Smooth scrolling is provided in a video display terminal having a cathode ray tube (CRT) controller which, by itself, is only capable of discontinuous, jump scrolling. The start-of-display address modification technique of advancing the start-of-display a single row at a time is combined with a display vertical position control normally used for changing the position of the display on the CRT faceplate. By sequentially erasing the top scan line, moving the entire display up one scan line by means of the vertical position control, erasing the second scan line, restoring the vertical position control to its original value, and advancing the CRT controller start address by two scan lines, the character rows are scrolled upward in a smooth, continuous manner. This sequence of operations is repeated a predetermined number of times for each character line with the "wrap-around" feature of a video memory used to provide new information for the bottom scan line.
A method for scrolling, at a desired rate and in a given direction, a graphic character on a display having a predetermined number of actual scan lines and a vertical blanking interval occurring between successive display of all the actual horizontal scan lines of the display, involves the creation of fractional scan lines between successive vertical blanking intervals, the identification of leading and trailing edges of the character and the selective changing of the color or shading of pixels of the leading and trailing edges to effect scolling of the character.
Text image on a monitor can be scrolled pixel-by-pixel instead of line-by-line or character-by-character. An application window (for showing images generated by an application) and a child window are generated. The text image is drawn on the child window instead of on the application window. The size of the application window is smaller than the child window. Only the portion of the child window overlapping the application window is displayed by a computer screen. If a user desires scrolling, the child window is moved, a pixel at a time, in a direction corresponding to the direction of scrolling. When a full line or a full character is scrolled, the child window clears itself and returns to its original position. At the same time, the text image is scrolled one line or one character on the child window so as to match the pixel-based scrolling. As a result, the user sees a smooth scrolling of a text image.
In response to a "PAUSE RELEASE" command, a CD drive 1 resumes a playback operation earlier than the "PAUSE" position. The control module 2 analyzes whether continuity is recognized in the time information between a newly entered instruction and a finally processed instruction memorized in the memory 7. Graphic processing and development processing are canceled until the continuity is found. The image data developed in an internal memory 8 is transferred to an external memory 10 through a format conversion module 9. The control module 2 cancels a processing of the newly entered instruction when the newly entered instruction is either Soft Scroll Screen with Preset instruction or Soft Scroll Screen with Copy instruction having a scroll dot number smaller than a predetermined number. Alternatively, all the dot units scroll can be canceled while only the character units scroll can be performed.
Text image on a monitor can be scrolled pixel-by-pixel instead of line-by-line or character-by-character. An application window (for showing images generated by an application) and a child window are generated. The text image is drawn on the child window instead of on the application window. The size of the application window is smaller than the child window. Only the portion of the child window overlapping the application window is displayed by a computer screen. If a user desires scrolling, the child window is moved, a pixel at a time, in a direction corresponding to the direction of scrolling. When a full line or a full character is scrolled, the child window clears itself and returns to its original position. At the same time, the text image is scrolled one line or one character on the child window so as to match the pixel-based scrolling. As a result, the user sees a smooth scrolling of a text image.
A display system including a programmable video graphic controller allows for continuous smooth panning through memory which is larger than the system's video memory. The video memory is continuously updated with new image data so as to form two duplicate images within video memory. When an edge of video memory is reached, the displayed image may be shifted from one of the duplicate images to the other within video memory to allow continuous panning without the need to stop and refresh the image data every time an edge of video memory is reached.
