D29684: Improve opengl debug messages

zzag added inline comments.

INLINE COMMENTS

> zzag wrote in scene_opengl.cpp:414
>   while (message[length] == '\0')
>       length--;
> 
> will cutoff the last character, e.g. if we have "abcd\0" then only "abc" will be printed. More conservative trimming algorithm will look something like this
> 
>   while (message[length - 1] == '\n' || message[length - 1] == '\r')
>       --length;

while (length && isspace(message[length - 1])
      --length;

this one is a bit more safer

REPOSITORY
  R108 KWin

REVISION DETAIL
  https://phabricator.kde.org/D29684

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