[MSPAINT] Improve Undo/Redo and finishing tool (#4324)

- Fix Undo/Redo mechanism.
- Finish drawing when the tool is to be chanaged and when the file is to be saved.
- Add ToolBase::OnFinishDraw to virtualize finishing drawing.
- Extend bClearRedo parameter to ImageModel::Undo.
- Add ImageModel::DrawSelectionBackground and ImageModel::DeleteSelection methods.
- Fix some WM_PAINT message handling.
CORE-17969

base/applications/mspaint/palette.cpp

@@ -19,9 +19,9 @@ LRESULT CPaletteWindow::OnPaint(UINT nMsg, WPARAM wParam, LPARAM lParam, BOOL& b
     HBRUSH oldBrush;
     int i, a, b;
 
-    DefWindowProc(WM_PAINT, wParam, lParam);
+    PAINTSTRUCT ps;
+    HDC hDC = BeginPaint(&ps);
 
-    HDC hDC = GetDC();
     for(b = 2; b < 30; b++)
         for(a = 2; a < 29; a++)
             if ((a + b) % 2 == 1)
@@ -54,7 +54,7 @@ LRESULT CPaletteWindow::OnPaint(UINT nMsg, WPARAM wParam, LPARAM lParam, BOOL& b
         DeleteObject(SelectObject(hDC, oldBrush));
         DeleteObject(SelectObject(hDC, oldPen));
     }
-    ReleaseDC(hDC);
+    EndPaint(&ps);
     return 0;
 }