[MSPAINT] Improve Zoom tool (#5781)

- Delete CCanvasWindow::drawZoomFrame.
- Invalidate the canvas on mouse move when
  the active tool is Zoom tool.
- Add ZoomTool::OnDrawOverlayOnCanvas to
  draw the zoom rectangle without flickering.
- Improve the zoom trackbar position.
- Display the zoom rate on changing the value
  of the zoom trackbar.
- Reverse the direction of the zoom trackbar.
- Don't draw the focus rectangle.
CORE-19215, CORE-19216

base/applications/mspaint/mouse.cpp

@@ -569,6 +569,21 @@ struct ZoomTool : ToolBase
     {
     }
 
+    void OnDrawOverlayOnCanvas(HDC hdc) override
+    {
+        CRect rc;
+        canvasWindow.GetImageRect(rc);
+        canvasWindow.ImageToCanvas(rc);
+
+        POINT pt;
+        ::GetCursorPos(&pt);
+        ::ScreenToClient(canvasWindow, &pt);
+
+        // FIXME: Draw the border of the area that is to be zoomed in
+        if (rc.PtInRect(pt))
+            DrawXorRect(hdc, &rc);
+    }
+
     void OnButtonDown(BOOL bLeftButton, LONG x, LONG y, BOOL bDoubleClick) override
     {
         if (bLeftButton)