initial commit

Signed-off-by: Peter Siegmund <mars3142@noreply.mars3142.dev>

libs/wxWidgets-3.3.1/docs/contributing/how-to-add-new-xrc-handler.md

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+How to add a new XRC handler
+============================
+
+0. 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.
+
+
+2. 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
+
+
+3. Update the sample
+--------------------
+
+Demonstrate that the new handler works by adding a control using it to
+samples/xrc/rc/controls.xrc.