Re: [Libreoffice-commits] core.git: editeng: Eliminate unecessary padding in classes

On 11/04/2015 09:16 AM, Daniel Robertson wrote:
> commit f57a6593e21d45008173352fc29ededdbc2c8878
> Author: Daniel Robertson <danlrobertson89@gmail.com>
> Date:   Tue Nov 3 14:14:08 2015 -0500
>
>      editeng: Eliminate unecessary padding in classes
>
>      Edit the order of SvxLRSpaceItem and PaintFirstLineInfo members to
>      remove unecessary padding due to data alignment.
>
>      Change-Id: Icf2c92ef86a32384e51d1cb6f1a079b10995dfd5
>      Reviewed-on: https://gerrit.libreoffice.org/19763
>      Tested-by: Jenkins <ci@libreoffice.org>
>      Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
[...]
> diff --git a/include/editeng/lrspitem.hxx b/include/editeng/lrspitem.hxx
> index 40da999..94daed8 100644
> --- a/include/editeng/lrspitem.hxx
> +++ b/include/editeng/lrspitem.hxx
> @@ -50,15 +50,15 @@
>
>   class EDITENG_DLLPUBLIC SvxLRSpaceItem : public SfxPoolItem
>   {
> -    short   nFirstLineOfst;     // First-line indent _always_ relative to nTxtLeft
>       long    nTxtLeft;           // We spend a sal_uInt16
>       long    nLeftMargin;        // nLeft or the negative first-line indent
>       long    nRightMargin;       // The unproblematic right edge
>
>       sal_uInt16  nPropFirstLineOfst, nPropLeftMargin, nPropRightMargin;
> +    short   nFirstLineOfst;     // First-line indent _always_ relative to nTxtLeft

With micro-optimization changes like these, I would leave it to some 
domain expert to decide whether it is actually worth it (i.e., whether 
on the one hand the existing member order had been chosen deliberately, 
to aid human comprehension, and whether on the other hand enough 
instances of that class are created to warrant any such optimization).

>       bool        bAutoFirst  : 1;    // Automatic calculation of the first line indent
> -    bool        bExplicitZeroMarginValRight;
> -    bool        bExplicitZeroMarginValLeft;
> +    bool        bExplicitZeroMarginValRight : 1;
> +    bool        bExplicitZeroMarginValLeft : 1;

It is unclear whether that is an optimization or a pessimization.