  The variation of the solar diameter is the subject of hot debates due to the
possible effect on Earth climate and also due to different interpretations of
long period solar variabilities, including the total solar irradiance. We
shortly review the topic and show that rather long term variations,
corresponding to a length well over a a solar magnetic cycle, are interesting
to consider. The very recently launched mission "Picard" is entirely devoted to
the topic but will just permit a short term evaluation. At the time of the last
total solar eclipse of 11/07/2010, several experiments were prepared to
precisely measure the transit time of the Moon related to the precise value of
the solar diameter. Preliminary results coming from the use of a specially
designed CNES photometer, put on different atolls of the French Polynesia, are
presented. In addition the results of new experiments devoted to fast
observations of flash spectra, including their precise chronodating, are
illustrated and discussed. A new definition of the edge of the Sun, free of
spurious scattered light effects strongly affecting all out of eclipse
observations, is emerging from these observations, in agreement with the most
advanced attempts of modelling the outer layers of the photosphere. We also
argue for a definite answer concerning the solar diameter measurement from
eclipses based on a better precision of lunar profiles coming from lunar
altimetry space experiments which will be possible in the following decades.
