add linux watch

build.zig

@@ -18,6 +18,7 @@ pub fn build(b: *std.build.Builder) void {
         exe.linkLibC();
         exe.addIncludeDir("/usr/include/");
         exe.linkSystemLibrary("X11");
+        exe.linkSystemLibrary("Xfixes");
     }
     if (std.builtin.os.tag == .windows) {
         // exe.linkLibC();

src/main.zig

@@ -2,6 +2,7 @@ const std = @import("std");
 const c = @cImport({
     @cInclude("limits.h");
     @cInclude("X11/Xlib.h");
+    @cInclude("X11/extensions/Xfixes.h");
 });
 
 fn printSelection(display: *c.Display, window: c.Window, bufname: [*c]const u8, fmtname: [*c]const u8, writer: anytype) !bool {
@@ -45,6 +46,31 @@ fn printSelection(display: *c.Display, window: c.Window, bufname: [*c]const u8,
     return false;
 }
 
+fn watch(display: *c.Display, window: c.Window, bufname: [*c]const u8, writer: anytype) !void {
+    var event_base: c_int = undefined;
+    var error_base: c_int = undefined;
+    var event: c.XEvent = undefined;
+    var bufid = c.XInternAtom(display, bufname, c.False);
+
+    _ = c.XFixesQueryExtension(display, &event_base, &error_base);
+    _ = c.XFixesSelectSelectionInput(display, c.XDefaultRootWindow(display), bufid, c.XFixesSetSelectionOwnerNotifyMask);
+
+    while (true) {
+        _ = c.XNextEvent(display, &event);
+
+        // _ = try writer.print("{d} == {d} + {d}. {d} == {d}", .{ event.type, event_base, c.XFixesSelectionNotify, event.xselection.selection, bufid });
+        // _ = std.debug.print("{}", .{event.xselection});
+
+        if (event.type == event_base + c.XFixesSelectionNotify and
+            event.xselection.property == bufid)
+        {
+            _ = try writer.print("y", .{});
+            if (!try printSelection(display, window, bufname, "UTF8_STRING", writer))
+                _ = try printSelection(display, window, bufname, "STRING", writer);
+        }
+    }
+}
+
 pub fn main() !u8 {
     const stdout = std.io.getStdOut().writer();
     var display: *c.Display = c.XOpenDisplay(null).?;
@@ -53,6 +79,18 @@ pub fn main() !u8 {
     var color = c.XBlackPixel(display, default_screen);
     var window = c.XCreateSimpleWindow(display, c.XDefaultRootWindow(display), 0, 0, 1, 1, 0, color, color);
     defer _ = c.XDestroyWindow(display, window);
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    defer _ = gpa.deinit();
+    const allocator = &gpa.allocator;
+    var args = std.process.args();
+    defer args.deinit();
+    while (args.next(allocator)) |arg_or_err| {
+        const arg = try arg_or_err;
+        defer allocator.free(arg);
+        if (std.mem.eql(u8, arg, "-w")) {
+            try watch(display, window, "CLIPBOARD", stdout);
+        }
+    }
     var result = (try printSelection(display, window, "CLIPBOARD", "UTF8_STRING", stdout)) or
         (try printSelection(display, window, "CLIPBOARD", "STRING", stdout));
     if (result)