dllcall

[layer]

hey guys, trying to make a little paint application using dllcall and need a little help :"> heres my code so far to see if i could even paint in the window...

#include <GUIConstants.au3>
$hwnd= GUICreate ("paint some stuff :)", 300, 400)
GUISetState ()
GUISetCursor (3)
$getdc= DllCall ("user32.dll", "int", "GetDC", "hwnd", $hwnd)
Func _IsPressed($hexKey)

  
  Local $aR, $bRv
  $hexKey = '0x' & $hexKey
  $aR = DllCall("user32", "int", "GetAsyncKeyState", "int", $hexKey)
 
  If $aR[0] <> 0 Then
     $bRv = 1
  Else
     $bRv = 0
  EndIf
  
  Return $bRv
EndFunc 
DLLCall ("user32.dll", "int", "ReleaseDC", "hwnd", $hwnd, "int", $getdc)
While 1
   $pos= MouseGetPos ()
   $get= GUIGetMsg ()
   If $get= -3 Then
      Exit
   EndIf
   If _IsPressed('01') = 1 Then
      $pen= DllCall ("Gdi32.dll", "int", "CreatePen", "int", $getdc, "int", "PS_SOLID", "int", 1, "int", 0xffffff) 
      $draw= DllCall ("Gdi32.dll", "int", "SetPixel", "int", $getdc, "int", $pos[0], "int", $pos[1], "int", 0xffffff)
   EndIf
   WEnd

i did some research on the dll functions up there but they don't seem to paint!?!?! could someone point out to me what im doing wrong?

[layer]

i know one of you has the answer

[layer]

pretty please

[Jon]

Before we even start working out if drawing on a window at the mouse position is possible (will probably get wiped as soon as you move the mouse) the following are wrong:

- You are calling ReleaseDC before the while loop

- IsPressed('01')? What key is 0x01?

- You are Creating a pen lots of times without freeing it.

Edit: Also from the docs on CreatePen:

After an application creates a logical pen, it can select that pen into a device context by calling the SelectObject function. After a pen is selected into a device context, it can be used to draw lines and curves.

[SumTingWong]

pretty please

<{POST_SNAPBACK}>

@layer

You're trying to run before you can walk. You don't seem to understand how to use DllCall properly so if I want to help you with what you are doing, I will have to hold your hand through all the basics.

Anyway, I start by quoting this section of the help entry for DllCall

If the function call fails then @error is set to 1. Otherwise an array is returned that contains the function return value and a copy of all the parameters (including parameters that the function may have modified).

$return[0]= function return value

$return[1] = param1

$return[2] = param2

...

$return[n] = paramn

Therefore, the real DC after your GetDC call is $getdc[0]

Next, you should put your _IsPressed UDF and ReleaseDC call after your main program loop. When passing a string to DllCall such as "PS_SOLID", you should specify "str" as the type description and not "int"

Amended code below:

#include <GUIConstants.au3>
$hwnd= GUICreate ("paint some stuff :)", 300, 400)
GUISetState ()
GUISetCursor (3)
$getdc= DllCall ("user32.dll", "int", "GetDC", "hwnd", $hwnd)
While 1
   $pos= MouseGetPos ()
   $get= GUIGetMsg ()
   If $get= -3 Then
      Exit
   EndIf
   If _IsPressed('01') = 1 Then
      $pen= DllCall ("Gdi32.dll", "int", "CreatePen", "int", $getdc[0], "str", "PS_SOLID", "int", 1, "int", 0xffffff) 
      $draw= DllCall ("Gdi32.dll", "int", "SetPixel", "int", $getdc[0], "int", $pos[0], "int", $pos[1], "int", 0xffffff)
   EndIf
   WEnd
DLLCall ("user32.dll", "int", "ReleaseDC", "hwnd", $hwnd, "int", $getdc[0])

Func _IsPressed($hexKey)  
  Local $aR, $bRv
  $hexKey = '0x' & $hexKey
  $aR = DllCall("user32", "int", "GetAsyncKeyState", "int", $hexKey)

  If $aR[0] <> 0 Then
     $bRv = 1
  Else
     $bRv = 0
  EndIf
  
  Return $bRv
EndFunc

I have only corrected the mistakes I spotted in your code. The rest is up to you.

[Jon]

When passing a string to DllCall such as "PS_SOLID", you should specify "str" as the type description and not "int"

PS_SOLID is a int value, he needs to find out what it is from a windows header file.

[layer]

theres one thing i dont get... (maybe many in your point of view) the return type...

Help File says...

Type Details

none no value (only valid for return type - equivalent to void in C)

short a 16 bit integer

int a 32 bit integer

long a 32 bit integer

short_ptr a pointer to a 16 bit integer 

int_ptr a pointer to a 32 bit integer

long_ptr a pointer to a 32 bit integer

str a string

wstr a wide character string (converted to/from an ANSI string during the call)

hwnd a window handle

ptr a general pointer (void *)

could someone just please explain what those mean? i think i know int, str, and hwnd... but the rest, i have no clue

EDIT: cause like, what would be the return type of SelectObject... hwnd right? could someone please verify

EDIT: Return Values

If the selected object is not a region and the function succeeds, the return value is a handle to the object being replaced. If the selected object is a region and the function succeeds, the return value is one of the following values.

:"> thats from msdn just to let ye know

Edited January 1, 2005 by layer