app_server: Drawing mode fixups

* TODO: squash commit before merge into master

src/servers/app/DrawState.cpp

@@ -526,21 +526,26 @@ DrawState::SetPattern(const Pattern& pattern)
 }
 
 
-void
+bool
 DrawState::SetDrawingMode(drawing_mode mode)
 {
-	if (!fDrawingModeLocked)
+	if (!fDrawingModeLocked) {
 		fDrawingMode = mode;
+		return true;
+	}
+	return false;
 }
 
 
-void
+bool
 DrawState::SetBlendingMode(source_alpha srcMode, alpha_function fncMode)
 {
 	if (!fDrawingModeLocked) {
 		fAlphaSrcMode = srcMode;
 		fAlphaFncMode = fncMode;
+		return true;
 	}
+	return false;
 }
 
 

src/servers/app/DrawState.h

@@ -100,11 +100,11 @@ public:
 								{ return fPattern; }
 
 							// drawing/blending mode
-		void				SetDrawingMode(drawing_mode mode);
+		bool				SetDrawingMode(drawing_mode mode);
 		drawing_mode		GetDrawingMode() const
 								{ return fDrawingMode; }
 
-		void				SetBlendingMode(source_alpha srcMode,
+		bool				SetBlendingMode(source_alpha srcMode,
 								alpha_function fncMode);
 		source_alpha		AlphaSrcMode() const
 								{ return fAlphaSrcMode; }

src/servers/app/ServerPicture.cpp

@@ -626,8 +626,8 @@ set_pen_location(Canvas* canvas, BPoint pt)
 static void
 set_drawing_mode(Canvas* canvas, drawing_mode mode)
 {
-	canvas->CurrentState()->SetDrawingMode(mode);
-	canvas->GetDrawingEngine()->SetDrawingMode(mode);
+	if (canvas->CurrentState()->SetDrawingMode(mode))
+		canvas->GetDrawingEngine()->SetDrawingMode(mode);
 }
 
 

src/servers/app/ServerWindow.cpp

@@ -2200,7 +2200,8 @@ fDesktop->LockSingleWindow();
 
 			if (opacity != 255) {
 				fCurrentView->CurrentState()->SetDrawingMode(B_OP_ALPHA);
-				fCurrentView->CurrentState()->SetBlendingMode(B_PIXEL_ALPHA, B_ALPHA_COMPOSITE);
+				fCurrentView->CurrentState()->SetBlendingMode(B_PIXEL_ALPHA,
+					B_ALPHA_COMPOSITE);
 				fCurrentView->CurrentState()->SetDrawingModeLocked(true);
 			}
 
@@ -3466,7 +3467,8 @@ ServerWindow::_DispatchPictureMessage(int32 code, BPrivate::LinkReceiver& link)
 
 			if (opacity != 255) {
 				fCurrentView->CurrentState()->SetDrawingMode(B_OP_ALPHA);
-				fCurrentView->CurrentState()->SetBlendingMode(B_PIXEL_ALPHA, B_ALPHA_COMPOSITE);
+				fCurrentView->CurrentState()->SetBlendingMode(B_PIXEL_ALPHA,
+					B_ALPHA_COMPOSITE);
 				fCurrentView->CurrentState()->SetDrawingModeLocked(true);
 			}