Differences in Application Programming
About the Font Mapper
The font is dynamic resource in the system. Because user can customize the set of fonts to optimize his or her working environment, the set of fonts are vary between the systems. The font mapper absorbs these differences. It reduces application development work load, and increases the document portability between the systems.
Different from OS/2 logical font, the Windows logical font is truly device
independent. It is created without any device information. It just describes
the 'desired logical properties' of the font. Because the set of available
fonts are vary between the physical devices, the font mapper is expected
to solve these differences. This satisfies the minimum requirement from
applications to achieve the WYSIWYG functionality.
About the Character Set
In Windows platforms, the system decides the output language from the character set specified in the realized font. Because the font mapper treats the character set as the most significant attribute, application can expect that the text is drawn at least with the desired set of characters, even if the extact matching font is not installed in the system.
Because every Windows font has specific character set id in the font metrics, and the font for different language has different facename qualifier or different scriptname, the user can select an output language just by selecting a font for specific language on the font dialog. Applications can use this information as another trigger to switch the input language.