We decide between simple widgets which handles MEASURE_SPEC_AT_MOST the same way as
MEASURE_SPEC_EXACTLY, and complex widgets which handles MEASURE_SPEC_AT_MOST by measuring the content
implements android.graphics.Typeface (always uses default
typeface for now), one version of Canvas.drawText, one version
of Paint.measureText, and Paint.ascend
Using the C API provided by SkiaSharp's skia fork instead of using cairo
significantly improves performance. The API is also closer to the android
Canvas API, which makes the implementation more straightforward.
A custom GtkLayoutManager is set to these objects, which calls into the
java handlers when measure or layout is requested.
Androids onMeasure method is quite different from GTKs measure method,
because Android already defines the final size during onMeasure.
Therefore, we call onMeasure from GTKs allocate callback instead of the
measure callback.
GtkWidgets extend GInitiallyUnowned and are automatically freed when
removing from parent widget. We need to add an extra reference, to make
sure the object keeps alive as long as the java widget has a reference
to it
Makes it easier to overwrite behavior in subclasses. Have a fallback
implementation for ViewGroup.
Save some _GET_LONG_FIELD / _SET_LONG_FIELD calls by directly passing
the native pointers to and from native methods.
