BColorControl: Rebuild control after mode switch

App Server sends each window a message that the screen has changed:
https://www.haiku-os.org/legacy-docs/bebook/BWindow.html#BWindow_ScreenChanged
Propegate B_SCREEN_CHANGED message to all child views first

Tell BColorControl to read the B_SCREEN_CHANGED message and reinitialize itself.

* Only reinit if switching to or from B_CMAP8
* Initialize all pointers to NULL in constructor
* Don't destroy and rebuild offscreen view (and text views) on reinit
* Reinitialize offscreen view on reinit.

Fixes #8035

Also initialzing the pointers to NULL in constructor fixes #12673

src/kits/interface/ColorControl.cpp

@@ -52,7 +52,12 @@ BColorControl::BColorControl(BPoint leftTop, color_control_layout layout,
 	float cellSize, const char* name, BMessage* message, bool useOffscreen)
 	:
 	BControl(BRect(leftTop, leftTop), name, NULL, message,
-		B_FOLLOW_LEFT | B_FOLLOW_TOP, B_WILL_DRAW | B_NAVIGABLE)
+		B_FOLLOW_LEFT | B_FOLLOW_TOP, B_WILL_DRAW | B_NAVIGABLE),
+	fRedText(NULL),
+	fGreenText(NULL),
+	fBlueText(NULL),
+	fBitmap(NULL),
+	fOffscreenView(NULL)
 {
 	_InitData(layout, cellSize, useOffscreen, NULL);
 }
@@ -60,7 +65,12 @@ BColorControl::BColorControl(BPoint leftTop, color_control_layout layout,
 
 BColorControl::BColorControl(BMessage* data)
 	:
-	BControl(data)
+	BControl(data),
+	fRedText(NULL),
+	fGreenText(NULL),
+	fBlueText(NULL),
+	fBitmap(NULL),
+	fOffscreenView(NULL)
 {
 	int32 layout;
 	float cellSize;
@@ -174,6 +184,7 @@ BColorControl::_InitData(color_control_layout layout, float size,
 	ResizeToPreferred();
 
 	if (useOffscreen) {
+		if (fOffscreenView != NULL) {
 			BRect bounds = _PaletteFrame();
 			fBitmap = new BBitmap(bounds, B_RGB32, true, false);
 			fOffscreenView = new BView(bounds, "off_view", 0, 0);
@@ -181,6 +192,7 @@ BColorControl::_InitData(color_control_layout layout, float size,
 			fBitmap->Lock();
 			fBitmap->AddChild(fOffscreenView);
 			fBitmap->Unlock();
+		}
 	} else {
 		fBitmap = NULL;
 		fOffscreenView = NULL;
@@ -363,6 +375,36 @@ BColorControl::MessageReceived(BMessage* message)
 			Invoke();
 			break;
 		}
+
+		case B_SCREEN_CHANGED:
+		{
+			BRect frame;
+			uint32 mode;
+			if (message->FindRect("frame", &frame) == B_OK
+				&& message->FindInt32("mode", (int32*)&mode) == B_OK) {
+				if ((fPaletteMode && mode == B_CMAP8)
+					|| (!fPaletteMode && mode != B_CMAP8)) {
+					// not switching to or from B_CMAP8, break
+					break;
+				}
+
+				// fake an archive message (so we don't rebuild views)
+				BMessage* data = new BMessage();
+				data->AddInt32("_val", Value());
+
+				// reinititialize
+				bool useOffscreen = fOffscreenView != NULL;
+				_InitData((color_control_layout)fColumns, fCellSize,
+					useOffscreen, data);
+				if (useOffscreen)
+					_InitOffscreen();
+
+				// cleanup
+				delete data;
+			}
+			break;
+		}
+
 		default:
 			BControl::MessageReceived(message);
 	}

src/kits/interface/View.cpp

@@ -4955,6 +4955,18 @@ BView::MessageReceived(BMessage* message)
 			case B_FONTS_UPDATED:
 				break;
 
+			case B_SCREEN_CHANGED:
+			{
+				// propegate message to child views
+				int32 childCount = CountChildren();
+				for (int32 i = 0; i < childCount; i++) {
+					BView* view = ChildAt(i);
+					if (view != NULL)
+						view->MessageReceived(message);
+				}
+				break;
+			}
+
 			default:
 				BHandler::MessageReceived(message);
 				break;

src/kits/interface/Window.cpp

@@ -1111,8 +1111,17 @@ FrameMoved(origin);
 				BRect frame;
 				uint32 mode;
 				if (message->FindRect("frame", &frame) == B_OK
-					&& message->FindInt32("mode", (int32*)&mode) == B_OK)
+					&& message->FindInt32("mode", (int32*)&mode) == B_OK) {
+					// propegate message to child views
+					int32 childCount = CountChildren();
+					for (int32 i = 0; i < childCount; i++) {
+						BView* view = ChildAt(i);
+						if (view != NULL)
+							view->MessageReceived(message);
+					}
+					// call hook method
 					ScreenChanged(frame, (color_space)mode);
+				}
 			} else
 				target->MessageReceived(message);
 			break;