Initial version built with xlib

.gitignore

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+/target

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
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+ "exec",
+ "x11",
+]
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+ "pkg-config",
+]

Cargo.toml

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+[package]
+name = "superl_launch"
+version = "1.0.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+exec = "0.3"
+x11 = { version = "2.21", features = ["xlib"]}

src/main.rs

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+extern crate exec;
+extern crate x11;
+
+use std::env;
+use std::process;
+use std::ptr;
+
+const KEYID_LSUPER: u32 = 130;
+
+fn usage(prog: &String) -> () {
+    println!("usage: {prog} [cmd...]");
+    println!("Launch command if only Left Super is pressed then released.");
+}
+
+fn x11_open_display() -> Option<*mut x11::xlib::Display> {
+    unsafe {
+        let display = x11::xlib::XOpenDisplay(ptr::null());
+        if display == ptr::null_mut() {
+            return None;
+        }
+        return Some(display);
+    }
+}
+
+fn x11_close_display(display: *mut x11::xlib::Display) {
+    unsafe {
+        x11::xlib::XCloseDisplay(display);
+    }
+}
+
+fn x11_check_lsuper() -> Option<bool> {
+    match x11_open_display() {
+        Some(display) => {
+            loop {
+                let mut keymap: [i8; 32] = [0; 32];
+                unsafe {
+                    x11::xlib::XQueryKeymap(display, keymap.as_mut_ptr());
+                }
+                let (count, keyid, _) : (u32, u32, bool) = keymap.iter().fold(
+                    (0, 0, false), |x, y| match x {
+                        (c, k, s) => (c + y.count_ones(),
+                                      if s {k} else {k + y.leading_zeros()},
+                                      if s {s} else {y.leading_zeros() < 8}),
+                });
+                if count == 0 {
+                    x11_close_display(display);
+                    return Some(true);
+                }
+                if count > 1 || keyid != KEYID_LSUPER {
+                    x11_close_display(display);
+                    return Some(false);
+                }
+            }
+        },
+        None => {
+            println!("Error: can't open display");
+            return None;
+        }
+
+    }
+}
+
+fn single_release_launch(cmd: &String, argv: &[String]) -> () {
+    match x11_check_lsuper() {
+        Some(ret) => {
+            if ret == true {
+                println!("Error: {}", exec::Command::new(cmd).args(argv).exec());
+            }
+        },
+        None => (),
+    }
+}
+
+fn main() -> () {
+    let args: Vec<String> = env::args().collect();
+    match &args[..] {
+        [prog] => usage(prog),
+        [_, cmd] => single_release_launch(cmd, &[]),
+        [_, cmd, argv @ ..] => single_release_launch(cmd, argv),
+        _ => (),
+    }
+    process::exit(1);
+}