2 Visual Components Manuals

Introduction to Visual Components 2.3
endif
if ready = 1 then
VA_Saccess(1,VC_HANDLE)= if
0 then
VA_Redraw (1,VC_HANDLE)
VA_Srelease(1,VC_HANDLE)
endif
endif
3.3.8.21.3 Example for C Programming
#include
#include
#include
UINT _GLOBAL ready;
unsigned long VC_HANDLE;
_CYCLIC void Cyclic(void)
{
if (!ready)
{
VC_HANDLE = VA_Setup(1 "vga"); ,
if (VC_HANDLE)
ready = 1;
}
if (ready)
{
if (!VA_Saccess(1,VC_HANDLE))
{
VA_Srelease(1,VC_HANDLE);
}
}
}
VA_Redraw (1,VC_HANDLE);
3.3.8.22 Requirements and Initialization − VA_Saccess
This is one of the most important functions in the VISAPI. VA_Saccess makes it possible to carry out drawing
operations.
Drawing is ONLY possible if this function returns ERR_OK. This means that this function has to be called before
any drawing commands. If ERROR_BUSY is returned, the VA_Saccess function must be called again in the
next cycle. This occurs until ERR_OK is returned.
Important:
No VISAPI function can be used until VA_Saccess(...) returns ERR_OK.
After that, any number of VISAPI functions can be executed. After all of this, VA_Srelease must be called in
each case.
The following rules must absolutely be followed:
• Drawing functions can only be written between a VA_Saccess and VA_Srelease block
• VA_Srelease should only be called if VA_Saccess returned ERR_OK.
3.3.8.22.1 Parameter
I/O Parameter Type Meaning
IN enable BOOL This function is only executed if enable is TRUE.
IN VCHandle UDINT The handle returned by VA_Setup
OUT Return Value UINT Not equal to 0 if error occurs
3.3.8.22.2 Example for Automation Basic
(* cyclic program *)
if ready 1 then
VC_HANDLE = VA_Setup(1 "vga") ,
3.3.8.21 Graphics and Text Output − VA_Redraw 157