There is no reason to reserve pixel space in macros replacement text,
which is not editable. This makes macros more compact and eases the
writing of lib/symbols.
* introduce new InsetMath::drawMarkers and friends that do nothing
when nested inside a macro. This required to move macro_nesting
inside MetricsBase, and to pass MetricsInfo & to metricsMarkers.
* keep track of nesting when drawing rows or macros.
Empty insets should use a minimal amount of space, especially when
they are part of a built-in macro in lib/symbols.
With this change, blue rectangles signal actually editable places.
Empty macros in editable data are shown as grey boxes, but they do not
appear when further nested.
This is done by adding a new type BOX of MathRow::Element object and a
MetricsInfo::macro_nesting that keeps track of macros (and is reset to
0 in editable macro arguments).
* new MathRow class which contains the description of a MathData
object in terms of math class and spacing
+ macros and their arguments used in the MathData object are
linearized (replaced with their contents) so that all math insets
are typeset as a string together. To this end, we introduce a
method addToMathRow to InsetMath and MathData. This method allows
to linearize recursively a MathData object.
+ It is then necessary to set manually the dimension and position of
the macros and arguments.
+ the class class and spacing are computed using the MathClass helpers.
The MathRow data is cached in the MathData object in a bufferview-dependent
way (different dpi for different screens).
* delegate most of the work MathData::metrics/draw to MathRow metrics/draw.
The case of draw is trickier, since many draw() methods rely on their
metrics without any spacing added.
