SetProcessDPIAware

SetProcessDPIAware is a Windows API function in user32.dll that marks the calling process as DPI aware. When a process is DPI aware, Windows does not apply DPI virtualization to the process and instead scales UI according to the system DPI. The function is intended for older applications that do not opt into DPI awareness through a manifest or newer APIs.

The prototype is BOOL SetProcessDPIAware(void). It returns a nonzero value if the call succeeds, or zero on failure. If it fails, extended error information can be obtained with GetLastError. The function has been available since Windows XP and is considered a compatibility mechanism for legacy software.

Usage considerations include timing and scope. It should be called early in process initialization, before any windows are created, to ensure that UI elements are sized and laid out using the correct system DPI. Calling it after windows have been created can lead to inconsistent scaling or improper layout, since some UI may have already been sized under DPI virtualization.

Limitations and modern alternatives: SetProcessDPIAware only enables system-DPI awareness and does not provide per-monitor DPI awareness. For modern applications, Microsoft recommends using newer APIs and manifest-based configuration to opt into higher levels of DPI awareness, such as SetProcessDpiAwareness (in SHCORE) or per-monitor awareness with SetProcessDpiAwarenessContext, and corresponding per-thread or per-window APIs. SetProcessDPIAware remains available for compatibility but is superseded in new development by these newer DPI awareness mechanisms.