Malayalam fonts: Beyond Latin font metrics

This year’s annual international conference organized by TeX Users Group — TUG2020 — was held completely online due to the raging pandemic. In TUG2020, I have presented a talk on some important Malayalam typeface design factors and considerations.

The idea and its articulation of the talk originated with K.H. Hussain, designer of well-known fonts such as Rachana, Meera, Meera Inimai, TNJoy etc. In a number of discussions that ensued, this idea was developed and later presented at TUG2020.

Opening keynote to TUG2020 was delivered by Steve Matteson, about the design of Noto fonts. He mentioned that Noto was originally envisaged to be developed as a single font containing all Unicode scripts; but that was changed due to a couple of reasons: (1) huge size of resulting font and (2) the design of many South/South-East Asian characters do not fit well within its Latin font metrics.

This second point set up the stage nicely for my talk, in which we argued that a paradigm shift from established Latin font metrics is necessary in designing and choosing font metrics for Indic scripts, in particular with Malayalam as a case study.

Indic scripts have abundant conjunct characters (basic characters combined to form a distinct shape). The same characters may join ‘horizontally’ (e.g. ത്സ/thsa) or ‘vertically/stacked’ (e.g. സ്ത/stha); and Malayalam script in particular has plenty of stacked conjuncts even in contrast with other Indic scripts. This peculiarity also makes the glyph design of fonts challenging — to balance aesthetics, legibility/readability and leading/line spacing. Specifically, following the usual x-height/cap-height/ascender/descender metrics used in Latin fonts put a lot of constraints in the design of stacked conjuncts. We propose to break away from this conventional metrics and adopt different proportions of the above- and below-base glyphs (even if they are the same characters, e.g. സ in the double conjunct സ്സ), still conforming to the aesthetics of the script yet managing the legibility and leading.

Fig. 1: Malayalam stacked conjuncts beyond conventional Latin font metrics.

Details of this study, argument and proposal can be found in the slides of the presentation available at the program details as well as the recorded talk now available on TUG YouTube channel.

TUG2020 presentation.

The conference paper, edited by Barbara Beeton and Karl Berry will be published in the next issue of TUGBoat journal.

Okular 20.08 — redesigned annotation tools

Last year I wrote about some enhancements made to Okular’s annotation tool and in one of those, Simone Gaiarin commented that he was working on redesigning the Annotation toolbar altogether. I was quite interested and was also thinking of ‘modernizing’ the tool — only, I had no idea how much work it would be.

The existing annotation tool works, but it had some quirks and had many advanced options which were documented pretty well in the Handbook but not obvious to an unscrupulous user. For instance, if the user would like to highlight some part of the text, she selects (single-clicks) the highlighter tool, applies it to a block of text. When another part of text is to be highlighted, you’d expect the highlighter tool to apply directly; but it didn’t ‘stick’ — tool was unselected after highlighting the first block of text. There is an easy way to make the annotation tool ‘stick’ — instead of single-click to select the tool, simply double-click, and it persists. Another instance is the ‘Strikeout’ annotation which is not displayed by default, but can be added to the tools list.

Simone, with lots of inputs, testing and reviews from David Hurka, Nate Graham and Albert Astals Cid et al., has pulled off a magnificent rewrite of Okular’s annotation toolbar. To get an idea of the amount of work went into this, see this phabricator task and this invent code review. The result of many months of hardwork is a truly modern, easy to explore-and-use annotation support. I am not aware of any other libre PDF reader with such good annotation features.

Annotation toolbar in Okular 20.08.

Starting from the left, default tools are: Highlight (brush icon), Underline (straight line) and Squiggle (wobbly line), Strike out, Insert text (Typewriter), Inline note, Popup note, Freehand drawing and Shapes (arrows, lines, rectangles etc.). The line thickness, colour, opacity and font of the tools can be customized easily from the drawer. Oh, and the selected annotation tool ‘sticks’ by default (see the ‘pin’ icon at the right end of toolbar).

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Line width and colour of ‘Arrow’ tool.

When upgrading to okular-20.08 from a previous version, it will preserve the customized annotation tools created by the user and make those available under ‘Quick annotations’, and these can be quickly applied using Alt+n (Alt-1, Alt-2 etc.) short cuts. It did reset my custom shortcuts keys for navigation (I use Vim keys gg to go to the first page and G to go to the last page), which can be manually added back.

Custom tools (Quick annotations) can be applied with short cuts.

Here is the new toolbar in action.

Complex text shaping fixed in Konsole 20.08

Konsole was one of the few terminal emulators with proper complex text shaping support. Unfortunately, complex text (including Malayalam) shaping was broken around KDE Applications release 18.08 (see upstream bug 401094 for details).

Broken Malayalam text shaping in Konsole 20.04

Mariusz Glebocki fixed the code in January this year which I tested to work correctly. There’s a minor issue of glyphs with deep vertical components being cut-off (notice rendering of “സ്കൂ”), but otherwise the shaping and rendering is good. The patches are also merged upstream and will be part of the KDE Applications Bundle 20.08.

Proper Malayalam text shaping in Konsole 20.04 with shaping fixes.

If you don’t want to wait that long, I have made a 20.04 release with the fixes on top available for Fedora 31 & 32 in this COPR.