SetProcessDpiAwarenessContext

SetProcessDpiAware (and related functions sometimes referred to by the truncated form “SetProcessDpiA…”) are Windows API mechanisms for controlling how a process handles high-DPI scaling. They allow an application to declare its level of DPI awareness so that the operating system can scale graphics and text appropriately on displays with different DPI settings. The goal is to avoid blurry UI and ensure consistent sizing across monitors.

The legacy API SetProcessDPIAware marks the calling process as DPI aware at the system level. It is a simple boolean decision and is one of the older methods for handling DPI. It is typically used by applications that have not adopted per-monitor scaling and manifests, and it should be called early in process initialization before creating windows. It returns a nonzero value on success and zero on failure.

A more general approach is SetProcessDpiAwareness, introduced with Windows 8.1. This function allows you to specify one of several DPI awareness levels via the PROCESS_DPI_AWARENESS enum: DPI_UNAWARE, DPI_SYSTEM_AWARE, or DPI_PER_MONITOR_DPI_AWARE. It provides more nuanced control than the legacy API and can be set at runtime. The function returns an HRESULT indicating success or failure and requires linking with Shcore.lib.

For finer control, SetProcessDpiAwarenessContext (Windows 10) accepts a DPI_AWARENESS_CONTEXT value, including options such as UNAWARE, SYSTEM_AWARE, and PER_MONITOR_AWARE (including a v2 variant). This enables more dynamic or context-specific DPI handling, such as per-monitor scaling with newer Windows builds.

Guidance generally favors declaring DPI awareness in the application manifest (for modern Windows versions) and using per-monitor aware contexts where appropriate. These APIs help ensure accurate UI scaling across diverse display setups.