Cell binding allows one to bind a range of cells of one sheet to another
range of cells of an arbitary sheet, including any empty cells in the
range.
The binding is implemented with PropertyExpressionEngine and
PropertySheet::setPathValue(), which binds a special path of
PropertySheet, such as
.cells.Bind.A1.D1
to an expression, such as
tuple(.cells, <<A2>>, <<A5>>)
The A1 and D1 in the example above specifies the binding start and end
cell address. And <<A2>> and <<A5>> are the range of cells to bind to.
Note that you can use any expression that evalutes to string for the
binding destination, e.g. <<A%d>> % B1, which uses the value inside B1
to construct the binding destination. The '.cells' in the tuple shown
above is an example to bind cells of the same PropertySheet. It can be
change to to reference to any other spreadsheet, even those outside the
current document, e.g. Document#Spreadsheet001.cells
Any object reference inside this function is treated as hidden to
exclude it from dependency calculation. This function allows some form
of cyclic depdenency.
Merger note: renamed from "HREF" to "HIDDENREF" to avoid confusion with
the standard "hypertext reference" use of HREF.
* Support sub-object reference syntax using the following syntax,
Part.<<Box.>>.Placement
or, with sub-object label referencing
Part.<<$Cube.>>.Placement
* Extend indexing support, including range based indexing, e.g.
A1[B2+1][C3][D4:-1]
* Add new constants, None, True, true, False, false.
PropertyExpressionEngine is changed to derived from a new class
PropertyExpressionContainer, which is in turn derives from
PropertyXLinkContainer. This makes PropertyExpressionEngine a link type
property that is capable of external linking. It now uses the unified
link property APIs for dependency management and tracking of object
life time, re-labeling, etc.
ObjectIdentifier is modified to support sub-object reference, but is
not exposed to end-user, because expression syntax is kept mostly
unchanged, which will be submitted in future PR. There is, however,
one small change in expression syntax (ExpressionParser.y) to introduce
local property reference to avoid ambiguity mentioned in
FreeCAD/FreeCAD#1619
Modified Expression/ExpressionModifier interface to support various link
property API for link modification.
