0002126: Rectangle>>areasOutside: has a bug

Viewing Issue Simple Details [ Jump to Notes ]

[ View Advanced ] [ Issue History ] [ Print ]

Category

Severity

Reproducibility

Date Submitted

Last Update

0002126

[Squeak] Graphics

minor

always

10-25-05 20:46

02-16-06 10:01

Reporter

BGaertner

View Status

public

Assigned To

andreas

Priority

normal

Resolution

fixed

Status

closed

Product Version

3.9

Summary

0002126: Rectangle>>areasOutside: has a bug

Description

The instance method areasOutside: of Rectangle has a subtle bug that can cause a result with lots of rectangles of height zero. To see the problem, you can evaluate this piece of code:

| frame rects visibleBackground cnt |

cnt := 0.
visibleBackground := [:f :rc | | visibleAreas |
  visibleAreas := Array with: f.
  rc do: [:rect | | remnants |
      remnants := OrderedCollection new.
      visibleAreas do: [:a | remnants addAll: (a areasOutside: rect)].
      visibleAreas := remnants.
       cnt := cnt + 1.
      Transcript show: cnt printString; show: ' '; show: visibleAreas size
printString; cr.
  ].
  visibleAreas
].

frame := 0@0 extent: 300@300. /> rects := OrderedCollection new: 80.
0 to: 9 do: [:i |
  0 to: 7 do: [:j |
        rects add: (i@j * 20 extent: 10@10)
]].

( visibleBackground value: frame value: rects) size

-----------------
Here we have a large rectangle (frame) and 80 small rectangles
that are placed on the large rectangle. The block is a piece
of code that computes the part of the large rectangle that is
not covered by small rects.

replace the last statement of the code above with

(( visibleBackground value: frame value: rects)
   reject: [:r | r area = 0]
) size

to see that most of the rectangles have no area.

The many useless rectangles of height zero are created becaue areasOutside: uses a wrong test for intersection. The test ignores the fact that the bottom line and the right border line of a rectangle are not part of the rectangle.

Attached you find
1. a proposed fix (Rect-areasOutside-bg.1.cs)
2. some additional tests for class Rectangle. (RectangleAdditionalTests.2.cs)

Additional Information

The bug is also present in earlier versions of Squeak.

Attached Files

Rect-areasOutside-bg.1.cs [^] (1,326 bytes) 10-25-05 20:47

RectangleAdditionalTests.2.cs [^] (3,013 bytes) 10-25-05 20:48

Relationships

Notes
(0002978 - 118 - 118 - 118 - 118 - 118 - 118) BGaertner 10-25-05 20:50	For some reason, the description text is displayed in a very ugly form. I am sorry about that, but I cannot change it.

(0002980 - 37 - 37 - 37 - 37 - 37 - 37) andreas 10-26-05 02:30	Now integrated. Thanks for reporting.

(0003880 - 10 - 10 - 10 - 10 - 10 - 10) MarcusDenker 02-16-06 10:01	integrated

Issue History
Date Modified	Username	Field	Change
10-25-05 20:46	BGaertner	New Issue
10-25-05 20:47	BGaertner	File Added: Rect-areasOutside-bg.1.cs
10-25-05 20:48	BGaertner	File Added: RectangleAdditionalTests.2.cs
10-25-05 20:50	BGaertner	Note Added: 0002978
10-25-05 20:52	BGaertner	Issue Monitored: BGaertner
10-25-05 21:49	andreas	Assigned To	=> andreas
10-25-05 21:49	andreas	Status	new => assigned
10-25-05 21:49	andreas	Category	System => Graphics
10-26-05 02:30	andreas	Status	assigned => resolved
10-26-05 02:30	andreas	Fixed in Version	=> 3.9
10-26-05 02:30	andreas	Resolution	open => fixed
10-26-05 02:30	andreas	Note Added: 0002980
02-16-06 10:00	MarcusDenker	Issue Monitored: MarcusDenker
02-16-06 10:01	MarcusDenker	Status	resolved => closed
02-16-06 10:01	MarcusDenker	Note Added: 0003880

Mantis 1.0.8[^]

56 total queries executed.
37 unique queries executed.