Incorrect scale_factor on Windows

[caesay]

If dpiAware is set in application manifest eg.

  <application xmlns="urn:schemas-microsoft-com:asm.v3">
    <windowsSettings>
      <dpiAware xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">True</dpiAware>
      <dpiAwareness xmlns="http://schemas.microsoft.com/SMI/2016/WindowsSettings">PerMonitorV2</dpiAwareness>
    </windowsSettings>
  </application>

Then xcap will return scale_factor = 1.0 always, which is incorrect. The GetDpiForMonitor function should be used to determine the monitor scale.

[nashaofu]

#177
Please review this to see if it meets your requirements. Note that I haven't conducted any actual testing, so you may need to help adjust the parameters accordingly.

features: https://learn.microsoft.com/zh-cn/windows/win32/api/shellscalingapi/ne-shellscalingapi-monitor_dpi_type

    let dpi_type = {
        cfg_if! {
            if #[cfg(feature = "windows_hi_dpi_effective")] {
                use windows::Win32::UI::HiDpi::MDT_EFFECTIVE_DPI;
                MDT_EFFECTIVE_DPI
            } else if #[cfg(feature = "windows_hi_dpi_angular")] {
                use windows::Win32::UI::HiDpi::MDT_ANGULAR_DPI;
                MDT_ANGULAR_DPI
            } else {
                use windows::Win32::UI::HiDpi::MDT_RAW_DPI;
                MDT_RAW_DPI
            }
        }
    };

[nashaofu]

@caesay Does this align with your expectations?

[caesay]

Hi, thanks for looking at this, and I think the changes you made will work fine for me, but the only valid flag for determining screen DPI is MDT_EFFECTIVE_DPI, so I'm not sure the cargo features are needed to gate this.

If I could provide a suggestion, ideally the implementation should just use GetDpiForMonitor automatically if Windows >= 8.1, since the current approach of GetDeviceCaps will give incorrect results on multi-monitor computers. If xcap is supporting older versions of windows than 8.1, then use libloading to access GetDpiForMonitor dynamically, instead of statically importing the function.

The current implementation in #177 means that I have to choose whether I target windows 7/8 or 8.1+ at compile time, since without the feature it will not work on 8.1+ and with the feature it will not work on 7.

[nashaofu]

The cargo features have been removed and replaced with dynamic linking. Additionally, it now detects whether the current process has DPI awareness enabled, and automatically switches the method for obtaining DPI accordingly.

use std::time::Instant;
use windows::Win32::UI::HiDpi::{
    SetProcessDpiAwareness, PROCESS_DPI_AWARENESS, PROCESS_PER_MONITOR_DPI_AWARE,
};
use xcap::Monitor;

fn change_windows_dpi_awarness(val: PROCESS_DPI_AWARENESS) {
    unsafe {
        SetProcessDpiAwareness(val).unwrap();
    }
}

fn main() {
    // Modify the program's DPI awareness. You can set the value to PROCESS_DPI_UNAWARE or PROCESS_PER_MONITOR_DPI_AWARE for testing.
    // 修改程序的 DPI 感知，你可以将值设置为 PROCESS_DPI_UNAWARE 或 PROCESS_PER_MONITOR_DPI_AWARE 进行测试
    change_windows_dpi_awarness(PROCESS_PER_MONITOR_DPI_AWARE);
    let start = Instant::now();
    let monitors = Monitor::all().unwrap();
    println!("Monitor::all() 运行耗时: {:?}", start.elapsed());

    for monitor in monitors {
        println!(
            "Monitor:\n id: {}\n name: {}\n position: {:?}\n size: {:?}\n state:{:?}\n",
            monitor.id(),
            monitor.name(),
            (monitor.x(), monitor.y()),
            (monitor.width(), monitor.height()),
            (
                monitor.rotation(),
                monitor.scale_factor(),
                monitor.frequency(),
                monitor.is_primary()
            )
        );
    }

    let monitor = Monitor::from_point(100, 100).unwrap();

    println!("Monitor::from_point(): {}", monitor.name());
    println!(
        "Monitor::from_point(100, 100) 运行耗时: {:?}",
        start.elapsed()
    );

    println!("运行耗时: {:?}", start.elapsed());
}

[nashaofu]

Released https://github.com/nashaofu/xcap/releases/tag/v0.1.1

[nashaofu]

This issue is now closed. If it is not resolved, please reopen it.