OSC 52: Clipboard Control (#52)

This adds support for OSC 52 -- applications can read/write the clipboard. Due to the security risk of this, the default configuration allows for writing but _not reading_. This is configurable using two new settings: `clipboard-read` and `clipboard-write` (both booleans).

src/Window.zig

@@ -592,9 +592,80 @@ pub fn handleMessage(self: *Window, msg: Message) !void {
         },
 
         .cell_size => |size| try self.setCellSize(size),
+
+        .clipboard_read => |kind| try self.clipboardRead(kind),
+
+        .clipboard_write => |req| switch (req) {
+            .small => |v| try self.clipboardWrite(v.data[0..v.len]),
+            .stable => |v| try self.clipboardWrite(v),
+            .alloc => |v| {
+                defer v.alloc.free(v.data);
+                try self.clipboardWrite(v.data);
+            },
+        },
     }
 }
 
+fn clipboardRead(self: *const Window, kind: u8) !void {
+    if (!self.config.@"clipboard-read") {
+        log.info("application attempted to read clipboard, but 'clipboard-read' setting is off", .{});
+        return;
+    }
+
+    const data = glfw.getClipboardString() catch |err| {
+        log.warn("error reading clipboard: {}", .{err});
+        return;
+    };
+
+    // Even if the clipboard data is empty we reply, since presumably
+    // the client app is expecting a reply. We first allocate our buffer.
+    // This must hold the base64 encoded data PLUS the OSC code surrounding it.
+    const enc = std.base64.standard.Encoder;
+    const size = enc.calcSize(data.len);
+    var buf = try self.alloc.alloc(u8, size + 9); // const for OSC
+    defer self.alloc.free(buf);
+
+    // Wrap our data with the OSC code
+    const prefix = try std.fmt.bufPrint(buf, "\x1b]52;{c};", .{kind});
+    assert(prefix.len == 7);
+    buf[buf.len - 2] = '\x1b';
+    buf[buf.len - 1] = '\\';
+
+    // Do the base64 encoding
+    const encoded = enc.encode(buf[prefix.len..], data);
+    assert(encoded.len == size);
+
+    _ = self.io_thread.mailbox.push(try termio.Message.writeReq(
+        self.alloc,
+        buf,
+    ), .{ .forever = {} });
+    self.io_thread.wakeup.send() catch {};
+}
+
+fn clipboardWrite(self: *const Window, data: []const u8) !void {
+    if (!self.config.@"clipboard-write") {
+        log.info("application attempted to write clipboard, but 'clipboard-write' setting is off", .{});
+        return;
+    }
+
+    const dec = std.base64.standard.Decoder;
+
+    // Build buffer
+    const size = try dec.calcSizeForSlice(data);
+    var buf = try self.alloc.allocSentinel(u8, size, 0);
+    defer self.alloc.free(buf);
+    buf[buf.len] = 0;
+
+    // Decode
+    try dec.decode(buf, data);
+    assert(buf[buf.len] == 0);
+
+    glfw.setClipboardString(buf) catch |err| {
+        log.err("error setting clipboard string err={}", .{err});
+        return;
+    };
+}
+
 /// Change the cell size for the terminal grid. This can happen as
 /// a result of changing the font size at runtime.
 fn setCellSize(self: *Window, size: renderer.CellSize) !void {