[LAD] memory leak assistance

[Paul Davis]

On Wed, Dec 30, 2009 at 7:47 AM, hermann <brummer- at web.de> wrote:

> We use also level meters in guitarix and jcgui, what we do to create the
> notch scale is, move it to a background box, a simple hbox, witch we
> connect with a expose call. This way the values and scale only redraw
> when needed. This is the call we use:

ardour's Gtkmm2ext::FastMeter optimizes even more. we compute the
difference between the last drawn instance of the meter and the new
appearance and only draw that the delta. this means that we often get
away with drawing just a single row of pixels.

http://subversion.ardour.org/svn/ardour2/branches/2.0-ongoing/libs/gtkmm2ext/fastmeter.cc

see the vertical_expose() and horizontal_expose() methods. Note that
we are also using precomputed pixbufs and just blitting them.