多屏幕显示器编程( 二 )

Programming for Multiple Monitors in Windows 98
Installing Multiple Monitors

Continued from Introduction

Setting up multiple monitors is relatively easy, but there are a few ground rules. Both of your video cards must be on the PCI bus, and your secondary display must be one of the devices supported by Windows. Most popular brands of PCI display adapters are currently supported, and the list will surely expand by the time Windows 98 is released.

One minor issue in the installation process is that the newly added video card will become your primary display. The documentation states that this inconvenience stems from a limitation of the PCI bus. If you want your current video card to be your primary display, you will need to do some installation juggling. Just remember that any newly added display adapter will become your primary desktop.

Once you've installed a second monitor, the Display Properties control panel will contain a new Monitors tab (see Figure 1), which replaces the Settings tab. From the Monitors tab you can change the positioning of your monitors and the display settings of each individual display, such as resolution and number of colors. Windows uses the monitors' resolution and relative positioning to set up the virtual desktop and its coordinate system (see Figure 2). The top-left corner of the primary display is always position (0,0), with the x-coordinates increasing as you move right and the y-coordinates increasing as you move down. The coordinates of additional monitors are determined by their positions relative to the primary display. Since Windows 98 allows negative coordinates within the desktop window, your programs should not assume that a negative number is invalid when dealing with desktop coordinates.

Because Windows was originally designed to handle only one monitor, some applications will not behave correctly on a multiple-monitor system. While the problems are more often annoying than fatal, most applications will require some slight changes to operate optimally on a system with more than one monitor.

Next: New Multiple-Monitor Win32 API functions

Published as Power Programming in the 4/7/98 issue of PC Magazine.

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