===== .scheme files =====

These define the fonts, colours, styles and keywords for languages that Programmer's Notepad (via Scintilla) has built-in support for. PN contains code that parses/lexes and understands a lot of languages already. These files surface and configure that support.

===== .schemedef files =====
 
These define the syntax for a language as well as the fonts, colours... The files are interpreted by a plugin for PN called customscheme.lexer which provides code to tell PN how to interpret text according to the rules in the .schemedef.

===== key attribute =====
 
As PN scans the text in a file it assigns every character in the file a "style", represented by a key.
Unfortunately each different built-in language can and often does use the keys to mean different things. So in C++ style 5 is used for keywords whereas HTML uses style 5 for numbers. There is one definitive source of information mapping key numbers to meanings, and that's the .properties files shipped with the SciTE distribution - SciTE is the test editor developed alongside Scintilla.

One style number that is almost always unchanged is that 32 is the default text style - normally this means text with no specific meaning.

When using a .schemedef file, the style keys are fixed:

  * 32: Default 
  * 1: Line Comment Style 
  * 2: Block Comment Style 
  * 3: First Identifiers Type 
  * 4: Numbers 
  * 5: Keywords 
  * 6: Keywords 2 
  * 7: Keywords 3 
  * 8: Keywords 4 
  * 9: Keywords 5 
  * 10: First String Type 
  * 11: Second String Type 
  * 12: Pre-processor 
  * 13: Second Identifiers Type 

===== Keywords =====

The limitation to keyword sets is defined by two hard limits: The first is that Scintilla supports a fixed maximum number of keyword sets, currently 8. The second is that each language lexer only uses the keyword sets that the author thought were necessary - this means that often a language will support only one or two sets of keywords. The .schemedef lexer supports 5 as when it was developed that was the Scintilla limit. 

===== User Configuration and Caches =====

The changes a user makes to fonts and colours are not stored in the original .scheme or .schemedef files, the configuration of these things is instead stored in a file called UserSettings.xml in the per-user PN application data directory. Unless you're using the portable edition of PN, this will likely be here:

Vista: c:\users\[your username]\AppData\Roaming\Echo Software\PN2
XP: c:\documents and settings\[your username]\Application Data\Echo Software\PN2

The configuration in usersettings.xml is applied to the schemes you have installed, and the result is cached in a binary format in the .cscheme files you'll find in that directory.