============ Enable Tools ============ Enable ``Tools`` are ``Interator`` subclasses that do not have to have any visual representation, and which can be dynamically added and removed from components by adding or removing them from the component's ``tools`` list. This permits developers to quickly build up complex behaviours from simple, reproducible parts without having complex inheritance hierarchies. Basic Tools ----------- Enable provides a number of basic tools for common interactions. ButtonTool ~~~~~~~~~~ The :py:class:`ButtonTool` provides basic push-button or checkbox interactions, depending on how it is configured. The primary interface it provides is a :py:attr:`clicked` event which is fired when the user clicks in the region of the underlying component, or when the :py:meth:`click` method is called. The :py:attr:`clicked` event is fired on mouse up. To get checkbox-style behaviour, set :py:attr:`togglable` to ``True`` and then every click will invert the :py:attr:`checked` trait. The toggle state can also be changed via the :py:meth:`toggle` method, which does not fire the :py:attr:`clicked` event when called. For buttons with multi-state toggles, subclasses can override the :py:meth:`toggle` method to perform more complex state changes. By default, the tool responds to clicks that are within the associated component, but subclasses can override this behaviour by replacing the :py:meth:`is_clickable` method with something else. It will commonly be the case that components or :py:class:`ButtonTool` subclasses which draw may wish to respond to user interactions by drawing themselves in a highlighted or selected mode when the mouse is down inside the button region. The :py:attr:`down` trait provides this information conveniently, so that users of the tool can change their drawing state and request redraws when it changes. DragTool ~~~~~~~~ The :py:class:`DragTool` is an abstract base class that provides basic interaction support for draging within Enable. Many other tools within Enable and Chaco use it. HoverTool ~~~~~~~~~ The :py:class:`HoverTool` is a simple tool that calls a callback when the mouse has been held steadily over the component for a period of time. MoveTool ~~~~~~~~ A :py:class:`DragTool` subclass that allows a user to move a component around its container by dragging. ResizeTool ~~~~~~~~~~ A :py:class:`DragTool` subclass that allows a user to resize a component by dragging from the edges of the component. ValueDragTool ~~~~~~~~~~~~~ A :py:class:`DragTool` subclass that allows a drag operation to set an arbitrary value. Undo/Redo Support ----------------- The `enable.tools.pyface` package has a number of modules that provide classes for working with Pyface's Undo/Redo stack. This permits Enable tools to add Commands to the Undo/Redo stack, and provides variants of the MoveTool and ResizeTool that are undoable. In addition, a tool is provided which binds keystrokes to send undo and redo requests to the Pyface UndoManager. High-Level Tools ~~~~~~~~~~~~~~~~ There are three tools that provide convenient facilities and reference implementations of interacting with the undo/redo stack. UndoTool ^^^^^^^^ The ``UndoTool`` binds keystrokes to undo and redo operations. The ``undo_keys`` and ``redo_keys`` attributes each take a list of ``KeySpec`` objects which should trigger the relevant operations. The default values bind undo to 'Ctrl+Z' and redo to 'Ctrl+Shift+Z'. The ``UndoTool`` must be provided with an ``IUndoManager`` that will actually perform the undo and redo operations. For example, to bind undo to 'Ctrl+Left arrow', and redo to 'Ctrl+Right arrow':: undo_tool = UndoTool( my_component, undo_manager=my_undo_manager, undo_keys=[KeySpec('Left', 'control')], redo_keys=[KeySpec('Right', 'control')] ) my_component.tools.append(undo_tool) MoveCommandTool ^^^^^^^^^^^^^^^ The ``MoveCommandTool`` is a subclass of ``MoveTool`` that by default issues a ``MoveCommand`` at the end of every successful drag move. A ``MoveCommand`` stores the new and previous position of the component so that it can undo and redo the move. The ``MoveCommandTool`` needs to be provided with an ``ICommandStack`` instance that it will push commands to, but is otherwise identical to the usual ``MoveTool``. The command tool has a ``mergeable`` attribute which indicates whether subsequent move operations with the same component immediately following this one can be merged into one single move operation. Typical usage would be something like this:: move_tool = MoveCommandTool(my_component, command_stack=my_command_stack) my_component.tools.append(move_tool) Users of the tool can provide a different factory to create appropriate ``Command`` instances by setting the ``command`` trait to a callable that should expect keyword arguments ``component``, ``data`` (the new position), ``previous_position``, and ``mergeable``. ResizeCommandTool ^^^^^^^^^^^^^^^^^ The ``ResizeCommandTool`` is a subclass of ``ResizeTool`` that issues ``ResizeCommand`` s at the end of every successful drag move. A ``ResizeCommand`` stores the new and previous position and bounds of the component so that it can undo and redo the resize. The ``ResizeCommandTool`` needs to be provided with an ``ICommandStack`` instance that it will push commands to, but is otherwise identical to the usual ``ResizeTool``. The command tool has a ``mergeable`` attribute which indicates whether subsequent resize operations with the same component immediately following this one can be merged into one single resize operation. Typical usage would be something like this:: move_tool = ResizeTool(my_component, command_stack=my_command_stack) my_component.tools.append(move_tool) Users of the tool can provide a different factory to create appropriate ``Command`` instances by setting the ``command`` trait to a callable that should expect keyword arguments ``component``, ``data`` (the new rectangle as a tuple ``(x, y, width, height)``), ``previous_rectangle``, and ``mergeable``. Command Classes ~~~~~~~~~~~~~~~ The library provides some useful ``Command`` subclasses that users may want to create specialized instances or subclass to customize the behaviour of their applications. They may also be of use to ``CommandAction`` subclasses outside of the Enable framework (such as menu items or toolbar buttons) which want to interact with Enable components. ``ResizeCommand`` This command handles changing the size of a component. The constructor expects arguments ``component``, ``new_rectangle`` and (optionally) ``previous_rectangle``, plus optional additional traits. If ``previous_rectangle`` is not provided, then the component's current rectangle is used. Instances hold references to the ``Component`` being resized in the ``component`` attribute, the new and previous rectangles of the component as tuples ``(x, y, width, height)`` in the ``data`` and ``previous_rectangle`` attributes, and whether or not subsequent resize operations on the same component should be merged together. The tool handles the logic of changing the position and bounds of the component appropriately, as well as invalidating layout and requesting redraws. It also provides a default ``name`` attribute of ``Resize `` plus the ``component_name`` (which in turn defaults to a more human-readable variant of the component's class). Instances can improve this by either supplying a full replacement for the ``name`` attribute, or for the ``component_name``. Finally, there is a ``move_command`` class method that creates a ``ResizeCommand`` that just performs a move and is suitable as the command factory of a ``MoveCommandTool``, which allows easy merging between resize and move operations, if required for the application. ``MoveCommand`` This command handles changing the position of a component. The constructor expects arguments ``component``, ``previous_position`` and (optionally) ``new_position``, plus optional additional traits. If ``new_position`` is not provided, then the component's current position is used. Instances hold references to the ``Component`` being moved in the ``component`` attribute, the new and previous positions of the component as tuples ``(x, y)`` in the ``data`` and ``previous_position`` attributes, and whether or not subsequent move operations on the same component should be merged together. The tool handles the logic of changing the position of the component appropriately, as well as invalidating layout and requesting redraws. It also provides a default ``name`` attribute of ``Move `` plus the ``component_name`` (which in turn defaults to a more human-readable variant of the component's class). Instances can improve this by either supplying a full replacement for the ``name`` attribute, or for the ``component_name``. Base Classes ~~~~~~~~~~~~ There are two simple base classes of tools that are potentially of use to authors of new tools. ``BaseUndoTool`` Tools which need to be able to trigger undo and redo actions, or otherwise interact with an undo manager (for example, to set the current command stack or clear the command history) can inherit from this class. It has an ``undo_manager`` attribute which holds a reference to an ``IUndoManager`` and provides convenience methods for ``undo`` and ``redo`` using the undo manager. ``BaseCommandTool`` Tools which need to perform undoable actions may want to inherit from this class. It provides a standard ``command_stack`` attribute which holds a reference to an ``ICommandStack``. It also has a ``command`` callable trait that can be overriden by subclasses to create an appropriate command when demanded by the UI. In addition to these simple base tools, authors of Tools or Actions that perform undoable operations on Enable or Chaco components may want to make use of the following ``Command`` subclass: ``ComponentCommand`` This class is an abstract base class for commands which act on Enable ``Components``. It provides a ``component`` attribute which holds a reference to the component that the command should be performed on, and a ``component_name`` attribute that can be used to help build the ``name`` of the ``Command`` to be used in textual representations of the command (eg. in menu item labels). The default ``component_name`` is just a more human-friendly version of the component's class name, with camel-case converted to words. Users are encouraged to override with something even more user-friendly.