| They're way, way easier than they used to be. In the example from that article, by the time we got GENGRADD, writing a driver was easy enough that I did it (I wanted to make a display driver that made everything green since at the time I heard everything-green is easier on the eyes, and it was a few hours of work to cook up a driver that did that). In contrast, I worked on a driver about 4 years earlier and the amount of labour was utterly crazy. A Windows 3.1, 95, or OS/2 system needed, at a minimum, these drivers: - The base BIOS necessary for booting - A VESA implementation in the BIOS (optional, but would mean the below code could be copy-and-pasted far more easily from a generic SVGA driver) - (OS/2 only) a "BVH" driver which would set full screen modes, although the default VGA/SVGA was usually enough. Windows 3.1 and 95 would just use the BIOS. - A 32-bit "virtual" device driver to handle DOS sessions which want to talk to the display adapter, basically making a working VM environment for that specific hardware. The codebase for this was different on Windows 3.x, Windows 95, and OS/2, even though the actual function would be nearly identical. (A Windows 3.x virtual driver could in theory be used on Windows 95, but these usually had odd stability problems.) - A 16-bit Windows 3.x display driver (could be re-used for OS/2) - Another 16-bit Windows 3.x display driver for sharing the display between a Windows and the OS/2 desktop, known as "seamless" - these were notoriously difficult to write - A 32-bit Windows 95 and/or 32-bit OS/2 display driver for the main session... except in the OS/2 2.0 era, the OS/2 display driver would have to be 16-bit, even though the rest of the OS was 32-bit. Windows 95 could use the 16-bit display driver, albeit at reduced performance. Another frustrating quirk was that the display driver (for both Win 3.1, 95, and OS/2 before version 4.0) would require an implementation of pretty much all of the graphics primitives, even ones that just rendered to a buffer in memory. Most people would write their display driver by taking Microsoft's Video 7 sample code and re-use the primitives in there. |