OpenEuphoria

2. RE: where to find info of win32lib constant ?

• Posted by Bernie Ryan <xotron at localnet.com> May 25, 2001
• 416 views

jimmy17 at indosat.net.id wrote:
> hi...
> 
> i'm currently learning win32lib, but i have trouble about win32lib 
> constant.
> for example
> 
> create(aClass, sTitle, aParent, iX, iY, iCx, iCy, aFlags)
> 
> where can i find information about aFlags ?
> 
> thanks
> 
> 

jimmy:

    There are about 1600 procedures and functions and about
    6000 constants used in windows programming ( and still growing ).

    The only way to know what constants to use is to get a windows
    reference and lookup the particular function you are interested
    in using. All this information is available at the MS WEB site
    or from the other references that various list user have given
    you to download.

     And important thing to understand about windows constants is
     to understand how the names are formed.
     
     The first few letters of the name ( before the underscore )
     represents what group the constant is used for.
     
     examples:
          WS_......... -- Window Style
          WM_......... -- Window Message
          CB_......... -- Combo Box
          CBS_........ -- Combo Box Style
          CS_......... -- Class Style 
          DI_......... -- Draw Icon
          DS_......... -- Dialog Style
          ETC.

    The rest of the constant name ( after the underscore ) defines
    what the constant effects or controls.

    The numeric value of each constant is assigned so that they
    use unique BIT POSITIONS and when they are logically OR-ED
    together they use less space in the program ( used as a 
    single parameter in a function ) but EACH IS UNIQUE
    and DISCERNABLE from the other.

    example:
  
    If you OR-ED all of the following constants

    -- Window Styles
global constant
    WS_OVERLAPPED   = #0,
    WS_POPUP        = #80000000,
    WS_CHILD        = #40000000,
    WS_MINIMIZE     = #20000000,
    WS_VISIBLE      = #10000000,
    WS_DISABLED     = #8000000,
    WS_CLIPSIBLINGS = #4000000,
    WS_CLIPCHILDREN = #2000000,
    WS_MAXIMIZE     = #1000000
 
   The result would be #FF000000 so we would only have to use
   this single value represent all of the above window styles,
   yet windows can know each style by masking out certain bits.
   This saves having to pass a seperate parameter for each style
   in some windows function.

   I hope this helps you to better understand whats going on in
   windows. Remember that the constants values are determined and
   defined by MS windows not by the w32lib that is why you have to
   go to a MS documentation to find out more about them.
    
Bernie