Apparatus and method of formatting a list for display on a touchscreen

An apparatus and method of formatting for display within a designated list window of a touchscreen, the list including a plurality of list members with a touchable element and text associated therewith. The method includes the following steps: setting a minimum required distance between the touchable elements of adjacent list members; setting an area for each touchable element of the list members, wherein the area has a vertical component and a horizontal component; positioning a first list member within the list window; and, spacing each subsequent list member vertically and horizontally from an immediately preceding list member such that the minimum required distance between adjacent touchable elements is maintained. The vertical spacing between adjacent touchable elements may be set, with the horizontal spacing between touchable elements being determined from the minimum required distance between adjacent touchable elements, the interline spacing, and the vertical component of the touchable elements. Alternatively, the horizontal spacing between adjacent touchable elements can be set, with the vertical spacing between adjacent touchable elements being determined from the minimum required distance between adjacent touchable elements and the horizontal spacing. The touchable elements may be spaced in a repeating pattern, where the number of horizontal levels in the pattern can be selected by the user, determined as a function of the minimum required distance between adjacent touchable elements and the vertical spacing between adjacent touchable elements, or determined as a function of the physical size of the list window, the field width required for the associated text, and the indentation distance. The touchable element spacing within the list window is maximized by evaluating the number of lines of text to be displayed and the interline spacing, where adjacent touchable elements are offset horizontally when all list members cannot be displayed and spaced vertically by at least the minimum required distance between adjacent touchable elements.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to a computer-controlled 
touchscreen display and, more particularly, to an apparatus and method of 
formatting a list for display on a touchscreen which more efficiently 
utilizes the area of a list window within the touchscreen without 
increasing selection ambiguity. 
2. Description of Related Art 
Various types of computer-based devices have been developed for 
communications, information processing and other purposes. Among these 
devices are personal computers, personal digital assistants, and a 
relatively new class of devices known as portable intelligent 
communications devices. Unlike the first two devices, the portable 
intelligent communications device is designed extensively to be a 
communications device, rather than just a mobile computer, and as such it 
includes a computer integrated with communications hardware and software 
to provide telephony, messaging and information services. To enable at 
least some of these features, the portable intelligent communications 
device is able to be connected to the Internet by either a wired link or a 
wireless link. 
It will also be understood that certain software applications are provided 
within the portable intelligent communications device which facilitate the 
aforementioned features, as well as other desirable features such as a 
Personal Information Manager (PIM), games and the like. An exemplary 
portable intelligent communications device is shown and disclosed in a 
patent application entitled "Switching Of Analog Signals In Mobile 
Computing Devices" and having Ser. No. 08/796,119, which is owned by the 
assignee of the present invention and is hereby incorporated by reference. 
Portable intelligent communications devices, like other computer-controlled 
devices, include a screen or display panel to enable a user to interact 
with the computer through a graphical user interface. This interaction is 
oftentimes accomplished by way of a mouse or other pointing device. To 
input or select information from the screen, the user manipulates the 
mouse to direct a cursor to the appropriate screen area. Once at the 
appropriate area, the user selects the item or information by using a 
mouse button or entering a command or text through a keyboard. 
In mouse-based systems, text at a common logic level, such as in a display 
list, is typically aligned vertically along the left side of the screen 
display. FIG. 1 depicts an exemplary screen display 10 containing a 
representative display list 12 from a phonebook software application, such 
as which may be used to save and group business card information on a 
portable intelligent communications device or similar computer. It will be 
noted that screen display 10 includes a title bar 14 (i.e., "PhoneDialer") 
located in a top window therein, as well as a main control panel 16 
including a plurality of tabbed areas which, in the representative 
application, are designated as "Phone," "Setup" and "Help." A second level 
of menu choices or control buttons 18 appear after selection of one of the 
tabbed areas in main control panel 16. In the representative screen 
display 10, control buttons 18 available under the Phone tab are denoted 
as "Call," "Transfer," "End," "Hold," "Volume" and "Mute," respectively. A 
third set of control buttons 20 appear after selection of one of second 
level control buttons 18. It will be noted that control buttons 20 
available under the "Call" button in the representative application are 
denoted as "Previous," "List," "BC" and "Next". A bottom rectangular area 
22 of screen display 10 includes a set of control buttons 24 denoted as 
"KeyPad," "Speed Dial," "Phone Book" and "Voice Mail," as well as a 
message window 26 for displaying status information. A fourth set of 
command options is provided along the right side of screen display 10, as 
designated generally by numeral 28. 
Screen display 10 further includes a work area 30 (otherwise known herein 
as a list window) having a width W and a height H within which 
representative list 12 is displayed. Since the size of list window 30 will 
typically be too small to display all list members 13 of list 12 at one 
time, a vertical scroll bar 32 is provided therein for stepping between 
such list members 13. It will be seen in screen display 10 that each list 
member 13 is a name aligned under the subgroup heading "Personal" for the 
overall group heading of "Phonebooks." Accordingly, selection of any one 
of list members 13 causes the aforementioned portable intelligent 
communications device to retrieve a phone number for the name 
corresponding thereto, which preferably is automatically dialed by the 
telephony feature of the device. It will be noted that display list 12 in 
FIG. 1 is depicted in a typical mouse-based format, where list members 13 
(in this case names) are aligned along left side 34 of list window 30. In 
this format, adjacent list members are separated by a designated interline 
spacing, identified by reference numeral 36, that is sufficient to enable 
any one of list members 13 to be selected unambiguously with a cursor. 
While the display list format depicted in FIG. 1 is acceptable for 
mouse-based systems which utilize a cursor, it becomes problematic for 
other types of systems, such as touch-based systems, in which a user 
interacts with the computer by touching designated areas on the screen. In 
a touch-based system, it will be understood that representing display 
lists in the manner depicted in FIG. 1 leads to selection errors, as 
caused by the alignment of such list members and the close, interline 
spacing therebetween. Further, such display list format does not 
efficiently utilize the limited real estate of list window 30. 
FIG. 2 illustrates another screen display 11, similar to that of FIG. 1, in 
which the presentation of a display list 15 has been adapted for a 
touchscreen. The panels and control buttons in FIG. 2 are the same as 
those described with respect to FIG. 1 and, therefore, are identified by 
the same reference numerals. As shown in FIG. 2, individual list members 
17 of display list IS remain vertically aligned adjacent left side 34 of 
list window 30. In order to accommodate finger-based selection, however, 
icons or touchable elements 38 are provided as a touch target for each 
list member 17 and placed immediately to the left of the text associated 
with such list member. Further, interline spacing 37 between adjacent list 
members 17 is necessarily increased to reduce the selection ambiguity that 
would otherwise be created by the size difference between a finger and a 
cursor. 
While increasing interline spacing 37 between list members 17 reduces the 
problem of selection ambiguity, it also reduces the number of list members 
17 that can be displayed in list window 30. This is undesirable given the 
already limited size of the touchscreen on many computer-controlled 
devices, such as the aforementioned portable intelligent communications 
device. Thus, because the time required to find a desired list member 17 
is increased and the user-friendliness of the device is therefore 
decreased, formatting display lists as shown in FIG. 2 is not considered 
an efficient solution. 
Accordingly, it is a primary object of the present invention to provide an 
apparatus and method of formatting a list for display on a touchscreen 
which maximizes the number of list members displayed for a given area of 
the touchscreen without creating selection ambiguity. 
It is another object of the present invention to provide an apparatus and 
method of formatting a list for display on a touchscreen in which the 
distance between list members is increased over that of a mouse-based 
system without increasing the vertical area required to display the list. 
It is still another object of the present invention to provide an apparatus 
and method of formatting a list for display on a touchscreen in which the 
spacing between the touchable elements of adjacent list members have both 
a vertical component and a horizontal component. 
Yet another object of the present invention is to provide an apparatus and 
method in a portable intelligent communications device of formatting a 
display list, in which the spacing between list member touchable elements 
is optimized based upon the dimensions of the list window, the total 
number of list members in the list, the interline spacing between adjacent 
list members, and the distance required between adjacent touchable 
elements for unambiguous selection. 
These objects and other features of the present invention will become more 
readily apparent upon reference to the following description when taken in 
conjunction with the following drawings. 
SUMMARY OF THE INVENTION 
In accordance with a first aspect of the present invention, a method of 
formatting a list for display within a designated list window of a 
touchscreen is disclosed. The list includes a plurality of list members 
with a touchable element and text associated therewith. The method 
includes the following steps: setting a minimum required distance between 
touchable elements of adjacent list members; setting an area for each 
touchable element of the list members, wherein the area has a vertical 
component and a horizontal component; setting a required interline spacing 
between touchable elements of adjacent list members; calculating a 
line-space for each list member as a function of the vertical component of 
the touchable element area and the interline spacing; positioning a first 
list member within a designated line-space of the list window; and, 
spacing each subsequent list member vertically and horizontally a 
specified amount from an immediately preceding list member in the list so 
that at least the minimum required distance between adjacent touchable 
elements is maintained. 
In accordance with a second aspect of the present invention, an alternative 
method of formatting a list for display within a designated list window of 
a touchscreen is disclosed where the list also includes a plurality of 
list members with a touchable element and text associated therewith. The 
method includes the following steps: setting a minimum required distance 
between touchable elements of adjacent list members; setting an area for 
each touchable element of the list members, wherein the area has a 
vertical component and a horizontal component; setting an indentation 
distance between touchable elements of adjacent list members; positioning 
a first list member at a designated location within the list window; 
horizontally spacing each subsequent list member from an immediately 
preceding list member in the list by at least the indentation distance; 
and, vertically spacing each subsequent list member from an immediately 
preceding list member by an amount calculated as a function of the 
indentation distance and the minimum required distance between adjacent 
touchable elements. 
In accordance with a third aspect of the present invention, a method of 
displaying a list for finger-based selection in a computer system having a 
memory circuit, a processing circuit and a touchscreen is disclosed. The 
method includes the steps of formatting and displaying, under the control 
of the processing circuit, a plurality of touchable elements and 
associated text within a list window on the touchscreen. Each of the 
touchable elements is spaced from immediately adjacent touchable elements 
a specified distance to permit selection of any one of the touchable 
elements without any other of the adjacent touchable elements being 
simultaneously selected, the specified distance having a horizontal 
component and a vertical component. 
In accordance with a fourth aspect of the present invention, a portable 
intelligent communications device is disclosed as including circuitry for 
performing telephony operations, a memory circuit for storing at least one 
display list, a processing circuit, and a touchscreen coupled to the 
processing circuit for displaying lists. The processing circuit associates 
a touchable element with each list member of the display list and formats 
the touchable elements within a list window of the touchscreen so that 
immediately adjacent touchable elements are spaced vertically and 
horizontally a minimum specified distance to permit finger-based selection 
of any one of the touchable elements without simultaneous selection of any 
adjacent touchable elements. The vertical spacing between adjacent 
touchable elements may be set, with the horizontal spacing being 
determined by the processing circuit as a function of the minimum 
specified distance, the vertical spacing, and the height of the touchable 
elements. Alternatively, the horizontal spacing between adjacent touchable 
elements may be set, with the vertical spacing being determined by the 
processing circuit as a function of the minimum required distance and the 
horizontal spacing. 
In accordance with a fifth aspect of the present invention, a method of 
formatting a list of touchable elements and associated text on a 
touchscreen of a portable intelligent communications device is disclosed, 
where the number of touchable elements and associated text displayed 
within a list window on the touchscreen is maximized without creating 
selection ambiguity. The method includes the following steps: setting a 
minimum required distance between touchable elements of adjacent list 
members; setting an area for each touchable element of the list members, 
wherein the area has a vertical component and a horizontal component; 
setting a required interline spacing between touchable elements of 
adjacent list members; calculating a line-space for each list member as a 
function of the vertical component of the touchable element area and the 
interline spacing; determining a horizontal offset spacing between 
adjacent touchable elements; determining a maximum number of offset levels 
for a repeating pattern of the touchable elements; positioning a first 
touchable element and associated text within a first line-space on the 
list window; spacing each subsequent touchable element horizontally and 
vertically from an immediately preceding touchable element by the offset 
spacing in an offset pattern until the maximum offset level is reached; 
and, repeating the offset pattern until all the touchable elements and 
associated text in the list are displayed.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the drawings in detail, wherein identical numerals 
indicate the same elements throughout the figures, FIG. 3 depicts a 
portable intelligent communications device identified generally by the 
numeral 40. It will be understood that portable intelligent communications 
device 40 is principally a communications device, and includes circuitry 
and components which allow it to function in such capacity through 
cellular, landline, infrared data association (IrDA), phone cards, and 
other modes. Portable intelligent communications device 40 also includes 
circuitry which enables it to function in the capacity of a computer and a 
plurality of software applications may be utilized therewith. Because of 
this combination, portable intelligent communications device 40 is 
uniquely suited to interface software applications with the communications 
hardware and software, particularly where connection to an Internet 
address is desired. In this regard, it will be understood that portable 
intelligent communications device 40 generally operates in accordance with 
a device shown and described in a patent application entitled "Switching 
Of Analog Signals In Mobile Computing Devices" and having Ser. No. 
08/796,119, which is also owned by the assignee of the present invention 
and is hereby incorporated by reference. 
As seen in FIG. 3, portable intelligent communications device 40 includes a 
casing 42 for housing the communications and other circuitry as will be 
discussed in greater detail hereinafter. A handset 44 is positioned within 
a top portion 46 of casing 42 and preferably includes a built-in speaker 
48 for use when handset 44 is maintained therein. A pivotable antenna 50 
(shown in FIG. 3 in the open or use position) is provided to enable a 
communications function, as when portable intelligent communications 
device 40 is in a cellular mode of operation. It will be understood that 
various ports, jacks, and interfaces will be provided to further enable 
communications functions by portable intelligent communications device 40. 
Control buttons 51 and 53 are also shown as being located on top portion 
46 of casing 42. 
Portable intelligent communications device 40 further includes a display 
screen 52, which preferably is a touchscreen. It will be appreciated that 
a stylus 54 may optionally be utilized to indicate a particular area more 
specifically than can be accomplished with the user's finger, although 
most designated areas are sized for touch interaction by a typically sized 
finger. Since portable intelligent communications device 40 preferably is 
no larger than a standard business desk telephone, display screen 52 is 
sized to be approximately eight (8) inches measured diagonally across. 
This puts screen display 52 in a distinct size class, as it is smaller 
than normal monitor sizes for personal and portable computers and larger 
than screen displays for personal digital assistants (PDAs), calculators, 
and other similar personal electronic devices. 
Turning to FIG. 4, the internal circuitry of portable intelligent 
communications device 40 includes a processing circuit 56, which may, for 
example, be a Motorola microprocessor known by the designation Power PC 
821. It will be seen that processing circuit 56 is connected to both Read 
Only Memory (OM) 58 and Random Access Memory (RAM) 60, which store both 
operating systems and software applications. An optional bulk storage 
device 62 is further provided for storing databases. Processing circuit 56 
is also coupled to display screen 52 through a standard driver (not shown) 
in order to control the images displayed thereon, as well as receive 
information through graphical user interfaces in which the user of 
portable intelligent communications device 40 may indicate chosen options. 
The communications functions of portable intelligent communications device 
40 are also handled through processing circuit 56 via a serial and/or 
parallel port 64 to the particular circuitry of a communications mode 
designated generically by reference numeral 66. As noted hereinabove, 
there are several communication mode options available, including 
cellular, landline, IrDA, and phone cards, and it will be appreciated that 
more than one such option may be utilized at a given time. A keyboard 68 
may also be connected to processing circuit 56, where keyboard 68 can be 
depicted on display screen 52 or be a separate physical package which can 
be utilized with portable intelligent communications device 40 such as 
through a keyboard IR port 70 (see FIG. 3). 
FIG. 5 depicts a schematic block diagram of the software architecture for 
portable intelligent communications device 40. As seen therein, the 
software is divided into three basic areas: applications software 72, 
desktop software 74, and system operating software 76 (which includes 
everything else from the class libraries down to the device drivers for 
portable intelligent communications device 40). It will be understood that 
neither applications software 72 nor desktop software 74 will ever 
interact with anything other than the top layer of system operating 
software 76. Exemplary software applications are shown within applications 
software 72, with particular reference being made to phonebook software 
application 78. 
FIG. 6 depicts an exemplary screen display 80, similar to that described 
with respect to FIGS. 1 and 2, on which a list 79 from phonebook software 
application 78 is formatted to maximize use of list window space on a 
touchscreen in accordance with the present invention. The panels and 
control buttons in FIG. 6 are the same as those previously described with 
respect to FIGS. 1 and 2, and therefore are identified by the same 
reference numerals. Further, while the present invention is described with 
respect to display list 79 from phonebook software application 78, it is 
to be understood that the present invention is applicable to any type of 
list displayed on any type of computer-controlled touchscreen without 
departing from the scope of the invention. 
Contrary to the prior list formats depicted in FIGS. 1 and 2, the real 
estate defining list window 30 in FIG. 6 is maximized by offsetting or 
spacing each list member 87 from adjacent list members in both a 
horizontal direction 83 and a vertical direction 85. By horizontally 
offsetting or indenting list members 87, the absolute distance between 
such list members 87 can be increased without increasing the vertical 
distance required to display list 79 beyond that utilized in a mouse-based 
system. The savings in vertical display area is apparent by comparing FIG. 
2, in which list members 17 are spaced in only a vertical direction 
(identified by reference numeral 81), with FIG. 6, in which the spacing 
between list members 87 is on a diagonal (identified by reference numeral 
82). By comparing the two Figs, it will be seen that diagonally spacing 
list members 87 significantly reduces the vertical space required to 
display list 79. Further, indenting selected members of list 79 does not 
decrease the visibility of list 79 because only a portion of width W of 
list window 30 is typically utilized when a list is displayed. Preferably, 
list members 87 are indented in a repeating pattern, such as those 
depicted in FIGS. 6, 8 and 9. 
FIG. 7 is an enlarged, diagrammatic partial view of FIG. 6 to better show 
the spacing between list members 87 in accordance with the present 
invention. The present invention will be described with respect to a set 
of three icons or touchable elements, which are identified by reference 
numerals 84, 86 and 88, respectively, in FIG. 7. It will be understood 
that each touchable element 84, 86 and 88 acts as a graphical user 
interface, is associated with a particular list member of display list 79, 
and has one or more lines of text associated therewith to describe the 
respective list member or the function which would be performed upon 
activation thereof. The one or more lines of text associated with each 
touchable element are positioned within a text field, indicated by 
reference numeral 90 in FIG. 7. While the invention is to be described 
with respect to three touchable elements, it will be understood that the 
present invention is applicable to any type of display list having any 
number of lines of text and touchable elements without departing from the 
scope of the invention. 
Touchable elements 84, 86 and 88 preferably have the same size and shape 
and, as seen in FIG. 7, are depicted as circles having a diameter "h" and 
a corresponding area A.sub.1. It will be understood that area A.sub.1 of 
touchable elements 84, 86 and 88 may be set for a given application, with 
the size of the associated list text being based on the set element area. 
Alternatively, the text size associated with each list member may be set 
(i.e., via font size), with the vertical component of touchable element 
area A.sub.1 then being determined therefrom. In either case, height t of 
the display list text is preferably less than or equal to the vertical 
component (in this case diameter h) of the touchable elements. Within each 
touchable element 84, 86 and 88 is preferably a target area A.sub.2 (shown 
as being cross-hatched) that is less than or equal to the area A.sub.1 of 
such virtual, touchable element. This target area A.sub.2 is preferably 
centered within the respective touchable element and is defined as the 
area that a finger must contact in order to "select" the touchable element 
or cause its function to be activated. In FIG. 7, these target areas are 
represented within the touchable elements by the reference numeral 92. 
While touchable elements 84, 86 and 88 are depicted as circles having an 
area A.sub.1, it is to be understood that such touchable elements are 
preferably any convex shape (defined as a region in which a line 
connecting any two points in the region is entirely enclosed 
therein--e.g., a circle, oval, rectangle, etc.), provided that the area of 
the touchable element is sufficient to enable it to be touched with 
sufficient accuracy by a finger. It has been found that for a touchscreen 
situation, the preferred minimum touchable element area A.sub.1 for 
sufficient accuracy is approximately fifty square millimeters. 
For a touchscreen, there is typically a minimum required physical distance 
that must be maintained between target areas in the touchable elements in 
order for the graphical user interface to differentiate the selection of 
one touchable element from that of immediately adjacent touchable 
elements. This minimnum required distance is referred to herein as the 
element-space or "e", and is indicated in FIG. 7 by reference numeral 94. 
Element-space 94 can be measured either from edge-to-edge of touchable 
elements 84, 86 and 88 or between the centers of adjacent elements (as 
shown in FIG. 7) so long as the same reference scheme is used throughout. 
It will also be recognized that the measurement may be from the edge or 
center of the target area 92 within each respective touchable element. The 
value of element-space 94 can vary depending upon the software application 
that generates the display list, but is preferably within a range of 10-16 
millimeters. 
In addition to being separated by at least element-space 94, each of 
touchable elements 84, 86 and 88 (as well as associated text in display 
list 79) also occupies a vertical distance within list window 30 referred 
to as the line-space "I". This dimension is indicated in FIG. 7 by 
reference numeral 96. Line-space 96 is the sum of two separate parameters, 
i.e., height t of the text associated with the touchable element and the 
interline spacing (indicated as "y" in FIG. 7) between touchable elements. 
The value of line-space 96 may be set within a particular software 
application, depending upon the desired interline spacing y, the vertical 
component of the touchable elements, and the font size of the associated 
text for each list member. Although there presently is not a standard 
value for line-space 96, the preferred value therefor is in the range of 
3.88-4.76 millimeters for a font size in the 10-12 pt. range. As an 
alternative to setting the value of line-space 96 in an application, this 
parameter may be calculated from element-space 94 and horizontal spacing 
or indentation between touchable elements, as will be described in more 
detail below. 
In addition to element-space 94 and line-space 96, a third parameter for 
formatting display list 79 is the horizontal spacing or indentation ("i") 
between touchable elements, indicated by reference numeral 98 in FIG. 7. 
Indentation 98 may be a set parameter for the application or determined by 
processing circuit 56 from the values of element-space 94 and line-space 
96. It will be understood from FIG. 7 that processing circuit 56 
determines an indentation 98 which maximizes the spacing of list members 
87 in display list 79 by applying the Pythagorean theorem when 
element-space 94 and line-space 96 are set in a given application. 
Accordingly, the value of indentation 98 is equal to the square root of 
the difference between the square of element-space 94 and the square of 
line-space 96 (i.e., .sqroot.e.sup.2 -l.sup.2 ). 
Once indentation 98 is calculated, display list 79 may be formatted by 
positioning a first touchable element 84 and its associated text within a 
first line-space and at an initial horizontal location, preferably within 
the upper left-most area of list window 30 available (beneath any 
directory or group heading and/or subheading). After first touchable 
element 84 and its associated text is positioned within list window 30, 
each subsequent touchable element and its associated text is spaced from 
the preceding touchable element horizontally by the distance of 
indentation 98 and vertically by line-space 96. Each of the subsequent 
touchable elements is preferably offset horizontally from an immediately 
preceding touchable element until a maximum level of horizontal spacing or 
offset is reached (see FIGS. 8 and 9). This maximum level of horizontal 
spacing can be calculated from the left side 34 of list window 30 or the 
horizontal location of first touchable element 84, and is dependent upon 
one or more of the width W of list window 30, a required width for text 
field 90 (with the maximum spacing being selected so that text field 90 is 
not cut off by right side 35 of list window 30), the optimal level of 
indentation (as calculated from element-space 94 and line-space 96), and 
the maximum number of indentations acceptable to the user. 
Once the maximum indentation or offset level is reached, horizontal spacing 
98 may be set to zero so that the next touchable element in the list is 
positioned at the horizontal position of first touchable element 84 in 
list window 30. This format is depicted in FIG. 8, where display list 79 
is indented to a maximum of two levels. Alternatively, horizontal spacing 
98 for the next touchable element may be shifted in the opposite direction 
and preferably reduced by the value of indentation spacing 98 so that the 
next touchable element is spaced to the left of the previous touchable 
element by indentation spacing 98. This repeating pattern therefore has a 
zigzag format, as depicted in FIG. 9 where display list 79 is also 
indented to a maximum of two levels. 
As mentioned above, indentation spacing 98 between adjacent touchable 
elements may be provided as a fixed parameter for a particular software 
application that generates display list 79 or it may be designated as a 
user input. When indentation spacing 98 is provided as a fixed parameter 
or input, processing circuit 56 determines the vertical spacing or 
line-space 96 for display list 79 from element-space 94 and indentation 
spacing 98. 
Again applying the Pythagorean theorem, line-space 96 in this instance 
would be equal to the square root of the difference between the square of 
element-space 94 and the square of indentation spacing 98 (i.e., 
.sqroot.e.sup.2 -i.sup.2 ). Once line-space 96 is calculated, display list 
79 may be formatted within list window 30 by once again placing a first 
touchable element 84 in a first lines-pace and at a designated horizontal 
position within list window 30, and thereafter vertically and horizontally 
spacing each subsequent touchable element and its associated text in the 
desired pattern (up to the maximum pattern or offset level in the manner 
described above). 
A flow chart depicting the overall process performed by processing circuit 
56 in the present invention is depicted in FIGS. 10A and 10B. The method 
of the invention is described with reference to this flowchart for the 
situation in which element-space 94 and line-space 96 are fixed 
parameters, but may be modified in the case where element-space 94 and 
indentation space 98 are the fixed parameters as discussed hereinafter. 
It will be seen that certain parameters are set initially, i.e., the 
physical height and width of list window 30 (box 100), the minimum 
required distance between touchable elements, or element-space 94, of 
adjacent list members 87 (box 102), and the area A.sub.1 of each touchable 
element, including the vertical and horizontal components thereof (box 
104). 
Accordingly, the total number of list members 87 for display list 79 is 
determined (106) so that a quotient for the list window height and the 
total number of list members 87 is calculated (box 108). The vertical 
spacing between lines in list window 30, or the interline spacing, is then 
set (box 110), with the line-space 96 then being calculated therefrom (box 
112). It will be recalled that line-space 96 is preferably the sum of the 
text height t (corresponding to the font size thereof) and the interline 
spacing y (see FIG. 7), although it may alternatively be equivalent to the 
sum of the vertical component of the touchable element area and the 
interline spacing. 
Nevertheless, processing circuit 56 then determines which of element-space 
94, line-space 96 and the quotient calculated in box 108 is greatest. This 
is seen in the flow chart from decision boxes 114, 116 and 118. More 
specifically, decision box 114 determines whether the quotient from box 
108 is greater than the minimum required distance (i.e., element-space 
94). If the answer is positive, then decision box 116 next determines 
whether the quotient is greater than the calculated line-space 96. In the 
instance where such quotient is the greatest, the vertical spacing between 
adjacent touchable elements is set to the quotient (box 120) and the 
horizontal spacing between adjacent touchable elements is set to zero (box 
122). It will be seen that if the quotient is not greater than calculated 
line-space 96, the vertical spacing between adjacent touchable elements is 
set to such calculated line-space (box 124) and the horizontal spacing 
between adjacent touchable elements is set to zero (box 126). Decision box 
118 determines whether the calculated line-space 96 is greater than the 
minimum required distance (element-space 94) in the instance when the 
quotient from box 108 is not greater than such element-space 94 (i.e., a 
negative answer to decision box 114). If the answer to decision box 118 is 
positive, then the vertical spacing and horizontal spacing of adjacent 
touchable elements is set in accordance with the previously described 
boxes 124 and 126. Thus, it will be understood that no horizontal spacing 
between adjacent touchable elements is required when element-space 94 is 
not greater than both the quotient from box 108 and line-space 96. 
When element-space 94 is greater than both the quotient of box 108 and the 
calculated line-space 96, then the vertical spacing between adjacent 
touchable elements is set to the calculated line-space 96 (box 128) and 
the horizontal spacing between adjacent touchable elements is calculated 
(box 130). It will be recalled that such horizontal spacing, also known 
herein as the indentation 98, is the square root of the difference between 
the element-space 94 squared and the line-space 96 squared. 
It will be seen that processing circuit 56 next displays the touchable 
element (and the associated text immediate thereto) of a first list member 
at a designated vertical and horizontal position within list window 30 
(box 132). This typically will be adjacent an upper left hand corner of 
list window 30, as depicted in FIG. 6. In accordance with the vertical and 
horizontal spacing set or calculated from the steps described above, the 
touchable element (and associated text) of the subsequent list member is 
then spaced from the touchable element of the preceding list member (box 
134). 
In order to prevent the touchable element and associated text of a list 
member 87 from extending past the physical width W of list window 30, a 
maximum horizontal offset from the original horizontal position of the 
first touchable element preferably is determined (box 136). This may be 
accomplished by dividing the difference of the list window width W and the 
required text width 90 associated with each list member by the indentation 
distance 98 calculated in box 130 above, dividing a preset maximum 
indentation depth by indentation distance 98, or dividing the 
element-space 94 by the vertical spacing between adjacent touchable 
elements. Alternatively, a horizontal scroll (not shown) may be provided 
within list window 30 so that the user of touchscreen 52 can shift display 
list 79. It will be noted that this is relevant only in the case where 
element-space 94 is greater than the quotient from box 108 and the 
calculated line-space 96. 
As seen from decision box 138, processing circuit 56 determines whether the 
horizontal position of the touchable element for the subsequent list 
member as spaced is less than or equal to the maximum horizontal offset 
determined in box 136. If the determination is negative, the touchable 
element must be shifted horizontally in the opposite direction of the 
normal indentation spacing 98 (box 140). It will be understood that the 
touchable element can be moved back to the original horizontal position of 
the first touchable element and proceed as before therefrom (see FIG. 8) 
or incrementally through the previous indentation levels until the 
original horizontal position is attained in zigzag fashion (see FIG. 9), 
provided the horizontal spacing maintains the minimum required spacing 
between touchable elements. Once an acceptable horizontal position of the 
touchable element is found, the touchable element and the text associated 
therewith for the list member is displayed within list window 30 (box 
142). 
Finally, processing circuit 56 determines whether the list member is the 
last one of display list 79 (decision box 144). If so, the process is 
completed (box 146). Otherwise, a feedback loop 148 returns to box 134 so 
that the next subsequent list member may be spaced and displayed. 
It will be understood that instead of setting the vertical spacing between 
lines in list window 30 (box 110), the method of the present invention may 
set the horizontal spacing or indentation 98 (dashed box 111). In this 
way, the interline spacing may be calculated (dashed box 113) as a 
function of element-space 94 and indentation 98 (i.e., the square root of 
the difference of element-space 94 squared and indentation 98 squared). 
Then, the line-space 96 may be calculated as described hereinabove in box 
112. Of course, there is no need to calculate the horizontal spacing as 
before in box 130. 
From the foregoing, it will be seen that the present invention more 
efficiently utilizes list window real estate on a touchscreen by reducing 
the vertical spacing between adjacent list members in the situation where 
the vertical spacing or line-space 96 is less than the minimum required 
distance 94 between touchable elements for maintaining selection 
consistency. This space savings is evident by comparing the amount of 
unused space for a traditional touchscreen display list presentation, in 
which the list members are aligned along left edge 34 of list window 30, 
with the present invention. In the traditional presentation, the amount of 
unused space is equal to the difference between element-space 94 and 
line-space 96, multiplied by the physical width of list window 30, or 
((e-1).times.W). By contrast, the amount of unused space according to the 
present invention is equal to the product of the maximum number of 
indentation levels I, indentation spacing 98 and line-space 96, or 
(I.times.i.times.1). 
The following example, depicted in FIGS. 11 and 12, illustrates this space 
savings where element-space 94 is equal to 12 millimeters, line-space 96 
is equal to 4 millimeters, and the width W of list window 30 is 63.5 
millimeters. Further, display list 79 is indented to a maximum of two 
levels. Following the process described above, indentation 
i=.sqroot.e.sup.2 -l.sup.2 or 11.3 millimeters. Therefore, the amount of 
unused space under the previous method is (12 millimeters-4 
millimeters).times.63.5 millimeters=508 square millimeters. By comparison, 
the amount of unused space in list window 30 under the present inventive 
method is 3.times.11.3 millimeters.times.4 millimeters=135.6 square 
millimeters. Thus, the present invention results in a space savings of 
over 70% from the traditional method since less vertical space is required 
between list members. This will permit more list members 87 of display 
list 79 to be displayed on touchscreen 52 for the same amount of real 
estate for list window 30, thereby increasing user satisfaction. 
Having shown and described the preferred embodiment of the present 
invention, further adaptations of the apparatus and method for displaying 
a list on a touchscreen can be accomplished by appropriate modifications 
by one of ordinary skill in the art without departing from the scope of 
the invention.