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Next: Common Tools Abstractions Up: PLT Tools: DrScheme Extension Previous: Send us your Web

Implementing DrScheme Tools

Tools are designed for major extensions in DrScheme's functionality. To extend DrScheme to extend the appearance or the functionality the DrScheme window (say, to annotate programs in certain ways, or to add buttons on the frame) use a tool. The Static Debugger and the Syntax Checker are implemented as tools.

Libraries are for extensions of DrScheme that only want to add new functions and other values bound in the users namespace. See the DrScheme manual for more information on constructing libraries.

Tools rely heavily on MzScheme's units. See units for information on how to construct units. They also require understanding of libraries and collections

When DrScheme starts up, it looks in the tools subdirectory of the drscheme collection directory to determine which tools are installed. For each subdirectory of the tools directory, it looks for two files: unit.ss and sig.ss. If sig.ss exists it is loaded when all of the signatures of DrScheme are loaded. The file unit.ss is required to exist. It must evaluate to a unit that imports 6 units matching the signatures:

The drscheme:export^ signature contains the parameters defined in the parameters section, and the other classes described in the next subsections.

If the tools raises an error as it is loaded or invoked, DrScheme catches the error and displays a message box. Then, DrScheme continues to start up, without the tool.

For example, 

(unit/sig ()
  (import mred^
          mzlib:core^
          framework^
          [print-convert : mzlib:print-convert^]
          [drscheme : drscheme:export^]
          [zodiac : zodiac:system^])

  (message-box "tool example" "tool loaded"))

is a simple tool that opens a dialog as drscheme is started up.



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