enum gdk::ChangeData lacks variant UInt(u32)

[cshuaimin]

I'm porting some C code using XCB to gdk:

xcb_change_property(c,
                    XCB_PROP_MODE_REPLACE,
                    win,
                    XCB_ATOM_WM_TRANSIENT_FOR,
                    XCB_ATOM_WINDOW,
                    32,
                    1,
                    &parent);

You see the format argument is 32 and data_len is 1, but gdk::property_change() cannot do such work because the argument type gdk::ChangeData has only u8, u16 and u64 variants.

Seems that passing a u64 should work, but I failed. I have to use gdk-sys crate and everything behaves same as the C code.

[sdroege]

It's not an u64 variant but a gulong / libc::c_ulong, so this would actually be an u32 on 32 bit platforms (and Windows x64). That should be the variant you would use and with a cast back and forth this should also work.

Can you provide a minimal testcase that shows how this fails?

[cshuaimin]

Thank you! Here's my code:

In Cargo.toml:

[dependencies.gdk]
version = "0.12.1"
features = ['v3_16']

[dependencies.gtk]
version = '0.8.0'
features = ['v3_16']

[dependencies.gio]
version = "0.8.1"
features = ['v2_44']

main.rs:

use gio::prelude::*;
use gtk::prelude::*;
use gtk::{Application, ApplicationWindow, Button};

fn main() {
    let application =
        Application::new(Some("com.github.gtk-rs.examples.basic"), Default::default())
            .expect("failed to initialize GTK application");

    application.connect_activate(|app| {
        let window = ApplicationWindow::new(app);
        window.set_title("First GTK+ Program");
        window.set_default_size(350, 70);

        let button = Button::new_with_label("Click me!");
        button.connect_clicked(|_| {
            println!("Clicked!");
        });
        window.add(&button);

        window.show_all();

        let gdk_window = window.get_window().unwrap();
        let parent: u32 = 0x1e0000e;
        gdk::property_change(
            &gdk_window,
            &gdk::Atom::intern("WM_TRANSIENT_FOR"),
            &gdk::Atom::intern("WINDOW"),
            32,
            gdk::PropMode::Replace,
            gdk::ChangeData::ULong(parent as u64),
        );
    });

    application.run(&[]);
}

Then I use xprop to inspect the window, but xprop displays some random number, and each run is different:

WM_TRANSIENT_FOR(WINDOW): window id # 0x7e719c80

Maybe I made some mistakes in the casting?

[sdroege]

That looks correct to me but I don't really know this API. Did you figure it out in the meantime? Does it behave the same wrong way in C if you use the GDK API?