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Extended Character Set

For the non-standard characters in the range of ASCII codes above 127, the p-System version of PCVideo use the specially-created set of bitmaps called ETC.CHARSET. Since Turbo Pascal dialogues may run on displays of different vertical resolutions, PCVideo now chooses between 2 available files of special-character bitmaps: CHSET_14.ETC, for use at resolutions giving 14 pixels per row or more; and CHSET_8.ETC, for 8 pixels per row or more. Both must be included in the startup directory of distribution discs.

The current version of PCVideo uses the bitmapping abilities of FastImage to put these bitmaps on the screen in the appropriate colours for the character at the time. This has two drawbacks: since FastImage relies on PCVideo to obtain information about the screen, this usage is circular, which hinders compilation; and FastImage supplies more generalised bitmap drawing than character fonts require, which somewhat slows down the printing. Although the speed difference is not noticeable when slowed writing is used, it becomes very noticeable when text is to be printed as fast as possible.

Although Borland graphics supports the loading of other fonts to be used through the OutText primitive, of a type called ``stroked'' fonts, they were found to be unacceptable for our uses:

• They can be drawn at any size on the screen that the caller wishes; but aliasing effects leave them lumpy and inconsistent in appearance. Since they would have to adapt to different runtime resolutions, this caused a serious legibility problem.
• Since each of their characters must be drawn graphically as a series of points, they are too slow to draw.