win: Added helper function to tell Windows to respect the users scali…

…ng factor

Fixes #370

CHANGES.md

@@ -4,6 +4,7 @@
 
 ## Added
 - macOS: Add to support Mouse special key(Back, Forward)
+- win: Helper function to tell Windows to respect the users scaling settings `set_dpi_awareness`. Read the docs before using it
 
 ## Removed
 

Cargo.toml

@@ -50,6 +50,7 @@ windows = { version = "0.58", features = [
     "Win32_UI_TextServices",
     "Win32_UI_WindowsAndMessaging",
     "Win32_UI_Input_KeyboardAndMouse",
+    "Win32_UI_HiDpi",
 ] }
 
 [target.'cfg(target_os = "macos")'.dependencies]

examples/mouse.rs

@@ -10,6 +10,13 @@ use std::time::Duration;
 
 fn main() {
     env_logger::try_init().ok();
+
+    #[cfg(target_os = "windows")]
+    // This is needed on Windows if you want the application to respect the users scaling settings.
+    // Please look at the documentation of the function to see better ways to achive this and
+    // important gotchas
+    enigo::set_dpi_awareness().unwrap();
+
     let wait_time = Duration::from_secs(2);
     let mut enigo = Enigo::new(&Settings::default()).unwrap();
 

src/lib.rs

@@ -73,6 +73,8 @@ pub mod agent;
 mod platform;
 pub use platform::Enigo;
 
+#[cfg(target_os = "windows")]
+pub use platform::set_dpi_awareness;
 #[cfg(target_os = "windows")]
 pub use platform::EXT;
 

src/win/mod.rs

@@ -1,2 +1,2 @@
 mod win_impl;
-pub use win_impl::{Enigo, EXT};
+pub use win_impl::{set_dpi_awareness, Enigo, EXT};

src/win/win_impl.rs

@@ -531,6 +531,31 @@ impl Enigo {
     }
 }
 
+/// Sets the current process to a specified dots per inch (dpi) awareness
+/// context [see official documentation](https://learn.microsoft.com/en-us/windows/win32/api/shellscalingapi/nf-shellscalingapi-setprocessdpiawareness)
+/// If you want your applications to respect the users scaling, you need to set
+/// this. Otherwise the mouse coordinates and screen dimensions will be off.
+///
+/// It is recommended that you set the process-default DPI awareness via
+/// application manifest, not an API call. See [Setting the default DPI awareness for a process](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-setprocessdpiawarenesscontext) for more information. Setting the process-default DPI
+/// awareness via API call can lead to unexpected application behavior.
+/// It also needs to be set before any APIs are used that depend on the DPI and
+/// before a UI is created.
+/// Enigo is a library and should not set this, because
+/// it will lead to unexpected scaling of the application. Only use it for
+/// examples or if you know about the consequences
+///
+/// # Errors
+/// An error is thrown if the default API awareness mode for the process has
+/// already been set (via a previous API call or within the application
+/// manifest)
+pub fn set_dpi_awareness() -> Result<(), ()> {
+    use windows::Win32::UI::HiDpi::SetProcessDpiAwareness;
+    use windows::Win32::UI::HiDpi::PROCESS_PER_MONITOR_DPI_AWARE;
+
+    unsafe { SetProcessDpiAwareness(PROCESS_PER_MONITOR_DPI_AWARE) }.map_err(|_| ())
+}
+
 impl Drop for Enigo {
     // Release the held keys before the connection is dropped
     fn drop(&mut self) {