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How To Add New Xrc Handler

docs/contributing/how-to-add-new-xrc-handler.md

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How to add a new XRC handler

  1. Purpose

This note describes what needs to be done to add a new XRC handler, i.e. add support for loading the objects of some class wxFoo from XRC.

  1. Implement the handler

By convention, the XRC handler for a class wxFoo declared in wx/foo.h is called wxFooXmlHandler and is declared in the file wx/xrc/xh_foo.h (this last rule wasn't always respected in the past, however it's not a reason to not respect it in the future). The steps for adding a new handler are:

  • Add handler declaration in include/wx/xrc/xh_foo.h, it will usually be the same as in the other files so you can get inspiration for your brand new handler from e.g. wx/xrc/xh_srchctrl.h. Notice the use of wxUSE_FOO if wxFoo is guarded by this symbol.

  • Add implementation in src/xrc/xh_foo.cpp: again, it will be almost always very similar to the existing controls. You will need to add support for the control-specific styles.

  1. Update the other files

There are a few other files to update to make wxWidgets aware of the new handler:

  • Add the new files created above to build/bakefiles/files.bkl: search for "xh_srchctrl" to see where you need to add them

  • Add #include "wx/xrc/xh_foo.h" to wx/xrc/xh_all.h.

  • Register the new handler in wxXmlResource::InitAllHandlers() in src/xrc/xmlrsall.cpp

  1. Update the sample

Demonstrate that the new handler works by adding a control using it to samples/xrc/rc/controls.xrc.