message: Rename button_state to prev_state for clarity
diff: @@ -494,7 +494,7 @@ impl<'a, A: ActionContext + 'a> Processor<'a, A> {
  }
  pub fn mouse_input(&mut self, state: ElementState, button: MouseButton, modifiers: ModifiersState) {
  - let button_state = match button {
  + let prev_state = match button {
  MouseButton::Left => Some(mem::replace(&mut self.ctx.mouse_mut().left_button_state, state)),
  MouseButton::Middle => Some(mem::replace(&mut self.ctx.mouse_mut().middle_button_state, state)),
  MouseButton::Right => Some(mem::replace(&mut self.ctx.mouse_mut().right_button_state, state)),
  @@ -502,8 +502,8 @@ impl<'a, A: ActionContext + 'a> Processor<'a, A> {
  MouseButton::Other(_) => None,
  };
  - if let Some(button_state) = button_state {
  - if button_state != state {
  + if let Some(prev_state) = prev_state {
  + if prev_state != state {
  match state {
  ElementState::Pressed => self.on_mouse_press(button, modifiers),
  ElementState::Released => self.on_mouse_release(button, modifiers),
  