Writing User Interface (UI) Objects with Min

This documentation extends the Min Guide to Writing Objects by adding information specific to user interface objects.

UI Objects

User Interface objects in Max are, in most respects, like any other object in Max: they respond to messages, possess attributes, and communicate with inlets and outlets. What is different is that they customize the display of their box instead of using the typical text-filled box. UI objects also may respond to gestures made with the mouse or other input devices.

Class Definition

In addition to inheriting from the object<> class, your audio objects will now also inherit from ui_operator<>. This requires two template arguments which are the default width and the default height of your UI object.

The min.textslider examples in the Min-DevKit provides an excellent starting point.

class min_textslider : public object<min_textslider>, public ui_operator<140,24> {
	/// ...

Inlets and Outlets

Your UI object will define inlets and outlets as with non-ui objects.

class min_textslider : public object<min_textslider>, public ui_operator<140,24> {
	inlet<>	input	{ this, "(number) value to set" };
	outlet<> output	{ this, "(number) value" };

	/// ...


There are a variety of messages to which ui_operator<> classes may wish to respond. The only message that is required is the paint message which will define how the object will be drawn on the screen.

Supported messages:


If defined, the mousenter message is called when the mouse enters the box for your UI object.

	message<> mouseenter { this, "mouseenter",
			m_mouseover = true;
			if (m_showvalue)
			return {};


If defined, the mousedown message is called when the mouse is clicked (button pressed down) in the box for your UI object.

	message<> mousedown { this, "mousedown",
			ui::target	t { args };
			number		x { args[2] };
			number		y { args[3] };
			int			modifiers { args[4] };

			// cache mouse position so we can restore it after we are done
			m_mouse_position[0] = t.x() + x;
			m_mouse_position[1] = t.y() + y;

			// Jump to new value on mouse down?
			if (m_clickjump) {
				auto delta = MIN_CLAMP((x - 1.0), 0.0, t.width() - 3.0);		// substract for borders
				delta = delta / (t.width() - 2.0) * m_range_delta + m_range[0];
				if (modifiers & c74::max::eCommandKey)
					m_number(static_cast<long>(delta));							//when command-key pressed, jump to the nearest integer-value
					m_number(delta);											// otherwise jump to a float value

			m_anchor = m_value;
//			c74::max::jbox_set_mousedragdelta(maxobj(), 1);
			return {};

The message will be passed four arguments: the target, the x-coordinate, the y-coordinate, and a mask that defines what modifier keys are being held down during the click.