clean up doccomments and formatting in texplain content handler

There is an intention to replace the render interface and it will be
helpful to reduce the size of the exposed API as much as
possible. This is the first step towards that goal.

render/textplain.h

@@ -17,12 +17,14 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-/** \file
- * Content for text/plain (interface).
+/**
+ * \file
+ *
+ * Interface to content handler for plain text.
  */
 
-#ifndef _NETSURF_RENDER_TEXTPLAIN_H_
-#define _NETSURF_RENDER_TEXTPLAIN_H_
+#ifndef NETSURF_RENDER_TEXTPLAIN_H
+#define NETSURF_RENDER_TEXTPLAIN_H
 
 #include <stddef.h>
 #include "netsurf/mouse.h"
@@ -32,20 +34,106 @@ struct hlcache_handle;
 struct http_parameter;
 struct rect;
 
+/**
+ * Initialise the text content handler
+ *
+ * \return NSERROR_OK on success else appropriate error code.
+ */
 nserror textplain_init(void);
 
-/* access to lines for text selection and searching */
+
+/**
+ * Retrieve number of lines in content
+ *
+ * \param[in] c Content to retrieve line count from
+ * \return Number of lines
+ */
 unsigned long textplain_line_count(struct content *c);
+
+
+/**
+ * Retrieve the size (in bytes) of text data
+ *
+ * \param[in] c Content to retrieve size of
+ * \return Size, in bytes, of data
+ */
 size_t textplain_size(struct content *c);
 
+
+/**
+ * Return byte offset within UTF8 textplain content.
+ *
+ * given the co-ordinates of a point within a textplain content. 'dir'
+ * specifies the direction in which to search (-1 = above-left, +1 =
+ * below-right) if the co-ordinates are not contained within a line.
+ *
+ * \param[in] c   content of type CONTENT_TEXTPLAIN
+ * \param[in] x   x ordinate of point
+ * \param[in] y   y ordinate of point
+ * \param[in] dir direction of search if not within line
+ * \return byte offset of character containing (or nearest to) point
+ */
 size_t textplain_offset_from_coords(struct content *c, int x, int y, int dir);
+
+
+/**
+ * Given a range of byte offsets within a UTF8 textplain content,
+ * return a box that fully encloses the text
+ *
+ * \param[in] c     content of type CONTENT_TEXTPLAIN
+ * \param[in] start byte offset of start of text range
+ * \param[in] end   byte offset of end
+ * \param[out] r    rectangle to be completed
+ */
 void textplain_coords_from_range(struct content *c,
 		unsigned start, unsigned end, struct rect *r);
+
+/**
+ * Return a pointer to the requested line of text.
+ *
+ * \param[in] c        content of type CONTENT_TEXTPLAIN
+ * \param[in] lineno   line number
+ * \param[out] poffset receives byte offset of line start within text
+ * \param[out] plen    receives length of returned line
+ * \return pointer to text, or NULL if invalid line number
+ */
 char *textplain_get_line(struct content *c, unsigned lineno,
 		size_t *poffset, size_t *plen);
+
+
+/**
+ * Find line number of byte in text
+ * 
+ * Given a byte offset within the text, return the line number
+ * of the line containing that offset.
+ *
+ * \param[in] c       content of type CONTENT_TEXTPLAIN
+ * \param[in] offset  byte offset within textual representation
+ * \return line number, or -1 if offset invalid (larger than size)
+ */
 int textplain_find_line(struct content *c, unsigned offset);
-char *textplain_get_raw_data(struct content *c,
-		unsigned start, unsigned end, size_t *plen);
+
+
+/**
+ * Return a pointer to the raw UTF-8 data, as opposed to the reformatted
+ * text to fit the window width. Thus only hard newlines are preserved
+ * in the saved/copied text of a selection.
+ *
+ * \param[in] c     content of type CONTENT_TEXTPLAIN
+ * \param[in] start starting byte offset within UTF-8 text
+ * \param[in] end   ending byte offset
+ * \param[out] plen receives validated length
+ * \return pointer to text, or NULL if no text
+ */
+char *textplain_get_raw_data(struct content *c, unsigned start, unsigned end, size_t *plen);
+
+
+/**
+ * Get the browser window containing a textplain content
+ *
+ * \param[in] c text/plain content
+ * \return the browser window
+ */
 struct browser_window *textplain_get_browser_window(struct content *c);
 
 #endif