Area input and redraws

日本語

A drawing callback displays state. Change state in input callbacks or timers, then call queue_redraw_all to schedule the next draw. queue_redraw_all does not draw immediately.

x = 80.0
y = 80.0
brush = UIng::Area::Draw::Brush.new(:solid, 0.2, 0.4, 0.8, 1.0)

handler = UIng::Area::Handler.new do
  draw do |_area, params|
    params.context.fill_path(brush) do |path|
      path.add_rectangle(x, y, 24, 24)
    end
  end

  mouse_event do |area, event|
    x = event.x
    y = event.y
    area.queue_redraw_all
  end

  key_event do |area, event|
    handled = !event.up? && event.ext_key == UIng::Area::ExtKey::Left
    x -= 8 if handled
    area.queue_redraw_all if handled
    handled
  end

  scroll_event do |area, event|
    puts "Scroll: #{event.delta_x}, #{event.delta_y}"
    true # Consume the event; return false for normal scrolling in a scrolling Area.
  end
end

area = UIng::Area.new(handler)

Input callbacks

• mouse_event receives coordinates, button state, and modifiers.
• mouse_crossed receives pointer enter/leave changes.
• drag_broken can restore state when a drag is interrupted.
• key_event returns true when it handled the key and false otherwise.
• scroll_event receives wheel and trackpad movement in delta_x and delta_y; call handler.scroll_event(nil) to clear it.

Scroll deltas are signed device amounts, not drawing coordinates. Their size varies by device and platform. Positive values mean right and down.

Call area.focus to request keyboard focus after attaching it to a visible window. Check area.focused? if needed; the native window system may reject the request.

Call begin_user_window_move and begin_user_window_resize only inside mouse_event while event.down != 0. For animation, avoid creating drawing resources every frame and redraw only after state changes.

area_events.cr visualizes keyboard and mouse input. area_analog_clock.cr and reversi.cr combine state with redraws.