[platform-swt-dev] Canvas Scrolling

[Manuel SELVA <manuel.selva@xxxxxx>]

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