Windows Glyph Processing
By Sachin Karnik - Microsoft Corporation
| The demands of these application and font support for these complex scripts require all the features of character string processing and glyph substitution and positioning that are available through OpenType, Uniscribe and OTLS. |
| In addition, because glyph processing is an absolute requirement of their rendering, complex scripts demand the attention of developers hoping to produce fonts and software for the significant markets that use them. Sophisticated typographic controls for non-complex scripts should not be treated as secondary to complex script support or necessarily of a lower priority. It is likely, however, that many application developers will first encounter system components like Uniscribe and libraries like OTLS during internationalization development involving complex scripts. |
| Windows glyph processing model does not force particular solutions on application developers, although it does expect certain things. For example, applications are responsible for storing backing strings of text codepoints, for buffering them when necessary for line justification and breaking (this is particularly crucial for complex scripts), and for all aspects of memory management. |
| Applications are entirely free to choose how to present layout features to users, and free to select which features to support. It should be noted that all the line layout, character reordering and glyph substitution and positioning features discussed in this article can be implemented entirely at the application level, or across application suites, using private code and DLLs. However, this requires major investments in code writing and maintenance, and in understanding implementation of individual scripts with very complex requirements. |
| Developers can insulate themselves from script support issues and from much of the nuts and bolts of glyph processing by using the Uniscribe APIs and helper functions in the OTLS library. It always remains possible for client applications to override or supplement Windows glyph processing. |