GetDpiForWindow

GetDpiForWindow is a Windows API function in User32.dll that returns the dots-per-inch (DPI) value for a specific window. It is used to support per-window DPI awareness by allowing an application to adjust layout and rendering on a per-window basis.

The function signature is UINT GetDpiForWindow(HWND hwnd). The hwnd parameter identifies the target window. The returned DPI reflects the monitor that contains that window and respects the DPI awareness context associated with the window.

Return value: The function returns the DPI as an unsigned value in DPI units (for example, 96 for 100%, 120 for 125%, 144 for 150%). This value can be used to scale fonts, controls, and graphics.

Usage: Call GetDpiForWindow on the thread that owns the window, typically after window creation or when a DPI change is detected. Applications can respond to DPI changes by querying the new value and adjusting layout accordingly. The function relies on the process's DPI awareness settings; if the process is not DPI-aware, the returned value may reflect the system DPI rather than the per-monitor DPI.

See also: GetDpiForSystem, SetProcessDpiAwarenessContext, WM_DPICHANGED.