Source code for traitsui.handler
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#
# This software is provided without warranty under the terms of the BSD
# license included in LICENSE.txt and may be redistributed only under
# the conditions described in the aforementioned license. The license
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""" Defines the Handler class used to manage and control the editing process in
a Traits-based user interface.
"""
# avoid deprecation warning
from inspect import getfullargspec
from traits.api import HasPrivateTraits, HasTraits, Instance
from .toolkit import toolkit
from .help import on_help_call
from .view_element import ViewElement
from .helper import user_name_for
from .ui_info import UIInfo
# -------------------------------------------------------------------------
# Closes a DockControl (if allowed by the associated traits UI Handler):
# -------------------------------------------------------------------------
[docs]def close_dock_control(dock_control):
"""Closes a DockControl (if allowed by the associated Traits UI Handler)."""
# Retrieve the traits UI object set when we created the DockControl:
ui = dock_control.data
# Ask the traits UI handler if it is OK to close the window:
if not ui.handler.close(ui.info, True):
# If not, tell the DockWindow not to close it:
return False
# Otherwise, clean up and close the traits UI:
ui.dispose()
# And tell the DockWindow to remove the DockControl:
return True
[docs]class Handler(HasPrivateTraits):
"""Provides access to and control over the run-time workings of a
Traits-based user interface.
"""
[docs] def init_info(self, info):
"""Informs the handler what the UIInfo object for a View will be.
This method is called before the UI for the View has been
constructed. It is provided so that the handler can save the
reference to the UIInfo object in case it exposes viewable traits
whose values are properties that depend upon items in the context
being edited.
"""
pass
[docs] def init(self, info: UIInfo) -> bool:
"""Initializes the controls of a user interface.
This method is called after all user interface elements have been
created, but before the user interface is displayed. Override this
method to customize the user interface before it is displayed.
Parameters
----------
info : UIInfo object
The UIInfo object associated with the view
Returns
-------
initialized : bool
A Boolean, indicating whether the user interface was successfully
initialized. A True value indicates that the UI can be displayed;
a False value indicates that the display operation should be
cancelled. The default implementation returns True without taking
any other action.
"""
return True
[docs] def position(self, info):
"""Positions a dialog-based user interface on the display.
This method is called after the user interface is initialized (by
calling init()), but before the user interface is displayed. Override
this method to position the window on the display device. The default
implementation calls the position() method of the current toolkit.
Usually, you do not need to override this method, because you can
control the window's placement using the **x** and **y** attributes
of the View object.
Parameters
----------
info : UIInfo object
The UIInfo object associated with the window
"""
toolkit().position(info.ui)
[docs] def close(self, info, is_ok):
"""Handles the user attempting to close a dialog-based user interface.
This method is called when the user attempts to close a window, by
clicking an **OK** or **Cancel** button, or clicking a Close control
on the window). It is called before the window is actually destroyed.
Override this method to perform any checks before closing a window.
While Traits UI handles "OK" and "Cancel" events automatically, you
can use the value of the *is_ok* parameter to implement additional
behavior.
Parameters
----------
info : UIInfo object
The UIInfo object associated with the view
is_ok : Boolean
Indicates whether the user confirmed the changes (such as by
clicking **OK**.)
Returns
-------
allow_close : bool
A Boolean, indicating whether the window should be allowed to
close.
"""
return True
[docs] def closed(self, info, is_ok):
"""Handles a dialog-based user interface being closed by the user.
This method is called *after* the window is destroyed. Override this
method to perform any clean-up tasks needed by the application.
Parameters
----------
info : UIInfo object
The UIInfo object associated with the view
is_ok : Boolean
Indicates whether the user confirmed the changes (such as by
clicking **OK**.)
"""
return
[docs] def show_help(self, info, control=None):
"""Shows the help associated with the view.
This method is called when the user clicks a **Help** button in a
Traits user interface. The method calls the global help handler, which
might be the default help handler, or might be a custom help handler.
See **traitsui.help** for details about the setting the
global help handler.
Parameters
----------
info : UIInfo object
The UIInfo object associated with the view
control : UI control
The control that invokes the help dialog box
"""
if control is None:
control = info.ui.control
on_help_call()(info, control)
[docs] def perform(self, info, action, event):
"""Perform computation for an action.
The default method looks for a method matching ``action.action`` and
calls it (sniffing the signature to determine how to call it for
historical reasons). If this is not found, then it calls the
:py:meth:`~traitsui.menu.Action.perform` method of the action.
Parameters
----------
info : UIInfo instance
The UIInfo assicated with the view, if available.
action : Action instance
The Action that the user invoked.
event : ActionEvent instance
The ActionEvent associated with the user action.
Notes
-----
If overriding in a subclass, the method needs to ensure that any
standard menu action items that are needed (eg. "Close", "Undo",
"Redo", "Help", etc.) get dispatched correctly.
"""
if action.action != "":
method_name = action.action
else:
method_name = "_{}_clicked".format(action.name.lower())
for object in self.get_perform_handlers(info):
method = getattr(object, method_name, None)
if method is not None:
# call the action method
specification = getfullargspec(method)
if len(specification.args) == 1:
method()
else:
method(info)
# and we are done
return
# otherwise, call the perform method of the action
specification = getfullargspec(action.perform)
if len(specification.args) == 1:
action.perform()
else:
action.perform(event)
[docs] def get_perform_handlers(self, info):
"""Return a list of objects which can handle actions.
This method may be overridden by sub-classes to return a more relevant
set of objects.
Parameters
----------
info : UIInfo instance or None
The UIInfo associated with the view, or None.
Returns
-------
handlers : list
A list of objects that may potentially have action methods on them.
"""
handlers = [self]
if info is not None:
additional_objects = ["object", "model"]
handlers += [
info.ui.context[name]
for name in additional_objects
if name in info.ui.context
]
return handlers
[docs] def setattr(self, info, object, name, value):
"""Handles the user setting a specified object trait's value.
This method is called when an editor attempts to set a new value for
a specified object trait attribute. Use this method to control what
happens when a trait editor tries to set an attribute value. For
example, you can use this method to record a history of changes, in
order to implement an "undo" mechanism. No result is returned. The
default implementation simply calls the built-in setattr() function.
If you override this method, make sure that it actually sets the
attribute, either by calling the parent method or by setting the
attribute directly
Parameters
----------
info : UIInfo instance
The UIInfo for the current UI
object : object
The object whose attribute is being set
name : string
The name of the attribute being set
value
The value to which the attribute is being set
"""
setattr(object, name, value)
[docs] def trait_view_for(self, info, view, object, object_name, trait_name):
"""Gets a specified View object."""
# If a view element was passed instead of a name or None, return it:
if isinstance(view, ViewElement):
return view
# Generate a series of possible view or method names of the form:
# - 'view'
# trait_view_for_'view'( object )
# - 'class_view'
# trait_view_for_'class_view'( object )
# - 'object_name_view'
# trait_view_for_'object_name_view'( object )
# - 'object_name_class_view'
# trait_view_for_'object_name_class_view'( object )
# where 'class' is the class name of 'object', 'object' is the object
# name, and 'name' is the trait name. It returns the first view
# or method result which is defined on the handler:
klass = object.__class__.__name__
cname = "%s_%s" % (object_name, trait_name)
aview = ""
if view:
aview = "_" + view
names = [
"%s_%s%s" % (cname, klass, aview),
"%s%s" % (cname, aview),
"%s%s" % (klass, aview),
]
if view:
names.append(view)
for name in names:
result = self.trait_view(name)
if result is not None:
return result
method = getattr(self, "trait_view_for_%s" % name, None)
if callable(method):
result = method(info, object)
if result is not None:
return result
# If nothing is defined on the handler, return either the requested
# view on the object itself, or the object's default view:
return object.trait_view(view) or object.trait_view()
# -- 'DockWindowHandler' interface implementation -------------------------
[docs] def can_drop(self, info, object):
"""Can the specified object be inserted into the view?"""
from pyface.dock.api import DockControl
if isinstance(object, DockControl):
return self.can_import(info, object.export)
drop_class = info.ui.view.drop_class
return (drop_class is not None) and isinstance(object, drop_class)
[docs] def dock_control_for(self, info, parent, object):
"""Returns the DockControl object for a specified object."""
from pyface.dock.api import IDockable, DockControl
from .dockable_view_element import DockableViewElement
try:
name = object.name
except:
try:
name = object.label
except:
name = ""
if len(name) == 0:
name = user_name_for(object.__class__.__name__)
image = None
export = ""
if isinstance(object, DockControl):
dock_control = object
image = dock_control.image
export = dock_control.export
dockable = dock_control.dockable
close = dockable.dockable_should_close()
if close:
dock_control.close(force=True)
control = dockable.dockable_get_control(parent)
# If DockControl was closed, then reset it to point to the new
# control:
if close:
dock_control.trait_set(
control=control, style=parent.owner.style
)
dockable.dockable_init_dockcontrol(dock_control)
return dock_control
elif isinstance(object, IDockable):
dockable = object
control = dockable.dockable_get_control(parent)
else:
ui = object.get_dockable_ui(parent)
dockable = DockableViewElement(ui=ui)
export = ui.view.export
control = ui.control
dc = DockControl(
control=control,
name=name,
export=export,
style=parent.owner.style,
image=image,
closeable=True,
)
dockable.dockable_init_dockcontrol(dc)
return dc
[docs] def open_view_for(self, control, use_mouse=True):
"""Creates a new view of a specified control."""
from pyface.dock.api import DockWindowShell
DockWindowShell(control, use_mouse=use_mouse)
[docs] def dock_window_empty(self, dock_window):
"""Handles a DockWindow becoming empty."""
if dock_window.auto_close:
dock_window.control.GetParent.Destroy()
# -- HasTraits overrides: -------------------------------------------------
[docs] def edit_traits(
self,
view=None,
parent=None,
kind=None,
context=None,
handler=None,
id="",
scrollable=None,
**args,
):
"""Edits the object's traits."""
if context is None:
context = self
if handler is None:
handler = self
return self.trait_view(view).ui(
context,
parent,
kind,
self.trait_view_elements(),
handler,
id,
scrollable,
args,
)
[docs] def configure_traits(
self,
filename=None,
view=None,
kind=None,
edit=True,
context=None,
handler=None,
id="",
scrollable=None,
**args,
):
"""Configures the object's traits."""
return super().configure_traits(
filename,
view,
kind,
edit,
context,
handler or self,
id,
scrollable,
**args,
)
# -- Private Methods: -----------------------------------------------------
def _on_undo(self, info):
"""Handles an "Undo" change request."""
if info.ui.history is not None:
info.ui.history.undo()
def _on_redo(self, info):
"""Handles a "Redo" change request."""
if info.ui.history is not None:
info.ui.history.redo()
def _on_revert(self, info):
"""Handles a "Revert all changes" request."""
if info.ui.history is not None:
info.ui.history.revert()
self.revert(info)
def _on_close(self, info):
"""Handles a "Close" request."""
if (info.ui.owner is not None) and self.close(info, True):
info.ui.owner.close()
# -------------------------------------------------------------------------
# Default handler:
# -------------------------------------------------------------------------
_default_handler = Handler()
[docs]def default_handler(handler=None):
"""Returns the global default handler.
If *handler* is an instance of Handler, this function sets it as the
global default handler.
"""
global _default_handler
if isinstance(handler, Handler):
_default_handler = handler
return _default_handler
[docs]class Controller(Handler):
"""Defines a handler class which provides a view and controller for a
specified model.
This class is used when implementing a standard MVC-based design. The
**model** trait contains most, if not all, of the data being viewed,
and can be referenced in a Controller instance's View definition using
unadorned trait names. (e.g., ``Item('name')``).
"""
# -- Trait Definitions ----------------------------------------------------
#: The model this handler defines a view and controller for
model = Instance(HasTraits)
#: The Info object associated with the controller
info = Instance(UIInfo)
# -- HasTraits Method Overrides -------------------------------------------
def __init__(self, model=None, **metadata):
"""Initializes the object and sets the model (if supplied)."""
super().__init__(**metadata)
if model is not None:
self.model = model
[docs] def trait_context(self):
"""Returns the default context to use for editing or configuring
traits.
"""
return {"object": self.model, "controller": self, "handler": self}
# -- Handler Method Overrides ---------------------------------------------
[docs] def get_perform_handlers(self, info):
"""Return a list of objects which can handle actions.
By default this returns the Controller instance and the model.
Parameters
----------
info : UIInfo instance or None
The UIInfo associated with the view, or None.
Returns
-------
handlers : list
A list of objects that may potentially have action methods on them.
"""
return [self, self.model]
[docs] def init_info(self, info):
"""Informs the handler what the UIInfo object for a View will be."""
self.info = info
[docs]class ModelView(Controller):
"""Defines a handler class which provides a view and controller for a
specified model.
This class is useful when creating a variant of the standard MVC-based
design. A subclass of ModelView reformulates a number of traits on
its **model** object as properties on the ModelView subclass itself,
usually in order to convert them into a more user-friendly format. In
this design, the ModelView subclass supplies not only the view and
the controller, but also, in effect, the model (as a set of properties
wrapped around the original model). Because of this, the ModelView
context dictionary specifies the ModelView instance itself as the
special *object* value, and assigns the original model object as the
*model* value. Thus, the traits of the ModelView object can be
referenced in its View definition using unadorned trait names.
"""
# -- HasTraits Method Overrides -------------------------------------------
[docs] def trait_context(self):
"""Returns the default context to use for editing or configuring
traits.
"""
return {"object": self, "handler": self, "model": self.model}
