Air Date:
Latest update:
Pandoc can prepare LaTeX math for MathJax via its eponymous
--mathjax option. It wraps formulas in <span class="math">
elements and injects a <script> tag that points to
cdn.jsdelivr.net, which means rendering won't work offline or in
case of the 3rd-party server failure. You can mitigate this by
providing your own copy of the MathJax library, but the mechanism
still fails when the target device doesn't support JavaScript (e.g.,
many epub readers).
At the same time, practically all browsers support MathML. Use it
(pandoc's --mathml option), if you care only about the information
superhighway: your formulas will look good on every modern device and
scale delightfully. Otherwise, SVGs are the only truly portable
option.
Now, how can we transform the html produced by
$ echo 'Ohm'\''s law: $I = \frac{V}{R}$.' |
pandoc -s -f markdown --mathjax
into a fully standalone document where the formula gets converted into
SVG nodes?
- Use an html parser like Nokogiri, and replace each
<span class="math"> node with an image. There are multiple ways to
convert a TeX-looking string to an SVG: using MathJax itself (which
provides a corresponding CLI example), or by doing it in a
'classical' fashion with pdflatex. (You can read more about this
method in A practical guide to EPUB, chapters 3.4 and 4.6.)
- Alternatively, load the page into a headless browser, inject
MathJax scripts, and serialise the modified DOM back to html.
I tried the 2nd approach in 2016 with the now-defunct phantomjs. It
worked, but debugging was far from enjoyable due to the strangest bugs
in phantomjs. I can still run the old code, but it depends on an
ancient version of the MathJax library that, for obvious reasons,
isn't easily upgradable within the phantomjs pre-es6 environment.
Nowadays, Puppeteer would certainly do, but for this kind of task
I prefer something more lightweight.
There's also jsdom. Back in 2016, I tried it as well, but it was much
slower than running phantomjs. Recently, I gave jsdom another try and
was pleasantly surprised. I'm not sure what exactly tipped the scales:
computers, v8, or jsdom itself, but it no longer feels slow in
combination with MathJax.
$ wc -l *js *conf.json
24 loader.js
105 mathjax-embed.js
12 mathjax.conf.json
141 total
Roughly 50% of the code is nodejs infrastructure junk (including CL
parsing), the rest is a MathJax config and jsdom interactions:
let dom = new JSDOM(html, {
url: `file://${base}/`,
runScripts: /* very */ 'dangerously',
resources: new MyResourceLoader(), // block ext. absolute urls
})
dom.window.my_exit = function() {
cleanup(dom.window.document) // remove mathjax <script> tags
console.log(dom.serialize())
}
dom.window.my_mathjax_conf = mathjax_conf // user-provided
let script = new Script(read(`${import.meta.dirname}/loader.js`))
let vmContext = dom.getInternalVMContext()
script.runInContext(vmContext)
The most annoying step here is setting url property that jsdom uses
to resolve paths to relative resources. my_exit() function is called
by MathJax when its job is supposedly finished. loader.js script is
executed in the context of the loaded html:
window.MathJax = {
output: { fontPath: '@mathjax/%%FONT%%-font' },
startup: {
ready() {
MathJax.startup.defaultReady()
MathJax.startup.promise.then(window.my_exit)
}
}
}
Object.assign(window.MathJax, window.my_mathjax_conf)
function main() {
var script = document.createElement('script')
script.src = 'mathjax/startup.js'
document.head.appendChild(script)
}
document.addEventListener('DOMContentLoaded', main)
The full source is on Github.
Intended use is as follows:
$ echo 'Ohm'\''s law: $I = \frac{V}{R}$.' |
pandoc -s -f markdown --mathjax |
mathjax-embed > 1.html
The resulting html doesn't use JavaScript and doesn't fetch any
external MathJax resources. mathjax-embed script itself always works
offline.
Tags: ойті
Authors: ag
Air Date:
Latest update:
At the time of writing, the most recent Adobe Reader 25.x.y.z 64-bit
installer for Windows 11 weights 687,230,424 bytes. After
installation, the program includes 'AI' (of course), an auto-updater,
sprinkled ads for Acrobat online services everywhere, and 2 GUIs:
'new' and 'old'.
For comparison, the size of SumatraPDF-3.5.2 installer is 8,246,744
bytes. It has no 'AI', no auto-updater (though it can check for new
versions, which I find unnecessary, for anyone sane would install it
via scoop anyway), and no ads for 'cloud storage'.
The following chart shows how the Adobe Reader installer has grown in
size over the years. When possible, 64-bit versions of installers were
used.
Next Day Update:
Best comment on Hacker News: "Looks like a chart crime scene."
Alright, here's your linear graph, along with the
source from which both graphs were generated. All
point labels are version numbers.
Tags: ойті
Authors: ag
Air Date:
Latest update:
Peter Weinberger (the "w" in awk), while working at Bell Labs,
wrote an experimental
implementation of a network file system. Included with Research Unix
v8 (Feb 1985, licensed strictly for educational use), it allowed to
share / (yes) with other machines running v8 by specifying a mapping
between a local uid/gui and the desired view from the LAN.
Weinberger described peculiarities of his netfs as
"If A mounted B's file system somewhere, and B mounted A's, then the
directory tree was infinite. That's mathematics, not a bug."
His /usr/src/netfs/TODO contained an existential question:
'why does it get out of synch?'
The connection of this netfs and Sun's NFS is murky.
Steve Johnson:
"I remember Bill Joy visiting Bell Labs and getting a very complete
demo of RFS and being very impressed. Within a year, Sun announced
NFS."
Unix System V SVR3, released by AT&T in 1987, included a different
version of netfs, which they officially began calling RFS. Appearing
18 months after Sun announced NFS, it briefly attempted to compete,
but failed on 2 fronts simultaneously: ⓐ big vendors (Dec, IBM, HP)
disliked its licensing terms, and ⓑ the protocol's brittleness
discouraged ports to non-Unix systems. NFS won, becoming widely
used--even by NeXTSTEP.
Lyndon Nerenberg:
'We ran RFS on a "cluster" of four 3B2s [AT&T microcomputers], and
while it worked, to varying degrees, the statefulness of the
protocol inevitably led to the whole thing locking up, requiring a
reboot of all four machines to recover.'
Tags: ойті
Authors: ag
Air Date:
Latest update:
In the dining room there is an old (2013) 1080p telly with an old (2020)
Android TV box connected to it. The TV box contains an ancient
Amlogic S905X3 SoC inside. It has just enough power to play
Youtube & 1080p movies from a network drive but not much else.
Some time ago I heard about repurposing this particular model (Vontar
X3) as a retro-gaming console, but anticipating battles similar to
those with openwrt-on-outers--where 2 devices with the exact same name
have slightly different hardware revisions (& as a result, nothing
works as expected)--I've been putting off the adventure.
The easiest Linux gaming distro to deploy is a French one called
Batocera. Its
wiki describes perfomance of a particular device in terms of console
generation support:
| Gén |
Consoles |
| 3 |
NES |
| 4 |
SNES, Sega Mega Drive |
| 5 |
PlayStation (psx), PlayStation Portable (psp) |
(I've skipped the irrelevant generations.)
In my tests, while the modest S905X3 runs most psx & psp games
acceptably, some titles have such a perceived frame drop (that do not
occur on a desktop PC running the same emulator as Batocera) that it
makes them unplayable. The prominent unsuccessful examples are CTR:
Crash Team Racing (psx) and MotorStorm: Arctic Edge (psp).
The last Batocera version for the Vontar X3 is 35 (the OS images for
this device haven't been updated since '22). I dd'ed
batocera-s905gen3-tvbox-gen3-35-20220910.img onto a 32GB SD card,
inserted the card into the TV box, pressed its reset button with a
toothpick, plugged in the power cable, & saw this:
The TV's info popups indicated that the resolution of this shaky image
was 1080i (interlaced?) instead of the expected 1080p. I then tried 2
completely different (albeit much newer) TVs, as well as a capture
card--none of them had any problems negotiating a proper resolution
with Batocera.
After pointlessly suffering with various kernel parameters, I ended up
with the following kludge to disable the interlaced mode:
Connect the device to your LAN via the ethernet port. Batocera runs
Avahi, hence we can just say
$ ssh root@batocera.local
(The password is 'linux'.)
Run
# batocera-resolution listModes | head -10
max-1920x1080:maximum 1920x1080
max-640x480:maximum 640x480
0.0.1920x1080.60:HDMIA 1920x1080 60Hz (1920x1080i)
0.1.1920x1080.60:HDMIA 1920x1080 60Hz (1920x1080)
0.2.1920x1080.60:HDMIA 1920x1080 60Hz (1920x1080)
0.3.1920x1080.60:HDMIA 1920x1080 60Hz (1920x1080i)
0.4.1920x1080.50:HDMIA 1920x1080 50Hz (1920x1080)
0.5.1920x1080.50:HDMIA 1920x1080 50Hz (1920x1080i)
0.6.1920x1080.24:HDMIA 1920x1080 24Hz (1920x1080)
0.7.1920x1080.24:HDMIA 1920x1080 24Hz (1920x1080)
inside Batocera. Take a note of a mode you'd like to see.
Turn the device off. Extract the SD card out of it & insert it into
a PC. The card has 2 partition: the 1st one is fat32 that has
batocera-boot.conf file. Add a line to it:
es.resolution=0.1.1920x1080.60
The picture will still incessantly jerk from left to right, but only
during the boot phase:
# batocera-info
Disk format: ext4
Temperature: 66°C
Architecture: tvbox-gen3
Model: Shenzhen Haochuangyi Technology Co., Ltd H96 Max
System: Linux 5.10.134
Available memory: 624/932 MB
Cpu model: ARMv8 Processor rev 0 (v8l)
Cpu number: 4
Cpu max frequency: 1908 MHz
There is little to add here. You copy your .nes/.sfc/.chd/.iso files
to /userdata/roms/{nes,snes,psx,psp} either directly onto the 2nd
partition of the SD card, or via ssh, or even smb, for Batocera runs
Samba.
- I couldn't find any guidance on how to pronouce it:
there is a type of beetles called /bə'tosərə/, but some youtubers say
it as /bαto'sɛrα/.
Tags: untagged
Authors: ag