App Server: Don't set workspace in Desktop::MoveWindowBy

This fixes a bug that's been annoying me - when I use Workspaces to
move a terminal that's scrolling/moving on another workspace, the
terminal begins drawing into the current workspace; this also happens with
some other apps, like Qemu. I tracked this down to Desktop::MoveWindowBy,
where we update an invisible window's current workspace to the one it's
being moved on. Trouble is, the current workspace is set to -1 for windows
on another workspace, and IsVisible just returns whether the current
workspace is >=0, so doing this causes IsVisible to return true when it
shouldn't.

This patch replaces that call with one that sets a separate
invisible workspace member variable, which preserves all window moving
functionality without improperly setting a window as visible. It also fixes a
minor graphical glitch when moving off-workspace tiled windows.

Fixes #6722

Change-Id: I2c4f04602caed85bf08391d0ea99e4dc74c1e1d8
Reviewed-on: https://review.haiku-os.org/c/haiku/+/9256
Reviewed-by: waddlesplash <[email protected]>

src/servers/app/Desktop.cpp

@@ -1484,7 +1484,7 @@ Desktop::MoveWindowBy(Window* window, float x, float y, int32 workspace)
 					}
 
 					stackWindow->Anchor(workspace).position += BPoint(x, y);
-					stackWindow->SetCurrentWorkspace(workspace);
+					stackWindow->SetPriorWorkspace(workspace);
 					_WindowChanged(stackWindow);
 				}
 			}

src/servers/app/Window.cpp

@@ -112,6 +112,7 @@ Window::Window(const BRect& frame, const char *name,
 	fFeel(feel),
 	fWorkspaces(workspaces),
 	fCurrentWorkspace(-1),
+	fPriorWorkspace(-1),
 
 	fMinWidth(1),
 	fMaxWidth(32768),

src/servers/app/Window.h

@@ -222,11 +222,16 @@ public:
 	inline	bool				IsMinimized() const { return fMinimized; }
 
 			void				SetCurrentWorkspace(int32 index)
-									{ fCurrentWorkspace = index; }
+									{ fCurrentWorkspace = index; fPriorWorkspace = index; }
 			int32				CurrentWorkspace() const
 									{ return fCurrentWorkspace; }
 			bool				IsVisible() const;
 
+			void				SetPriorWorkspace(int32 index)
+									{ fPriorWorkspace = index; }
+			int32				PriorWorkspace() const
+									{ return fPriorWorkspace; }
+
 			bool				IsDragging() const;
 			bool				IsResizing() const;
 
@@ -430,6 +435,7 @@ protected:
 			uint32				fFlags;
 			uint32				fWorkspaces;
 			int32				fCurrentWorkspace;
+			int32				fPriorWorkspace;
 
 			int32				fMinWidth;
 			int32				fMaxWidth;

src/servers/app/stackandtile/SATGroup.cpp

@@ -530,9 +530,10 @@ WindowArea::_MoveToSAT(SATWindow* triggerWindow)
 	float deltaByY = round(frameSAT.bottom - frame.bottom);
 
 	int32 workspace = triggerWindow->GetWindow()->CurrentWorkspace();
+	if (workspace < 0)
+		workspace = triggerWindow->GetWindow()->PriorWorkspace();
 	Desktop* desktop = triggerWindow->GetWindow()->Desktop();
-	desktop->MoveWindowBy(topWindow->GetWindow(), deltaToX, deltaToY,
-		workspace);
+	desktop->MoveWindowBy(topWindow->GetWindow(), deltaToX, deltaToY, workspace);
 	// Update frame to the new position
 	desktop->ResizeWindowBy(topWindow->GetWindow(), deltaByX, deltaByY);
 

src/servers/app/stackandtile/SATWindow.cpp

@@ -389,11 +389,16 @@ BRect
 SATWindow::CompleteWindowFrame()
 {
 	BRect frame = fWindow->Frame();
-	if (fDesktop
+	if (fDesktop && fWindow->IsVisible()
 		&& fDesktop->CurrentWorkspace() != fWindow->CurrentWorkspace()) {
 		window_anchor& anchor = fWindow->Anchor(fWindow->CurrentWorkspace());
 		if (anchor.position != kInvalidWindowPosition)
 			frame.OffsetTo(anchor.position);
+	} else if (fDesktop && !fWindow->IsVisible() && fWindow->PriorWorkspace() >= 0
+		&& fDesktop->CurrentWorkspace() != fWindow->PriorWorkspace()) {
+		window_anchor& anchor = fWindow->Anchor(fWindow->PriorWorkspace());
+		if (anchor.position != kInvalidWindowPosition)
+			frame.OffsetTo(anchor.position);
 	}
 
 	AddDecorator(frame);