I'm working on a Win32 app with multiple windows, some of which use WS_POPUPWINDOW style (no caption) and some of which use WS_OVERLAPPEDWINDOW style. The app has System DPI awareness.
When I move the overlapped windows between monitors, they scale to match the current monitor DPI as expected. But the popup windows only do this if there are no other open overlapped windows. Otherwise, they always try to match the scaling of the last active overlapped window in the same process, even if it's on another monitor with a different scale factor.
I guess this makes sense for some use cases, since you'd always want eg. a popup menu to match the scale of the current window. But I want my popups to behave as independent windows with their own scale factor.
How do I make popup windows always match the DPI of the monitor that they're positioned on?
As a quick fix before I eventually convert the app to per-monitor DPI awareness, I created an invisible overlapped owner window for the popup that tracks its position / size. This ensures that whenever the popup is active, it updates to use its owner's scaling, which always matches the current monitor.