Improvements in the calculation of text extents

[logari81]

Currently, the calculation of the extent of text objects in Octave is
very limited. For example it doesn't take into account the rotation
angle:

Revision 11407 of Octave:

octave:1> backend fltk
octave:2> hx = xlabel('x label');
octave:3> get (hx, 'extent')
ans =
   1.6832e-17  -7.7629e-17   6.2500e-02   3.6252e-02
octave:4> set(hx, 'rotation', 90)
octave:5> get (hx, 'extent')
ans =
   1.6832e-17  -7.7629e-17   2.6210e-02   8.6447e-02

For this reason I have worked in cleaning up and improving the
calculation of text extents and positioning of text. My modifications
can be found in the attached changeset. The result of the previous
example after these changes becomes rotation aware:

With the attached changeset:

octave:1> backend fltk
octave:2> hx = xlabel('x label');
octave:3> get (hx, 'extent')
ans =
  -0.033266  -0.039041   0.062500   0.036252
octave:4> set(hx, 'rotation', 90)
octave:5> get (hx, 'extent')
ans =
  -0.0020161  -0.0460123   0.0262097   0.0864473

For comparison see the corresponding result from ML:

>> hx = xlabel('x label');
>> get (hx,'extent')
ans =
    0.4458   -0.1115    0.0982    0.0541
>> set (hx, 'rotation', 90)
>> get (hx,'extent')
ans =
    0.4761   -0.1521    0.0605    0.1521

The attached patch does not only fix this small problem but also
prepares all necessary infrastructure for handling the tightinset
property later.

The first two components of the extent property implemented in the
attached changeset are not compatible with ML. The convention that ML
uses for these two components makes sense only in 2D plots and I don't
think that it is good idea to follow the ML convention in this case.

Please test the attached patch and give me some feedback in case it
breaks anything. Otherwise I think it is a good idea to commit it since
it cleans up a few things.

BR

Kostas

text-extents.changeset
Description: Text document