Synchronicity? How I miss it...

[mvaughn]

Used to be that when I wrote code, I expected it to faithfully follow the course that I had outlined.
B always came after A, and code blocks never jumped in line.

I remember in Visual Basic 6 that there was a fabulous command that prevented application lockup while undergoing a CPU intensive task.
It also worked great during long loops that would otherwise render the app useless until it was completed.
The command?

DoEvents

I bring this up because I sorely miss that command.

Case in point:

I have an AJAX callback to run an XBasic function that compiles a report into a PDF and then email it.
That part works great. Maybe a little too great.

The code is so happy to run that it hogs the CPU until it has completed.

Enter the lowly Message Box...

I need to inform humble user to "Please wait while your request is being processed."

I place a call to A5.msgBox.show(blah) right above the AJAX callback thinking that it will be executed first.
What happens is that the Message Box gets pushed aside until AFTER the callback has completed.

Ok, I thought... I'll also try MouseUp and MouseDown, thinking that I will beat that callback to the starting line.

Of course that did not work either.

I tried an e.javascript command within the xbasic function but that didn't work either.

The days of Synchronicity at least ensured straight-line code execution.
And there was always DoEvents to get you out of a bottleneck.

I am still trying to cajole a Message Box to appear before the callback...

[DaveF]

Re: Synchronicity? How I miss it...

Hi Michael,

If you plan on converting to V12, there is a way to perform Action Javascript routines synchronously. There is also a new Action Javascript routine to display a wait message to block input on a control or an entire component during an AJAX callback. Other A5 developers have created a background work queue process to handle these server-intensive actions and return control back to the client-side immediately. This is something you have to configure on your own and has not been automated in V12 as far as I know. Have you tried using the Report Server? It has multiple threads reserved for report processing. I have not tested this yet, but it should offload the PDF creation from the WAS so it is free to service requests from other clients. It won't help your current situation, but its definitely something to consider if you have lots of users.

[TheSmitchell]

Re: Synchronicity? How I miss it...

Wrap a setTimeout around your ajaxCallback function. Like, setTimeout({grid.object}.ajaxCallback(...), 100);

Your message box should display before setTimeout is triggered. 100 ms should be sufficient enough wait time. If not, double it.

Since the A5.msgBox.show is non-blocking, the code keeps executing. I imagine that showing your msgBox takes a wee bit longer to propagate than an ajax callback. JavaScript runs asynchronously at times. FYI.

[mvaughn]

Re: Synchronicity? How I miss it...

I have an image (wait.gif) that I want shown before an ajax callback begins.
The image show/hide is conditional upon the value of a textbox (SHOWBUSY=1)

Button Inline Javascript:

{dialog.Object}.setValue('SHOWBUSY',1);
var id = setTimeout({grid.Object}.ajaxCallback('G','{Grid.RowNumber}:all','addtocart2','','',{}), 200);

SetValue always occurs AFTER the callback.

How on earth can I get wait.gif to be shown BEFORE the callback?

[mvaughn]

Re: Synchronicity? How I miss it...

Ok, got it working finally. It was the setTimeout syntax.

This works...

{dialog.Object}.setValue('SHOWBUSY',1);
setTimeout([COLOR="#FF0000"]function(){[/COLOR]{grid.Object}.ajaxCallback('G','{Grid.RowNumber}:all','addtocart2','','',{})[COLOR="#FF0000"]}[/COLOR],3000);

[TheSmitchell]

Re: Synchronicity? How I miss it...

Great! You found the error. :)

[mvaughn]

Re: Synchronicity? How I miss it...

yoda4.jpg Sarah, you did err not. To the force you wisely led me back. Within, the answer was. Yes, hmmm.

[TheSmitchell]

Re: Synchronicity? How I miss it...

Oh! My example was wrong. Woop woop.

Wrap a setTimeout around your ajaxCallback function. Like, setTimeout({grid.object}.ajaxCallback(...), 100);

setTimeout wants functions:

var func = function () { {grid.object}.ajaxCallback(...) };
setTimeout(func, 100);

//or

setTimeout(function () { {grid.object}.ajaxCallback(...); }, 100);