# Directives

WRITE WINDOW DATA | Send Data to Another Session

## Format

WRITE WINDOW DATA strexpr$ TO windowHandle WITH CTL ctlValue [ , ERR=stmtref ]

Where:

strexpr$ | String expression that contains the data to be sent to the receiving window.
windowHandle | Internal Windows handle to which you want to send the data.
ctlValue | CTL value that will be placed into the input queue of the receiving PxPlus program. If the target window is not a PxPlus program, this value will be placed in the dwData portion of the COPYDATASTRUCT passed.
stmtref | Identifies the statement to which control will be transferred in case of an error.

## Description

#### Note:
WRITE WINDOW DATA is a Windows-only directive and can only be used on a Windows version of PxPlus.

This directive will send the data provided to the windows specified, and if the receiving program is a PxPlus program, place the CTL value specified into the input queue. Internally, this directive uses the WM_COPYDATA message to send a COPYDATASTRUCT to the receiving program.

Every WRITE must be offset by a READ to avoid getting the data out-of-sync. See Example.

(The WRITE WINDOW DATA directive was added in PxPlus 2016.)

## See Also

READ WINDOW DATA Receive Data from Another Session

## Example

The WRITE WINDOW DATA directive is designed to send information to an application on the same Windows machine. The receiving application should wait at an INPUT (or OBTAIN) directive pending the receipt of the CTL value sent via the WRITE WINDOW DATA directive. When the CTL is received, the receiving program should issue a READ WINDOW DATA directive to get the data being sent.

Example:

Below is a sample "Sending" program:

> 0010 let a=dll("User32","FindWindowA",0,"Target App"+$00$)
> 0020 if a=0 then print "Cannot find window"; stop
> 0030 select record R$ from "DataFile"
> 0040 write window data R$ to a with ctl 1234
> 0050 next record
> 0060 write window data "" to a with ctl 9999 ! Send EOF signal

This sending program uses the Windows FindWindow DLL call to locate a window on the system whose caption line is "Target App", then sends the contents of the file "DataFile" to that process. Each line is sent with a CTL value of 1234, and a final EOF signal is sent with a CTL of 9999.

Below is a sample "Receiving" program:

> 0010 print 'caption'("Target App")
> 0020 while 1
> 0030 input *
> 0040 if ctl=1234 then read window data x$ from a; print x$
> 0050 if ctl=9999 then read window data x$ from a; print "*EOF*"; break
> 0060 wend

This receiving program will wait at the INPUT directive on line 30 for the receipt of a CTL event. When the CTL event of 1234 is received (this being the CTL value used in the WRITE WINDOW DATA directive), it will then issue the READ WINDOW DATA directive to obtain the data sent and display it. If the CTL received was 9999, then the program will exit the loop.

#### Note:
It is important to always issue a READ WINDOW DATA whenever receiving a CTL event sent from another application using a WRITE WINDOW DATA directive. Failure to do so can cause the INPUT queue to get out-of-sync with the queued data.