Expose shortcut actions

[jpnurmi]

Allow passing in custom actions for e.g. scrolling shortcuts.

[jpnurmi]

For example:

TerminalView(
  ...
  shortcuts: const {
    ...
    SingleActivator(LogicalKeyboardKey.arrowUp, control: true, shift: true): ScrollUpIntent(),
    SingleActivator(LogicalKeyboardKey.arrowDown, control: true, shift: true): ScrollDownIntent(),
    SingleActivator(LogicalKeyboardKey.pageUp, shift: true): ScrollPageUpIntent(),
    SingleActivator(LogicalKeyboardKey.pageDown, shift: true): ScrollPageDownIntent(),
    SingleActivator(LogicalKeyboardKey.home, shift: true): ScrollToTopIntent(),
    SingleActivator(LogicalKeyboardKey.end, shift: true): ScrollToBottomIntent(),
  },
  actions: {
    ScrollUpIntent: ScrollUpAction(_scrollController),
    ScrollDownIntent: ScrollDownAction(_scrollController),
    ScrollPageUpIntent: ScrollPageUpAction(_scrollController),
    ScrollPageDownIntent: ScrollPageDownAction(_scrollController),
    ScrollToTopIntent: ScrollToTopAction(_scrollController),
    ScrollToBottomIntent: ScrollToBottomAction(_scrollController),
  },
)

class ScrollUpIntent extends Intent {
  const ScrollUpIntent();
}

class ScrollDownIntent extends Intent {
  const ScrollDownIntent();
}

class ScrollPageUpIntent extends Intent {
  const ScrollPageUpIntent();
}

class ScrollPageDownIntent extends Intent {
  const ScrollPageDownIntent();
}

class ScrollToTopIntent extends Intent {
  const ScrollToTopIntent();
}

class ScrollToBottomIntent extends Intent {
  const ScrollToBottomIntent();
}

class ScrollUpAction extends Action<ScrollUpIntent> {
  ScrollUpAction(this.controller);

  final ScrollController controller;

  @override
  Object? invoke(covariant ScrollUpIntent intent) {
    controller.jumpTo(controller.position.pixels - 10); // TODO: line height?
    return null;
  }
}

class ScrollDownAction extends Action<ScrollDownIntent> {
  ScrollDownAction(this.controller);

  final ScrollController controller;

  @override
  Object? invoke(covariant ScrollDownIntent intent) {
    controller.jumpTo(controller.position.pixels + 10); // TODO: line height?
    return null;
  }
}

class ScrollPageUpAction extends Action<ScrollPageUpIntent> {
  ScrollPageUpAction(this.controller);

  final ScrollController controller;

  @override
  Object? invoke(covariant ScrollPageUpIntent intent) {
    controller.jumpTo(
        controller.position.pixels - controller.position.viewportDimension);
    return null;
  }
}

class ScrollPageDownAction extends Action<ScrollPageDownIntent> {
  ScrollPageDownAction(this.controller);

  final ScrollController controller;

  @override
  Object? invoke(covariant ScrollPageDownIntent intent) {
    controller.jumpTo(
        controller.position.pixels + controller.position.viewportDimension);
    return null;
  }
}

class ScrollToTopAction extends Action<ScrollToTopIntent> {
  ScrollToTopAction(this.controller);

  final ScrollController controller;

  @override
  Object? invoke(covariant ScrollToTopIntent intent) {
    controller.jumpTo(controller.position.minScrollExtent);
    return null;
  }
}

class ScrollToBottomAction extends Action<ScrollToBottomIntent> {
  ScrollToBottomAction(this.controller);

  final ScrollController controller;

  @override
  Object? invoke(covariant ScrollToBottomIntent intent) {
    controller.jumpTo(controller.position.maxScrollExtent);
    return null;
  }
}