Documentation work.

docs/input.dox

@@ -146,16 +146,30 @@ The `GLFW_KEY_LAST` constant holds the highest value of any
 [named key](@ref keys).
 
 
-@subsection input_char Unicode character input
+@subsection input_char Text input
 
-If you wish to receive Unicode code point input, set a character callback.
+GLFW supports text input in the form of a stream of
+[Unicode code points](https://en.wikipedia.org/wiki/Unicode), as produced by the
+operating system text input system.  Unlike key input, text input obeys keyboard
+layouts and modifier keys and supports composing characters using
+[dead keys](https://en.wikipedia.org/wiki/Dead_key).  Once received, you can
+encode the code points into
+[UTF-8](https://en.wikipedia.org/wiki/UTF-8) or any other encoding you prefer.
+
+Because an `unsigned int` is 32 bits long on all platforms supported by GLFW,
+you can treat the code point argument as native endian
+[UTF-32](https://en.wikipedia.org/wiki/UTF-32).
+
+There are two callbacks for receiving Unicode code points.  If you wish to
+offer regular text input, set a character callback.
 
 @code
 glfwSetCharCallback(window, character_callback);
 @endcode
 
 The callback function receives Unicode code points for key events that would
-have led to regular text input on that platform.
+have led to regular text input and generally behaves as a standard text field on
+that platform.
 
 @code
 void character_callback(GLFWwindow* window, unsigned int codepoint)
@@ -163,9 +177,9 @@ void character_callback(GLFWwindow* window, unsigned int codepoint)
 }
 @endcode
 
-If you wish to receive all Unicode code point events generated by the system, or
-just want to know exactly what modifier keys were used, set a character with
-modifiers callback.
+If you wish to receive even those Unicode code points generated with modifier
+key combinations that a plain text field would ignore, or just want to know
+exactly what modifier keys were used, set a character with modifiers callback.
 
 @code
 glfwSetCharCallback(window, charmods_callback);