The present invention relates generally to resetting the video display in a computer system. More particularly, a method of controlling a video display is described which permits the user to alter display characteristics such as the screen resolution and/or the color depth without requiring that either the currently open application(s) or the operating system be exited and reloaded.
Most modern computer monitors are capable of displaying in a variety of screen resolutions. By way of example, many monitors for personal computers are capable of at least displaying images having resolutions of 640.times.480, 800.times.600 and 1024.times.768 pixels. There are many circumstances in which a user may want to utilize different screen resolutions for different applications. For example, when using a word processor, most users prefer a relatively low screen resolution (such as 640.times.480) so that the letters appear relatively large and thus are easy to read. On the other hand, when using a spreadsheet having a large number of columns, it may be desirable to switch to a higher resolution (such as 1024.times.768) so that a more complete view of the spreadsheet can be seen on the screen.
Similarly, the video cards associated with most color monitors are capable of displaying in a variety of different pixel ,depth modes. That is, they can be arranged to display different numbers of colors. By way of example, video cards capable of displaying 16, 256, or 32K colors are common and many state of the art video cards are capable of displaying as many as 16M or more colors. There are many circumstances in which a user may want to utilize different color (pixel) depths for different applications. For example, when using a word processor, there is little need for using a large number of colors. Therefore, since operating the word processing software at a large color depth (such as 16M colors) slows the operation of the software considerably, it is preferable to run the word processing software at a low color depth (such as 16 or 256 colors). On the other hand, when the user is running imaging software or the like, the use of a higher color depth is highly desirable and is worth the speed losses associated therewith.
In view of the forgoing, users occasionally desire to change the video display mode. Currently, one of the most popular operating systems for IBM PC compatible personal computers is the MS-DOS based Windows operating system marketed by Microsoft Corporation. Within Windows, various video display characteristics such as the screen resolution and color depth are controlled by software based video card screen drivers, Each video card requires a number of dedicated screen drivers. For example, traditionally, a separate video driver has been provided for each screen resolution and color depth that is supported by the video card and monitor. More recently, multi-resolution drivers have been used, however separate drivers for different color depths are still the norm. In order to switch the screen resolution or the color depth, it is typically necessary to exit any open application(s), exit Windows and then change the screen resolution or color depth in DOS. This is typically accomplished by loading a new driver program, or in the case of changing the screen resolution using a multi-resolution driver, the application requesting the new resolution saves the desired resolution values to the disk before exiting Windows. After the new driver has been loaded (or the appropriate resolution values saved), both Windows and the desired application programs must be restarted. Obviously, this procedure is slow and cumbersome and it would be desirable to provide a mechanism that permits the user to alter the screen resolution and/or color depth without having to exit Windows, when Windows is the operating system that is currently running.