Currently, the conversion from em to units is done by using the
default font name inside the backend. For actors using their own
font/text layout we need a way to specify the font name along
with the quantity we wish to transform.
A GValue containing a ClutterUnit should be transformable into a
GValue holding an integer, a floating point value or a fixed point
value.
This means adding more transformation functions when registering
the ClutterUnit GType.
The GValue and GParamSpec integration of ClutterUnit was still
using the old, fixed-point based logic.
Storing ClutterUnits in a GValue should use floating point values,
and ClutterParamSpecUnit should follow suit.
Instead of recomputing the number of units needed to fit in
an em each time clutter_units_em() is called, we can store this
value into the default Backend along with the resolution and
font name. The value should also be updated each time the
resolution and font are changed, to keep it up to date.
An em is a unit of measurement in typography, equal to the point
size of the current font.
It should be possible to convert a value expressed in em to
ClutterUnits by using the current font and the current DPI as
stored by the default backend.
The stage-with/height-percentage converters had been broken by
the multiple-stages support of Clutter 0.8. They are also made
useless by the fact that Units are now floating point values.
The millimeters and typographic points converters also depended
on the default stage, but they can be reworked to use the default
DPI coming from the default Backend instead.
Bug #902 - Support transform from G_TYPE_INT to ClutterUnit
* clutter/clutter-units.c:
(clutter_value_transform_int_unit),
(clutter_unit_get_type): Add GValue transformation function from
integer values to ClutterUnit. (#902)
(param_unit_validate): Fix validation for ClutterParamSpecUnit;
this allows writable ClutterUnit properties.
* clutter/clutter-fixed.c:
(clutter_value_transform_int_fixed),
(clutter_value_transform_double_fixed),
(clutter_value_transform_float_fixed): Add GValue transformation
functions from native types (int, double, float) to ClutterFixed.
(clutter_fixed_get_type): Register the new transformation functions.
(param_fixed_validate): Fix validation for ClutterParamSpecUnit;
this allows writable ClutterFixed properties.
* clutter/clutter-units.c (param_unit_init): Use the right
macros to set the default minimum and maximum values.
* clutter/clutter-fixed.c (param_fixed_init): Ditto as above.
* clutter/clutter-fixed.c:
(clutter_value_transform_fixed_int),
(clutter_value_transform_fixed_double),
(clutter_value_transform_fixed_float),
(clutter_fixed_get_type): Add GValue transformation functions
for ClutterFixed; copying a CLUTTER_TYPE_FIXED GValue into
a G_TYPE_FLOAT/G_TYPE_DOUBLE one will automatically transform
the fixed point representation into a floating point one. Also
add the G_TYPE_INT transformation function to do a plain
fixed->int copy.
* clutter/clutter-units.c:
(clutter_value_transform_unit_int),
(clutter_unit_get_type): Add a unit->int transformation function.
* clutter/Makefile.am: Add clutter-units.c
* clutter/clutter-units.[ch]: Add a ClutterUnit fundamental
type, and wrappers for storing it into GValues; also add a
GParamSpec subclass for defining parameters holding ClutterUnit
values. This allows creating GObject properties using units.
* doc/reference/clutter-sections.txt: Document the newly
added API.
