[squeak-dev] Cuis font sizes

> Hi Juan -
>
> This is mostly to Juan but others might be able to help as well. I
> noticed that the Cuis fonts disagree in their pixel sizes
> significantly with that we get from the plain DejaVu true type fonts
> in Squeak. A bit of math reveals that at the (assumed) screen
> resolution of 96dpi a 12pt font should result in 16px high font
> (12*96/72 see Eqn. 3 in [1]). The corresponding Bitmap DejaVu 12pt
> font, however, is 19px high which would mean a screen resolution of
> 114dpi (19*72/12).
>
> Is this choice intentional? Unfortunately, none of the pixel sizes for
> Bitmap DejaVu correspond exactly to a point size when assuming 96dpi.

> On Sat, Aug 29, 2009 at 12:18:18PM -0300, Juan Vuletich wrote:
>  
>> I never found a clear specification of the meaning of  '12 point', and
>> I'm totally for making the fonts behave properly.
>>    
>
> http://en.wikipedia.org/wiki/Point_(typography)
>
> 72 points = 1 inch
>
> Dave
>  

> Hi Andreas,
>
> Andreas Raab wrote:
>> Hi Juan -
>>
>> This is mostly to Juan but others might be able to help as well. I
>> noticed that the Cuis fonts disagree in their pixel sizes
>> significantly with that we get from the plain DejaVu true type fonts
>> in Squeak. A bit of math reveals that at the (assumed) screen
>> resolution of 96dpi a 12pt font should result in 16px high font
>> (12*96/72 see Eqn. 3 in [1]). The corresponding Bitmap DejaVu 12pt
>> font, however, is 19px high which would mean a screen resolution of
>> 114dpi (19*72/12).
>>
>> Is this choice intentional? Unfortunately, none of the pixel sizes
>> for Bitmap DejaVu correspond exactly to a point size when assuming
>> 96dpi.
>
> The BitmapDejaVu 12 has the glyphs rendered by FreeType when requested
> for 12 pt. In those glyphs, the H (for example) is 12 pixels high. Max
> ascent for uppercase letters with Latin umlauts is 15 pixels. Max
> descent in those glyphs is 4. Therefore instances of BitmapDejaVu 12
> StrikeFont answer 15 to #ascent, 4 to #descent and 19 (15+4) to #height.
>
> I never found a clear specification of the meaning of  '12 point', and
> I'm totally for making the fonts behave properly. So, the first
> question is: Are the glyphs correct? I mean, are the glyphs for DejaVu
> 12 rendered by Squeak TTF and Freetype the same size? If so, how does
> Squeak TTF fit glyphs that might need up to 19 pixels (15+4) in 16? I
> suspect that FreeType and Squeak TTF don't agree on the meaning of
> point size, but I don't have time right now for checking.
>
> I'll have time for this on Monday. I guess the first thing to do is to
> understand what is the correct font for '12 point'. I mean, the
> correct ascent/descent and line grid, and the correct shape of the
> glyphs. Some specification of mean kerning / length of strings would
> be nice too. I'll read the link you sent. I want to understand and get
> this right!

> On Saturday 29 Aug 2009 8:48:18 pm Juan Vuletich wrote:
> > I'll have time for this on Monday. I guess the first thing to do is to
> > understand what is the correct font for '12 point'. I mean, the correct
> > ascent/descent and line grid, and the correct shape of the glyphs. Some
> > specification of mean kerning / length of strings would be nice too.
> In traditional typography, the point referred to the size of the metal block
> used to carve shapes (glyphs).  The size of a Point depended on
> regional/political affiliations :-). Anglo-american point was about 72.27 points
> to an inch. Not all shapes would be contained within its metal block base.
> Some (see g in the picture http://ilovetypography.com/2008/03/23/sunday-type-
> bright-type/) would also extend (kern) beyond its base. String length would be
> the sum of metal block widths. The sum of shape widths in a run of characters
> could differ from the string length due to kerns.
>
> Digital typography uses co-ordinate grids instead of a metal block. It defines
> Point (aka DTP point or Postscript point) as 1/72th of an inch. Grid size
> varies for different fonts. TTF uses grids of 512, 1024 or 2048. The point size
> used in font names are 'design size'. i.e. a modern 12pt TTF contains glyphs
> drawn inside a 2048x2048 grid that will *look like* a 12pt metal typeface when
> scaled to various digital canvases like a 96dpi screen or 1200 dpi printer.
>
> Though we continue using the term 'glyph' (carving), images are computed on
> the grid using a 'pictal' process and then scaled to the target canvas. A
> Truetype font is actually a bytecode program interpreted by a font engine
> (e.g. Freetype) to scale glyphs at run time. Internally, glyphs are defined in
> terms of lines and curves in a grid (called em-square) of size 512, 1024 or
> 2048. Given a canvas (dpi, depth), a glyph code and a point size "hint", the
> font engine will scale a glyph and tweak them using 'hints' expressed in
> bytecodes. For instance, stretching a '(' vertically may scale only the middle
> part and leave the tips alone. The o in "xo" will slightly overshoot x for
> good visual flow.
>
> However, aesthetic rendering requires a context and a run of characters. The
> spacing between one character to the next is dictated by kern and direction.
> Sometimes, adjacent glyphs may coalesce into a more compact or even different
> shape (e.g. ffi) called a ligature. Runs are handled by a text rendering engine
> (e.g. Pango, Qt, ghostscript). Of course, the ligated glyph shape should exist
> in the font.
>
> Squeak's text printing algorithms only consider boxes and kerns - no
> ligatures, no hyphenation, no direction. Building a true multilingual layout
> engine is a non-trivial task. Mac and Wintel have only one shaping engine
> while Linux has multiple options (Pango, Qt, ICU, m17n, Graphite). Pango and
> Qt are widely used. Squeak should be able detect and load shaping engines on
> the fly on Linux or allow command line options to pick a wrapper plugin.
>
> There is also the blue plane approach proposed in FoNC paper - treat text
> boxes like graphic objects. A Font engine is just a specialized vector graphic
> editor that avoids intensive geometric computations by caching precomputed
> shapes in a glyph table. Allow graphic objects to have class level editors.
> Then when a glyph is missing for a character code, open a glyph editor and
> allow a new shape to be defined on the fly or imported from a public font
> definition file. Beats displaying $?.
>
> Subbu

> Date: Fri, 28 Aug 2009 20:22:19 -0700
> From: [hidden email]
> To: [hidden email]
> Subject: [squeak-dev] Cuis font sizes
>
> Hi Juan -
>
> This is mostly to Juan but others might be able to help as well. I
> noticed that the Cuis fonts disagree in their pixel sizes significantly
> with that we get from the plain DejaVu true type fonts in Squeak. A bit
> of math reveals that at the (assumed) screen resolution of 96dpi a 12pt
> font should result in 16px high font (12*96/72 see Eqn. 3 in [1]). The
> corresponding Bitmap DejaVu 12pt font, however, is 19px high which would
> mean a screen resolution of 114dpi (19*72/12).
>
> Is this choice intentional? Unfortunately, none of the pixel sizes for
> Bitmap DejaVu correspond exactly to a point size when assuming 96dpi.
>
> The reason this is causing me grief is that I am trying to set up a
> mechanism for allowing people to drop the DejaVu fonts into their images
> and have any glyphs not part of the cuis fonts rendered in DejaVu
> truetype instead. I can probably get the truetype rendering to spit out
> a precise pixel size to match it but I think it'd be good if we had
> clarity on how these pixel sizes came into being.
>
> Any insights appreciated!
>
> Cheers,
> - Andreas
>
> [1] http://www.emdpi.com/emsquare.html
>

> On Sat, Aug 29, 2009 at 12:18:18PM -0300, Juan Vuletich wrote:
>>
>> I never found a clear specification of the meaning of  '12 point', and
>> I'm totally for making the fonts behave properly.
>
> http://en.wikipedia.org/wiki/Point_(typography)
>
> 72 points = 1 inch
>
> Dave
>
>
>

>
> 2009/8/29 David T. Lewis <[hidden email]>:
> > On Sat, Aug 29, 2009 at 12:18:18PM -0300, Juan Vuletich wrote:
> >>
> >> I never found a clear specification of the meaning of ?'12 point', and
> >> I'm totally for making the fonts behave properly.
> >
> > http://en.wikipedia.org/wiki/Point_(typography)
> >
> > 72 points = 1 inch
>
> I thought it was 72.27

>
> Am 2009-08-31 um 02:35 schrieb David T. Lewis:
>
>> On Sun, Aug 30, 2009 at 10:12:06PM +0200, Nicolas Cellier wrote:
> […]
>>>>
>>>> http://en.wikipedia.org/wiki/Point_(typography)
>>>>
>>>> 72 points = 1 inch
>>>
>>> I thought it was 72.27
>>
>> Nicolas,
>>
>> You are absolutely right. The discrepancy is apparently due to my  
>> having
>> less than four significant figures worth of linear precision on my  
>> computer
>> screen ;-)
>>
>> Thanks for the correction, also noted in Subbu's excellent reply  
>> earlier
>> today.
>>
>
> Didn’t know you were hot-metal typesetters ;)
> But, no kidding, an inch is both equal 72.27 _and_
> equal 72 Point.
>  Refer to the already mentioned Wikipedia article;
> TeX and hot-metal- (i.e. traditional) typesetting, are
> using a 72.27 pt = 1 in relation, whereas PostScript
> is using the rounded 72 pt = 1 in. The WP article
> states, that the latter is the now more common def-
> inition of a Point.
>  By the way, which system is Squeak (Freetype?)
> using?

>
> Okay, I figured it out. It turns out that for computing the line
> spacing one needs to use the OS/2 table from the truetype font if
> present. What confused me was that DejaVu Sans had a linegap (leading)
> of zero in its horizontal header table which *should* make things very
> easy. Except that in its OS/2 table it has a non-zero linegap/leading.
> If we use the values from that table we end up with the right sizes
> but it seems that for rendering we then need to use the "original"
> values (from the hhea table). With these issues addressed, the bitmap
> and the outline versions are virtually indistinguishable in size and
> spacing (see screenshot).

>
>> Finally, any reason not to use FreeType? It looks like a good
>> alternative for Unicode.
>
> No particular reason other than that I like this font stuff, and that
> I think that carrying 500k for a plugin out of which you only use the
> auto-hinter is kinda insane ;-) Seriously, if someone would port the
> auto-hinter we could make fonts that are every bit as good as Freetype.
>
> But it's still an interesting idea and I should check it out to see
> how different (or not) things are.
>
> Cheers,
>   - Andreas
>
> ------------------------------------------------------------------------
>

> On Monday 31 Aug 2009 11:50:14 am Ronald Spengler wrote:
> > Thank you; you should put this on a wiki or a blog somewhere. If you don't
> > have time, I would gladly do that for you (and of course put your name on
> > it.) This is some really good writing, and I really appreciate the work.
> > It's easy to lose track of historical context amongst all of the ones and
> > zeros.
> http://wiki.squeak.org/squeak/6144
>
> My first swiki entry,
> Subbu