Font Dialog and Device Font Considerations

There are two types of fonts:

• System fonts, which can be used for both displays and printers, and therefore, are generally more flexible.

• Device fonts, which are specific to a particular device. Device fonts for printers can be built-in or be installed with font cartridges by a user. Device fonts also can be available on diskette (also termed soft fonts) and can be downloaded to the printer as required by the printer driver.

  The advantage of device fonts is that, usually, they are printed in the highest resolution of the device and are faster than system fonts.

Note: Some printer drivers, in particular, the HP LaserJet (LASERJET) and the LaserPrinter (IBM4019) printer drivers provide an intermediate solution. An option on the job properties dialog enables system fonts to be downloaded to the printer as soft fonts.

As stated earlier, an application must provide the user with the ability to choose fonts and, in particular, to choose a device font over a system font to achieve better performance. A standard font dialog box should be used (see WinFontDlg).

When an application uses device fonts, and the output mixes text and graphics pictures, the device fonts are clipped per character. System fonts give more precise clipping to the pel. The following figure illustrates the results from clipping two lines of text: one generated in a system font; the other, in a device font.

Character Clipping Results for Device and System Fonts

The available device fonts can be queried, using GpiQueryFonts, in either an OD_INFO or an OD_QUEUED device context. Device fonts are returned with negative lMatch numbers. Then the appropriate logical font can be used after calling GpiCreateLogFont.

If, during the printing process, a logical font is not created, the printer driver uses its default font for the printer, which usually is 12-point Courier.

There are two design choices for device fonts:

• Use system fonts for the display. When printing, query the printer driver and attempt to choose a device font that closely matches the system font. If no match is found, then print using the system font. A device's font metrics and character spacing might not match exactly, so the printed output might not be exactly the same as the display.

• Use a printer font if the user selects one. Determine the metrics and find a system font that shares the same characteristics (for example, a style such as Courier or Serifed). The character string to be displayed is sent to the printer driver and the inter-character spacing is returned, using GpiQueryCharStringPos. The individual character positions are used when the string is sent to the display, using GpiCharStringPos with the flOptions parameter of CHS_VECTOR. While the display output can take longer to display to the screen, true WYSIWYG (What You See Is What You Get) is achievable.