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Archive for December, 2017

Casting Coursera

MOOC’s (Massive Open Online Courses) are an excellent way to enhance your career or to explore subjects you missed in your school days. You can watch MOOC lectures from sites like Coursera, Udacity, or edX on your computer, your tablet, or even your phone, but for an even better experience, you can cast them to your big-screen TV.

I have a Roku 3 and a Galaxy S6 Edge. When I first tried to cast from my phone to my Roku a few years ago, both video and audio were extremely laggy.

Recently, I tried again with the Android Smart View feature, and the results are much better. Games are still laggy, but Coursera videos play smoothly. The only problem I noticed was audio skipping occasionally. However, when I turned off my sound bar and used the TV’s own sound instead, the audio was fine. I don’t really need extra bass for a deep learning lecture.

Of course, if you have a Chromecast, you can just use the Chromecast for your own private lecture hall.

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Recently, I found myself in a situation… After uninstalling an application from my Macbook Pro, its icon was still visible in the Launchpad. Clicking the icon would do nothing.

How do you get rid of orphaned Launchpad icons? Thanks to Google and Stack Overflow, I discovered that Launchpad icons are stored in a SQLite database in /private/var/folders with

com.apple.dock.launchpad in the name. The find command is useful:

sudo find /private/var/folders -name com.apple.dock.launchpad

finds the directory /private/var/folders/m4/hh39vth91396mblmwt46crkw0000gn/0/com.apple.dock.launchpad. A little poking around with ls reveals that the database itself is db/db.

ls -l /private/var/folders/m4/hh39vth91396mblmwt46crkw0000gn/0/com.apple.dock.launchpad/db
total 22656
-rw-r--r-- 1 shanglin staff 7495680 Dec 1 10:26 db
-rw-r--r-- 1 shanglin staff 32768 Nov 29 00:27 db-shm
-rw-r--r-- 1 shanglin staff 2290752 Dec 3 22:05 db-wal

Let’s use sqlite3 to see what’s in the database:

sudo sqlite3 /private/var/folders/m4/hh39vth91396mblmwt46crkw0000gn/0/com.apple.dock.launchpad/db/db

sqlite> .tables
app_sources dbinfo image_cache widgets
apps downloading_apps items
categories groups widget_sources

sqlite> .schema apps
CREATE TABLE apps (item_id INTEGER PRIMARY KEY, title VARCHAR, bundleid VARCHAR, storeid VARCHAR,category_id INTEGER, moddate REAL, bookmark BLOB);

The rogue app had the name “Spelunky” in it. We can use a SQL wildcard to find apps with the word “Spelunky” in the title:

sqlite> select * from apps where title like '%Spelunky%';
<p class="p1">92|Spelunky HTML5|com.google.Chrome.app.Default-mhagnkphcmpkmabhocgimoncfaihkpof|||519537375.0|book

Let’s delete Spelunky’s entry:

sqlite> delete from apps where title='Spelunky HTML5';

After exiting the sqlite shell, I restarted the dock:

killall Dock

and the Spelunky icon was gone. Success!

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