WtWorkProc Function

Registers a work procedure for background processing.

Usage

status = WtWorkProc(function, parameters)

Parameters

function:

'Add' — Registers the specified work procedure.

'Remove' — Removes the previously registered work procedure.

parameters:

If 'Add' is specified, also provide these two parameters:

workproc — A work procedure name (string).

client_data — (optional) A variable.

If 'Remove' is specified, also provide the following parameter:

id — The ID of the work procedure to be removed.

Returned Value

For 'Add':

status — The work procedure ID; zero (0) indicates failure.

For 'Remove':

status — One (1) indicates success; zero (0) indicates failure.

Keywords

Noparams — If nonzero, calls the work procedure with two parameters: wid (the top-level shell of the application), and client_data.

Once_only — If nonzero, calls the work procedure one time only.

Discussion

WtWorkProc is modeled after functionality available in the X Windows Intrinsics library with XtAddWorkProc and XtRemoveWorkProc. When a work procedure is added, it is executed in its entirety unless a REMOVE call to WtWorkProc is issued before the procedure has been called. If the work procedure does a large amount of processing it could block the widget interface until it has finished running.

A typical implementation using WtWorkProc to perform a large amount of background processing is to break down the processing into a number of discrete steps and execute the steps one at a time in a work procedure which issues another ADD call to WtWorkProc to start the next step. Repeat this process until all the steps have been completed.

For information on the requirements for writing work procedures, see "Adding Work Procedures" in the PV‑WAVE Application Developer’s Guide.

Note:

Rogue Wave has ported a subset of the Widget Toolbox (Wt) functionality available for Motif to Microsoft Windows. Because the Widget Toolbox under Windows is not a complete implementation, we recommend that Windows developers use the PV‑WAVE Widgets (Ww) layer or the VDA Tools when developing GUI applications.

Example

PRO workp1, wid, client_data

   PRINT, 'Executing workp1 Once. Data: ', client_data

END

PRO workp2, wid, client_data, unused, workproc_id

   print,'Executing workp2 Repeatedly. Data: ', client_data

END

PRO ButtonCB, wid, index

   COMMON wp, wpid2, wp2init

   CASE index of

      1: wpid1 = WtWorkProc('add', 'workp1', 'User Data1', $

         /NoParams, /Once_only)

      2: BEGIN

         wp2init = 1

         wpid2 = WtWorkProc('Add', 'workp2', 'User Data2')

END

      3: BEGIN

         IF wp2init EQ 1 THEN $

            status = WtWorkProc('Remove', wpid2)

         wp2init = 0

END

   ENDCASE

END

PRO ex1

   COMMON wp, wpid2, wp2init

   topshell = WwInit('app_name', 'appclass_name', workarea)

   labels = ['Start 1', 'Start 2', 'Stop 2']

   bbox = WwButtonBox(workarea, labels, 'ButtonCB')

   wp2init = 0

   status = WwSetValue(topshell, /Display)

   WwLoop

END

Output

Output when 'Start 1' is pressed:

Executing workp1 Once. Data: User Data1

Output when Start 2 is pressed (message repeats until 'Stop 2' button is pressed:

Executing workp2 Repeatedly. Data: Iser Data 2