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Working with DLLs in PxPlus - Examples |
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The following examples illustrate the use of the functions described earlier for working with Windows DLLs in PxPlus.
For examples of UNIX/Linux function calls, see Working with DLL Calls in UNIX/Linux.
The following statement swaps the left and right mouse buttons:
0010 A=DLL("USER32.DLL","SwapMouseButton",1) ! Passes 32-bit value
An integer value of zero swaps the mouse buttons back.
Pointers are commonly used to pass string values, usually terminating with a null byte. This passes a pointer to a DLL to return the handle of a window with the title Notepad:
0030 A=DLL("USER32.DLL","FindWindowA",0,"Notepad"+$00$)
Sometimes a pointer refers to a region of memory or a structure to receive information from a DLL. You must pre-allocate a string variable to receive the data. The example below returns the window title, given the handle. The returned string terminates with a null byte ($00$):
DIM X$(256)
0030 A=DLL("USER32.DLL","GetWindowTextA",Hndl,X$,LEN(X$))
To pass a pointer to a number, define a two or four byte string and read the value after swapping the bytes, as follows:
DIM X$(256)
A=DLL("SOME.DLL","GetSomething",Hndl,X$)
X=DEC($00$+SWP(X$)
Program DLLS1 in this example starts Notepad, locates the handle and closes the window handle:
0010 !dlls1 Start Notepad and Close It
0020 INVOKE "NOTEPAD"
0030 INPUT "Press enter after Notepad has started ",X$
0040 LET HWND%=DLL("USER32.DLL","FindWindowA","Notepad"+$00$,0)
0050 IF HWND%<=0 THEN PRINT "Notepad not found!"; STOP
0060 LET WM_CLOSE=DEC($0010$),WPARAM%=0,LPARAM=0
0070 LET X=DLL("USER32.DLL","SendMessageA",HWND%,
0070:INT(WM_CLOSE),WPARAM%,LPARAM)
The following example illustrates inter-task communication. The program DLLS3 starts a second PVXWIN32 session, finds its Window handle, sends CTL values 101 through 103, defines an atom (pointing to a string variable in a global string table) and passes the atom reference to the second session. Then it waits for the second session to terminate.
1340 X=DLL("USER32.DLL","SendMessageA",HWND%,INT(WM_USER),WPARAM%,LPARAM)
00010 ! DLLS3 - Inter-task communication - Send CTLS & a string
00020 MAX_COL=MXC(0)+1,MAX_ROW=MXL(0)+1
00030 PRINT 'SHOW'(-1),'DIALOGUE'(0,0,MAX_COL,INT(MAX_ROW/2)-1, \ "Inter-task com0030:munication",'MODE'($000F$)+'CS'),
00040 IF ARG(1,ERR=*NEXT)="Receiver" \ THEN GOTO RECEIVER
01000 ! !^1000
01010 LOOP=0
01100 ! !^100 - Find Receiver & start if necessary
01110 IF LOOP++>1 \ THEN PRINT "Cannot start/find the Receiver!"; STOP
01120 HWND%=DLL("USER32.DLL","FindWindowA",0,"PVXWIN32 - Receiver"+$00$)
01130 IF HWND%>0 \ THEN GOTO 1200
01140 INVOKE ARG(0)+" "+PGN+" -ARG Receiver"
01150 WAIT 1
01160 GOTO 1100
01200 ! !^100 - Send CTL 101 to 103 to Receiver
01210 WM_USER=DEC($0400$),WPARAM%=0,LPARAM=0
01220 FOR WPARAM%=101 TO 103
01230 PRINT "Sending CTL value of",WPARAM%," to Receiver"
01240 X=DLL("USER32.DLL","SendMessageA",HWND%,INT(WM_USER),WPARAM%,LPARAM)
01250 NEXT
01300 ! !^100 - Send CTL 104 & the address of a String
01310 WM_USER=DEC($0400$),WPARAM%=104,LPARAM=0
01320 ATOM$="Message to Send",LPARAM=DLL("KERNEL32.DLL","GlobalAddAtomA", \ ATOM$+$00$)
01330 PRINT " Sending CTL Value ",WPARAM%,"to Receiver with message:", \ 'BR',ATOM$,'ER'
01340 X=DLL("USER32.DLL","SendMessageA",HWND%,INT(WM_USER),WPARAM%,LPARAM)
02000 ! !^1000
02010 LOOP=0; PRINT "Waiting for Receiver to shutdown",
02020 HWND%=DLL("USER32.DLL","FindWindowA",0,"PVXWIN32 - Receiver"+$00$)
02030 IF HWND%<=0 \ THEN GOTO 2100
02040 PRINT ".",; IF LOOP++<30 \ THEN WAIT 1; GOTO 2020
02100 ! !^100
02110 X=DLL("KERNEL32.DLL","GlobalDeleteAtom")
02120 PRINT 'DROP'(-1),'SHOW'(2),
02130 STOP
03000 ! !^1000 - Receive CTL values from Sender
03010 RECEIVER:
03020 PRINT 'CAPTION'("PVXWIN32 - Receiver"),'MOVE'(0,INT(MAX_ROW/2)+1),
03030 INPUT "Press F4 when finished ",*; PRINT @(0),'BR',"Received CTL=",CTL,'ER','CL'
03040 IF CTL=4 \ THEN GOTO 3200
03050 IF CTL<>104 \ THEN GOTO 3030
03060 ATOM=TCB(81) ! Atom identifier
03070 DIM ATOM$(512)
03080 X=DLL("KERNEL32.DLL","GlobalGetAtomNameA",ATOM,ATOM$,LEN(ATOM$))
03090 X=DLL("KERNEL32.DLL","GlobalDeleteAtom") ! Release Atom
03100 X=POS($00$=ATOM$); IF X \ THEN ATOM$=ATOM$(1,X-1)
03110 PRINT "Received: ",'BR',ATOM$,'ER'
03120 GOTO 3030
03200 ! !^100
03210 STOP