Why does GetImage fail here?

[owenthewizard]

use x11rb::{connection::Connection, image::Image};

pub fn main() -> Result<(), Box<dyn std::error::Error>> {
    let (conn, screen_pref) = x11rb::connect(None)?;
    let setup = conn.setup();
    let screen = &setup.roots[screen_pref];

    let (_img, _) = Image::get(
        &conn,
        screen.root,
        0,
        0,
        screen.width_in_pixels,
        screen.height_in_pixels,
    )?;

    Ok(())
}

Error: X11Error(X11Error { error_kind: Match, error_code: 8, sequence: 1, bad_value: 1257, minor_opcode: 0, major_opcode: 73, extension_name: None, request_name: Some("GetImage") })

[psychon]

TL;DR: I do not know why this fails for you.

---

Uhm... Works For Me (tm). I just ran this in cargo init --bin foo and after adding this to Cargo.toml:

x11rb = { version = "*", features=["image"]}

Running under xtrace says:

000:<:0001: 20: Request(73): GetImage format=ZPixmap(0x02) drawable=0x000004a9 x=0 y=0 width=3840 height=1080 plane-mask=0xffffffff
000:>:0001:16588832: Reply to GetImage: depth=0x18 32-bit values got=4147200 visual=0x00000021

---

https://www.x.org/releases/X11R7.6/doc/xproto/x11protocol.html#requests:GetImage says:

If the drawable is a window, the window must be viewable, and it must be the case that, if there were no inferiors or overlapping windows, the specified rectangle of the window would be fully visible on the screen and wholly contained within the outside edges of the window (or a Match error results).

I do not understand why part of the root window would not be visible on screen... Does the bad_value: 1257 mean anything to you? Is it the width or height the root window, perhaps?

[eduardosm]

I am getting the same error on KDE Wayland, where the bad_value is the ID of the root window. I believe that it is because the root window is not a real window on Xwayland.

[owenthewizard]

Yep, that's it! Xwayland usually doesn't use a root window. I disabled Sway's Xwayland, ran it normally (with a root window), and it works fine.