OnKey Events on Forms

Handling Key Events

The general approach to intercepting and handling keystrokes in your application is as follows.

IF a_user.key.value = "{<Key_to_be_trapped>}" THEN

a_user.key.handled = .T.

IF a_user.key.event = "down" THEN

<Action_to_be_taken>

END IF

Macro Recorder Example

Here is an example script that records and plays back keystroke macros within a form. The script is defined in a form’s OnKey event.

Note : This script can be found in the Samples\Xbasic directory off the directory in which you installed Alpha Five. Open the Xbasic database and then open the MacroExample form.

Application Help Example

Note : The following script is presented as an example of how to call the Windows API. as a practical matter, in V5 the following script is obsolete because V5 has a WINHELP_SHOW() function.

Here is a collection of examples scripts that intercepts the F1 key and lets the application redefine HELP. The help topic is set by each field’s OnArrive event, and cleared on the field’s OnDepart event. In this example, it is assumed that the Xbasic application programmer has provided a windows HELP file. :

Note : These scripts can be found in the Samples\Xbasic directory off the directory in which you installed Alpha Five. Open the Xbasic database and then open the CustomHelp form.

OnKey event for form:

' Declare the WinHelp function – Published windows

‘ function name is WinHelpA (A is for ASCII single byte)

‘ there is also a WinHelpW that is multibyte (i.e. Unicode)

‘ WinHelp is the name our Xbasic program uses

declare user32 WinHelp@WinHelpA LLCLL

‘ Define some useful constants

constant global HELP_COMMAND = 258

constant global HELP_KEY = 257

constant global HELP_PARTIAL_KEY = 261

constant global HELP_INDEX = 3

dim shared helptopic as C

HELP_FILENAME = :a5.get_path()+ "\invoice.hlp"

‘ If the user hit the {F1} key...

if (A_USER.KEY.value = "{F1}" ) then

‘ eat the key and invoke help with our help file

A_USER.KEY.handled = .T.

if (A_USER.KEY.event = "down") then

if (helptopic <> "") then

‘ if a topic is defined, use the topic in the help call

WinHelp(0, HELP_FILENAME, HELP_PARTIAL_KEY,helptopic)

else

‘ If no help topic defined, then just show an index

WinHelp(0, HELP_FILENAME, HELP_INDEX,"")

end if

OnArrive event for INV_NO field:

‘ Set the topic to be invoice numbers

dim shared helptopic as C

helptopic = "Invoice Numbers"

OnDepart event for INV_NO field:

‘ No longer on the invoice number field, so un-define the topic

dim shared helptopic as C

helptopic = ""

OnArrive event for Vendor_ID field:

‘ Set the topic to be Vendor

dim shared helptopic as C

helptopic = "Vendor"

OnDepart event for Vendor_ID field:

‘ No longer on the Vendor_ID field, so

‘ undefine the topic

dim shared helptopic as C

helptopic = ""