Re: calculating text length

[Owen Taylor <otaylor redhat com>]

On Wed, 2007-04-18 at 10:43 +0300, Tapani P�i wrote:
> Hello,
> 
> I have a performance problem with Matchbox window manager calculating
> window title width rather slowly with Pango when doing ellipsation for
> the title. The current algorithm is rather poor but produces good result
> and works nicely for short titles, however when our browser puts the
> title of a webpage as window title and webpage titles seem to sometimes
> be even 300 characters long ...
> 
> Current algorithm takes the title, goes from title's end to begin and
> inserts '...\0' to end and check if it would fit now. Result is always
> perfect. However it calls several Pango funcs when checking the width
> and besides of the algorithm I'd like to optimize width check aswell. It
> calls pango_itemize() and then pango_shape, pango_glyph_string_extents
> for each resulted item (word?) just like when rendering text. I thought
> one way would be to take 'average char width' and then calculate some
> pessimistic result out of that (?) I'd like to know if there's a quick
> way to have extents for all characters in a string or maybe some other
> way to quickly check how many characters of $string would fit in $w pixels.

Can't you just use the ellipsization feature of Pango? That's going to
be considerably faster than the algorithm you describe.

						- Owen