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LocationSolver: implement support for elided elements (#1128)

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when used in a pattern for matching against the UI tree,
an element marked as UIC_ELIDED = "." is treated as existentially quantified.

This means, we assume / verify there *is* an element at that level,
but we do not care about what this element actually is. Within the
implementation, the handling is similar to a wildcard, yet such a
spec is not classified as a wildcard (it *is* an explicit element,
just not explicitly named).

The relevant consequence is that such an element matches at a leaf
position, while match on wildcards on leaf positions is prohibited,
to prevent arbitrary and nonsensical wildcard matches against
open ended patterns. Especially we need such an existential pattern
to express a rule to create elements from scratch, but within a
specific window with arbitrary (but existing) perspective.
This commit is contained in:
Fischlurch 2018-02-16 04:34:45 +01:00
parent 6665fb68d6
commit 0b21e816e3
2 changed files with 7 additions and 2 deletions
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4
src/gui/interact/ui-coord-resolver.cpp
View file

@ -129,6 +129,7 @@ namespace interact {
{
return patt == Symbol::ANY
or patt == Symbol::EMPTY
or patt == UIC_ELIDED // "existentially quantified"
or (isAnchored() and curr == res_.anchor and depth == UIC_WINDOW);
}; // transitive argument: assuming res_.anchor was computed for
// the same coordinate pattern used here for patch resolution
@ -153,7 +154,8 @@ namespace interact {
coverage.setAt (depth,curr); // record match rsp. interpolate wildcard into output
iter.expandChildren(); // next iteration will match one level down into the tree
}
return patt == curr; // only direct match counts as (partial) solution
return patt == curr // direct match counts as (partial) solution
or patt == UIC_ELIDED; // existentially quantified elements also accepted
})
.filter ([&](auto& iter)
{

5
src/gui/interact/ui-coord-resolver.hpp
View file

@ -550,7 +550,9 @@ namespace interact {
/** establish a trivial anchorage and coverage, if possible.
* @note when the UICoord contains wildcards or is incomplete,
* a full resolution with backtracking is necessary to
* determine anchorage and coverage
* determine anchorage and coverage. The same is true
* when the pattern uses an elided element, since such
* an existentially quantified item must be interpolated.
*/
void
attempt_trivialResolution()
@ -558,6 +560,7 @@ namespace interact {
res_.anchor = query_.determineAnchor (this->uic_);
if (not uic_.isExplicit()) return;
res_.depth = query_.determineCoverage(this->uic_);
if (util::contains (this->uic_, UIC_ELIDED)) return; // existentially quantified
res_.isResolved = true;
}