failed to capture windows - DeleteObject HBITMAP(0x5d050727) failed - Process not DPI aware

[louis030195]

some of my users get this error

xcap/src/windows/capture.rs

Line 91 in 66feae0

log::error!("DeleteObject {:?} failed", val);

Process not DPI aware

claude says:

Let me help analyze this Windows GDI code and the DPI awareness issue. Let's think through this:

1. The error occurs when deleting a bitmap object and seems related to DPI awareness
2. Windows scales UI elements based on DPI settings, which can cause issues if the application isn't properly DPI aware
3. The code is using GDI functions for screen capture and needs to handle DPI scaling correctly

Here's how we can fix this:

// ... existing code ...

// Add this at the start of the file after the imports
use windows::Win32::UI::HiDpi::{SetProcessDpiAwareness, PROCESS_DPI_AWARENESS};

// Add this function
pub fn init_dpi_awareness() -> XCapResult<()> {
    unsafe {
        SetProcessDpiAwareness(PROCESS_DPI_AWARENESS::PROCESS_PER_MONITOR_DPI_AWARE)?;
    }
    Ok(())
}

// In the capture_window function, modify the scale factor handling:
pub fn capture_window(
    hwnd: HWND, 
    scale_factor: f32,
    window_info: &WINDOWINFO,
) -> XCapResult<RgbaImage> {
    unsafe {
        // ... existing code ...

        // Update how we handle the scaling
        width = (width as f32 * scale_factor).round() as i32;  // Use round instead of ceil
        height = (height as f32 * scale_factor).round() as i32;

        // ... rest of existing code ...
    }
}

The changes:

1. Added DPI awareness initialization that should be called when your application starts
2. Changed ceil() to round() for more accurate scaling calculations
3. The bitmap deletion error should be resolved once the application is properly DPI aware

You'll need to call init_dpi_awareness() early in your application startup, before any window or screen capture operations. This ensures Windows knows how to handle DPI scaling for your application.

The error you're seeing ("Process not DPI aware") indicates that Windows is trying to handle DPI scaling automatically, which can cause issues with GDI operations. By making the process DPI aware, we tell Windows that we'll handle the scaling ourselves.

[nashaofu]

Couldn't replicate the problem.

[louis030195]

this is new, did not have until we moved from

xcap = "0.0.12"

to

xcap = { package = "xcap", git = "https://github.com/nashaofu/xcap", rev = "214cb44" }

cc @ologbonowiwi

i use windows through https://parsec.app/

[louis030195]

so it broke here a6f508a#diff-7407bb83d66acb353fa8805d9df99c53215ad7da7bf40ee2a0fef6e3ab56311b

[ologbonowiwi]

so it broke here a6f508a#diff-7407bb83d66acb353fa8805d9df99c53215ad7da7bf40ee2a0fef6e3ab56311b

I changed screenpipe-vision/Cargo.toml to

xcap = "0.2.2"

and the DeleteObject error is gone, although I still see the Process not DPI aware info log

[sorry77]

请问这里的if判断是否忘记取反了？捕获正常也每次都报

                if DeleteObject(val.into()).as_bool() {
                    log::error!("DeleteObject {:?} failed", val);
                }

[ologbonowiwi]

you are totally right @sorry77, nice catch.

opened #195, inverting the condition. it works perfectly now.