clipping_rect)clippedBounds);
-				fWindow->MarkContentDirty(dirty);
+				fWindow->MarkContentDirty(dirty, expose);
 			}
 		}
 	}
@@ -1426,7 +1426,7 @@ View::RebuildClipping(bool deep)
 
 
 BRegion&
-View::ScreenAndUserClipping(BRegion* windowContentClipping, bool force) const
+View::ScreenAndUserClipping(const BRegion* windowContentClipping, bool force) const
 {
 	// no user clipping - return screen clipping directly
 	if (!fUserClipping.IsSet())
@@ -1477,7 +1477,7 @@ View::InvalidateScreenClipping()
 
 
 BRegion&
-View::_ScreenClipping(BRegion* windowContentClipping, bool force) const
+View::_ScreenClipping(const BRegion* windowContentClipping, bool force) const
 {
 	if (!fScreenClippingValid || force) {
 		fScreenClipping = fLocalClipping;

src/servers/app/View.h

@@ -170,8 +170,8 @@ public:
 
 			// for background clearing
 			virtual void	Draw(DrawingEngine* drawingEngine,
-								BRegion* effectiveClipping,
-								BRegion* windowContentClipping,
+								const BRegion* effectiveClipping,
+								const BRegion* windowContentClipping,
 								bool deep = false);
 
 			virtual void	MouseDown(BMessage* message, BPoint where);
@@ -204,7 +204,7 @@ public:
 			// clipping
 			void			RebuildClipping(bool deep);
 			BRegion&		ScreenAndUserClipping(
-								BRegion* windowContentClipping,
+								const BRegion* windowContentClipping,
 								bool force = false) const;
 			void			InvalidateScreenClipping();
 	inline	bool			IsScreenClippingValid() const
@@ -228,7 +228,7 @@ protected:
 	virtual	void			_ScreenToLocalTransform(
 								SimpleTransform& transform) const;
 
-			BRegion&		_ScreenClipping(BRegion* windowContentClipping,
+			BRegion&		_ScreenClipping(const BRegion* windowContentClipping,
 								bool force = false) const;
 			void			_MoveScreenClipping(int32 x, int32 y,
 								bool deep);

src/servers/app/Window.cpp

@@ -81,7 +81,6 @@ Window::Window(const BRect& frame, const char *name,
 	fVisibleRegion(),
 	fVisibleContentRegion(),
 	fDirtyRegion(),
-	fDirtyCause(0),
 
 	fContentRegion(),
 	fEffectiveDrawingRegion(),
@@ -289,6 +288,7 @@ Window::MoveBy(int32 x, int32 y, bool moveStack)
 	// take along the dirty region which is not
 	// processed yet
 	fDirtyRegion.OffsetBy(x, y);
+	fExposeRegion.OffsetBy(x, y);
 
 	if (fContentRegionValid)
 		fContentRegion.OffsetBy(x, y);
@@ -737,7 +737,7 @@ Window::DrawingRegionChanged(View* view) const
 
 
 void
-Window::ProcessDirtyRegion(BRegion& region)
+Window::ProcessDirtyRegion(const BRegion& dirtyRegion, const BRegion& exposeRegion)
 {
 	// if this is executed in the desktop thread,
 	// it means that the window thread currently
@@ -760,8 +760,8 @@ Window::ProcessDirtyRegion(BRegion& region)
 		ServerWindow()->RequestRedraw();
 	}
 
-	fDirtyRegion.Include(&region);
-	fDirtyCause |= UPDATE_EXPOSE;
+	fDirtyRegion.Include(&dirtyRegion);
+	fExposeRegion.Include(&exposeRegion);
 }
 
 
@@ -770,7 +770,7 @@ Window::RedrawDirtyRegion()
 {
 	if (TopLayerStackWindow() != this) {
 		fDirtyRegion.MakeEmpty();
-		fDirtyCause = 0;
+		fExposeRegion.MakeEmpty();
 		return;
 	}
 
@@ -778,13 +778,15 @@ Window::RedrawDirtyRegion()
 	if (IsVisible()) {
 		_DrawBorder();
 
-		BRegion* dirtyContentRegion =
-			fRegionPool.GetRegion(VisibleContentRegion());
+		BRegion* dirtyContentRegion = fRegionPool.GetRegion(VisibleContentRegion());
+		BRegion* exposeContentRegion = fRegionPool.GetRegion(VisibleContentRegion());
 		dirtyContentRegion->IntersectWith(&fDirtyRegion);
+		exposeContentRegion->IntersectWith(&fExposeRegion);
 
-		_TriggerContentRedraw(*dirtyContentRegion);
+		_TriggerContentRedraw(*dirtyContentRegion, *exposeContentRegion);
 
 		fRegionPool.Recycle(dirtyContentRegion);
+		fRegionPool.Recycle(exposeContentRegion);
 	}
 
 	// reset the dirty region, since
@@ -795,7 +797,7 @@ Window::RedrawDirtyRegion()
 	// get write access, since we're holding
 	// the read lock for the whole time.
 	fDirtyRegion.MakeEmpty();
-	fDirtyCause = 0;
+	fExposeRegion.MakeEmpty();
 }
 
 
@@ -812,7 +814,7 @@ Window::MarkDirty(BRegion& regionOnScreen)
 
 
 void
-Window::MarkContentDirty(BRegion& regionOnScreen)
+Window::MarkContentDirty(BRegion& dirtyRegion, BRegion& exposeRegion)
 {
 	// for triggering AS_REDRAW
 	// since this won't affect other windows, read locking
@@ -821,27 +823,26 @@ Window::MarkContentDirty(BRegion& regionOnScreen)
 	if (fHidden || IsOffscreenWindow())
 		return;
 
-	regionOnScreen.IntersectWith(&VisibleContentRegion());
-	fDirtyCause |= UPDATE_REQUEST;
-	_TriggerContentRedraw(regionOnScreen);
+	dirtyRegion.IntersectWith(&VisibleContentRegion());
+	exposeRegion.IntersectWith(&VisibleContentRegion());
+	_TriggerContentRedraw(dirtyRegion, exposeRegion);
 }
 
 
 void
-Window::MarkContentDirtyAsync(BRegion& regionOnScreen)
+Window::MarkContentDirtyAsync(BRegion& dirtyRegion)
 {
 	// NOTE: see comments in ProcessDirtyRegion()
 	if (fHidden || IsOffscreenWindow())
 		return;
 
-	regionOnScreen.IntersectWith(&VisibleContentRegion());
+	dirtyRegion.IntersectWith(&VisibleContentRegion());
 
 	if (fDirtyRegion.CountRects() == 0) {
 		ServerWindow()->RequestRedraw();
 	}
 
-	fDirtyRegion.Include(&regionOnScreen);
-	fDirtyCause |= UPDATE_REQUEST;
+	fDirtyRegion.Include(&dirtyRegion);
 }
 
 
@@ -860,7 +861,6 @@ Window::InvalidateView(View* view, BRegion& viewRegion)
 
 //fDrawingEngine->FillRegion(viewRegion, rgb_color{ 0, 255, 0, 255 });
 //snooze(10000);
-			fDirtyCause |= UPDATE_REQUEST;
 			_TriggerContentRedraw(viewRegion);
 		}
 	}
@@ -1767,16 +1767,27 @@ Window::_ShiftPartOfRegion(BRegion* region, BRegion* regionToShift,
 
 
 void
-Window::_TriggerContentRedraw(BRegion& dirtyContentRegion)
+Window::_TriggerContentRedraw(BRegion& dirty, const BRegion& expose)
 {
-	if (!IsVisible() || dirtyContentRegion.CountRects() == 0
-		|| (fFlags & kWindowScreenFlag) != 0)
+	if (!IsVisible() || dirty.CountRects() == 0 || (fFlags & kWindowScreenFlag) != 0)
 		return;
 
 	// put this into the pending dirty region
 	// to eventually trigger a client redraw
+	_TransferToUpdateSession(&dirty);
 
-	_TransferToUpdateSession(&dirtyContentRegion);
+	if (expose.CountRects() > 0) {
+		// draw exposed region background right now to avoid stamping artifacts
+		if (fDrawingEngine->LockParallelAccess()) {
+			bool copyToFrontEnabled = fDrawingEngine->CopyToFrontEnabled();
+			fDrawingEngine->SetCopyToFrontEnabled(true);
+			fDrawingEngine->SuspendAutoSync();
+			fTopView->Draw(fDrawingEngine.Get(), &expose, &fContentRegion, true);
+			fDrawingEngine->Sync();
+			fDrawingEngine->SetCopyToFrontEnabled(copyToFrontEnabled);
+			fDrawingEngine->UnlockParallelAccess();
+		}
+	}
 }
 
 
@@ -1841,8 +1852,6 @@ Window::_TransferToUpdateSession(BRegion* contentDirtyRegion)
 
 	// add to pending
 	fPendingUpdateSession->SetUsed(true);
-//	if (!fPendingUpdateSession->IsExpose())
-	fPendingUpdateSession->AddCause(fDirtyCause);
 	fPendingUpdateSession->Include(contentDirtyRegion);
 
 	if (!fUpdateRequested) {
@@ -2058,13 +2067,7 @@ Window::_ObeySizeLimits()
 Window::UpdateSession::UpdateSession()
 	:
 	fDirtyRegion(),
-	fInUse(false),
-	fCause(0)
-{
-}
-
-
-Window::UpdateSession::~UpdateSession()
+	fInUse(false)
 {
 }
 
@@ -2094,17 +2097,8 @@ void
 Window::UpdateSession::SetUsed(bool used)
 {
 	fInUse = used;
-	if (!fInUse) {
+	if (!fInUse)
 		fDirtyRegion.MakeEmpty();
-		fCause = 0;
-	}
-}
-
-
-void
-Window::UpdateSession::AddCause(uint8 cause)
-{
-	fCause |= cause;
 }
 
 

src/servers/app/Window.h

@@ -81,11 +81,6 @@ class WorkspacesView;
 // TODO: move this into a proper place
 #define AS_REDRAW 'rdrw'
 
-enum {
-	UPDATE_REQUEST		= 0x01,
-	UPDATE_EXPOSE		= 0x02,
-};
-
 
 class Window {
 public:
@@ -149,15 +144,19 @@ public:
 			bool				DrawingRegionChanged(View* view) const;
 
 			// generic version, used by the Desktop
-			void				ProcessDirtyRegion(BRegion& regionOnScreen);
+			void				ProcessDirtyRegion(const BRegion& dirtyRegion,
+									const BRegion& exposeRegion);
+			void				ProcessDirtyRegion(const BRegion& exposeRegion)
+									{ ProcessDirtyRegion(exposeRegion, exposeRegion); }
 			void				RedrawDirtyRegion();
 
 			// can be used from inside classes that don't
 			// need to know about Desktop (first version uses Desktop)
 			void				MarkDirty(BRegion& regionOnScreen);
 			// these versions do not use the Desktop
-			void				MarkContentDirty(BRegion& regionOnScreen);
-			void				MarkContentDirtyAsync(BRegion& regionOnScreen);
+			void				MarkContentDirty(BRegion& dirtyRegion,
+									BRegion& exposeRegion);
+			void				MarkContentDirtyAsync(BRegion& dirtyRegion);
 			// shortcut for invalidating just one view
 			void				InvalidateView(View* view, BRegion& viewRegion);
 
@@ -322,7 +321,8 @@ protected:
 									int32 yOffset);
 
 			// different types of drawing
-			void				_TriggerContentRedraw(BRegion& dirty);
+			void				_TriggerContentRedraw(BRegion& dirty,
+									const BRegion& expose = BRegion());
 			void				_DrawBorder();
 
 			// handling update sessions
@@ -348,13 +348,19 @@ protected:
 
 			BRegion				fVisibleRegion;
 			BRegion				fVisibleContentRegion;
-			// our part of the "global" dirty region
-			// it is calculated from the desktop thread,
-			// but we can write to it when we read locked
-			// the clipping, since it is local and the desktop
-			// thread is blocked
+
+			// Our part of the "global" dirty region (what needs to be redrawn).
+			// It is calculated from the desktop thread, but we can write to it when we read locked
+			// the clipping, since it is local and the desktop thread is blocked.
 			BRegion				fDirtyRegion;
-			uint32				fDirtyCause;
+
+			// Subset of the dirty region that is newly exposed. While the dirty region is merely
+			// showing out of date data on screen, this subset of it is showing remains of other
+			// windows. To avoid glitches, it must be set to a reasonable state as fast as possible,
+			// without waiting for a roundtrip to the window's Draw() methods. So it will be filled
+			// using background color and view bitmap, which can all be done without leaving
+			// app_server.
+			BRegion				fExposeRegion;
 
 			// caching local regions
 			BRegion				fContentRegion;
@@ -386,7 +392,6 @@ protected:
 	class UpdateSession {
 	public:
 									UpdateSession();
-		virtual						~UpdateSession();
 
 				void				Include(BRegion* additionalDirty);
 				void				Exclude(BRegion* dirtyInNextSession);
@@ -400,16 +405,9 @@ protected:
 		inline	bool				IsUsed() const
 										{ return fInUse; }
 
-				void				AddCause(uint8 cause);
-		inline	bool				IsExpose() const
-										{ return fCause & UPDATE_EXPOSE; }
-		inline	bool				IsRequest() const
-										{ return fCause & UPDATE_REQUEST; }
-
 	private:
 				BRegion				fDirtyRegion;
 				bool				fInUse;
-				uint8				fCause;
 	};
 
 			UpdateSession		fUpdateSessions[2];

src/servers/app/WorkspacesView.cpp

@@ -358,14 +358,14 @@ WorkspacesView::_Invalidate() const
 	BRect frame = Bounds();
 	LocalToScreenTransform().Apply(&frame);
 
-	BRegion region(frame);
-	Window()->MarkContentDirty(region);
+	BRegion region(frame), expose;
+	Window()->MarkContentDirty(region, expose);
 }
 
 
 void
-WorkspacesView::Draw(DrawingEngine* drawingEngine, BRegion* effectiveClipping,
-	BRegion* windowContentClipping, bool deep)
+WorkspacesView::Draw(DrawingEngine* drawingEngine, const BRegion* effectiveClipping,
+	const BRegion* windowContentClipping, bool deep)
 {
 	// we can only draw within our own area
 	BRegion redraw(ScreenAndUserClipping(windowContentClipping));

src/servers/app/WorkspacesView.h

@@ -23,8 +23,8 @@ public:
 	virtual	void	DetachedFromWindow();
 
 	virtual	void	Draw(DrawingEngine* drawingEngine,
-						BRegion* effectiveClipping,
-						BRegion* windowContentClipping, bool deep = false);
+						const BRegion* effectiveClipping,
+						const BRegion* windowContentClipping, bool deep = false);
 
 	virtual	void	MouseDown(BMessage* message, BPoint where);
 	virtual	void	MouseUp(BMessage* message, BPoint where);