OpenEuphoria

Re: Object-oriented preprocessor

• Posted by jmduro Aug 26, 2022
• 2232 views

Let's take an example with win32lib.

Original code:

global procedure drawRectangle( integer id, integer filled, 
	    	    integer x1, integer y1, 
	    	    integer x2, integer y2 ) 
 
    -- draw a rectangle 
    atom hdc 
 
    -- get the device context 
    hdc = getDC( id ) 
 
    -- create a pen 
    createPen( id, hdc ) 
 
    -- create the brush 
    createBrush( id, filled, hdc ) 
 
    -- call Rectangle 
    VOID = w32Func( xRectangle, {hdc, x1, y1, x2, y2 } ) 
 
    -- release the device context 
    releaseDC( id ) 
end procedure 

You would probably define a generic class TRect then specify properties of its instance rect as follows:

--generic class 
sequence TRect = class("TRect")  
TRect = addProperty(TRect,"x1",0)  
TRect = addProperty(TRect,"y1",0)  
TRect = addProperty(TRect,"x2",0)  
TRect = addProperty(TRect,"y2",0)  
 
-- specific instance: x2 and y2 differ from default values 
sequence rect = classes:new(TRect) 
rect = setProperty(rect, "x2", 10) 
rect = setProperty(rect, "y2", 10) 

Class-like code first version (needs to rewrite win32lib):

global procedure drawRectangle( integer id, integer filled, 
	    	    sequence rect ) 
    integer x1 = getProperty(rect, "x1") 
    integer y1 = getProperty(rect, "y1") 
	  integer x2 = getProperty(rect, "x2") 
    integer y2 = getProperty(rect, "y2") 
     
    -- draw a rectangle 
    atom hdc 
 
    -- get the device context 
    hdc = getDC( id ) 
 
    -- create a pen 
    createPen( id, hdc ) 
 
    -- create the brush 
    createBrush( id, filled, hdc ) 
 
    -- call Rectangle 
    VOID = w32Func( xRectangle, {hdc, x1, y1, x2, y2 } ) 
 
    -- release the device context 
    releaseDC( id ) 
end procedure 
 
drawRectangle(win, 1, rect ) 

Class-like code second version (uses original win32lib):

TRect = addMethod(TRect, "drawRectangle", routine_id("drawRectangle"))  
void = callMethod(rect, "drawRectangle", {id, filled, 
  getProperty(rect, "x1"), 
  getProperty(rect, "y1"), 
  getProperty(rect, "x2"), 
  getProperty(rect, "y2") 
}) 

It remains verbose compared to classical Openeuphoria style.

To get something more easy to program, I think the preprocessor version is more adequate (untested).

include win32lib as win 
 
class TRect 
  integer x1, y1, x2, y2 
  procedure drawRectangle(sequence params) 
    win:drawRectangle(params[1], params[2], 
	    	    self.x1, self.y1, 
	    	    self.x2, self.y2 ) 
  end procedure 
end class 
 
sequence rect = new(TRect) 
rect.x2 = 10 
rect.y2 = 10 
rect.drawRectangle({win, filled}) 

Jean-Marc