This patch enables sharing of an nsAttrValue's MiscContainer between nodes for style rules. MiscContainers of type eCSSStyleRule are now refcounted (with some clever struct packing to ensure that the amount of memory allocated for MiscContainer remains unchanged on 32 and 64 bit). This infrastructure can be used to share most MiscContainer types in the future if we find advantages to sharing other types than just eCSSStyleRuley. A cache mapping strings to MiscContainers has been added to nsHTMLCSSStyleSheet. MiscContainers can be shared between nsAttrValues when one nsAttrValue is SetTo another nsAttrValue or when there is a cache hit in this cache. This patch also adds the ability to tell a style rule that it belongs to an nsHTMLCSSStyleSheet, with appropriate accessor functions to separate that from the existing case of belonging to an nsCSSStyleSheet.
The primary use case is to reduce memory use for pages that have lots of inline style attributes with the same value. This can happen easily with large pages that are automatically generated. An (admittedly pathological) testcase in Bug 686975 sees over 250 MB of memory savings with this change. Reusing the same MiscContainer for multiple nodes saves the overhead of maintaining separate copies of the string containing the serialized value of the style attribute and of creating separate style rules for each node. Eliminating duplicate style rules enables further savings in layout through style context sharing. The testcase sees the amount of memory used by style contexts go from over 250 MB to 10 KB.
Because the cache is based on the text value of the style attribute, it will not handle attributes that have different text values but are parsed into identical style rules. We also do not attempt to share MiscContainers when the node's base URI differs from the document URI. The effect of these limitations is expected to be low.
gfxTextObjectPaint::GetFillPattern/GetStrokePattern should take the destination's CTM
as a parameter in order to set up the pattern matrix correctly, since the pattern matrix
is combined with the CTM by cairo/Thebes --- but we want the pattern rendering to be
independendt of the CTM, instead depending only on the TM set up when we initialized
the gfxTextObjectPaint.
We make SVGTextObjectPaint store matrices that map device space to pattern space.
This adds entries for property aliases as though they are shorthands.
This fits with the CSS working group's recent resolution to describe
aliases as shorthands, recorded in
http://lists.w3.org/Archives/Public/www-style/2012Aug/0770.html .
The property_database.js entries themselves are copied from the
non-alias entries for the properties, with these changes:
(1) The property name is changed to the prefixed form
(2) The domProp entry is changed to the prefixed form
(3) Adding alias_for entries for each property.
(4) When type is CSS_TYPE_LONGHAND in the target of the alias, type for
the alias is CSS_TYPE_SHORTHAND_AND_LONGHAND and a subproperties
entry is added with the target of the alias.
There are also some indentation fixes to the copied entries in
property_database.js (made before they were copied, and thus affecting
the original as well).
This currently only affects the testing of overflow, but it will also
affect -moz-transform (and any other aliases implemented the same way)
after the later patches in this bug.
This special-cases text-decoration because text-decoration: inherit causes
the color to inherit in a way that we can't serialize the result (since
it's no longer "foreground"). (This isn't great; we might want to
consider fixing it somehow.)
Separate out background layers into separate display-list items, so that
backgrounds that are a mix of fixed and non-fixed layers will be treated
individually.
This propagates the non-inherited (in the nsChangeHint sense, not the
CSS inheritance sense) parts of the parent's change hint through
ReResolveStyleContext so that we can use them in
nsStyleContext::CalcDifference. In the cases where we don't know the
parent's hint, we assume the worst, that all the non-inherited hints
were present in the parent's style change.
This should be a significant performance improvement handling simple
style changes (such as a style attribute change setting a non-inherited
property) on elements with large numbers of descendants that have data
in ForceCompare structs that can't be stored in the rule tree (for
example, margins or widths in em or rem units).
This is in preparation for adding an additional caller.
nsChangeHint_NonInherited_Hints will be reintroduced in patch 6, but as
the maximum set of such hints rather than the minimal set, and with the
less confusing name nsChangeHint_Hints_NotHandledForDescendants.
