Ideally we'd make this property inaccessible to Web content style sheets, but
that seems hard since view-source and plain text documents seem to load in a
context that's very similar to Web content as far as the style system is
concerned. It doesn't matter much since it's quite safe and unlikely to be
discovered or used by anyone.
--HG--
extra : rebase_source : 009aafc992afd07fd76a9026afe0f6994b4b214a
This adds CSS parser error reporting for parsing of custom properties
and normal properties that have variable references.
When re-parsing a normal property that had a variable reference, we
report any parse error to be at the beginning of the property value.
This is because it is difficult to keep track of where exactly each
variable substitution came from to point to the particular value
that would have caused the parse error. For example, with this:
:root {
var-a: 1px 2px;
var-b: 3px var(a);
}
p {
margin: var(a) var(b);
}
we would end up resolving the value of 'margin' to:
" 1px 2px 3px 1px 2px"
In this string, the parse error occurs when we encounter the final
"2px", but by this point we don't know where that value came from.
So instead we just point to the line on which 'margin' was declared.
We extend ErrorReporter with an OutputError overload that takes the
specific line and column number to use in the error report to get this
right, and we store the line and column number for each token stream
we parse on the nsCSSValueTokenStream object.
This re-parses property values at computed value time if
they had a specified value that was a token stream. We add
a function nsRuleNode::ResolveVariableReferences that looks
at all the values in the nsRuleData and calls in to a new
nsCSSParser::ParsePropertyWithVariableReferences function if they have a
token stream value.
We add a nsCSSExpandedDataBlock::MapRuleInfoInto function that will
take the re-parsed property value and copy it back into the nsRuleData.
nsRuleNode::ResolveVariableReferences returns whether any variables
were attempted to be resolved, so that nsRuleNode::WalkRuleTree wil
recompute the rule detail in case any became 'inherit'.
This adds a new eCSSUnit_SharedList type for nsCSSValue, which is a
reference counted object that contains an nsCSSValueList. We need this
so that nsStyleDisplay::mSpecifiedTransform can hold a strong reference
to a specified transform list value. When 'transform' is specified
using a variable reference, the resulting nsCSSValue does not stick
around in the Declaration object, so we wouldn't be guaranteed that
it lives long enough for nsStyleDisplay to keep referencing it.
We add a new class CSSVariableResolver whose job is to take the
inherited computed variables and the specified variable declarations and
to perform cycle removal and resolution of the variables, storing the
result in the CSSVariableValues object on an nsStyleVariables. We use
CSSVariableResolver in nsRuleNode::ComputeVariablesData.
The variable resolver does this:
1. Asks the CSSVariableValues and CSSVariableDeclarations objects
to add their variables to it.
2. Calls in to a new nsCSSParser function
EnumerateVariableReferences that informs the resolver which
other variables a given variable references, and by doing so,
builds a graph of variable dependencies.
3. Removes variables involved in cyclic references using Tarjan's
strongly connected component algorithm, setting those variables
to have an invalid value.
4. Calls in to a new nsCSSParser function ResolveVariableValue
to resolve the remaining valid variables by substituting variable
references.
We extend nsCSSParser::ParseValueWithVariables to take a callback
function to be invoked when encountering a variable reference. This
lets EnumerateVariableReferences re-use ParseValueWithVariables.
CSSParserImpl::ResolveValueWithVariableReferences needs different
error handling behaviour from ParseValueWithVariables, so we don't
re-use it.
CSSParserImpl::AppendImpliedEOFCharacters is used to take the
value returned from nsCSSScanner::GetImpliedEOFCharacters while
resolving variable references that were declared using custom
properties that encountered EOF before being closed properly.
The SeparatorRequiredBetweenTokens helper function in nsCSSParser.cpp
implements the serialization rules in CSS Syntax Module Level 3:
https://dvcs.w3.org/hg/csswg/raw-file/3479cdefc59a/css-syntax/Overview.html#serialization
This adds an nsStyleVariables on which computed variable values
will be stored. We don't actually have any properties assigned to
nsStyleVariables; eCSSPropertyExtra_Variables which we added earlier
isn't a real property. To avoid compiler errors for gVariableFlags
being a zero length array, we stick a dummy entry in there.
nsRuleNode::ComputeVariablesData does nothing for the moment.
nsStyleVariable nsChangeHint calculations always return 0, as later
we will compare the actual properties that reference variables to
see what changes are required for them.
