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[platform-swt-dev] Canvas Scrolling
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Hi all,
Sorry for posting this question here, but i posted it on the newsgroup
without success ...
I am trying to understand the scrolling mechanism for Canvas. I played a
lot with the Snippet48 allowing to scroll into a browsed image. I
understand the code of this snippet but still have a question concerning
the scrolling is done.
In this sample the scrolling is realized in two stages:
- First the image is scrolled, for a scrolling to the right the current
visible part of the image is translated to the left, an area on the
right need to be repaint
- Next, resulting from this scroll, the area that need repainting is
repainted. This is done inside the Paint listener added to the canvas
My question is the following : why the canvas is scrolled since inside
the paint listener the full image is redrawn ?? (the area needed repaint
is represented by e.x, e.y, e.width, e.height that are unused).
Modifying the scroll bar listener to just compute new image origin and
then telling the canvas to redraw results in the same way. Is there any
performances issues underneath that i missed ?
Regards,
Manuel Selva