# HG changeset patch
# User Thinker K.F. Li <thinker@branda.to>
# Date 1249018243 -28800
# Node ID 1f900a67bd385eabd74345955961ce435404c1a3
# Parent  76b61d4472258b9ef98f0639f56b7afa19c37faa
Doc How to Define a Backend

diff -r 76b61d447225 -r 1f900a67bd38 dox/define_backend.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dox/define_backend.h	Fri Jul 31 13:30:43 2009 +0800
@@ -0,0 +1,29 @@
+/*! \page backend How to Define a Backend
+ *
+ * A backend is factory to initialize environment to make
+ * MadBufferfly available.  A backend should provide resources
+ * needed by MadButterfly, for example, to provide a surface
+ * that will show everything drawing on it.  It also translate and
+ * relay input events, mouse or keyboard, to MadButterfly.
+ * The tasks that a backend should do are listed following,
+ *  - to prepare a backend surface,
+ *  - to prepare a front surface,
+ *  - to translate and relay input events to MadButterfly,
+ *  - to handle a timer, and relay timeout events to MadButterfly.
+ * 
+ * The output device surface for X Window is a surface return by
+ * cairo_xlib_surface_create().  MadButterfly will copy everything
+ * from front surface to backend surface to show graphy to user.
+ * The copying is to avoid user find slowly redrawing.  The latency
+ * between X client and server can be large.  For this situation,
+ * we need a font surface as a buffer drawing, and copy image from
+ * front surface to backend surface after completion of a series
+ * of drawing.  A front surface can be an image surface for this
+ * situation.
+ *
+ * The input events of X Window should be translated to raw events of
+ * MadButterfly and sent them to rdman through notify_coord_or_shape()
+ * function.
+ *
+ * \see X_supp.c
+ */