Nice interface. One way to do it is the following. Rewrite all of
your controls as classes that do not inherit from RectControl. Add
Top, Left, Width, Height, Enabled, Visible, etc. properties to each.
Then add some methods.
Sub Draw(g as Graphics)
This method draws the control into g, using its coordinate properties
and state information.
The other big task you'll need to handle is mouse events. Probably the
way to do it is to add methods HandleMouseDown(X as Integer, Y as
Integer) as Boolean, HandleMouseDrag(X as Integer, Y as Integer) and
HandleMouseUp(X as Integer, Y as Integer). In these methods you would
set the draw state, call Action events, etc.
Given a mouse event on the Canvas, finding the appropriate control to
handle it will be an interesting problem, though one that has obviously
been solved before. The search should occur in the course of handling
MouseDown; once that occurs, MouseDrag and MouseUp are handled by the
same control. The simplest thing to do would be to search through the
list of control objects until you find the one in which the control
lies. A more complicated thing to do would be to keep a list of
controls sorted first by top, then by left. Then you could do a binary
search.
Charles Yeomans
On Feb 13, 2006, at 12:16 PM, Dave Addey wrote:
Hi Joe,
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). Each of the four wide rack devices is a
canvas, with the control elements on top of it. The entire window has
a
background canvas, which is used to scroll the rack devices when the
window
is smaller than the combined height of the four rack devices.
Using canvases as the control elements provides an excellent way for
me to
deal with the controls as objects and subclasses.
How should I best achieve all of this without using the layered
canvases?
Dave.
From: "Joseph J. Strout" <[EMAIL PROTECTED]>
Reply-To: REALbasic NUG <[email protected]>
Date: Mon, 13 Feb 2006 10:00:32 -0700
To: REALbasic NUG <[email protected]>
Subject: Re: Double-buffered windows on Windows
At 4:51 PM +0000 2/13/06, Dave Addey wrote:
I'm being very careful to double-buffer the individual controls when
drawing
control changes to them. But the problem is the redraw of the
window - each
control redraws (without flicker) in turn, but because some canvas
controls
are on top of others, the combined redraw is very obviously layered
and
looks flickery all the same.
The only way to avoid that is to stop layering canvases on top of
each other. Since a canvas is nothing but a rectangular portion of a
window in which you can draw, there is very rarely any need to
overlap them.
Best,
- Joe
--
Joseph J. Strout
[EMAIL PROTECTED]
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Charles Yeomans
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