735439 - reorder fields in gfxFontStyle for more efficient packing

Status: RESOLVED FIXED

(Core :: Graphics, defect)

Description

[Jonathan Kew [:jfkthame]]

Attachment: patch, optimize order of fields in gfxFontStyle to save space

The attached patch rearranges fields so that sizeof(gfxFontStyle) drops from 48 to 40 bytes on a 64-bit OS X build. Given that we can easily have thousands of gfxFontStyle records alive at any one time, this seems like a worthwhile saving.

Comment 1

[John Daggett (:jtd)]

Comment on attachment 605533 [details] [diff] [review]
patch, optimize order of fields in gfxFontStyle to save space


r+ with fix noted below.

> +    // The style of font (normal, italic, oblique)
> +    PRUint8 style : 6;

This should be 'style : 2', there's no real reason to be doing the
padding ourselves, this leads to bytes inadvertently being added when
new fields are added, as seems to be the case in the original 'style :
7' definition.

Comment 2

[Jonathan Kew [:jfkthame]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/5f438ea9ded4

Comment 3

[Marco Bonardo [:mak]]

https://hg.mozilla.org/mozilla-central/rev/5f438ea9ded4

Comment 4

[:Ms2ger (he/him; ⌚ UTC+1/+2)]

Comment on attachment 605533 [details] [diff] [review]
patch, optimize order of fields in gfxFontStyle to save space

Review of attachment 605533 [details] [diff] [review]:
-----------------------------------------------------------------

::: gfx/thebes/gfxFont.h
@@ +165,5 @@
> +    // Say that this font is used for print or print preview.
> +    bool printerFont : 1;
> +
> +    // The style of font (normal, italic, oblique)
> +    PRUint8 style : 6;

Note that MSVC apparently only packs members of the same type.