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Claims  |
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We claim:
1. A manipulative multi-window display method wherein display data rae
selectively transferred from a plurality of segment memory means
corresponding to windows to a bit map memory for a display screen in which
a plurality of overlapping windows are displayed on the display screen so
that only those portions of each of the windows which are not covered by
any other window are displayed, the method comprising:
a first step, in response to a command to display a new window on said
display screen, for making a first management record containing therein
information as to the position to be assumed by said new window and as to
a segment memory means corresponding to the new window and a second
management record defining those internal areas in said new window which
are to be displayed on said display screen and transferring to said bit
map memory data read out from that segment memory which is specified by
said first management record, said data being within that internal area
which is defined by said second management record;
a second step, in response to a command to display said new window as a
second window on said display screen in a display state in which a first
window has already been displayed on said screen, for checking the
positional relation between a display internal area defined by a second
management record concerning said first window and said second window to
determine whether or not there exist any overlapping partial areas
therebetween;
and upon determination that there does exist an overlapping partial area in
said second step,
a third step, after dividing the display internal area defined by a second
management record concerning said first window into said overlapping
partial area and the remaining partial area, for making a third management
record including defining said overlapping partial area as a non-display
internal area related to said second window and making a new second
management record defining said remaining partial area as a display
internal area;
a fourth step in response to a command to reverse the order of display
priority between a first window being displayed on said display screen and
a second window having higher display priority than said first window, for
finding any of the third management records which is related to said
second window; and
upon finding of such a third management record as being related to said
second window in said fourth step,
a fifth step for transferring to said bit map memory data read out from
that segment memory means which is specified by the first management
record concerning said first window, said data to be transferred being
within a display internal area which is newly defined, by a new second
management record, in place of non display internal area defined by said
third management record.
2. A method according to claim 1, in which said third step comprises
dividing said remaining area into a plurality of rectangular areas so that
said new second management record is made for each of said rectangular
areas.
3. A method according to claim 2, in which said division is carried out by
the use of an extension of one of the lateral and longitudinal sides of
said second window as division lines.
4. A manipulative multi-window display method wherein display data are
selectively transferred from a plurality of segment memory means
corresponding to windows to a bit map memory for a display screen in which
a plurality of overlapping windows are displayed on the display screen so
that only those portions of each of the windows which are not covered by
any other window are displayed, the method comprising:
a first step, in response to a command to display a new window on said
display screen, for making a first management record containing therein
information as to the position assumed by said new window and as to a
segment memory means corresponding to the new window and a second
management record defining those internal areas in said new window which
are to be displayed on said display screen and transferring to said bit
map memory data read out from that segment memory which is specified by
said first management record, said data being within that internal area
which is defined by said second management record;
a second step, in response to a command to display said new window as a
second window on said display screen in a display state in which a first
window has already been displayed on said screen, for checking the
positional relation between a first display internal area defined by a
second management record concerning said first window and said second
window to determine whether or not there exist any overlapping partial
areas therebetween;
and upon determination that there exists an overlapping partial area in
said second step,
a third step, after dividing the display internal area defined by a second
management record concerning said first window into said overlapping
partial area and the remaining partial area, for making a third management
record including defining said overlapping partial area as a non-display
internal area related to said second window and making a new second
management record defining said remaining partial area as a display
internal area;
a fourth step, in response to a command to delete a second window in a
display state wherein said second window having higher display priority
than said first window existing on said display screen, for finding any of
the third management records corresponding to said second window;
a fifth step, upon finding such a third management record pertaining to
said second window in said fourth step, for transferring to said bit map
memory data read out from that segment memory means which is specified by
the first management record concerning said first window, said data to be
transferred being within a display internal area which is newly defined,
by a new second management record, in place of a non-display internal area
defined by said third management record; and
a sixth step for deleting data for said second window remaining on said bit
map memory and invalidating the first and second management records
corresponding to said second window.
5. A manipulative multi-window display method wherein display data are
selectively transferred from a plurality of segment memory means
corresponding to windows to a bit map memory for a display screen in which
a plurality of overlapping window are displayed on the display screen so
that only those portions of each of the windows which are not covered by
any other window are displayed, the method comprising:
a first step, in response to a command to display a new window on said
display screen, for making a first management record containing therein
information as to the position assumed by said new window and as to a
segment memory means corresponding to the new window and a second
management record defining those internal areas n said new window which
are to be displayed on said display screen and transferring to said bit
map memory data read out from that segment memory which is specified by
said first management record, said data being within that internal area
which is defined by said second management record;
a second step, in response to a command to display said new window on said
display screen in a display state wherein at least two existing windows
have already been displayed on said screen, for selecting one by one an
object window among said existing windows and for checking the positional
relation between a display internal area defined by a second management
record concerning said object window and said new window to determine
whether or not there exist any overlapping partial areas therebetween; and
upon determination that there exists an overlapping partial area in said
second step,
a third step, after dividing the display internal area defined by a second
management record concerning said object window into said overlapping
partial area and the remaining partial area, for making a third management
record defining said overlapping partial area as a non-display internal
are a related to said new window and making a new second management record
defining said remaining partial area as a display internal area.
6. A method according to claim 5, further comprising:
upon issuance of a command to delete a second window in a display state
having first, second and third windows displayed on said display screen,
wherein said first window having a display priority lower than said second
window and in which said second window being lower than said third window
in the display priority, each of said first, second and third windows
correspond to a different one of said existing and new windows,
a fourth step for finding among the third management records concerning
said first window any record which is related to said second window;
upon finding of a such a third management record concerning said first
window and related to said second window in said fourth step, a fifth step
of collating a first non-display internal area defined by said found third
management record with a second non-display internal area defined by said
third management record made corresponding to said second window to find
an overlapping partial area therebetween;
upon finding of no overlapping partial area in said fifth step, a sixth
step for transferring to said bit map memory data read out from that
segment memory means which corresponds to said first window, said data to
be transferred being within a display internal area which is newly
defined, by a new second management record corresponding to said first
window, for said first non-display area, with said third management record
defining said first non-display area being invalidated;
upon finding of an overlapping partial area in said fifth step, a seventh
step, after dividing said first non-display internal area into said found
overlapping area and the remaining area, for making a third management
record defining said overlapping partial area as a non-display internal
area related to said third window, making a new second management record
defining said remaining partial area as a display internal area, and
transferring to said bit map memory data read out from that segment memory
means which is corresponding to said first window, said data being within
the display internal area defined by said new second management record,
with the third management record defining said first non-display internal
area being invalidated; and
eighth step of deleting data remaining on said bit map memory and
invalidating the first, second and third management records concerning
said second window. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
The present invention relates to a multi-window display system and a method
of displaying information in the form of separate or overlapping windows
on a display screen, wherein each information window can be made, deleted
or moved conveniently on the screen.
The conventional method of erasing or replacing some of overlapping
information windows on a display screen is to delete all information
windows and then put back the information windows after modification has
been made. This method, however, takes too long a time for displaying
information windows. Such a method is described, for example, in "BRUWIN:
An adaptable design strategy for window manager/virtual terminal systems"
by N. Meyrowitz et al., Proc. 8th Symp. Operating Systems Principles ACM.
N.Y. 1981.
SUMMARY OF THE INVENTION
An object of this invention is to provide a multi-window display system
capable of modifying part of overlapping information windows, thereby
allowing quick and natural display modification.
In order to achieve the above objective of this invention, each window is
subdivided into rectangles called "internal areas". For example, as shown
in FIG. 1, when a window 110 is partly covered by another window 120, that
portion of the window 110 which is not covered by the window 120 is
divided into internal areas called "display internal areas" and the other
portion of the window 110 that is covered by th window 120 is called a
"non-display internal area".
If the window 110 is replaced by another window not shown in the figure, it
is again divided into internal areas. A non-display internal area is not
further divided unless the window which directly covers the internal area
is removed.
Division of a window may be made in such a way that the horizontal and/or
vertical sides of the superimposed window or of the internal areas as
shown in FIG. 1 are extended. Information in internal areas are memorized
as a set of tables, and when the positional relation between overlapping
windows changes, the tables are modified so that display of only modified
internal areas is varied.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an illustration used to explain division of a window into
internal areas.
FIG. 2 is a general diagram of a display system to which the present
invention is applied.
FIG. 3 is an illustration of two overlapping windows on a displaced screen
processed according to the present invention.
FIGS. 4-7 are illustrations of a plurality of overlapping windows used for
explaining the processing technique or method of windowing in accordance
with the present invention in conjunction with using the cursor control
and keyboard, including selecting, changing the relative positioning of
the respective overlapping windows, as well as deleting a window.
Briefly, FIG. 4 illustrates three overlapping windows for explaining the
invention.
FIG. 5 shows three overlapping windows corresponding to a rearranging of
windows illustrated in FIG. 4.
FIG. 6 illustrates the remaining and rearranged overlapping windows
subsequent to a deletion of window 420 of FIG. 4.
FIG. 7 shows three overlapping windows subsequent to a different
rearrangement of the windows illustrated in FIG. 4.
FIG. 8 is a block diagram of a display system according to an embodiment of
the present invention.
FIG. 9 is a flowchart used to explain the operation according to an
embodiment of the present invention.
FIGS. 10a to 10d are a set of diagrams used to explain the arrangement of
the internal area tables.
FIGS. 11(a-d) illustrate the process of windowing by developing window
management records including non-display internal management records for
overlapping windows in accordance with the present invention.
FIGS. 12(a-d) through 15 illustrate exemplarily diagrams showing the
process of making a new window, deleting a window or changing relative
window positions by accordingly making, selecting and re-composing
internal areas of windows in accordance with the present invention.
FIG. 11a shows overlapping windows displayed on a CRT display unit in
conjunction with a coordinate system.
FIG. 11b shows the window management record related to the window W1 in
FIG. 11a.
FIG. 11c shows the non-display internal area management record of the
window management record in FIG. 11b.
FIG. 11d shows the internal area record for the non-display internal area
IA3 in FIG. 11a.
FIG. 12a shows a flowchart for describing the process of updating the
internal area table.
FIG. 12b illustrates a flow chart for creating a new window corresponding
to step 1210 in FIG. 12a.
FIG. 12c illustrates a flowchart corresponding to the window selection
processing program effected by depressing the window selection key 230 or
the window superimposition modification key 250 of the keyboard in FIG. 2.
FIG. 12d illustrates a flowchart corresponding to the process of deleting a
window after depressing the window deletion key 240 in the keyboard shown
in FIG. 2.
FIG. 12e illustrates a flow chart for the rearranging of the windows in a
plurality of superimposing or overlapping windows by depressing the window
superimposition modification key 250 in the keyboard shown in FIG. 2.
FIG. 13 illustrates the effect of creating a new window over an existing
display internal area on a display screen and as it relates to the window
making program shown in FIG. 12b.
FIG. 14 illustrates superimposed windows on a display screen in conjunction
with explaining the window selection process.
FIG. 15 illustrates the internal area relationships as they relate to the
development of the internal area table.
FIGS. 16a to 16c are a set of diagrams showing update of the internal area
tables.
Briefly, FIG. 16a shows overlapping or superimposed windows displayed on a
CRT screen and as it relates to the internal area table.
FIG. 16b shows a display of superimposed windows and the respective
internal area table after window 1620 has been removed from the display of
FIG. 16a.
FIG. 16c shows a display after the internal area 1630 has been rearranged
in the display of FIG. 16b.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An embodiment of the present invention will now be described in detail with
reference to the drawings. In FIG. 2, the inventive display system
consists of a keyboard 1, a CRT display unit 2 and a cursor control unit 3
which moves the cursor on the screen of the display unit 2. The keyboard 1
includes a window upper-left position setting key 210, a window
lower-right position setting key 220, a window selection key 230, a window
deletion key 240, a window superimposition modification key 250, and a
ten-key unit 260 including 10 numeric keys and a negative-sign key.
The following describes the procedure of displaying overlapping windows as
shown in FIG. 3 on the blank screen of the CRT display unit 2. First, the
operator operates the cursor control unit 3 to bring the cursor to the
upper left corner a of a window 310 to be created, and then presses the
window upper-left position setting key 210. Subsequently, the operator
moves the cursor to the lower right corner b of the window, and presses
the window lower-right position setting key 220. The system responds to
these operations, and the window 310 is displayed. Similarly, another
window 320 is displayed by positioning the cursor to the upper left corner
c and to the lower right corner d of the window, and pressing the window
upper-left position setting key 210 and window lower-right position
setting key 220, sequentially. Then, the window 320 is displayed over the
window 310.
Assuming the initial three window position shown in FIG. 4, if it is now
intended to rearrange the windows to display a window 410 that is
superimposed over the remaining two windows, the operator brings the
cursor to the displayed portion of the window 410 and presses the window
selection key 230. Then, display is modified as shown in FIG. 5. The same
result is reached by pressing the window superimposition modification key
250, the negative sign key and the numeric "3" key (since the window 410
is the third window counted from the top window) sequentially in this
order. If it is intended in FIG. 4 to delete the window 420, the operator
brings the cursor to the displayed portion of the window 420, and presses
the window deletion key 240. Then, display is modified as shown in FIG. 6.
If it is intended in FIG. 4 to move the window 430 to the position between
the windows 410 and 420, the operator presses the window superimposition
modification key 250 and the numeric "2" key (since the window 430 is
intended to be moved to the second position counted from the top window in
th current arrangement) sequentially in this order. Then, display is
modified as shown in FIG. 7.
FIG. 8 shows in block diagram an example of the inventive multi-window
display system. The processing of the system for modifying window display
will be described in detail with reference to FIG. 9.
The cursor is moved to the desired position through the operation of the
cursor control unit 3 (step 901). Cursor positional information is stored
in register 803 by CRT driver 801 (step 902). In response to operator's
action on one of the window upper-left position setting key 210, window
lower-right position setting key 220, window selection key 230, window
deletion key 240 and window superimposition modification key 250 (step
903), keyboard driver 802 generates a code (step 904) and it is stored in
register 804. CPU 805 which may be, for example, a 16 bit microcomputer
"68000" manufactured by Hitachi, commences a program in memory 806
depending on the code stored in the register 804 (steps 910, 920, 930,
940). The program first translates the cursor position on the CRT display
unit 2 as stored in the register 803 into a location in screen buffer 814
which contains display information as dot-matrix data, and stores the
converted window position in register 807.
In case the window upper-left position setting key 210 or the window
lower-right position setting key 220 has been pressed (steps 910, 915),
the content of the register 807 is transferred to register 809 or 810,
respectively. Stack 811 is provided to store window identifiers 1010-1040
as shown on the left-hand side of FIG. 10a on a first-in-last-out basis.
FIG. 10a shows on its right-hand side the content of the stack 811 which
is further added by a window identifier 1000.
Bit map processor 815 which moves, transfers or displays dot-matrix data in
the screen buffer 814 makes reference to cursor positional data stored in
the registers 809 and 810 to write a new window in the screen buffer 814.
Display controller 813 operates to display the new window on the CRT
display unit 2. The program updates the internal area table for
controlling internal areas of each window within the memory 808 by adding
window positional data stored in the registers 809 and 810 to the internal
area table (step 916).
In case the window selection key 230 has been pressed (step 920), test is
made to determine as to which window identifier in the stack 811 the
content of the register 803 corresponds to, and the address of the
relevant window identifier is stored in register 812. The bit map
processor 815 writes the content of the non-display internal area
addressed by the register 812 into the screen buffer 814. The program
makes reference to the register 812 and places the window identifier 1030
at the top of the stack 811. As shown in FIG. 10b, the identifier of the
window is stored at the top of the stack 811, and the internal area table
within the memory 808 is updated (step 921).
In case the window deletion key 240 has been pressed (step 930), test is
made to determine as to which window identifier in the stack 811 the
content of register 803 is consistent with, and the address of the
relevant window identifier is stored in the register 812. The bit map
processor 815 writes part of the non-display internal area of a window
covered by the display internal area of the window indicated by the
content of register 812 into the screen buffer 814. The program eliminates
the window identifier 1030 in the stack 811. As shown in FIG. 10c, the
stack 811 is modified, and the internal area table within the memory 808
is updated (step 931).
In case the window superimposition modification key 250 has been pressed
(step 940), the program waits for the subsequent key entry (steps 941,
942). If entry of the negative sign key follows (step 943), the processing
of step 921 for a window specified by the subsequent numeric key entry is
carried out (steps 946, 947, 948, 921). If a numeric key has been pressed
without being preceded by the negative sign key (step 944), the bit map
processor 815 writes the content of internal area that is included in a
window located above the keyed-in number N and covered directly by the
current top window into the screen buffer 814. The program moves the
identifier 1010 which is currently located at the top to the third place.
As shown in FIG. 10d, the window identifier 1010 is placed at the third
position from the top in the stack 811, and the internal area table within
the memory 808 is updated (step 945).
Next, the program implementation for updating the stack 811 and internal
area table will be described in detail with reference to the drawings. The
internal area table is an assembly of a window management table, a
non-display internal area management table and a data table. The window
management table contains window management records, the non-display
internal area management table contains non-display internal area
management records, and the data table contains internal area records.
The window management record WR shown in FIG. 11b is made up of window
identifier W, upper left position data WX and WY of the window in the
screen buffer 814, lateral length WA and longitudinal length WB of the
window, address WS of the segment buffer for storing the contents of the
window, starting address Pl of the internal area record related to the
display internal area included in the window W, starting address P2 of the
non-display internal area management record for controlling the
non-display internal area included in the window W, and address P3 of the
next window management record. The non-display internal area management
record IVR shown in FIG. 11c provides the starting address of the internal
area record related to the non-display internal area which is covered
directly by another window V, and it includes the starting address P4 of
the internal area record for the non-display internal area and the address
P5 of the next non-display internal area management record. The internal
area record IAR shown in FIG. 11d is made up of top left position data X
and Y of the internal area in the screen buffer 13, lateral length A and
longitudinal length B of the internal area, and address P6 of the next
internal area record.
FIG. 11a shows overlapping windows displayed on the CRT display unit. The
CRT screen has a coordinate system extending from the origin 0 at the
upper left corner to the right and to the bottom. The display shows that a
window W2 is placed over a window W1. The super-imposition of the windows
W1 and W2 causes the W1 to be divided into four internal areas IA1, IA2,
IA3 and IA4. The IA3 is a non-display internal area covered by W2, and the
remainder are display internal areas. Symbols S, T, F, G, x, y, a, and b
represent lengths as shown.
The WR shown in FIG. 11b is the window management record related to the
window W1, with P1 indicating the address of the internal area record for
the IA1, P2 indicating the address of the non-display internal area
management record caused by the W2. Entry for the WS and P3 are not filled
in the figure. The IVR stores W2 in V, indicating that the record is the
management information for the non-display internal area covered by the
window W2. The value of P4 represents the address of the non-display
internal area record IA3 covered actually by the window W2. Since the
state of FIG. 11a includes only one non-display internal area, the entry
of P5 in FIG. 11c is not filled.
FIG. 11d shows, as an example of the internal area record, the internal
area record for the non-display internal area IA3. In this case, the
coordinates of the upper left position are determined for W1. Although the
entry of P6 is not filled in FIG. 11d, if the internal area is located at
the end of the display or non-display internal area record, the address of
the window management record for the window which belongs to that internal
area, i.e., the address of WR, is stored in P6.
The following describes the method of updating the internal area table in
each case separately with reference to FIG. 12a.
When a new window NW is created, the window making program shown in FIG.
12b is started. In FIG. 13, common portions in the existing display
internal area IA and the new window NW is examined (step 1211). The bit
map processor 815 (FIG. 8) extracts the content of the display internal
area IA from the segment buffer indicated by WS of the corresponding
window management record and loads it into the screen buffer 814.
The existence of common portions for the two areas is determined by the
following set of conditional expressions.
x1<x3+a3
x3<x2
y1<y3+b3
y3<y2
where (x1, y1) represent the coordinates of the upper left corner of the
window NW, (x2, y2) represent the coordinates of the lower right corner of
the window NW, and (x3, y3) represent the coordinates of the upper left
corner of the display internal area IA.
If a common portion is found, the existing display internal area IA is
divided, and a new display internal area record and a non-display internal
area record to be covered by the window NW are added (step 1212). Division
of an area is carried out as follows. Suppose two rectangles A and B
exist. When the rectangle A (x coordinate of left side=Aleft; y coordinate
of upper side=Atop; x coordinate of right side=Aright; and y coordinate of
lower side=Abottom) is overlaid by the rectangle B (x coordinate of left
side=Bleft; y coordinate of upper side=Btop; x coordinate of right
side=Bright; and y coordinate of lower side=Bbottom), the rectangle A is
divided as follows.
(i) For Aleft>Bright, or Atop>Bbottom, or
Aright<Bleft, or Abottom<Btop:
There is no common portion for A and B.
The following is the processing for the case where A and B have a common
portion.
First, a common portion of A and B, i.e., a portion of A covered by B, is
obtained.
(ii) A rectangle shared by A and B is obtained as the x coordinate of the
left side being max(Aleft, Bleft), i.e., the larger of Aleft and Bleft
when they are not the same, y coordinate of upper side being max(Atop,
Btop), x coordinate of right side being min(Aright, Bright), i.e., the
smaller of Aright and Bright when they are not the same, and y coordinate
of lower side being min(Abottom, Bbottom).
Finally, it will be possible that A is not covered at all by B even though
A is overlaid by B, and such a portion is obtained as follows.
(iii) For Aleft Bleft: The following rectangles are not covered by B.
x coordinate of left side equals Aleft
y coordinate of upper side equals max(Atop, Btop)
x coordinate of right side equals Bleft-1
y coordinate of lower side equal min(Abottom, Bbottom)
(iv) For Atop.ltoreq.Btop: The following rectangles are not covered by B.
x coordinate of left side equals Aleft
y coordinate of upper side equals Atop
x coordinate of right side equals Aright
y coordinate of lower side equals Btop-1
(v) For Aright.gtoreq.Bright: The following rectangles are not covered by
B.
x coordinate of left side equals Bright+1
y coordinate of upper side equals max(Atop, Btop)
x coordinate of right side equals Aright
y coordinate of lower side equals min(Abottom, Bbottom)
(vi) For Abottom.gtoreq.Bbottom: The following rectangles are not covered
by B.
x coordinate of left side equals Aleft
y coordinate of upper side equals Bbottom+1
x coordinate of right side equals Aright
y coordinate of lower side equals Abottom
Accordingly, portions of A that are not covered by B are obtained as an
assembly of four rectangles (iii), (iv), (v) and (vi) at maximum.
The internal area record related to the display internal area IA is deleted
(step 1213). Subsequently, the window management record for the window NW
is added to the current window management table (step 1215). Assuming the
contents of registers 809 and 810 to be (x1, y1) and (x2, y2) as shown in
FIG. 13, the contents of the window management record WR (FIG. 11b) will
be WX=x1, WY=y1, WA=x2-x1, and WB=y2-y1. The segment buffer indicated by
WS contains the initial state of the window. P2 is blank. P3 indicates the
address of the top window management record in the internal area table,
and the internal area record pointed by Pl indicates the window NW itself.
The contents of the internal area record IAR (FIG. 11d) will be X=WX,
Y=WY, A=WA, B=WB, and P6=blank. In addition, the identifier of the window
NW is placed at the top of the stack 811 (step 1216).
The bit map processor 815 extracts the content of the newly added window NW
from the segment buffer pointed by WS of the corresponding window
management record, and stores it in the screen buffer. At this time, the
contents of common portion for the NW and IA are replaced with the content
of NW that has newly been stored.
Upon completion of updating, a plurality of windows are displayed on the
display unit, and after the record for the display and non-display areas
have been added to the window management record, the subsequent selecting
process is carried out.
The window selection key 230 or window super-imposition modification key
250 is used to start the window selection processing program shown in FIG.
12c when the existing window EW has been selected (step 1220). Selection
of the window EW means that for the cursor position of (x0, y0) with the
window management record for the window NW being WX=x4, WY=y4, WA=a4 and
WB=b4, both of x4<x0<x4+a4, y4<y0<y4+b4 are met, and there is no window
above the window EW that satisfies both of the above inequalities. At this
time, the stack 811 is checked for the common portion of each display
internal area VA of the window above the window EW which has already been
registered and each non-display internal area EWHA of the window EW which
has already been registered (step 1221), and if a common portion is found,
the window located above the window EW is divided into a certain number of
display internal areas an non-display internal areas. These areas are
added to the display internal area record and non-display internal area
record covered by the window EW (step 1222).
The bit map processor 815 (FIG. 8) extracts only the content of the newly
added display area from the segment buffer, and stores it in the screen
buffer 814. The old content of the screen buffer 814 is replaced with the
newly stored content.
The internal area record related to the window above the window EW is
deleted (step 1223). Subsequently, the stack 811 is checked for a common
portion for each non-display internal area HA of the window below the
window EW covered directly by the window EW and each non-display internal
area EWHA of the window EW (step 1225). If a common portion exists, the
area HA is divided into a non-display internal area covered by a window
which directly covers the area EWHA and a non-display internal area which
will be covered directly again by the window EW after modification. The
divided areas are added to the non-display internal area record covered by
the window which directly covers the area EWHA and the non-display
internal area record covered directly by the window EW (step 1226), and
then the old internal area record related to HA is deleted (step 1227).
The non-display internal area management record for the window EW and
internal area record are all deleted, and an internal area record
including the window EW itself as an internal area is created (step 1229),
and the stack 22 is modified so that the identifier for the window EW is
moved from the current position to the top (step 12291).
When the window deletion key 240 is used to delete the existing window DW,
the window deletion program shown in FIG. 12d is started (step 1230).
First, the stack 811 is checked for a common portion for each non-display
internal area LHA which belongs to a window below the window DW and
covered directly by the window DW and each non-display internal area DWHA
and each display internal area DWIA of the window DW (steps 1231, 1234).
If a common portion exists, a rectangle which is not displayed because of
being covered directly by a window which directly covers the area DWHA and
a rectangle which becomes displayed by deletion of the window DW, both
within the area LHA, are made to be new internal areas. The areas are
added to the non-display internal area record covered by a window which
directly covers the area DWHA and the display internal area record (steps
1232, 1235). The bit map processor 815 extracts only the content of the
newly added display area from the segment buffer, and stores it in the
screen buffer 814. The internal area record related to the LHA is deleted
(step 1237). The record related to the window DW is deleted (step 1239),
and the identifier for the window DW is deleted from the stack 811 (step
12391).
When the window superimposition modification key 250 is used to move the
window TW located at the top of the stck 811 to the position specified by
number N of numeric key entry, the superimposition modification processing
program shown in FIG. 12e is started (step 1240). The internal area record
for the non-display internal area HUA included in a window located at Nth
place or above and covered directly by the window TW is changed to the
display internal area (step 1241). Checking is made for a common portion
for the window TW and the internal area LA included in a window located at
the Nth place or below and covered directly by a window located above the
Nth position excluding the window TW (step 1243). If a common portion
exists, the area HA is divided into a rectangle which is not displayed
because of being covered directly by the window TW and a rectangle which
is not displayed because of being covered again by the window which covers
the area HA from the beginning. These rectangles are added to the
non-display internal area record covered directly by the window TW and the
non-display internal area record covered by a window which covers the area
HA from the beginning (step 1244), and the internal area record related to
the area LA is deleted (step 1245). Subsequently, the window TW is divided
into areas which are left displayed and areas which become undisplayed
because of being covered that would occur when the window TW is covered
sequentially with the (N-1)th through the second windows (step 1247). The
result is used to create the non-display internal area management table
and internal area record for the window TW (step 1248). The stack 811 is
modified so that the identifier located currently at the top, i.e., the
identifier for the window TW, is inserted between the (N-1)th and Nth
positions of the stack 811 (step 12491).
In modifying the table, internal areas are recomposed when necessary so
that the rectangle is as large as possible in the longitudinal or lateral
direction, and the number of internal areas is as small as possible (step
1250).
When a set of internal areas, S=Ri i=1, 2, . . . , n; where Ri is an
internal area, is given, these areas are composed as follows.
(i) Ri is removed from S one at a time, and it is checked whether the
resultant S can be composed with remaining Rj (j=1, . . . , i-1, i+1, . .
. , n) in each case.
(ii) If all of Ri (i=1, . . . , n) cannot be composed with any of Rj (j=1,
. . . , i-1, i+1, . . . , n), the set S is already composed.
(iii) If composition is made between Ri and Rj, a resultant set of internal
areas is defined as T=R1', . . . , Rm'. Substituting S.sup.U T-Ri,Rj to a
set S of internal areas, the above procedure beginning with (i) is
iterated.
The composition described above occurs when Ri and Rj have a positional
relationship as shown on the left-hand side of FIG. 15 (here, a
composition technique is employed, in which priority is given to the
lateral direction). Ri and Rj may be exchanged. The result of composition
is shown on the right-hand side in FIG. 15.
Finally, the method of updating the internal area table will be described
with reference to FIGS. 16a to 16c. FIG. 16a shows windows 1610, 1620 and
1630 displayed on the CRT screen 2. The window 1610 has only display
internal area 1611 which is the window 1610 by itself. The window 1620 has
display internal areas 1621 and 1623 and a non-display internal area 1622
covered by 1610. The window 1630 has display internal areas 1631 and 1633
and a non-display internal area 1632 covered by 1620. The CRT display
screen 2 has the origin 0. Forms (1610), (1620) and (1630) are the window
management records of the corresponding windows shown in FIG. 16a (entry
of WS is not filled). Forms (162001) and (163001) are non-display internal
area management records, and forms ( | | |
