xbmc/xbmc — pull request #3717 by bavison (2013-11-26 21:51:59+00:00)
Title: Add caching of infolabels

The functions CGUIInfoLabel::GetLabel and CGUIInfoLabel::GetItemLabel take
a number of strings returned from CGUIInfoManager::GetImage or
CGUIInfoManager::GetLabel, and combine them with various constant strings
which were determined during CGUIInfoLabel::Parse.

Rather than perform all the string operations on every call, this patch
changes to use a two-pass process: first it queries all the GetImage/GetLabel
strings, and then only if at least one of them has changed does it bother
rebuilding the resultant string - otherwise it re-uses the copy built on a
preceding call.

CGUIInfoLabel::GetLabel/GetItemLabel are also changed to return string
references, rather than forcing an additional string copy.

I have measured the effect while the Videos window of the default skin was
open (but idle) on a Raspberry Pi, and this reduced the CPU usage by 0.8%
from 36.2% to 35.4%:

Before After
Mean StdDev Mean StdDev Confidence Change
IdleCPU% 36.2 0.5 35.4 0.5 99.9% +2.2%