Hi everyone,
After all this time using RB canvases I have always done my own
computation and repainting instead of using Scroll, so now today I'm
playing around trying to figure out how Scroll can help me out. I'm
not sure I get it. It does scroll, but it doesn't scroll the entire
image like the docs say. Only the size of the canvas is scrolled,
leaving some artifacts not repainted. Here's a screen shot of what I
mean.
<http://homepage.mac.com/sroy/ScrollTest.png>
Here's an example. I set the Backdrop property of a canvas to some
image (much bigger than the canvas size). Then in the canvas event
handlers I have this code:
Function MouseDown(X as Integer, Y as Integer) as Boolean
AnchorX = x
AnchorY = y
return true
End Function
Sub MouseDrag(X as Integer, Y as Integer)
me.Scroll(x - AnchorX, y - AnchorY)
AnchorX = x
AnchorY = y
End Sub
Running it, the image does move when I drag the mouse on the canvas,
but only the portion of the image that was visible is repainted. The
result is the screen shot I linked above.
I tried passing the size of the image in Scroll() but all that
changed is that white was added to the visible portion that was
repainted. Basically it doesn't repaint the image. And if it doesn't,
then I wonder what good Scroll does me.
Scroll is good to scroll embedded controls, that works. But for an
image, what is the correct usage?
Thanks!
Steve
--
Steve Roy
<http://homepage.mac.com/sroy>
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