JPH01292424A - Picture information control and clipping system for multiwindow display - Google Patents

Abstract

PURPOSE:To rapidly clip also a window in a complex non-rectangular display area by dividing respective windows in a multiwindow into partial rectangular areas and using the coordinate information and boundary information of a partial rectangular area boundary for window control. CONSTITUTION:The whole display screen is divided into plural partial rectangular areas by extending respective boundaries of respective windows to form the boundary coordinate information of each partial rectangular area in the inside of each window in each window. In each window, boundary information indicating which part out of the inside and outside of a window display area and the boundary includes each partial boundary forming each partial rectangular area in the window is formed. Each partial boundary information forming each partial rectangular area in the window and its boundary coordinate information are used for window control information for controlling a window display screen.

Description

[Detailed Description of the Invention] [Summary] Regarding a screen information management method and a clipping method in a multi-window display that allows overlapping windows, the present invention provides high-speed clipping processing for non-rectangular windows, and screen information suitable for this clipping method. A screen information management method and clipping method for multi-window display that allows windows to be overlapped, and the entire display screen is divided into multiple partial rectangular areas by extending the border lines of each window. Divide the area, obtain boundary line coordinate information for each partial rectangular area, obtain boundary information indicating where the partial boundary line of each partial rectangular area is inside, outside, or on the boundary of the window display area, and calculate the boundary information and the boundary line. Screen information is managed using coordinate information as window management information, and this window management information is used to obtain clip line segment information in the display area of the window among the line segments to be clipped to perform clipping.

[Industrial application field]

The present invention relates to a method for clipping figures displayed in one window in a multi-window display screen that allows overlapping of windows, and a screen information management method in multi-window display suitable for this clipping method.

[Conventional technology]

Recently, in order to make effective use of the display screen,
2. Description of the Related Art A multi-window display system has come to be used in which a plurality of display areas called windows are provided on one display screen and different information is displayed in each window.

FIG. 4 shows an example of a multi-window display method. In the figure, 30 is a display screen, 31A, 31
B, 31C, etc. are each window (graphic part indicated by a solid line).

Each of the windows 31A to 31G has a display priority and is displayed in an overlapping manner as shown. In the case of the figure, the window 31A has the highest rank, followed by 31B→31C, but this rank can be changed arbitrarily.

By using such a multi-window display method, it is possible to run multiple applications in parallel, so each process can be executed efficiently.

In this multi-window display method, in order to prevent a graphic displayed in one window from entering the display area of another window, processing is performed to clip the input graphic outside the window display area.

For example, in FIG. 4, line segment P displayed in window 31B. When P is input, clipping is performed, and the line segments P + P z and PiP4 that are within the display area of the window 31B among the line segments Pa Ps are extracted as clipped line segments and displayed on the window 31B. . If the line segment Pa Ps is a line segment displayed in the window 31A, the line segment Pg Ps within the display area of the window 31A among the line segments Pa Ps is extracted as a clipped line segment by clipping, and 31A.

In multi-window display, the highest ranking window 31A is a rectangular window, but the other windows are usually non-rectangular windows with non-rectangular display areas, such as windows 31B and 31C. Clipping processing for a rectangular window 31A is simple, but processing for a non-rectangular window is complicated, for example, clipping is performed using the following methods.

■ Create a bit-corresponding window mask that matches the display area of each window, and when a figure for one window is input, mask the figure part outside the display area of that window with the corresponding window mask.

■ Divide a non-rectangular window into a plurality of small rectangular areas, treat these small rectangular areas as one window, and perform clipping for each of these rectangular windows.

[Problem to be solved by the invention]

Multi-window displays that allow overlapping windows generally include multiple non-rectangular windows, which complicates the clipping process as shown in ■ and ■ above.
There is a problem in that the processing time is longer than in a rectangular window. Furthermore, the method (■) requires a large amount of memory to store each window mask, and the method (■) requires unnecessary processing to determine whether clipping processing is to be performed even for small rectangular areas that do not include line segments. There was an inconvenience.

The present invention provides a clipping method in a multi-window display that is improved to perform high-speed clipping processing on non-rectangular windows in a multi-window display that allows overlapping windows, and a screen information management method in a multi-window display that is suitable for the clipping method. The purpose is to provide

[Means to solve the problem]

In order to solve the above-mentioned problem, the solution adopted by the present invention will be explained with reference to FIG. FIG. 1 shows a principle diagram of the screen information management method and clipping method in the multi-window display of the present application.

In FIGS. 1(A) to (D), 10 is a display screen, II
A, IIB, IIC, etc. are each window (graphical part indicated by a solid line). The windows IIA to IIC are displayed in a superimposed manner with display priorities. Figure 1 (
A) shows the entire multi-window display. In the case of the figure, window IIA has the highest rank, and the following 11
The ranking is B → 11C.

(1) Configuration of screen information management method in multi-window display.

The screen information management method is configured as follows.

(A) The entire display screen 10 is displayed in each window (11A to II).
C, etc.) is extended and divided into a plurality of partial rectangular areas, and boundary line coordinate information of each partial rectangular area within each window is created for each window.

(B) For each window, for each partial boundary line forming each partial rectangular area within that window, whether that partial boundary line exists within the display area, outside the display area, or on the display area boundary of that window. Create boundary information that instructs what to do.

(C) The boundary information of each partial boundary line forming each partial rectangular area within the window and the boundary line coordinate information are used as window management information for managing the window display screen.

(2) Configuration of clipping method in multi-window display.

The clipping method for multi-window display performs clipping using the window management information created by the window management information creation method described above.
It is composed as follows.

The configurations of (A) and (B) are the same as the configuration of the window management information creation method described above.

(C) Line segment for clipping! The intersection of this line segment 2 with each partial boundary line of each partial rectangular area in the window to be clipped and displayed is determined.

(D) From among the obtained intersection points, each intersection point located on the display area boundary of the window displaying the line segment l is extracted based on the boundary information of the partial boundary line where the intersection point exists.

(E) Create start point and end point information for each clip line segment to be displayed within the window display area based on each intersection point information on the extracted window display area boundary and the line segment information of line segment 2. Perform clipping.

[For production]

The functions of each invention will be explained separately for the screen information management method and the clipping method.

(1) Effects of the screen information management method The effects of the screen information management method in multi-window display will be explained with reference to FIGS. 1(A) to (C).
Taking as an example a case where IIC overlaps as shown by the solid line in FIG. 1(A), the processing order will be explained.

(2) The boundaries of the windows IIA to 11C on the display screen 10 are extended to divide the entire display screen 10 into a plurality of partial rectangular areas as shown by broken lines in FIG. 1(A). In FIG. 1(A), χ, to x6 are the X boundary line coordinates of the boundaries forming each partial rectangular region, and y1 to 'lb are the Y boundary line coordinates.

■ For each window, at least for each partial boundary line forming each partial rectangular area within that window, whether the partial boundary line is within the display area of that window, outside the display area,
Create boundary information that indicates where on the display area boundary it exists.

For example, for window IIB, boundary information is created as follows (FIG. 1(B)).

(See (C)).

FIG. 1(B) shows each partial rectangular area WB, ~WB formed within the window IIB, and their boundary line coordinates, that is, the X boundary line coordinate X1%X4 and the Y boundary line coordinate y2~
yS is shown.

For each partial boundary line of each partial rectangular area WB, -WB,
When the partial boundary line is within the display area, outside the display area, or on the display area boundary of the window 11B, for example, label 2, label O, and label l are respectively assigned as the boundary information.

As a result, each partial boundary line of each partial rectangular area W B + to WB is labeled O as shown in FIG. 1(C).
Boundary information indicated by ~2 is given.

Regarding the other windows 11A and IIC, boundary information of each partial boundary line of each partial rectangular area within the window can be obtained in the same manner.

(2) The boundary information of each partial boundary line of each partial rectangular area in the window and the boundary coordinate information obtained as above are held as window management information of the window display screen.

By creating such window management information and managing the multi-window display screen, it is possible to uniformly manage each window display screen information in the multi-window display.

Furthermore, as described in the following clipping method, clipping can be performed at high speed in non-rectangular windows in multi-window display.

Note that this window management information is created each time the display order of each window changes or the windows are changed.

(2) Effect of the clipping method The effect of the clipping method in multi-window display is explained in the non-rectangular window IIB having the non-rectangular display area shown in FIG. 1(A), with reference to FIGS. Taking the case of clipping a displayed line segment as an example, the processing order will be explained.

■ Similar to ■ of the screen information management method described above, the display screen l
The entire window II as shown in Figure 1 (A).
Each boundary line of A to IIC is extended and divided into a plurality of partial rectangular areas.

X, to X6 are the X boundary line coordinates of each partial rectangular region boundary line, and y1 to y6 are the X boundary line coordinates.

■ Similar to ■ of the screen information management method described above, for each window, for each partial boundary line forming each partial rectangular area within that window, if that partial boundary line is within the display area of that window, the display area Create boundary information that indicates whether the display area exists outside or on the display area boundary.

FIG. 1(B) shows each partial rectangular region WB formed within the window 11B as described above.

~W B 9 and the X boundary line coordinates of those boundaries X1~X
4 and Y boundary line coordinates y2 to y. In addition, FIG. 1(C) shows that for each partial boundary line of each partial rectangular area WB to WB9, the partial boundary line is located at the window 11.
This shows an example in which label 2, label 1, and label 0 are respectively assigned as boundary information when the display area B is inside the display area, outside the display area, or on the display area boundary.

■ Line segments for clipping! The intersection of this line segment l with each partial boundary line of each partial rectangular area in the window to be displayed is determined.

FIG. 1(D) shows the intersection of each partial boundary line of each partial rectangular area WB, to WB in the window 11B and the line segment l to be clipped. In the figure, Ps is the starting point of line segment l, P1 to P are the intersection points with each partial boundary line, P
e is the end point. Note that the starting point and ending point of the line segment are determined based on the Y-axis (or may be based on the X-axis).

- From among the obtained intersection points, each intersection on the boundary of the display area of the window that displays the line segment is extracted, based on the boundary information of the partial boundary line where the intersection exists.

In the case of Figure 1 (D), the intersections P, , Pt , p3 e
Each boundary information or label of P4 $ PS is 0, 0, 1, 2, 1, respectively. P, and P, since it indicates that the intersection of label 1 is on the display area boundary of window IIB.

is extracted as the desired intersection.

(2) Create line segment information for each clip line segment to be displayed within the display area of the window, based on the extracted information on each intersection point on the boundary of the display area of the window and the line segment information on the line segment l.

For example, in the case of FIG. 1(D), the intersection point P.

A set having the starting point as the starting point and the intersection point P2 as the ending point is output as the line segment information of the clip line segment to be displayed. There are various ways to create line segment information for clip line segments to be displayed, but the second
The figure shows an example of a method for creating line segment information for each clip line segment, taking the case of window IIB as an example.

First, each intersection point information on the boundary of the extracted window's display area is converted into a line segment! Sort in order using the starting point (or ending point) as the reference point.

As a result, when the starting point PS, which is the reference point of the line segment 2, is outside the display area of the window IIB, as shown in FIG. 2(A), the intersection points P1→P! →P、→
It is rearranged from P4 to the end point Pe. Also, the starting point P of line segment 2
When s is within the display area of window IIB, the second
As shown in Figure (B), the intersections p, −
It is rearranged as +p, -+p, -+p4-+end point Pe.

Line segment as shown in Figure 2 (A)! When the starting point Ps is outside the display area, the pair of starting points and ending points indicated by (PI Pg) and (PIP4), that is, the starting point is the odd-numbered intersection point (PI, .1) at -a and the next even-numbered The intersection point (Pg
-z) as the end point, each pair of start point and end point is output as line segment information of the crib line segment to be displayed. This means that
This holds true no matter how complex the window display area is.

Next, as shown in FIG. 2(B), when the starting point Ps of the line segment l is within the display area, (PsP+), (Pg P
s ), that is, (PsP
+), and generally even-numbered intersections (pz+-)
Each pair of start point and end point, with the start point at pt and the end point at the next odd-numbered intersection (pt, . . . ), is output as line segment information of the clip line segment to be displayed. This holds true no matter how complex the window display area is, a non-rectangular display area.

As described above, by performing clipping using the window management information created by the screen information management method, it is possible to clip at high speed no matter how complex a window has a non-rectangular display area, that is, a non-rectangular window. It can be carried out.

〔Example〕

Examples of screen information management methods and clipping methods in multi-window display will be described with reference to FIGS. 1, 2, and 3. FIG. 3 is a block diagram showing the configuration of an implementation system common to each embodiment of the invention. The principle diagram in FIG. 1 and the explanatory diagram of the clipping line segment information creation method in FIG. 2 have already been described.

(A) Configuration of Implementation System In FIG. 3, 21 is a processor (MPU), which controls the operation of each unit and each means described below, and controls the operation of the entire system.

A memory 22 stores line segment information of each figure displayed on the display, window information of each window, created window management information, and the like.

23 is a window management information creation means, which includes an area dividing section 23;
1 and a management information creation unit 232 to create window management information.

The area dividing unit 231 divides the entire display screen 10 into a plurality of partial rectangular areas by extending along the boundary line of each window, and obtains boundary line coordinate information of each partial boundary line forming each partial rectangular area for each window. (X boundary line coordinate information and Y boundary line coordinate information) is created and sent to the memory 22.

These operations are performed by the processor 21 based on its program. For each window, the management information creation unit 232 determines whether the partial boundary line is inside the display area, outside the display area, or on the display area boundary for each part boundary line forming each partial rectangular area in that window. Boundary information indicating whether it is present is created and sent to the memory 22.

These operations are performed by the processor 21 based on its program. 24 is a drawing calculation means, and the intersection calculation unit 2
41, drawing intersection information extraction unit 242, drawing line segment selection unit 24
3 and a drawing line segment information creation section 244.

The intersection calculation unit 241 finds the intersection between the line segment to be clipped and each partial boundary line of each partial rectangular area within the window displaying this line segment.

The drawing intersection information extraction unit 242 extracts each intersection point on the display area boundary of the window that displays the line segment from among the obtained intersection points, based on the boundary information of the partial boundary line where the intersection point exists. do.

Based on each intersection point information and the coordinate information of the line segment extracted by the drawing intersection point information extraction section 242, the drawn line segment selection section 243
Line segment information consisting of starting point and ending point information of each clipping line segment to be displayed within the display area of the window is created.

The drawn line segment information creation unit 244 includes the clip line segment selection unit 24
The starting point and end point of each clipping line segment selected in step 3 are interpolated, and coordinate data of each pixel on the two-dimensional grid of the frame memory closest to the clipping line segment is created.

A frame memory 25 stores each clip line segment information created by the drawing line segment information creation section.

A display 26 reads out the contents of the frame memory 25 and displays multi-windows and clipping graphics on the display screen 10.

Reference numeral 27 denotes a common bus that connects each of the aforementioned sections and transfers data and control signals.

(B) Operation of the embodiment of the screen information management method The operation of the embodiment of the screen information management method in multi-window display will be described with reference to FIGS. 1(A) to (C).
Taking as an example the case where C overlaps as shown by the solid line in FIG. 1(A), the processing order will be explained.

(2) The memory 22 stores window information for each of the windows IIA to 11C and information for each line segment of a figure to be drawn. The CPU 21 takes out window information from the memory 22 and inputs it to the area dividing section 231.

■ The area dividing unit 231 divides each window 11A to IIC on the display screen 10 based on the input window information.
By extending each boundary line of , the entire display screen 10 is shown in FIG.
Divide into multiple partial rectangular areas as shown by broken lines in , and create boundary line coordinate information (X boundary line coordinate information and boundary line coordinate information) of each partial boundary line forming each partial rectangular area for each window. and sends it to the memory 22. This boundary line coordinate information is created in the form of a matrix. These operations are performed by the processor 21 based on the operations.

For example, in the case of window IIB, it is divided into partial rectangular areas WB, ~WB, as shown in FIG.
z p Xz , X4 ), and the X boundary coordinate information is the Y boundary coordinate matrix CVt s
This border coordinate information is created for each window.

(2) When the processing of the area dividing unit 231 is completed, the MPU 21 sends the window information of each window and the boundary line coordinate information of each partial boundary of the partial rectangular area to the management information creating unit 232.

Based on this information, for each window, the management information creation unit 232 determines, for each partial boundary line forming each partial rectangular area within that window, that the partial boundary line is within the display area of that window. Create boundary information that indicates whether the display area is outside or on the display area boundary, and store it in memory 2.
Send to 2. These operations are performed by the processor 21 based on its program.

In this embodiment, when the partial boundary line is within the display area, outside the display area, or on the display area boundary of the window, label 2, label O, and label l are respectively assigned as the boundary information. As a result, for example, in the case of window IIB, boundary information indicated by labels 0 to 2 is given to each partial boundary line of its partial rectangular areas WB, ~WB, as shown in FIG. 1(C). .

In this embodiment, the boundary information includes horizontal boundary information α indicating boundary information of each partial boundary line in the horizontal direction (X direction);
The boundary information of each partial boundary line in the vertical direction (Y direction) is divided into vertical direction boundary information β indicating the vertical direction boundary information β, which is further created in the form of a matrix.

For example, in the case of the window 11B shown in FIG. 1(C), the horizontal boundary information α is given by a matrix of , and the vertical boundary information β is given by a matrix of . The matrix format of the horizontal boundary information α is in the form of a matrix whose elements are each label value shown in FIG. 1(C), but the matrix format of the vertical boundary information β is as shown in FIG. It is a transposed matrix whose elements are each label value shown in (C). In this way, both the horizontal and vertical boundary information become matrices of the same format (4×3), so that they can be easily stored in and read from the memory 22.

- The memory 22 stores X and Y coordinate information and horizontal and vertical direction boundary information (α, β) of the partial rectangular area boundary line for each window created by the area dividing unit 231 and the management information creating unit 232. , is retained as window management information.

(C) Operation of the embodiment of the clipping method The operation of the embodiment of the clipping method in multi-window display will be explained with reference to FIGS. 1(A) to (D) and FIG. 2.
A non-rectangular window 11B having a non-rectangular display area shown in
For example, when clipping a line segment displayed in
The processing will be explained in order. Clipping is performed using the window management information created using the screen information management method described above.

■ The MPU II retrieves the X and Y boundary line coordinate information of each partial rectangular area from the memory 22 from the line segment information of the line segment l to be clipped and the window management information of the window 11B that displays this line segment, and uses it in the intersection calculation unit. 241 to start the process.

The intersection calculation unit 241 calculates each partial boundary between the line segment l and each partial rectangular area WB, ~WB, in window IIB based on the input line segment information and each boundary line coordinate information of each partial rectangular area X and Y. Calculate the intersection with the line and draw intersection point information extraction unit 2
42 (see FIG. 1(D)).

This intersection point calculation can be performed in the same way as the conventional clipping process for rectangular windows, considering each partial rectangular area WB, -WB as one window. Note that for partial rectangular regions where at least one of the X and Y coordinates of the partial boundary line is smaller than the corresponding X or Y coordinates of the starting point and ending point of the line segment, intersection point calculation is not necessary and is therefore not performed. As a result, as shown in FIG. 1(D), the intersection points of the line segment and each partial boundary line of each partial rectangle WB, WB, WBh, WB, P y Pg s P3 ,
Pg and P are found.

■ When the intersection calculation process in the intersection calculation unit 241 is completed, the MPU II opens the window IIB in the memory 22.
Boundary information of each partial rectangular area boundary line (horizontal boundary information α and vertical boundary information β) from the window management information of
is extracted and sent to the drawing intersection information extraction unit 242 to start its processing.

When the intersection information and boundary information of each intersection P1 to P are input, the drawing intersection information extraction unit 242 extracts each intersection P+−PsO.
From among them, each intersection on the display area boundary of window IIB that displays line segment l is extracted based on the boundary information, that is, label information, of the partial boundary line where the intersection exists, and is sent to drawn line segment sequence selection unit 243. send. These operations are performed by the processor 21 based on its program.

The label information of the intersections P+, Pt, Ps, Pa, and p is 0.0, respectively, as shown in FIG. 1(D).
0, 1, 2.1, so the intersections P3 and P of label 1
5 is extracted as the intersection on the display area boundary of the window 11B.

■ When the process of the drawing intersection information extraction unit 242 is completed, the MPU 21 transmits the line segment information of the line segment l to the drawing line segment selection unit 243.
and start processing it.

The drawn line segment selection unit 243 selects a line segment having start point and end point information for each clip line segment to be displayed within the display area of the window 11B, based on the input line segment information and the intersection point information on the window display area boundary. Information is created and sent to the drawing line segment information creation section 244.

In the case of line segment 2, a set in which the starting point is intersection point P and the ending point is intersection point P2 is output as line segment information of the clipped line segment to be displayed.

Generally, as explained in the [Operation] section, each intersection point information on the boundary of the extracted window display area is converted into a line segment! Sort in order using the starting point (or ending point) as the reference point.

Then, as shown in FIG. 2(A), the reference point of line segment i (
If Ps (starting point) is outside the display area of the window, (
P, P3), (P, P5), the starting point is the odd-numbered intersection (Pz-+) and the next even-numbered intersection (Pg-z
) is output as line segment information of the clip line segment to be displayed.

Furthermore, as shown in FIG. 2(B), when the reference point (starting point) Ps of the line segment l is within the display area of the window, (P5
P, ), each pair of start and end points with the even-numbered intersection (P7) as the start point and the next odd-numbered intersection (Pz-+) as the end point is the line segment information of the clip line segment to be displayed. is output as These operations are performed by the processor 21 based on its program.

■ The drawn line segment information creation unit 244 interpolates between the start point and end point of each clip line segment selected by the clip line segment selection unit 243, and stores the frame memory 2 closest to the clip line segment.
The coordinate data of each pixel on the two-dimensional grid of No. 5 is created and stored in the frame memory 25. This coordinate data can be created using, for example, a known digital differential analyzer (DDA: Di).
Digital Differential Analyzes
er). These operations are performed by the processor 21 based on its program.

(2) The display 26 reads the contents of the frame memory 25 and displays the figure clipped on the display screen 10 in the corresponding window IIB.

〔Effect of the invention〕

As explained above, the invention of the screen information management method is to divide each window in a multi-window display into partial rectangular areas, and use the coordinate information and boundary information of the partial rectangular area boundary line for each window as window management information to create a multi-window display. Since the display screen is now managed, it is possible to uniformly manage the display screen information for each window in multi-window display, and by using this window management information, it is possible to manage windows with complex non-rectangular display areas. You can also perform fast clipping.

In addition, the invention of the clipping method uses window management information created by the screen information management method to perform clipping, so it is possible to perform high-speed clipping even for windows with complex non-rectangular display areas. can.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the principle of each invention of the present application, Fig. 2 is an explanatory diagram of the clip line segment selection method in the invention of the clipping method, and Fig. 3 is an explanation of the configuration of the implementation system of the embodiment of each invention of the present application. FIG. 4 is an explanatory diagram of the multi-window display method. 1 to 3, 10...display screen, IIA-11C...window, 21...processor (MPU), 22...memory, 23...window management information creation means, 231・・・
- Area division section, 232... Management information creation section, 24...
・Drawing calculation means, 241... Intersection calculation unit, 242...
・Drawing intersection information extraction unit, 243...Drawing line segment selection unit,
244...Drawing line segment information creation unit, 25...Frame memory, 26...Display, 27...Common bus. Patent applicant Fujitsu Limited

Claims (1)

[Scope of Claims] 1. A multi-window screen information management method for managing multi-window display screen information that allows windows to be overlapped, the method comprising: (A) displaying the entire display screen (10) in each window (11A, etc.); Extend each boundary line and divide it into multiple partial rectangular areas, create boundary line coordinate information of each partial rectangular area inside each window, (B) For each window (11A etc.), For each partial boundary line that forms each partial rectangular area in a window, create boundary information that indicates whether the partial boundary line exists within the display area, outside the display area, or on the display area boundary of the window. (C) A multi-window display characterized in that the boundary information of each partial boundary line forming each partial rectangular area within the window and the boundary line coordinate information are used as window management information for managing the window display screen. screen information management method. 2. A clipping method for multi-window display that allows overlapping windows, in which (A) the entire display screen (10) is divided into a plurality of partial rectangular areas by extending the boundaries of each window (11A, etc.). (B) For each window (11A, etc.), create boundary line coordinate information for each partial rectangular area within that window for each window. On the other hand, create boundary information indicating whether the partial boundary line exists within the display area of the window, outside the display area, or on the display area boundary, and (C) line segment l for clipping;
Find the intersection of this line segment l with each partial boundary line of each partial rectangular area in the window for clipping display, (D) From among the obtained intersection points, calculate the boundary information of the partial boundary line where the intersection exists. (E) Based on the information of each intersection on the boundary of the display area of the extracted window and the line segment information of line segment l, A clipping method for multi-window display, characterized in that clipping is performed by creating line segment information for each clip line segment to be displayed within a display area of a window. 3. Arrange each intersection point information on the extracted window display area boundary in order using the starting point or end point of line segment l as the reference point, and if the reference point of line segment l is outside the window display area, Each pair of start and end points, with the odd-numbered intersection as the start point and the next even-numbered intersection as the end point, is used as line segment information for the clip line segment to be displayed, and the reference point of line segment l is within the display area of the window. In this case, display the set with the reference point of line segment l as the starting point and the first intersection as the end point, and the set of each start point and end point with the even-numbered intersection as the start point and the next odd-numbered intersection as the end point. 3. The clipping method for multi-window display according to claim 2, wherein line segment information is used as power clip line segment information.