On 17 Lis, 10:44, Michael Geary <m...@mg.to> wrote:
> Here is how this really works:
>
> 1. Changes you make to the DOM always take effect immediately. If you make
> any change to the DOM and then immediately follow that with code that looks
> for your change, that code will indeed see the change. For example:
>
> $('#mydiv').html( 'hello' );
> alert( $('#mydiv').html() ); // alerts 'hello'
>
> 2. BUT... The browser does not refresh its display until your JavaScript
> code finishes running. So the user will not see any of your changes until
> then.
>
> 3. A synchronous Ajax call does not let your JavaScript code finish running.
> In that sense it's just like your hard loop. The user will not see anything
> you change in the DOM until after that call finishes and your code stops
> running.
Ok... thanks... I suspected something like that...
> Why do you need a synchronous Ajax call? This is a VERY bad idea. In
> single-threaded browsers such as Firefox, it's not just a matter of the page
> display not refreshing. Your code will completely lock up the browser's user
> interface - menus and all - and not just for the current browser tab or
> window, but for *all* browser tabs and windows.
The script I'm doing is not for a web page but for a Windows Sidebar
Gadget... in particular, a settings page for the gadget ( http://img694.image
shack.us/i/clipboard1d.png/ ) so the blocking isn't a big issue since
the user can't do anything with a widget if there isn't a working
connection anyway... When you click on the OK button a function is
called which must set a property of the closing event and beforehand I
must check if the settings the user entered are correct (the
connection with an external service can be established)... Here's more
info about it:
http://msdn.mic rosoft.com/en-us/library/bb655904(VS.85).aspx
http://msdn.mic rosoft.com/en-us/library/aa359280(VS.85).aspx
> Can you use the BlockUI plugin to simulate the effect you need? This would
> be MUCH better than using synchronous Ajax:
>
> http://www.malsup.com/jquery/block/
I'll try and see what I can come up with...
> If you must use a synchronous Ajax call and you want the user to see a
> message you put into the DOM, then you will need to yield control after you
> add the message but before issuing the Ajax call. You can do this with
> setTimeout.
>
> Where you have code like this:
>
> $('#message').html( 'Sorry, dude, I will now lock up your browser' );
> $.ajax({ async:false, ... });
>
> You need to change it to:
>
> $('#message').html( 'Sorry, dude, I will now lock up your browser' );
> setTimeout( function() {
> $.ajax({ async:false, ... });
> }, 1 );
>
> That will allow the user to see your message before you lock up the browser
> by issuing the Ajax call.
>
> But what would be the point? By using setTimeout() you've made the code
> asynchronous anyway. So you could just use asynchronous Ajax in the first
> place, with BlockUI to give the blocking effect you want in the UI.
Ok, thanks... I'll look into it...
--
nowotny
