Generating the SWT JNI Code for SWT 3.4
All of the C code used by SWT is generated by the JNIGeneratorApp
application from the org.eclipse.swt.tools project in Eclipse CVS.
This page describes how to use this tool when fixing bugs or adding
features to SWT.
Adding native methods
- Add the function prototype in OS.java, copying the style and structure
of the other functions in that file.
- Run JNIGeneratorAppUI from org.eclipse.swt.tools. This
is a GUI application for editing the metadata and a front end to the
generation phase. Select the appropriate class in the list and then
find the method you added in OS.java.
- Set any flags and modify the casts for any primitive types.
- Hit Generate All to generate the C code and metadata files.
- Refresh the org.eclipse.swt project to tell Eclipse about the C
changes, and refresh the org.eclipse.swt.tools project to see the
- Compile the new C code and copy the new libraries to the appropriate
fragment. To compile the code, right-click on the build.xml file in the
Eclipse SWT PI/ws/library directory for your window system, and choose
"Run As -> Ant Build...". Select the JRE tab, and check "Run in the same JRE as the workspace".
Select the Refresh tab, and check "Refresh resources upon completion" to refresh your workspace
after running the build to ensure Eclipse picks up the fresh binaries. Now select the "Run" button.
Often, methods return values or require parameters as a C struct. To
add a new structure, simply add a new class in the same package as
the OS.java file which matches the definition of the C structure.
This will be picked up and correctly handled by JNIGeneratorApp.
If a struct is input-only or output-only, this information can be used
by JNIGeneratorApp to generate more efficient C code. Use the
flags attribute of the native function to indicate this in the
- For GTK+ and Motif, all native functions must be wrapped in locking
code. When adding functions, simply copy the style and structure of the
other native functions.
- Many functions on Mac OS X return structs which use unions. For
an example of how to add the markup for a union, see the
ControlFontStyleRec structure and its metadata.
And there you go! If you're having trouble, please post to the SWT
mailing list or file a new bug in bugzilla.