Hi,

I was trying to understand how the display, and diagram works but I am 
confused at this moment.

 From diagramdata.h, it definds a Rectangle 'extents' and in display, 
there is a Rectangle called 'visible'.  What is extents used for? 
Because I saw the code in display.c in ddisplay_scroll() function, the 
new origin is checked against the extents of the diagram.  However when 
I try to output the value of both visible and extents, they are the 
same. (with 0,10,0,10 for left, right, top, bottom respectively; which 
is the default setting of the extents).  Now, if I am not 
misunderstanding it, is extents mean the complete drawing area? and 
visible should be part of the clipped rectangle of extents?  If so, then 
why whould extents and visible are of the same size while I can still 
scroll the "extents" with the scroll bar?  (btw, I can't scroll the 
display with keyboard; which is one of the reason why I am looking at 
ddisplay_scroll()).

The next thing is about units.  If the printable area (the blue lines of 
the display window) is *really* the printable area, and if I use UML 
objects.  It could easily occupy a few pages for just one simple UML 
diagram.  It seems the printable area is following the units of 
measurement of Dia (20 pixel == 1 cm, as it was said in display.h with 
the default zoom setting).  Which
means the UML objects are not displayed or drawn according to the zoom 
factor or units.

Please correct me if I am wrong. I just started using it and it seems to 
have a lot of potentials ;)

Regards,
Patrick

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