Display control system

Abstract: A display control system which comprises a display mem­ ory having a serial access port for sending data to a dis­ play device and a random access port for data communication with a graphic drawing device, a window buffer memory for storing image data such as sentences and graphic charts, a window controller for controlling the position of the window buffer memory content displayed on the display device, and a selection circuit for selecting a display mode or a graphic drawing mode.

Description: This invention relates to a display control system. Conventionally, image display is controlled by one of the following systems shown in Figs. 5(a), (b) and (c). The display control system shown in Fig. 5(a) is a so-called software window system involving raster operation. In this system, the image data of the windows A, B and C stored in a window memory 1 are transferred in blocks to a display memory 2 through raster operation so that picture editing such as positioning and superposing of the windows A, B and C are performed in the display memory 2. After editing the image data are read sequentially from the display memory 2 for multi-window display on a CRT 3. The display control system shown in Fig. 5(b) is a so-called hardware window system involving a mapping table. In this system, the address of the image data corresponding to the current scanning position on a CRT 6 is output sequentially from a hardware mapping table 5 during scanning operation by the CRT 6, and the image data of the windows A, B and C stored in a window memory 4 are read in shared time according to the above address and output directly to the CRT 6 for multi-window display. The display control system shown in Fig. 5(c) is so-called a software window system involving clipping. In this system, a picture is drawn in a display memory 8 using the code data for the image information of the windows A, B and C stored in a segment buffer 7 after clipping the code data of the image information outside the windows. The image data is then read sequentially from the display memory 8 for multi-window display on a CRT 9. The above conventional display control systems of Figs. (a), (b) and (c) have disadvantages, respectively. The disadvantage of the display control system of (a) involving raster operation is as follows. The image data in the window memory 1 must be transferred in blocks to the display memory 2 to edit a picture in the display memory 2 before the picture is displayed on the CRT 3. This operation must be carried out every time the window is moved on the CRT 3. Therefore, the window cannot be moved quickly. The disadvantage of the system of (b) involving a mapping table is as follows. The addresses of the image data in the window memory 4 are output sequentially from the mapping table 5 so that the image data stored at the addresses are read in shared time and displayed directly on the CRT 6. With this system, it is possible to move the window quickly. On the other hand, however, since graphic drawing in the window memory 4 is also performed in shared time, drawing speed is slow. The disadvantage of the system of (c) involving clipping is as follows. The code data of unnecessary image data in the segment buffer 7 is removed by clipping before the code data of the image data stored in the segment buffer 7 is transferred for graphic drawing on the display memory 8 and displayed on the CRT 9. To move the window on the CRT 9, therefore, the system requires a hardware for drawing graphics at a high speed on the display memory 8 from the code data stored in the segment buffer 7. A further example of prior art window systems is disclosed in EP-A-O 153 197, in which data has to be first written to screen buffers before being output to a screen. In order to alleviate at least some of the problems encountered in the prior art the present invention provides a display control system having: a full screen display memory for providing image data for display by a display device; a window memory for storing alphanumeric and/or graphic window image data defining one or more image portions to be displayed by the display device; first control means operable to selectively move the display position of the image portion or portions; and second control means for controlling the supply of image data and window image data to the display device, said second control means being operable in a direct access display mode of the system to cause window image data to be supplied direct from the window memory and image data to be supplied from the display memory, the window position being changeable in said direct access display mode by operation of said first control means, the system also being operable in a graphic drawing mode to permit data drawing and editing in the window memory. An advantage of the present invention is that in the direct access display mode it is possible to move the window on the display quickly while watching the screen and, in the graphic drawing mode it is possible to draw and edit graphics rapidly in the window memory, thus allowing the operator to edit a document at a high speed while watching the CRT screen. The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein: Fig. 1 is a block diagram of an embodiment of the present invention; Fig. 2 is a diagram for explaining the document editing by the embodiment of Fig. 1; Fig. 3 is a block diagram of another embodiment of the present invention; Fig. 4 is a block diagram of still another embodiment of the present invention; and Figs. 5(a) to (c) are diagrams for explaining the conventional display control systems. To display window buffer memory content directly on a display device overlapping display memory content, a selection circuit is set for the direct access display mode. Then, the operation timing of the window buffer memory is shared between the direct access display cycle and the graphic drawing cycle, so that window buffer memory content is displayed directly over the display memory content on the screen of the display device as the position of the window buffer memory content displayed is controlled by a window controller. Thus, in the direct access display mode, a window can be moved rapidly on the display screen. When window buffer memory content is not to be displayed directly on the display device, the selection circuit is set for the graphic drawing mode. Then, the operation timing of the window buffer memory is used solely for the graphic drawing cycle so that graphics are drawn and edited in the window buffer memory and display memory. Accordingly, in the graphic drawing mode, it is possible to draw graphics and edit display data in the window buffer memory and display memory at a high speed. Fig. 1 is a block diagram of an embodiment of the present invention. A display memory 11 is a bit map memory for display having memory elements corresponding to the picture elements on the display device. The display memory 11 is provided with a serial access port for sending data to the display device and a random access port for data communication with a graphic drawing device. A window buffer memory 12 is designed to store image data such as sentences, figures and tables. In this embodiment, the window buffer memory 12 also serves as a main memory for effective use of the memory. This feature has a demerit that a CPU 17 cannot make access to the main memory while a graphic controller 13 is making access to the window buffer memory 12. On the other hand, however, this feature permits the effective use of the window buffer memory 12 whose capacity increases with the amount of image data to be displayed. The graphic controller 13 transmits image data between the window buffer memory 12 and the display memory 11 via a bus line 18 or draws graphics on both memories. A window controller 14 allows the content of the window buffer memory 12 to be displayed directly with no intervention of the display memory 11, at a desired position overlapping the content of the display memory 11 on the display screen. This display position control is achieved by writing the status related to display in the register in the window controller 14. A selection circuit 15 selects the direct access display mode in which the content of the window buffer memory 12 is displayed directly on the display device or the graphic drawing mode in which the window buffer memory content is not displayed on the display device. When the direct access display mode is selected, the operation timing of the window buffer memory 12 is shared between the display cycle in which the window controller 14 makes access to the window buffer memory 12 and the graphic drawing cycle in which the graphic controller 13 makes access to the window buffer memory 12 via the bus line 18. When the graphic drawing mode is selected, the operation timing of the window buffer memory 12 is used only by the graphic drawing cycle so that the window buffer memory 12 is used 100% by the graphic controller 13. A raster operation circuit 16 sends image data output from the display memory 11 and image data output from the window controller 14 to the display device such as a CRT after logical operation. In the following description of the operation of the present embodiment, it is assumed that the window buffer memory 12 has stored the image data of sentences 21, a graphic chart 22 and a figure 23 as shown in Fig. 2. When the operator is to move the graphic chart 22 and the figure 23 to appropriate positions overlapping the sentences 21 on the display screen of the CRT 24 in real time while watching the picture on the screen and, draw the image data with the graphic chart 22 and the figure 23 fixed at their most appropriate positions, on the display memory 11, he operates the system as follows. (A) Transfer of the image data of the sentences 21 from the window buffer memory 12 to the display memory 11 The selection circuit 15 is set for the graphic drawing mode so that the operation timing of the window buffer memory 12 is used for graphic drawing cycle alone. With this setting, the display memory 11 which is a two-port memory can use about 97% of the cycle time for transferring image data while the window buffer memory 12 can use 100% of the cycle time for transferring image data. Accordingly, image data can be transferred in blocks at a high speed by the graphic controller 13. As a result, the image data of the sentences 21 in the window buffer memory 12 is transferred to the display memory 11 at a high speed. (B) Positioning of the graphic chart 22 and the figure 23 with respect to the sentences 21 To enable the operator to move the graphic chart 22 and the figure 23 in real time while watching the picture on the CRT 24, the selection circuit 15 is switched over for the direct access display mode so that the operation timing of the window buffer memory 12 is shared between the direct access display cycle and the graphic drawing cycle. In the direct access display cycle, the window controller 14 accesses the address of the window buffer memory 12 calculated according to the display status written in the internal register to read the image data of the graphic chart 22 or figure 23 and outputs the image data directly to the raster operation circuit 16 rapidly with no intervention of the display memory 11. Neanwhile, the image data of the sentences 21 already transferred from the window buffer memory 12 is output through the serial access part of the display memory 11. The raster operation circuit 16 executes logical operation for the image data of the sentences 21 output from the display memory 11 and for the image data of the graphic chart 22 and figure 23 output from the window buffer memory 12, and outputs the image data of the graphic chart 22 and figure 23 overlapping the sentences 21 to the CRT 24. At this time, the display positions of the graphic chart 22 and figure 23 can be changed quickly by changing the display status written in the register of the window controller 14. Since the operation timing of the window buffer memory 12 is time shared between the graphic drawing cycle and direct access display cycle, it is possible to draw graphics in the window buffer memory 12 when the operation timing is for the graphic drawing cycle. It must be noted, however, that the graphic drawing speed in this mode is slower than that in the graphic drawing mode (in which the operation timing is used only for the graphic drawing cycle). (C) Transfer of the graphic chart 22 and figure 23 to the display memory 11 When the graphic chart 22 and the figure 23 have been positioned on the display screen of the CRT 24, the selection circuit 15 is switched over for the graphic drawing mode so that the operation timing of the window buffer memory 12 can be used solely for the graphic drawing cycle. Then, the image data of the graphic chart 22 and figure 23 thus positioned is transferred at a high speed from the window buffer memory 12 to the specified address in the display memory 11 under the control by the graphic controller 13. As a result, the image data for a picture with a graphic chart 22' and a figure 23' overlapping with sentences 21' as shown in Fig. 2 is formed in the display memory 11. According to the above embodiment of the invention, as mentioned above, the direct access display mode or the graphic drawing mode is selected by the selection circuit 15. In the direct access display mode, the operation timing of the window buffer memory 12 is time shared between the direct access display cycle and the graphic drawing cycle so that the window controller 14 transfers the content of the window buffer memory 12 directly to the CRT 24, presenting an active window display at a high speed. In the graphic drawing mode, the operation timing of the window buffer memory 12 is used for the graphic drawing cycle alone so that data drawing and editing in the window buffer memory 12 can be conducted rapidly. As a result, the operator can edit document rapidly while watching the picture on the CRT 24. Fig. 3 shows another embodiment in which a window buffer memory 31 is used only for storing image data and a RAM (random access memory) 32 is provided separately as a main memory. Bus line comprises an image bus 37 for transmitting image data and an internal bus 36. The window buffer memory 31, the selection circuit 15, the window controller 14, the display memory 11 and an image editing processor 33 are connected with the image bus 37. A FIFO two-port RAM 34 is connected between the image bus 37 and the internal bus 36. The image bus 37 or the internal bus 36 is selected by the FIFO two-port RAM 34 to present an image display at a high speed. Fig. 4 shows still another embodiment of the invention in which image data transfer between the window buffer memory 12 and the display memory 11 or graphic drawing in the window buffer memory 12 or the display memory 11 is executed by a CPU 41. According to the above embodiment of the present invention, the display control system comprises a display memory having a random access port and a serial access port, a window buffer memory for storing image data, a window controller for controlling the position of the window buffer memory content displayed on a display device, and a selection circuit for setting the operation mode of the window buffer memory to the direct access display mode or to the graphic drawing mode. When the direct access display mode is selected, the window buffer memory content is presented directly on the display device in shared time as the position of the data displayed is controlled by the window controller. When the graphic drawing mode is selected, image data transmission between the window buffer memory and the display memory or graphic drawing in the window buffer memory is conducted without time sharing. Consequently, it is possible for an operator to move a window at a high speed while watching the picture on the CRT when the selection circuit is switched over for the display mode, and to draw and edit graphics in the window buffer memory at a high speed when the selection circuit is switched over for the graphic drawing mode. As a result, it is possible to edit a document actively and rapidly while watching the picture on the display device. While only certain embodiments of the present invention have been described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the present invention as claimed.

Claims: A display control system having: a full screen display memory (11) for providing image data for display by a display device; a window memory (12;31) for storing alphanumeric and/or graphic window image data defining one or more image portions to be displayed by the display device; first control means (14) operable to selectively move the display position of the image portion or portions; and second control means (15,16) for controlling the supply of image data and window image data to the display device, said second control means (15,16) being operable in a direct access display mode of the system to cause window image data to be supplied direct from the window memory (12;31) and image data to be supplied from the display memory (11), the window position being changeable in said direct access display mode by operation of said first control means (14), the system also being operable in a graphic drawing mode to permit data drawing and editing in the window memory (12;31). A display control system as claimed in claim 1, wherein: said display memory (11) comprises a serial access port for sending data to said display device and a random access port for data communication with a graphic drawing device; said first control means comprises a window controller (14) for controlling the position of the contents of the window memory (12;31) displayed on the display device; and said second control means comprises a raster operation circuit (16) and a selection circuit (15) for selecting said direct access display mode or said graphic drawing mode. A display control system as claimed in claim 2, wherein the selection circuit is switched over for the direct access display mode when the contents of the window memory (12;31) are to be transferred directly to the display device so as to be displayed overlapping with the contents of the display memory (11), and for the graphic drawing mode when the contents of the window memory (12; 31) are not to be displayed directly on the display device. A display control system as claimed in claim 1 or claim 2, wherein in the direct access display mode, the contents of the window memory (12;31) are displayed directly on the display device in shared time with graphic drawing in the window memory (12;31), and wherein, in the graphic drawing mode, image data transmission between the window memory (12;31) and the display memory (11) or graphic drawing in the window memory (12;31) is carried out without time sharing.

Inventors: KIYOHARA TOSHIMI, MORITA TOSHIYAM, KIYOHARA, TOSHIMI, MORITA, TOSHIYAM
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1988
Main classification: G09G1
IPC codes: G06F3, G06T11, G09G5