[libgd] README: add more background

[Marc-Andre Lureau <malureau src gnome org>]

commit 7ae66844d277c7cb1c90d8669104585cbc23748b
Author: Marc-Andrà Lureau <marcandre lureau gmail com>
Date:   Mon Aug 20 21:06:53 2012 +0200

    README: add more background

 README |   30 ++++++++++++++++++++++++++++++
 1 files changed, 30 insertions(+), 0 deletions(-)
---
diff --git a/README b/README
index eb61aec..83be2aa 100644
--- a/README
+++ b/README
@@ -19,10 +19,39 @@ a specific development version.
 GObject Introspection based bindings generation such as Javascript or
 Vala are also supported.
 
+More Background
+---------------
+
 libgd originates from the GNOME Documents project (written by Cosimo
 Cecchi), which was one of the first application to follow the novel
 GNOME 3 application design.
 
+Since other applications have similar needs, it makes sense to try to
+reuse and improve the exisiting work. However, the design being not
+frozen, and the code being not yet mattured enough and proven, it is
+not possible for the developpers to guarantee API and propose the
+addition to the respective projects (Gtk+, or GLib for example).
+
+Traditionnally, this problem is solved by copying often outdated
+snippets of code around, hardly centralized (libegg).
+
+In the past, there used to be some common GNOME application libraries
+above Gtk+ which has been slowly deprecated in favour of Gtk+ (gnomeui
+and friends).
+
+All approaches have pros and cons. A configurable git submodule
+approach has the following advantages:
+
+- no direct code copying necessary because API/ABI breakage (history
+  is preserved etc..)
+- code is shared and maintained in a common project
+- you can stick to a particular upstream version, or branch off your
+  own version if needed (hopefully you find your way back upstream)
+- update the submodule version when your project is ready
+- the libgd options should help you to configure a library to suit
+  your needs, taking care of some of autofoo stuff for you
+
+
 Usage
 =====
 
@@ -79,3 +108,4 @@ TODO
 - eventually add documentation generation
 - some licensing check
 - more modularity (not all in libgd.m4/Makefile.am)
+- CSS styling and data: shared only with gnome-themes-standard?
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