Fix #9993: Handle DPI changes on macOS and Windows

src/video/cocoa/cocoa_wnd.mm

@@ -1269,8 +1269,12 @@ void CocoaDialog(const char *title, const char *message, const char *buttonLabel
 /** Screen the window is on changed. */
 - (void)windowDidChangeBackingProperties:(NSNotification *)notification
 {
+	bool did_adjust = AdjustGUIZoom();
+
 	/* Reallocate screen buffer if necessary. */
 	driver->AllocateBackingStore();
+
+	if (did_adjust) ReInitAllWindows(true);
 }
 
 /** Presentation options to use for full screen mode. */

src/video/win32_v.cpp

@@ -38,6 +38,10 @@
 #define PM_QS_INPUT 0x20000
 #endif
 
+#ifndef WM_DPICHANGED
+#define WM_DPICHANGED 0x02E0
+#endif
+
 bool _window_maximize;
 static Dimension _bck_resolution;
 DWORD _imm_props;
@@ -670,6 +674,24 @@ LRESULT CALLBACK WndProcGdi(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
 			return TRUE;
 		}
 
+		case WM_DPICHANGED: {
+			auto did_adjust = AdjustGUIZoom();
+
+			/* Resize the window to match the new DPI setting. */
+			RECT *prcNewWindow = (RECT *)lParam;
+			SetWindowPos(hwnd,
+				NULL,
+				prcNewWindow->left,
+				prcNewWindow->top,
+				prcNewWindow->right - prcNewWindow->left,
+				prcNewWindow->bottom - prcNewWindow->top,
+				SWP_NOZORDER | SWP_NOACTIVATE);
+
+			if (did_adjust) ReInitAllWindows(true);
+
+			return 0;
+		}
+
 /* needed for wheel */
 #if !defined(WM_MOUSEWHEEL)
 # define WM_MOUSEWHEEL 0x020A