Can include date & time in plot title

This was requested in issue #28. It may not do everything that was
wanted, but it is better than nothing.

Signed-off-by: Jim Easterbrook <jim@jim-easterbrook.me.uk>

src/pywws/Plot.py

@@ -239,6 +239,11 @@
 ``<title>Today's weather</title>``. This title appears at the very top
 of the graph, outside any plot area.
 
+.. versionadded:: 15.06.0.dev1301
+   If the title contains any "%%" characters it will be used as a
+   strftime style format string for the datetime of the stop value. This
+   allows you to include the graph's date or time in the title.
+
 subplot
 ^^^^^^^
 
@@ -608,6 +613,10 @@ def DoPlot(self, input_file, output_file):
         if title:
             if sys.version_info[0] < 3:
                 title = title.encode(self.encoding)
+            if '%' in title:
+                x_hi = (self.x_hi -
+                        self.utcoffset).replace(tzinfo=utc).astimezone(Local)
+                title = x_hi.strftime(title)
             title = 'title "%s"' % title
         of.write('set multiplot layout %d, %d %s\n' % (self.rows, self.cols, title))
         # do actual plots

src/pywws/WindRose.py

@@ -2,7 +2,7 @@
 
 # pywws - Python software for USB Wireless Weather Stations
 # http://github.com/jim-easterbrook/pywws
-# Copyright (C) 2008-14  Jim Easterbrook  jim@jim-easterbrook.me.uk
+# Copyright (C) 2008-15  pywws contributors
 
 # This program is free software; you can redistribute it and/or
 # modify it under the terms of the GNU General Public License
@@ -80,12 +80,6 @@
 This is the root element of the graph XML file. It does not have to be
 called "graph", but there must be exactly one root element.
 
-windrose
-^^^^^^^^
-
-A separate plot is drawn for each windrose element, but all share the
-same time period.
-
 start
 ^^^^^
 
@@ -148,10 +142,22 @@
 title
 ^^^^^
 
-Sets the overall title of the plots. A single line of text, for
-example: ``<title>Today's weather</title>``. This title appears at the
+Sets the overall title of the plots. A single line of text, for example:
+``<title>Today's wind direction</title>``. This title appears at the
 very top, outside any plot area.
 
+.. versionadded:: 15.06.0.dev1301
+   If the title contains any "%%" characters it will be used as a
+   strftime style format string for the datetime of the stop value. This
+   allows you to include the graph's date or time in the title, for
+   example: ``<title>Wind over 24 hours ending %%H:%%M (mph)</title>``
+
+windrose
+^^^^^^^^
+
+A separate plot is drawn for each windrose element, but all share the
+same time period.
+
 xcalc
 ^^^^^
 

src/pywws/__init__.py

@@ -1,3 +1,3 @@
-__version__ = '15.06.0.dev1300'
-_release = '1300'
-_commit = '744a4ff'
+__version__ = '15.06.0.dev1301'
+_release = '1301'
+_commit = '0c54680'