Path: utzoo!utgpu!water!watmath!dalcs!garfield!john13
From: john13@garfield.UUCP (John Russell)
Newsgroups: comp.sys.amiga
Subject: Dealing with lots of messages
Keywords: messages IDCMP MOUSEMOVE
Message-ID: <4346@garfield.UUCP>
Date: 5 Jan 88 23:52:07 GMT
Distribution: na
Organization: CS Dept., Memorial U. of Newfoundland, St. John's
Lines: 35

None of the messages on dealing with many messages (esp. mousemove) from one
or more ports has mentioned a very simple technique that can speed up
response time greatly.

It goes something like this (this is from memory):

	msg = GetMsg(window->UserPort);

	class = msg->Class;
	x = msg->MouseX , y = msg->MouseY;

	ReplyMsg(msg);

	switch(class) {
		case MOUSEMOVE:
			if (window->MouseX != x || window->MouseY != y) 
			/* user has moved the mouse since this message
			   so I will ignore it */
				break;
			else
			<normal routine to deal with mouse movements>
	}

By doing this you can minimize the number of redraws (say when rubberbanding
a line). It gives a really great speedup when applied to a time-consuming
interactive operation, eg dragging a DPaint-style curve around the screen.
If you try to process all movement messages for that, you can easily move
the mouse enough so that it will take >10 seconds for the drawing to catch up.

John
-- 
"I hate to be the one to tell you this, Bryce, but there's more to life than
 interactive systems analysis."
"I know. It also involves number crunching!"
				-- Max Headroom