Introduction to actions¶
This section tries to explain everything you need to know about actions.
An action is a Python class that describes "something that an end user might want to do". Actions are rendered as menu items, toolbar buttons or simply clickable text in arbitrary places.
A series of standard actions gets installed more or less automatically on every
actor when Lino starts up. For example
TableInsert. They are defined in
As an application developer you can define new Writing custom actions, or also override standard actions with your own custom actions.
Some action attributes include:
- class lino.core.actions.Action
The text to place on the button or menu item. A short descriptive text in user language. Used e.g. on menu items. Also on toolbar buttons if they have neither
- button_text = None
The text to appear on buttons for this action. If this is not defined, the
Permission requirements to specify for whom and under which conditions this action is available.
The text to appear as tooltip when the mouse is over that button.
A help text that shortly explains what this action does. In a graphical user interface this will be rendered as a tooltip text.
If this is not given by the code, Lino will potentially set it at startup when loading the
Every custom action has handler function : which will be called when the action is invoked.
Actions are always linked to a given actor. Each actor has a list of actions that it "offers".
- bound action¶
An action that is bound to its actor.
Some standard actions¶
- class lino.core.actions.ShowTable¶
Open a window with a tabular grid editor on this table. The grid editor is that main widget of that window (otherwise it would be a slave table).
Most items of the main menu are
- class lino.core.actions.ShowDetail¶
Open the detail window on a table actor.
- class lino.core.actions.ShowInsert¶
Open an insert window on this actor. A new row will be inserted only when this window gets submitted, which is a separate action named
- class lino.core.actions.SubmitInsert¶
Create a new database row using the data specified in the insert window. Called when the Create button of an insert window was clicked.
Most database models share the same action instance of this, which is stored in the
Some actions do nothing but opening a new window on the client. We call them window actions.
Examples of window actions are
This behaviour is specified by the
Specifies whether this action opens a window. It is up to the front end to actually render that window.
Another class of actions also open a window, but that window is not their main purpose. For example the Merge action always opens a dialog window with miscellaneous parameters, and the action itself will execute only when the user confirms that dialog window. These actions are called parameter actions.
DeleteSelected action is visible in the toolbars of
the grid and the detail windows and in the context menu on a grid row.
SubmitInsertsend an AJAX request which causes something to happen on the server.
Whether this action claims to not change anything in the current database object.
A read-only action is an action that claims to not change anything in the current database object.
Note that this is just a claim. Even a read-only action may still actually modify the current database object or even other database objects. Lino doesn't control it. The
For example the
lino.modlib.printing.DirectPrintAction action is
read-only. Otherwise it would be disabled on a registered invoice.
ShowInsert is read-only because it does not modify the
current data object.
readonly to False will (1) disable the
action for readonly user types or when
True, and (2) will cause it to be logged when
log_each_action_request is set to True.
Maybe we should change the name
writing (and set the default value False). Because that would look
more intuitive for the application developer. Or --maybe better but probably
with even more consequences-- the default value should be False. Because
being read-only, for actions, is a kind of "privilege": they don't get logged,
they also exist for read-only users... It would be more "secure" when the
developer must explicitly "say something" in order to grant that privilege.
Another subtlety is the fact that this attribute is used by
lino.modlib.users.UserAuthored. For example the
StartTicketSession action in
Lino Noi is declared
readonly because we want Workers who are not
Triager to see this action even if they are not the author (reporter)
of a ticket. Similar for the state change actions of a ticket.
TicketAction.readonly is True because we want any
change the state of a ticket, not only its author. The
lino_xl.lib.tickets.TicketAction.get_action_permission() applies (i.e. you
need to be a Triager, and the project field may not be empty). In these use
cases the attribute name should rather be requires_authorship.
A same action instance can be shared by many actors. For example the
DeleteSelected action exists only as one instance shared among all
actors that use it.
Other actions can exist as different instances even on a same actor. For example
- instance action¶
An action that has been bound to a given database object.
An instance action exists only as long as the Python representation of the database object exists.
The default action of an actor¶
Each actor has a default action. The default action for table views is
ShowTable. That's why you can define a menu item by
simply naming the table view.
For example in the
setup_menu method in the Polls tutorial) we say:
def setup_menu(self, user_type, main): super(Site, self).setup_menu(user_type, main) m = main.add_menu("polls", "Polls") m.add_action('polls.Questions') m.add_action('polls.Choices')
(Above snippet is from
add_action method of
lino.core.menus.Menu is smart enough to understand
that if you specify a Table, you mean in fact that table's default