fltk-rs: [BUG] IME problem under wayland

Describe the bug

When I input ASCII characters, as long as the frequency is a little faster, repeated characters will appear. For example, “hello world” will become: “heeellllllooo wwooorrrlld”.

When I input Unicode characters, there is a high probability that the characters will be garbled, and sometimes the input characters will disappear.

The most outrageous thing is that sometimes it triggers the string to “flicker”.

https://github.com/fltk-rs/fltk-rs/assets/25324935/b70e5e3b-ca7f-422f-a3d8-195caa1f9f0a

In the video above, it looks like I’m constantly deleting text, but I’m not. I just typed emo.

Note: Only wayland triggers this issue, x11 does not.

This issue has rendered the input method of Wayland basically unusable, I hope it can be fixed.

To Reproduce

Cargo.toml

[dependencies]
fltk = { version = "1.4.28", features = [
    "use-ninja",
    "use-wayland",
] }

src: https://github.com/fltk-rs/fltk-rs/blob/682a7255df5a887412f5c3f2c228f133a602af74/fltk/examples/editor.rs

Expected behavior

Perfect support for Wayland.

Desktop info

• OS: Debian Sid GNU/Linux (x86_64)
• Version: 1.4.28
• Display: Wayland
• Desktop: KDE Plasma 5.27.10-1+b2

Additional info

(process:160445): Pango-WARNING **: 22:53:29.310: Invalid UTF-8 string passed to pango_layout_set_text()