The Fonts classes

A device-independent font specification is provided —TFontSpec (in the twips domain) — and the means to map the specification to a concrete device-dependent font CFont* (in the device domain). The GetNearestFontInTwips() function provides a means of getting from a TFontSpec to the CFont* which is the nearest font in the graphics device’s typeface store.

Due to the necessary number of calculations and typeface store searches involved in the GetNearestFontToMaxHeightInTwips() function, a font cache, holding a cache of TFontSpec - CFont* relations for the current graphics map, is provided as an alternative to invoking this function.

As the fonts supported by the device are stored in a device dependent form (TTypefaceSupport), pixels to twips functions are also provided to allow the list of supported font sizes to be presented in user dialogs as twips/points rather than pixels.

The typeface store mechanism allows any font to be used by more than one client and keeps an access count of the number of clients using a particular font. This access count is increased and decreased by the GetNearestFontToMaxHeightInTwips() and ReleaseFont() functions respectively, and a font is only deleted from memory when its access count reaches zero.