At 5:16 PM +0000 2/13/06, Dave Addey wrote:
Thanks for the tip. Unfortunately, I don't know how else to achieve the
interface I have:
http://www.dj1800.com/images/fullscreen.gif
Each of the control elements (knobs, sliders etc.) is a canvas (actually a
custom subclass of a canvas).
Well, you'd have to stop approaching it that way. Each control
element could still be an object, but it wouldn't be derived from
Canvas; it would just be derived from some base class that you would
make up. This base class would probably have Top, Left, Width, and
Height properties, just like a Canvas, and a drawing method or event.
Each of the subclasses would have to draw relative to their Top/Left
values, rather than to 0,0, since you can't shift the graphics origin
as the Canvas class does. But otherwise, these classes wouldn't have
to change too much.
Your window would have just one giant Canvas -- or perhas, no canvas
at all -- and just keep a list of all the control elements. It would
handle the Paint event by having all the controls draw into an
offscreen buffer, and then drawing this buffer to the screen (thus
eliminating the flicker). It would handle mouse events by zipping
through the list, finding out which one contains the mouse, and
calling the handler on that item.
When a control needs to repaint itself, things get slightly more
tricky: they need to tell the owner (the canvas or window) that the
need redrawn, and then it must make call Paint on on each interface
element within its bounds, again to the offscreen buffer. Then it
copies just that portion of the offscreen buffer to the screen. This
will be much faster than redrawing the entire window, yet still
eliminate flicker.
Using canvases as the control elements provides an excellent way for me to
deal with the controls as objects and subclasses.
Well, it provides *a* way to do it. But not the best way, as you
have discovered, in cases where the objects need to overlap. You can
still implement them as objects and subclasses; you just need to take
control of the drawing and mouse-interfacing yourself.
Best,
- Joe
P.S. I love the interface -- gorgeous work!
--
Joseph J. Strout
[EMAIL PROTECTED]
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