Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!dogie.macc.wisc.edu!uwvax!umn-d-ub!umn-cs!kulkarni
From: kulkarni@umn-cs.CS.UMN.EDU (Srinivas R. Kulkarni)
Newsgroups: comp.windows.x
Subject: Automatic Scrolling inside a Athena Viewport Widget(X11R3)
Keywords: Xaw,Viewport,X11R3
Message-ID: <17276@umn-cs.CS.UMN.EDU>
Date: 25 Nov 89 19:53:41 GMT
Distribution: usa
Organization: University of Minnesota, Minneapolis
Lines: 75



hello,

	i know this subject was discussed on the net a few months ago but i 

missed the details then. Sorry about that.

	I am trying to implement 'automatic scrolling' inside a Athena viewport

widget. In particular, whenever the user holds Button1 down and drags the 

cursor out of the viewport boundaries, i want the canvas underneath to start

scrolling and track the cursor.

	If anybody can mail me code that does this or can point out how i can 

calculate WHICH_X and WHICH_Y, i will be very thankful.

	Thankx in advance.

Srinivas R. Kulkarni
kulkarni@umn-cs.cs.umn.edu



	Relevant portions of the code follows:

----------------------code------------------------------

#define VIEWPORT_WIDTH          100
#define VIEWPORT_HEIGHT         80

#define CANVAS_WIDTH            1000
#define CANVAS_HEIGHT           800

Dimension 	viewport_width, viewport_height;
Widget        	horizontal, vertical;
Position  	child_x, child_y;

/* this proc is called whenever cursor moves with Button2 down */

Button2Motion_proc(curr_x,curr_y)
int	curr_x, curr_y;  /* 
{

  /* get horizontal and vertical scroll bar widget IDs */

  horizontal= XtNameToWidget(viewport,	"horizontal");
  vertical  = XtNameToWidget(viewport,	"vertical");

  /* get viewport width and height */

  i=0;
  XtSetArg(args[i],XtNwidth,  &viewport_width);     i++;
  XtSetArg(args[i],XtNheight,  &viewport_height);    i++;
  XtGetValues(viewport, args, i);

  /* get current position of canvas within viewport */

  i=0;
  XtSetArg(args[i],XtNx,  &child_x);     i++;
  XtSetArg(args[i],XtNy,  &child_y);    i++;
  XtGetValues(canvas, args, i);

  /* given child_x, child_y and the current position(curr_x, curr_y) of the 
   * cursor, 
	  how can i calculate WHICH_X and WHICH_Y ?
   */

  XtCallCallbacks(horizontal,XtNscrollProc, WHICH_X);
  XtCallCallbacks(vertical,  XtNscrollProc, WHICH_Y);

}