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From: jcb@frisbee.Eng.Sun.COM (Jim Becker)
Newsgroups: comp.windows.open-look
Subject: Re: Double Clicks in XView
Message-ID: <4074@exodus.Eng.Sun.COM>
Date: 6 Dec 90 19:03:00 GMT
References: <ZOO.90Nov26201641@grumpy.spa.umn.edu> <4039@exodus.Eng.Sun.COM>
Sender: news@exodus.Eng.Sun.COM
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In comp.windows.open-look Chris Kasso writes:

    In article <ZOO.90Nov26201641@grumpy.spa.umn.edu> zoo@aps1.spa.umn.edu writes:
    >Howdy.  I'm trying to write an application that needs to be able to
    >distinguish between single clicks and double clicks of a mouse button.
    >I am using XView 2, and this processing will be in the event procedure
    >of a canvas.
    >
    >Does anyone have sample code for this?  Thanks.
    >
    >david d [zoo] zuhn		Univ. of Minnesota Dept. of Astronomy
    >zoo@aps1.spa.umn.edu		      Automated Plate Scanner Project

    You probably want to use an interval timer to distinguish between double
    and single clicks of the mouse.  Here's some code that should do
    what you want:


An easier  method  is  simply  to  retain  the  `time'  field  in  the
XButtonEvent  associated  with  the last ACTION_SELECT event. Then the
`time' field associated with the next XButtonEvent  in  the  following
ACTION_SELECT  can  be  tested  in  terms  of  the double click timing
threshhold.

Here's some snippets of code:

/*
 * 	this does the check for multiclick and returns boolean
 */
static	int
txt_is_multiclick( textsw, tline, tindex )
Textob		*textsw;
int		tline, tindex;
{
	XButtonEvent	*bevent		= &textsw->xevent->xbutton;
	Time		curtime		= bevent->time;
	short		is_multiclick	= FALSE;

	if( tline  == textsw->last_tline && 
	    tindex == textsw->last_tindex ) 
		if( (curtime - textsw->last_time) <= textsw->click_timeout )
			is_multiclick	= TRUE;

	return is_multiclick;
}

static	int
text_notify_dispatch( textsw_pub, event, arg, type)
Textsw		textsw_pub;
Event		*event;
Notify_arg	arg;
Notify_event_type type;
{
	...
	XEvent			*aevent		= event->ie_xevent;
	XButtonEvent		*bevent		= aevent->xbutton;

	...

	textsw->click_timeout	= HARDCODED_MILLISECONDS;	/* init once */
	textsw->xevent		= aevent;


	...
	if( txt_is_multiclick( textsw, line, index ) ) {

		/* inside the threshhold */
	}
	else {
		/* outside the threshold */
	}		
	

	textsw->last_time	= bevent->time;
}



-Jim

--
--    
	 Jim Becker / jcb%frisbee@sun.com  / Sun Microsystems