Small Steps II — Making Things

Responding to mouse buttons

Respond to mouse buttons.

What you will learn

The mouse's position and button state are separate. Reading both lets you act at the clicked location.

Try it

void small_main()
{
    Window window;
    window.open(640, 480);

    while (window.is_open())
    {
        window.clear(White);

        if (window.mouse_down(MouseButton::Left))
            window.fill_circle(window.mouse_x(), window.mouse_y(), 30, Blue);
        else
            window.draw_circle(window.mouse_x(), window.mouse_y(), 30, Black);

        window.show();
    }
}

mouse_down(MouseButton::Left) asks whether the left button is held. The program draws a blue circle while held and a black outline when released.

mouse_pressed reports a new press; mouse_released reports a release. Use Pressed to remember a position once.

Exercise

Display a Red circle at the mouse position when the left button is held, and a Blue circle when the right button is held.

void small_main()
{
    Window window;
    window.open(640, 480);

    while (window.is_open())
    {
        window.clear(White);

        // Left = red, Right = blue.

        window.show();
    }
}

Hint

Check mouse_down for Left and Right separately.

void small_main()
{
    Window window;
    window.open(640, 480);

    while (window.is_open())
    {
        window.clear(White);

        if (window.mouse_down(MouseButton::Left))
            window.fill_circle(window.mouse_x(), window.mouse_y(), 30, Red);

        if (window.mouse_down(MouseButton::Right))
            window.fill_circle(window.mouse_x(), window.mouse_y(), 30, Blue);

        window.show();
    }
}