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Scrolling with Orthogonal Adjustment

IP.com Disclosure Number: IPCOM000118398D
Original Publication Date: 1997-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 81K

Publishing Venue

IBM

Related People

Okano, H: AUTHOR

Abstract

Disclosed is a device for scrolling a screen in a logical coordinate system to a position in which the screen covers as much as possible of a target object larger than itself. Four keys -- up, down, right, and left -- are used to control scroll operations (Fig. 1). When the up or down key is pressed, the screen's position is moved upward or downward, respectively, by a predetermined distance, and also rightward or leftward, i.e., in an orthogonal direction, by an appropriate distance, so that the screen covers as much as possible of the target object. Similarly, when the right or left key is pressed, the screen's position is adjusted upward or downward, i.e., in an orthogonal direction.

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Scrolling with Orthogonal Adjustment

      Disclosed is a device for scrolling a screen in a logical
coordinate system to a position in which the screen covers as much as
possible of a target object larger than itself.  Four keys -- up,
down, right, and left -- are used to control scroll operations (Fig.
1). When  the up or down key is pressed, the screen's position is
moved upward or  downward, respectively, by a predetermined distance,
and also rightward  or leftward, i.e., in an orthogonal direction, by
an appropriate distance, so that the screen covers as much as
possible of the target object.  Similarly, when the right or left key
is pressed, the screen's  position is adjusted upward or downward,
i.e., in an orthogonal direction.

      The following screen-scrolling algorithm is described, without
loss of generality, for the case of rightward scroll.  Let d_c be a
predetermined distance by which the screen's position moves rightward
when the right key is pressed.  The screen's position is adjusted in
an orthogonal direction, i.e., upward or downward, by a distance d
(-d_max <= d <= d_max), so that the screen covers as much as possible
of the target object (Fig. 2).  The target object should be expressed
as a set of points; for example, when the target object is a path on
a road map, the internal expression of the object may be the terminal
points of each segment in the path.

     Fig. 2  Rightward Scroll and Upward or Downward Adjustment

      To decide the distance d to be moved upward or downward, which
is an integral multiple of a fixed step, an integer array T of size S
= (h + d_max * 2) / r is used, where h is the height of the screen
and r (>0) is the...