terminal: implement DECRQM (request mode)

src/terminal/stream.zig

@@ -569,6 +569,35 @@ pub fn Stream(comptime Handler: type) type {
                     ),
                 },
 
+                // DECRQM - Request Mode
+                'p' => switch (action.intermediates.len) {
+                    2 => decrqm: {
+                        if (action.intermediates[0] != '?' and
+                            action.intermediates[1] != '$')
+                        {
+                            log.warn(
+                                "ignoring unimplemented CSI p with intermediates: {s}",
+                                .{action.intermediates},
+                            );
+                            break :decrqm;
+                        }
+
+                        if (action.params.len != 1) {
+                            log.warn("invalid DECRQM command: {}", .{action});
+                            break :decrqm;
+                        }
+
+                        if (@hasDecl(T, "requestMode")) {
+                            try self.handler.requestMode(action.params[0]);
+                        } else log.warn("unimplemented DECRQM callback: {}", .{action});
+                    },
+
+                    else => log.warn(
+                        "ignoring unimplemented CSI p with intermediates: {s}",
+                        .{action.intermediates},
+                    ),
+                },
+
                 // DECSCUSR - Select Cursor Style
                 // TODO: test
                 'q' => if (@hasDecl(T, "setCursorStyle")) try self.handler.setCursorStyle(

src/termio/Exec.zig

@@ -1267,6 +1267,27 @@ const StreamHandler = struct {
         }
     }
 
+    pub fn requestMode(self: *StreamHandler, mode_raw: u16) !void {
+        // Get the mode value and respond.
+        const code: u8 = code: {
+            if (!terminal.modes.hasSupport(mode_raw)) break :code 0;
+            if (self.terminal.modes.get(@enumFromInt(mode_raw))) break :code 1;
+            break :code 2;
+        };
+
+        var msg: termio.Message = .{ .write_small = .{} };
+        const resp = try std.fmt.bufPrint(
+            &msg.write_small.data,
+            "\x1B[?{};{}$y",
+            .{
+                mode_raw,
+                code,
+            },
+        );
+        msg.write_small.len = @intCast(resp.len);
+        self.messageWriter(msg);
+    }
+
     pub fn saveMode(self: *StreamHandler, mode: terminal.Mode) !void {
         // log.debug("save mode={}", .{mode});
         self.terminal.modes.save(mode);