Fix drawing wxTaskBarIcon under macOS in high DPI

Use a workaround to ensure the image is not distorted due to using a
wrong scale.

See #23042.

(cherry picked from commit 83e47a6)

docs/changes.txt

@@ -300,6 +300,7 @@ wxOSX:
 - Ensure that "Window" menu is inserted before "Help" (#22871).
 - Fix compiling with Xcode 7.3 and macOS 11 SDK (crazbot, #22988).
 - Always call wxTaskBarIcon::GetPopupMenu() (William Lindnilsson, #23008).
+- Fix scaling wxTaskBarIcon in high DPI (William Lindnilsson, #23042).
 - Add margins around wxListCtrl items to improve appearance (#23155).
 
 wxQt:

src/osx/cocoa/taskbar.mm

@@ -391,7 +391,14 @@ - (wxTaskBarIconCustomStatusItemImpl*) implementation
     m_icon = IconFromBundle(icon);
     NSImage* nsimage = m_icon.GetNSImage();
     [[m_statusItem button] setImageScaling: NSImageScaleProportionallyUpOrDown];
-    [[m_statusItem button] setImage: nsimage];
+
+    CGFloat statusBarThickness = [[NSStatusBar systemStatusBar] thickness];
+    NSSize statusBarSize = NSMakeSize(statusBarThickness, statusBarThickness);
+    NSImage* statusBarScaledImage = [NSImage imageWithSize:statusBarSize flipped:NO drawingHandler:^BOOL(NSRect dstRect) {
+        [nsimage drawInRect:dstRect fromRect:NSZeroRect operation:NSCompositingOperationSourceOver fraction:1];
+        return YES;
+    }];
+    [[m_statusItem button] setImage:statusBarScaledImage];
 
     wxCFStringRef cfTooltip(tooltip);
     [[m_statusItem button] setToolTip:cfTooltip.AsNSString()];