OpenEuphoria

Re: User32 And GDI32 Wrapper Feedback

• Posted by ghaberek (admin) Jul 20, 2012
• 1411 views

procedure WinHelp(atom handle,sequence str,atom ex,atom ex2) 
atom pStr 
	 c_proc(xWinHelp,{handle,allocate_string(str, 1),ex,ex2}) 
end procedure 

I'm really loving this feature, by the way. Here's a neat trick for passing optional "text" parameters that also accept NULL. I used this a lot when wrapping Newt.

namespace newt 
public procedure PushHelpLine( object text = NULL ) 
    if sequence( text ) then text = allocate_string( text, 1 ) end if 
    c_proc( x_newtPushHelpLine, {text} ) 
end procedure 

So if you call newt:PushHelpLine() with no parameters, it passes NULL automatically, if you pass an atom (assumed to be a string pointer) it passes it through directly, and if you pass a sequence (a text string) it is allocated into memory, flagged for collection, and then passed to the function.

You could also pre-allocate your strings as constant pointers and let Euphoria clean them up when it's done, although I can't see a direct advantage to this one way or the other (unless you're using a lot of strings on a really really slow machine).

constant helpText = allocate_string( "This is my help text", 1 ) 
 
newt:Init(1) 
newt:PushHelpLine( helpText ) 
newt:WaitForKey() 
newt:Finished() 
 
-- helpText will be freed automatically when we're done 

-Greg