slow initial rendering on latex doc with interesting fonts

[samth]

This document renders very slowly -- first a few characters appear, then it spins for a long time, and then everything else appears quickly.

This is with FF 32.0a1, PDF.js: 0.8.1334, Linux. No warnings on the console.

[timvandermeij]

I can confirm this using Windows 7 x64, Firefox Nightly 30.0a1 (64-bit, HWA on) and the latest PDF.js development version. Memory consumption is also high.

[yurydelendik]

Oh, wow! This PDF embeds about 500 fonts -- I guess one per letter :)

[samth]

Remarkably, it loads quite fast in evince.

[yurydelendik]

Right.... we are allocating too many cMaps and toUnicodes (even for Identity) -- in Chrome profiler size for those two ~2.6M and we have 420 of them.

[nnethercote]

Pretty much all the activity is here, from builtToUnicode():

      for (var i = firstChar; i <= lastChar; i++) {
        toUnicode[i] = String.fromCharCode(i);
      }

This loop is executed 400+ times, and every single time firstChar is 0 and lastChar is 65535. So 400 identical identity toUnicode maps are built.

The best thing would be to avoid building the maps altogether, similar to #5135. This will probably require abstracting these tables into a class, doing all accesses via getter/setter methods, and then having a special sub-class for identity maps.