Re: [ft] Vertical Center Justification

[Werner LEMBERG]

[On this list, please don't use top-posting but rather interleaved
 posting!  This makes it much easier to read the e-mail exchange.]

>> You haven't told us relative to *what* you would like to center the
>> icon...
>
> Good point.  I will answer your question.

Unfortunately, you didn't...

> I think it would help our discovery and learning process to explain
> the typical and usual calculation (algorithm) most "printing
> devices" use to vertically center justify glyphs within a defined
> field (text box).  Once we understand how this is accomplished we
> can apply the principle to our special case.

... since this is far too broad to be of any use.  Please send an
image as an example how you want to vertically center the icons.  And
please don't use the phrase `vertically center justify', which doesn't
make sense.

> I'm beginning to believe this is accomplished by using the bounding
> box dimensions and the vertical dimension of the text field and then
> some basic math to align the centers of the glyph with the center of
> the text box.

Without *seeing* I can't answer that.  Vertical centering within a
text string box looks ugly in most cases, since it ignores the text
string's baseline.  So again, one or two images will help improve the
answer.

> We are creating a TTF, so all of the font data tables exist.  It
> would be most helpful if you could point out the specific table
> values to use for this calculation & show us the math algorithm that
> is used.

Same comment as above.

> Of course, one of the variables in this calculation will be the
> vertical height of the text box. In our case this is a text box that
> has been defined as the available marking field by our product
> graphic designers.

Again, you don't give enough context to answer this.  Do you want to
add the graphical objects to an existing font?  Or should the font
contain only graphical objects?

> Can you explain to me how are the text box dimensions passed to the
> FreeType engine so that position justification can be calculated?

Text box dimensions are *not* passed to FreeType at all.  Basically,
you send FreeType a glyph index (or character code), and it returns a
bitmap for a specified size that you have to position by yourself.

> One of the things that is confusing us is the fact that the FreeType
> engine is perfectly centering the glyph horizontally but not
> vertically.

FreeType doesn't center by itself!  It simply returns what the font
contains.

It seems there is a fundamental misunderstanding and/or
miscommunication due to lack of information.  So please explain in
*much* more detail – with examples.


    Werner