Graphics>>Rectangle>>intersects: erroneous code 
Author Message
 Graphics>>Rectangle>>intersects: erroneous code

In the process of examining graphics primitive failures where line segments
extend beyond the 32K, I discovered that the method for

  Graphics>>Rectangle>>intersects:

appears to be in error. The current method

        ^ origin < aRectangle corner
                and: [aRectangle origin <  corner
                and: [ origin < corner
                and: [aRectangle origin < aRectangle corner]]]

appears to fail for aRectangle specified by Upper Left and Lower Right (or
lines with negative slope). My corrected method reads:

        (origin x min: corner x) > (aRectangle origin x max: aRectangle corner x)
                ifTrue: [ ^false ]. "aRect is entirely left of self"
        (origin x max: corner x) < (aRectangle origin x min: aRectangle corner x)
                ifTrue: [ ^false ]. "aRect is entirely right of self"
        (origin y max: corner y) < (aRectangle origin y min: aRectangle corner y)
                ifTrue: [ ^false ]. "aRect is entirely above self"
        (origin y min: corner y) > (aRectangle origin y max: aRectangle corner y)
                ifTrue: [ ^false ]. "aRect is entirely below self"
        ^true

I will be forwarding this to ObjectShare via our project's designated
contact.



Wed, 18 Jun 1902 08:00:00 GMT  
 
 [ 1 post ] 

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