Testing, Spacing, Kerning and Hinting Arabic Fonts

[Vladimir Tamari]

This topic was imported from the Typophile platform

There is a wealth of experience and documentation about testing, adjusting the spacing, kerning and hinting of Latin type. Arabic has a radically different sript structure - many letters are connected, dots and marks are significant design elements, and there is a lot more variation in the shapes of glyphs within one font. Software like FontLab are geared to Latin fonts for example there is no way to test Arabic using such rules of thumb as the XOX or HOH strategies. You are invited here to share your experience in dealing with these particular aspects of Arabic fonts, with thanks.

[John Hudson]

For a typical horizontal Arabic type, I think a similarity of approach between Latin and Arabic can be found in beginning with the spacing of upright letters, i.e. alif and lam. Start with a run of isolated alif glyphs and space them so that the overall colour produced by the rhythmic repetition of black and white is neither too heavy nor too light. In Latin type, one generally starts with letters with strong uprights but also internal white space, such as H and n, but the internal white space of Arabic letters tends to be more variable, so at this initial stage I would work with simple upright forms.

اااااا

Once the isolated alif has been spaced, this gives you a guide for the left side of the final alif and the right side of the isolated and initial lam. The next step is to space the medial and final form of lam and make the connections of the appropriate length, again using the isolated alifs as a visual guide.

اااللل

The right side spacing of the medial and final lam provide a guide for the right side of the final alif. You now have a set of guide glyphs between which you can test the spacing of left-right connecting letters, e.g.

ااالهاااا

As with Latin spacing, the more glyph combinations you space, the more pairs you have against which you can check new combinations or refine previous spacing.

[John Hudson]

PS. The spacing of a lot of Arabic typefaces is really bad, so trying to find good models can be difficult. We spend a lot of time on spacing (and also kerning of non connecting letters), and I think the Adobe Arabic fonts are worth looking at in this regard.

A major issue re. kerning is interaction between tightly spaced letters and vocalisation marks, which need to be contextually resolved to avoid unwanted collisions. Traditionally, this is done by shifting the marks, rather than by adjusting the spacing of the letters. I think that in a typographical environment, both techniques are valid, and can be used side-by-side and even in combination. However it is done, this is major work and one of the least attractive aspects of the OpenType approach to Arabic.

[Vladimir Tamari]

Thank you John. This is very helpful. Common and sensible advice for spacing Latin is to try to equalize the spaces within the outlines with those between the letters. In other words the line of text should have an even texture and 'color'. This is not always possible in Arabic- for example a downward-curving ra will always leave a void above it, while a tightly knotted initial heh will always look dark however one spaces it.
هرانت
Of course this effect will vary from font to font, and can be lessened with kerning. But generally-speaking why not simply accept this basic variability in the visual density of a line of Arabic text? Aesthetic and reading comfort considerations aside, this may well prove to be an in-built aid to legibility.

[John Hudson]

As I wrote, 'the internal white space of Arabic letters tends to be more variable', so you can't use the internal white space as a guide to inter-letter spacing as one can, to a certain extent, with Latin. This is why I start with the simple upright letters, because they enable one to establish a basic rhythm within which the more complex shapes can be optically spaced. In Latin script there are also letters, such as a and s, that can only be spaced by eye within the general rhythm established by other letters; in Arabic, there are simply more such letters.

[Vladimir Tamari]

>>>’the internal white space of Arabic letters tends to be more variable’>>>

...and even more so between one calligraphic style and another, and their equivelant manifestations in various fonts. For example in riq'a scrip the loops of letters like waw, ain, feh and so on are all closed, and a line of such script (or font) will have a rather spindly thorny appearance. On the other hand more geometrical Arabic fonts with strong uprights and horizontal 'spine' will appear more like a compact frieze pattern. I think this is all fine, and other distinguishing patterns and textures will appear in the scripts and fonts of other languages . That is why I am wary of the recent 'matchmaking' trend where Arabic fonts are forced to lose their character by following the x-height and other features of Latin fonts.

Having said that I feel there must be common guidelines applicable to all fonts in any language- for example a rule of thumb comparing letter width and the space between letter-outlines? The minimum or maximum size of dots and other martks? Human vision is an amazingly sophisticated system, and reading a font is an act of seeing to which the basics of perception must apply whatever is being seen and read.

[AzizMostafa]

Since All but 2 (Alif+Dal) out of the 17 Arabic sweet dancers are fonty,
then just soft space these 2 unless followed by hard space.

Or just duplicate the 2 making Tight+left-spaced ones
and screw the tight one at a hard (space)!

[Vladimir Tamari]

Dear Aziz- all I can answer is ...huh? :)

[AzizMostafa]

Misunderstood? Need Calrification?!
Ok, never use spaces in arabic fonts.
Neither right nor left spaces are necessary.
Happy designing with Flowers

[Vladimir Tamari]

Thank you Aziz for the flowers and clarification. I will try to dream of the 17 dancing letters tonight (which ones are they?) maybe in the morning everything will become clearer. Many many years ago a friend looked at my ordinary Arabic handwriting in astonishment and said it looked a like dancing script.

[Saad Abulhab]

Vladimir

In my projects, I divide Arabic letters and glyphs into two groups based on their connectivity: restricted and un-restricted.

Restricted letters can only connect from one side (Alif, Waw, Ra, Dal, ..) or never connect (Hamza). These glyphs need spaces on the left.

Un-Restricted letters can connect from both sides (the rest of the letters). No spaces are need for this group on either side.

I use minimum kerning depending on project and style.

-Saad

[Vladimir Tamari]

Thanks Saad. I guess by spacing I meant the fine-tuning of these Restricted letter spaces. For example if the alef width is considered as one unit, how many units of space would you give it? What if it were bold- do you make the aleph thicker but keep the space the same, or increase the space proportionally?

[John Hudson]

Note that when talking about 'spacing' in the context of Arabic, as should be plain from my comment earlier about spacing medial forms between initial lam and final alif, we need to consider both letters with actual space between them, e.g. waw followed by another letter, and also the relationship of connecting letters, i.e. the length of the connecting strokes. In the various classical styles of Arabic writing, these strokes are analysable as part of the fusion, i.e. as part of the letter in its appropriate form in a specific context. The advent of flat 'neo-naskh' and other typographic styles with a horizontal baseline stroke introduces a more Latin-like spacing model, in which the connecting stroke is analysable independently of the letter as a kind of spacing. This is demonstrated in the illustration below, in which we can say that the connecting stroke to the left of the mim is too short, and on the right it may be too long, i.e. that it is spaced too far to the left between the two upright letters. This could be a fault in the mim glyph, in the final alif glyph, in the initial lam, or any combination of the three. [Note that I messed with the spacing to produce this illustration; the actual font is not spaced like this.]

[AzizMostafa]

Just a minor correction:
"Unless" in my earlier comment shoud be replaced by (if not), so the phrase:
> then just soft space these 2 unless followed by hard space.
should now read:
then just soft space these 2 if not followed by hard space.
Or:
then just soft space these 2 if not hard-spaced.
Apologizing with Flowers

[AzizMostafa]

> [Note that I messed with the spacing to produce this illustration; the actual font is not spaced like this.]

Well John, the difference between your approach and mine is demonstrated here:
https://typography.guru/forums/topic/46706-forwarding
The tighter, the nicer?!

[Vladimir Tamari]

As John has demonstrated the the spaces between connected letters is as important as the space between unconnected ones. The figure above (using Segoe UI and some fun with Gimp) can be used to point out various aspects of spacing.

The colored areas are what I have been calling 'word shape' (perhaps another term is used in typography courses?). This shape is defined both by the letter outlines and the spaces between them. Arabic word shapes are irregular as compared to those of Latin, and arguably this helps legibility in Arabic because each word looks different than the other (an advantage erased by 'matchmaking').

Referring to the numbers in the figure I propose to use the term 'space' for 1,2,4,5 defined by the distance between the edge of the letter and the left or right sidebearings. Perhaps 'baseline distance' would be a good term for the distances defined by the length of the baseline in connected letters, such as in 3 (lam and meem). A 'gap' would be the visual space such as 3 or 8 that is defined by the word-shape and it depends on the design of the letters, the baseline distances and spaces involved.

-In this font the spaces 1 , 2 and 7 are all different I wonder if this is intentional?
-The gap 3 will be large even if the baseline distances are tightened to the extreme.
-The space 5 is unavoidable in most Arabic fonts (if kerning is not used) - is that similar to what Aziz was saying about the dal?
-4 and 6 are the only spaces between words here. In the Latin the spaces between the words appear more prominent.
-Final letters like the yeh, seen sad etc. leave a large gap such as 8.

In a good font the careful design of glyphs so that the gaps, spaces and baseline distances all combine to produce a pleasing balance. What would your idea of a 'pleasing balance' be? Examples of 'good' and 'bad' fonts in this respect would be useful for discussion.

[AzizMostafa]

Hope this better explains my approach.

All the Best with Flowers

[Vladimir Tamari]

That is beautiful calligraphy. But of course to reproduce this in type one will need either a yet-undesigned font in Tom Milo's Tasmeem or one mighty ligature. Note how the middle gap enhances the design. Aziz you appear to have mastered Arabic font design and the maxim "the tighter the nicer" should be inscribed in golden letters. But just how tight? Examples of tight and loose fonts would be appreciated. With thanks, and flowers of course.

[John Hudson]

Aziz: Hope this better explains my approach.

That would be my approach too, if I were designing that style of writing.

As I wrote previously: 'The advent of flat ’neo-naskh’ and other typographic styles with a horizontal baseline stroke introduces a more Latin-like spacing model, in which the connecting stroke is analysable independently of the letter as a kind of spacing.'

Spacing is part of a trinity of factors, along with style and size, and isn't something to which I would describe myself as having 'an approach'. The appropriate approach -- or options for possible approaches -- depends on the individual typeface.

[AzizMostafa]

John, in M$ Word 2003
Type>Format>Font>Character Spacing>Condensed up to
the logarithm of your "Font Size" and see yourself!

Vladimir, How Tight?
Thanks to the round limbs of AAOTF, you can screw further?!

Happy Experimenting with Flowers

[Vladimir Tamari]

>>>The appropriate approach ... depends on the individual typeface>>>
>>>...see yourself!>>>

True it all depends on the design, and perhaps the only way to space it correctly is to use an intuitive 'see for yourself' approach.

The spacing S of an Arabic script or font whatever its style might be quantified as follows:
S= M/W
where W is the typical width of a vertical letter like the alef, and M is the minimum horizontal distance between outlines in the font. For example in square kufi where the letter-width is exactly equal to the space between letters, S=1. In the texts above the space between alef and initial yeh (or the dot of the zain and the alef, or the dal and the alef) seem to have a typically minimum space between them.

Then, roughly-speaking, S=2 for the comfortably-spaced top line, S=1 for the middle and S=0.3 for the tightly squeezed bottom example. I guess one can also use other measures for example A/W where A is the average space.

[AzizMostafa]

@ Vladimir, Still talking about spaces?!
O Dotcoms!
O Dotorgs!
O WhoDotelse!
Remove all the spaces in your Arabic Fonts
save the ones to the left of Alif+Dal and their alike
and see how they look.

@ John, for more improvement to AAOTF, contact me to contact you.
All the Best with Flowers

[Vladimir Tamari]

>>>@ Vladimir, Still talking about spaces?!>>>
Not with those who do not wish to discuss it O Aziz!

[Saad Abulhab]

Vladimir, We are all interested!

Spaces, spaces, spaces!! We all like to talk spaces until we are "spaced out" !

>>The tighter, the nicer?!

I think the worst disease that have struck good old poor Arabic script was the many "self-appointing" prophets and guardians, complete with commandments and holly sermons! Reformers want to "fix it", calli-typographers want to freeze it in time.

Here is my commandment: the spacier the airier; and here is my second commandment: space it at 16 point, see it at 6 points! -:)

seriously, lets give theses Arabic letters a break. Calligrapher squeezed them, melted them, ligatured them, deprived them personality and independence, made art of them, claimed they were sacred .. This was (and still) fine and may be necessary IN CALLIGRAPHY . Still one thing the founding fathers of calligraphy did not do: they did not etch rules on stones, otherwise we would not have all these revoultionry different styles.

-Saad

[AzizMostafa]

Self-appointing prophets say:
Make Right + Left + Word Spaces to make the sweet too loose to suck?!
Reformers say:
1. Be rational not emotional.
2. Do not you see that you add up 3 spaces between words?!
So, why not integrate the 3 spaces into a single revolutionary space?!
Flowers to All