Command of the Day: WNDSTRING()

[Walt Decker]

WINSTRING() :

With a struct

With a return from a DLL

[Walt Decker]

Well, looks like no one wants to tackle this, so here goes.

Everything in memory has an address including compiled code. WINSTRING() returns a string only and is parially attached to LB's STRUCT concept and the address obtained from an element of the structure. However, WINSTRING() does not have to use a STRUCT element as long as the memory address is valid. I imagine it could use the address returned from the CALLBACK instruction but, unless one used the string in a hex editor, it would be meaningless.

That being said, let's take a look at a short structure.

STRUCT tDmy, _
TxtIn$ AS PTR, _
TxtLne AS LONG

tDmy.TxtIn$.struct does not contain ANSI characters, it contains the the beginning address of an ANSI string. For example, if you do PRINT tDmy.TxtIn$.struct you will get zero. However, if you do:

Ansi$ = "this is a string"
tDmy.TxtIn$.struct = Ansi$
PRINT tDmy.TxtIn$.struct you will get the beginning address(some number) of Ansi$, not the contents of Ansi$.

To illustrate the above I put together this little demo.
'
STRUCT tDmy, _
 TxtIn$ AS PTR, _
 TxtLen AS LONG

PRINT "The value of tDmy.TxtIn$.struct is "; tDmy.TxtIn$.struct
RetVal = 0
RetVal = FN.AddText()

PRINT "The value of tDmy.TxtIn$.struct is "; tDmy.TxtIn$.struct

PRINT "WINSTRING(tDmy.TxtIn$.struct) is "; WINSTRING(tDmy.TxtIn$.struct)
PRINT "The string is "; tDmy.TxtLen.struct; " characters long"

END

'------------------------------------
'------------------------------------

FUNCTION FN.AddText()

TxtIn$ = "Hello world!"
tDmy.TxtIn$.struct = TxtIn$
tDmy.TxtLen.struct = LEN(TxtIn$)

END FUNCTION
'

Above I mentioned that WINSTRING() is partially tied to LB's STRUCT but can use any valid memory address. To illustrate this I created a little 7 Kb dll and the following code. The Dll has three little ditties that it ranomly selects and returns the memory address of the text.
'
OPEN "DEMO.DLL" FOR DLL AS #DMO

FOR I = 1 TO 10
 CALLDLL #DMO, "FN_Demo", Addr AS ULONG
 PRINT "Memory address is "; Addr
 PRINT "WINSTRING() = "; WINSTRING(Addr)
 TIMER 200, [NXT.I]
 WAIT
 [NXT.I]
 TIMER 0
NEXT I

CLOSE #DMO
END
'

DEMO.ZIP (3.59 KB)

By using WINSTRING() in combination with API function GetObject() (Gdi32.dll) one should be able to blit the bgr bits of a memory bitmap into a string and then manipulate those bits any way one chooses.