The variable videomode tells a PXL program what type of graphic controller and which of the available modes should be used. Table vmodes contains a list of the possible videomode numbers. Note, however, that depending on the implementation and version not all numbers are possible in each version.
The variable videomode will usually be set in the startup file startup.pxl, since the display device is a system wide parameter, useful for each program. Some programs, however, may need special modes and thus choose to set videomode themselves. It may also be set in the parameter file or in the command line using option v. The default mode for any program is one that fits most demands.
screenwidth = 2260 screenheight = 1520in the file startup.pxl. Thus any program that reads this startup file would treat the display area as being 2260 pxlm wide and 1560 pxlm high. This also means that if the program uses other experimental variables that contain size parameters of screen objects, these have to be specified using the same units.
If a program uses a special mode of the graphic device then the size of the displayable area may change. In this case the parameter file may be used to set correct values for screensize and screenwidth. There is a demo application program called scrnsize (see Chapter demos) that may be used to find out what the correct size parameters are and modify startup.pxl accordingly.
If the only transformation to be applied is size scaling then one may also use screen raster fonts. For small raster font sizes PXL uses the graphics device's built in screen font. For larger raster font sizes PXL may use any raster font generated by D. Knuth's Metafont program (Knuth, 1991b) and coded as a PK-file. The PXL standard distribution currently contains a single sans serif font from Knuth's Computer Modernfamily of typefaces (Knuth, 1987), named dcss10 from 10 mm up to about 3 cm in size.
Application programs select fonts by their names and their size. Most aplications will use the experimental parameters msgfont for message text and textfont for text stimuli and msgsize and textsize for the respective sizes. The available font names are given in Table fontab. The name scrn selects a raster font. The raster font actually used is defined by the parameter rasterfont. Its default value is dcss10 which selects a sans serif font. dcr10 selects a roman font (available, but not contained in the standard distribution package). If the font size requested is less than the smallest available raster font size then the device's built in screen raster font is selected. Thus setting textfont and msgfont to "scrn" and setting the respective font size parameters textsize and msgsize to 1 selects the device's built in screen font. In this case the program will not need any external font file. This setting is the library default also.
PXL can use any TeX-Font as its raster font. Simply give rasterfont the name of the font file and make sure that it is accessible by the program. The vector font files are located in subdirectory \pxl\etc . Their file extension is chr. The raster font files are located in a subdirectory of directory \pxl\texfonts . The subdirectory name is the name of the font and the single files are named according to the resolution. Thus as an example the full names \pxl\texfonts\dcss10\200.pk and \pxl\texfonts\dcss10\3024.pk access the smallest and the largest dcss10 raster font files of the PXL standard distribution package. These have been created for a 200 and a 3024 dpi resolution device respectively. You can use Donald Knuth's \sf Metafont program (Knuth, 1985) for creating any new raster font sizes.
Installation of a different set of raster font files is easy. The fonts should be created for a 200 dpi device, since PXL uses this device resolution to compute the font name from the textsize and msgsize parameter. The font files should be copied into a subdirectory of \pxl\texfonts whose name is the new font name. This name must be given by the parameter rasterfont. Thus if the new font name is dcrm10 then set
rasterfont = dcrm10The single font files in directory \pxl\texfonts\dcrm10 should then be named 200.pk, ...acording to their size.
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