On Wed, May 2, 2012 at 8:55 AM, Bronislav Klučka
<[email protected]
<mailto:[email protected]>> wrote:
Bear with me...
Delphi (Object Pascal) Visual Component Library has concept
of Actions, some Actions can be assigned to Controls (those
would be here menu/contextmenu items of the browser, would be
great to be able to assign such Action (or some inherited
object) to my own <button>), one Action can be assigned to
unlimited number of controls. Action has 2 important
methods/events (either overriding the method or listening to
the event default method triggers). First one is Execute,
that is called, when Control default activation happens
(click/enter on button, click on menu item), which helps to
utilize functionality for several controls in one place
(essentially one event handler function, we can do that of
course in JS..)
The important thing is, Action also has Update method
(OnUpdate event), that is called every time application gets
to idle state (application receive message (system message
like click, paint, keydown, whatever), application processes
this message and any subsequent messages if any new are in
the queue and goes to idle). And in that idle state
application goes through all the Actions in the application
and calls Update method and then the Action can decide,
whether is enabled or not. And all Controls with this Action
assigned would change this property as well
I could express it in JS as
var deleteUserAction = new Action();
deleteUserAction.addEventHandler('execute', function()
{
//some code to delete all selected users
});
deleteUserAction.addEventHandler('update', function()
{
this.enabled = (myList.selectedUsers.length > 1) &&
havingRightsToDeleteUsers;
});
mainMenuItemDelete.action = deleteUserAction;
contextMenuItemDelete.action = deleteUserAction;
toolbarButtonDelete.action = deleteUserAction;
So the update handler allows you not to care about how many
controls should you disable/enable, just assign this action
to any control, in this action handler set up enabled to this
action and all controls are updated. So except the assignment
of Action to Control, no additional work needed. And the
concept of calling the update method guarantees, the UI is up
to date (user is doing something, messages are queued and
processed, the second there is time, all actions are
updated). Since it is in idle state, programmer does not have
to care when and how to set up all controls.
Action also has e.g. caption, image, etc. when updated again,
all assigned controls are updated to have the same caption,
image, etc...
I'm currently trying to implement this in my web application
(would be handy to have idle event), because it would
simplify UI management on programmers level, but something
like this could help to update browser's UI as well.
This is why I've suggested to tie command elements to execCommand
in
http://lists.w3.org/Archives/Public/public-webapps/2011OctDec/1232.html
to be used as a state machine.
