Most desktop applications run under system DPI awareness mode. System-DPI-aware applications typically scale to the DPI of the primary display (the display that the system tray was located on at the time the Windows session was started). When the DPI changes, Windows will bitmap stretch the UI of these applications, which often results in them being blurry. When updating a System DPI-aware application to become per-monitor-DPI aware, the code which handles UI layout needs to be updated such that it is performed not only during application initialization, but also whenever a DPI change notification (WM_DPICHANGED in the case of Win32) is received. This typically involves revisiting any assumptions in the code that the UI only needs to be scaled once.