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Threshold width and height for adding scrollbars [message #225854]

Fri, 16 March 2007 13:22

Raheel Ashraf

Messages: 2502
Registered: July 2009

Senior Member

Hi,
I have been trying to draw BIRT charts on SWT. I have noticed that if the
size of the canvas is reduced significantly then the charts become messed
up. Specifically:
- The bars in the bar charts either disappear or overlap and it looks
really bad
- For pie charts, the legend entries disappear and the pie chart itself
doesnt make sense because it is so small

So if we can define some heuristic for this threshold width and height we
can either:
- Not allow to resize once these threshold limits are reached or
- add scroll bars once these limits are reached

But there doesnt seem to be come up with some easy criteria for the
defining these thresholds. I was wondering if you can help with that. So I
know that somewhere in the engine code itself, there is some code that
decides when to make the bars or legend entries disappear. I was wondering
if its a good idea to use those criteria as our thresholds? If so, can
you point me to the code where that decision is made?
Any other criteria you can think of for these thresholds?

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Re: Threshold width and height for adding scrollbars [message #228055 is a reply to message #225854]

Mon, 19 March 2007 16:14

Raheel Ashraf

Messages: 2502
Registered: July 2009

Senior Member

Similarly, I have noticed that when you reduce the width of the chart, the
legend entries seem to appear in the "..." formal. So for example, if the
legend entry was "Canada", it might become "Cana...". So the time when
this thing happens can be used as the threshold width?

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Re: Threshold width and height for adding scrollbars [message #228467 is a reply to message #225854]

Tue, 20 March 2007 13:31

Raheel Ashraf

Messages: 2502
Registered: July 2009

Senior Member

Still waiting for a response on this one...

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Re: Threshold width and height for adding scrollbars [message #229026 is a reply to message #228467]

Wed, 21 March 2007 16:25

David Michonneau

Messages: 1145
Registered: July 2009

Senior Member

I think this could be a great enhancement, but unfortunately, it's very hard
to implement. The layout computations done in charting are complex and it
would require several passes to find out the minimal witdh and height to
ensure no loss in rendering of any part of the chart, using some kind of
dichotomia.

You suggest using heuristics, but it's difficult to come up with any, since
the chart contents can vary a lot based on the types, the data labels,
titles, legend entries, and so on. As well as their position and visibility.

It's also difficult to point you to one part of the code, there are many
places where clipping or ellipsis might occur, as each part is rendered
independently. I think we might enhance our layout framework in the future,
and we will take this into account. For now you can file a bugzilla
enhancement to track it.

Thanks,

David

"Raheel Ashraf" <rashraf@ca.ibm.com> wrote in message
news:36b481ba6459dae8a44eb95e128caca5$1@www.eclipse.org...
> Still waiting for a response on this one...
>

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