Passing UDT's to Win32 DLL Calls (DBP v6.0)

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CodemanV

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Joined: 25th Aug 2005

Location: South Wales Valleys, UK

Posted: 4th May 2006 04:26 Edited at: 4th May 2006 05:40

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Hello

Spooky just inspired me to actually post something but I do think it's about time I started putting some code up on these 'ere forums as they have helped me a lot in my quest to master DBP (I'm still a beginner but I've just finished level 3 of the quest

)

A "bug" in DBP allows you to get the pointer of a UDT array. This allows you to create a UDT and fill the UDT variables with just one call to a Win32 function - sort of C++ish.

The following code is a basic demonstration of how it works. I hope the comments are clear enough for you.

Remstart
   Project  : Simple Win32 UDT Filler Upperer
   Created  : 04/05/2006 02:04:53
   Author   : CodemanV
Remend

`CALL DLL number assignment
#Constant user32 1

`UDT's : C++ POINT and RECT structures
Type PointInfo
   x as integer
   y as integer
EndType

Type RectInfo
   left as integer
   top as integer
   right as integer
   bottom as integer
EndType

`Stores the DBP applicatioon window handle
Global hWnd  As dword

`Stores the mouse desktop coordinates
Dim Pnt() as PointInfo
Global msPtr as dword

`Stores the DBP app window coordinates
Dim Rect() as RectInfo
Global rectPtr as dword

`Setup a windowed display mode
   Set Display Mode 640, 800, 32
   Set Window On

Load DLL "user32.dll", user32

`Get the window handle of the active DBP application
   hWnd  = Call DLL(user32, "GetActiveWindow")

`Create the pointers to be passed to the Win32 DLL calls
   `A "bug" in DBP allows you to get the pointer of a UDT array
   `By setting a DWORD variable equal to a UDT array element,
   `The DWORD becomes a pointer to the structure contained within the UDT
   Add To Queue Rect()
   Add To Queue Pnt()
   msPtr = Pnt()
   rectPtr = Rect()

`***** Could do this also but the UDT's wouldn't be needed then
   `msPtr = Make Memory(8)
   `rectPtr = Make Memory(16)

Do
   `Looky here - the "pointers" are pointing to a UDT Array
   `so the UDT's variables get filled automatically :)

`Get the window position of the active DBP application
   retern = Call DLL(user32, "GetWindowRect", hWnd , rectPtr)

`Get the mouse cursor position in relation to desktop
   retern = Call DLL(user32, "GetCursorPos", msPtr)

`Notice the mouse movement updates the Pnt() UDT and if the window is moved, the Rect() UDT updates 
   `even though no values are actually being assigned to the UDT variables

`Check if the Mouse cursor is in the DBP app or not
   xChk = ((Pnt().x >= Rect().left) AND (Pnt().x <= Rect().right))
   yChk = ((Pnt().y >= Rect().top) AND (Pnt().y <= rect().bottom))

if (xChk) AND (yChk)
      tmp$ = "Mouse In active app"
   else
      tmp$ = "Mouse Out of active app"
   endif

`Show the current mouse and window info
   Cls
   print "Mouse x("; Pnt().x; " : "; Pnt().y; ")y"
   print tmp$
   print "xChk = "; xChk; "  :  yChk = "; yChk
   print
   print "Active window corners"
   print "---------------------"
   print "left = "; Rect().left
   print "top = "; Rect().top
   print "right = "; Rect().right
   print "bottom = "; Rect().bottom

Loop

`Unload DLL and delete the memory pointers
   Delete DLL user32
   Delete Memory msPtr
   Delete Memory rectPtr

+ Code Snippet

Remstart
   Project  : Simple Win32 UDT Filler Upperer
   Created  : 04/05/2006 02:04:53
   Author   : CodemanV
Remend

`CALL DLL number assignment
#Constant user32 1

`UDT's : C++ POINT and RECT structures
Type PointInfo
   x as integer
   y as integer
EndType

Type RectInfo
   left as integer
   top as integer
   right as integer
   bottom as integer
EndType


`Stores the DBP applicatioon window handle
Global hWnd  As dword

`Stores the mouse desktop coordinates
Dim Pnt() as PointInfo
Global msPtr as dword

`Stores the DBP app window coordinates
Dim Rect() as RectInfo
Global rectPtr as dword

   `Setup a windowed display mode
   Set Display Mode 640, 800, 32
   Set Window On

   Load DLL "user32.dll", user32

   `Get the window handle of the active DBP application
   hWnd  = Call DLL(user32, "GetActiveWindow")

   `Create the pointers to be passed to the Win32 DLL calls
   `A "bug" in DBP allows you to get the pointer of a UDT array
   `By setting a DWORD variable equal to a UDT array element,
   `The DWORD becomes a pointer to the structure contained within the UDT
   Add To Queue Rect()
   Add To Queue Pnt()
   msPtr = Pnt()
   rectPtr = Rect()

   `***** Could do this also but the UDT's wouldn't be needed then
   `msPtr = Make Memory(8)
   `rectPtr = Make Memory(16)

Do
   `Looky here - the "pointers" are pointing to a UDT Array
   `so the UDT's variables get filled automatically :)

   `Get the window position of the active DBP application
   retern = Call DLL(user32, "GetWindowRect", hWnd , rectPtr)

   `Get the mouse cursor position in relation to desktop
   retern = Call DLL(user32, "GetCursorPos", msPtr)

   `Notice the mouse movement updates the Pnt() UDT and if the window is moved, the Rect() UDT updates 
   `even though no values are actually being assigned to the UDT variables

   `Check if the Mouse cursor is in the DBP app or not
   xChk = ((Pnt().x >= Rect().left) AND (Pnt().x <= Rect().right))
   yChk = ((Pnt().y >= Rect().top) AND (Pnt().y <= rect().bottom))

   if (xChk) AND (yChk)
      tmp$ = "Mouse In active app"
   else
      tmp$ = "Mouse Out of active app"
   endif


   `Show the current mouse and window info
   Cls
   print "Mouse x("; Pnt().x; " : "; Pnt().y; ")y"
   print tmp$
   print "xChk = "; xChk; "  :  yChk = "; yChk
   print
   print "Active window corners"
   print "---------------------"
   print "left = "; Rect().left
   print "top = "; Rect().top
   print "right = "; Rect().right
   print "bottom = "; Rect().bottom

Loop

   `Unload DLL and delete the memory pointers
   Delete DLL user32
   Delete Memory msPtr
   Delete Memory rectPtr

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Phaelax

DBPro Master

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Joined: 16th Apr 2003

Location: Metropia

Posted: 4th May 2006 08:03

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very cool. I dont understand the part with the queue commands.

So this will work as long as the UDT matches the exact structure the windows call looks for?

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CodemanV

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Joined: 25th Aug 2005

Location: South Wales Valleys, UK

Posted: 4th May 2006 08:43 Edited at: 4th May 2006 08:48

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Cheers Phaelax

Notice in the above snippet that when the Pnt() and Rect() arrays are dimmed, there are no dimensions allocated, the arrays are initially empty.

In the example, the <ADD TO QUEUE> command was used for the 2 following reasons,

1 - the command creates element zero.
2 - the internal array pointers are automatically set to the element index number they create, in this case element zero.

This allows you to just type the array name without an index number in the bracket and the current array element will be accessed.

e.g.

+ Code Snippet

Type UDT
   varUDT as integer
EndType

`Create an empty array
Dim array() as UDT

`Adds next element which is zero
`Sets interal array pointer for array() to zero
Add To Queue array()

`the array dosen't need an index number for a value
`to be assigned or to be retrieved
array().varUDT = 10
print array().varUDT

You could also do it this way

+ Code Snippet

Type UDT
   varUDT as integer
EndType

`Create an array with 1 element in it
Dim array(1) as UDT

`You could do either of the following

indexChk = 0
if (indexChk = 0)
   `Sets interal array pointer for array() to zero
   Array Index To Queue array()

   `the array doesn't need an index number for a value
   `to be assigned or to be retrieved
   array().varUDT = 10
   print array().varUDT
else
   array(0).varUDT = 10
   print array(0).varUDT
endif

I have also been experimenting with the Array commands for dynamically increasing and shrinking arrays and lists so I'm used to using them now.

Quote: "So this will work as long as the UDT matches the exact structure the windows call looks for?"

As far as I know, yes, that should be the case. I've only done some basic stuff so far.

One possible flaw maybe if a C++ type structure contains other C++ structures, this could happen with DLL function calls with more complex parameters such as Window styles, callbacks, etc.

e.g.

+ Code Snippet

Type PointInfo
   x as integer
   y as integer
EndType

Type RectInfo
   left as integer
   top as integer
   right as integer
   bottom as integer
EndType

Type MultiUDT
   pnt as PointInfo
   rect as RectInfo
EndType

Although, thinking about it, as long as the C++ structures are strictly adhered to and the DLL calls are executed correctly , there shouldn't be a problem.

Hope my explanations are clear, even though I know what I mean, I might not convey the info as clearly as I think I have.

I should be posting some other memory stuff later, more graphics based though. I just want to make sure that there are no silly bugs in the code before I post it.

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