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Re: Clipboard API spec should specify beforecopy, beforecut, and beforepaste events

From: Bronislav Klučka <Bronislav.Klucka@bauglir.com>
Date: Wed, 02 May 2012 17:55:13 +0200
Message-ID: <4FA158E1.2060100@bauglir.com>
To: public-webapps@w3.org

On 2.5.2012 15:57, Boris Zbarsky wrote:
> On 5/2/12 2:23 AM, Aryeh Gregor wrote:
>> For the former, I'd suggest onbeforecontextmenu, with some way to
>> disable specific options
> I would think that disabling cut/copy/paste would apply to main menus 
> too, not just context menus.  Most people I know who use menus for 
> this (which is precious few, btw, for the most part people I know seem 
> to use keyboard shortcuts for cut/copy/paste) use the main menu, not 
> the context menu...
> One question is whether this use case (which I agree seems worth 
> addressing) requires a new event.  That is, is it better for the 
> browser to fire events every time a menu is opened, or is it better 
> for apps that want to maintain state like this to update some property 
> on the editable area whenever their state changes and for browsers to 
> just read those properties when opening a menu?
> The latter is, from my point of view as a browser implementor, 
> somewhat simpler to deal with, since it doesn't involve having to 
> worry about alert() or sync XHR or window.close() in menu-opening 
> code.  But I can see that it might be more complicated to author 
> against...
> -Boris
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 

  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) && 
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.

Received on Wednesday, 2 May 2012 15:55:44 UTC

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