Tuesday, June 21, 2016

Karabiner: Mouse/keyboard customizer for OS X


For beginners, or the one who migrated from Windows environment, Natural Gestures (Scrolling and Swiping) might be bit confusing. But, once you get familiarized with them, it may feel like "What was I doing, all those days?".

It all changed, when I connected external mouse to my Macbook. When you start using that WHEEL, you will be confused.
Luckily there is a setting for mouse, to change scroll behavior (natural or the other way).

But, here's the catch.
If you toggle that setting, it also toggles the same for TRACKPAD!!!!!

I've seen that many people were freaked out and even raised BUG report to Apple. But, all those reports were closed, saying that is not a bug, but intentional feature!!!

For those, who can't leave with such one-sided settings, here is a simple util, which came to my rescue: Karabiner
It's simple, powerful and stable mouse/keyboard customizer for OSX.

Without going into much detail, here's the configuration I used to retain by Natural Gestures of Trackpad and also the intuitive behavior of mouse wheel.

First enable the natural scrolling setting of your Trackpad (OSX Settings).
Then open Karabiner.

Following are the changes I made under "Change Key" tab:

  • Karabiner Core Settings > Exclude devices > Don't remap Apple's pointing devices
  • Pointing Device > Reverse scrolling direction > Reverse Vertical Scrolling
  • Click on "Reload XML" button, which is at the top right corner
That's it!!!!

There are lot more settings/tweaks you can make.

Thursday, June 9, 2016

USB port not working on Mac

USB port not working on Mac

Recently I connected an external hard-disk to my new MacBook and observed that it was not properly detected on one of the USB ports. But I can see that it is powering my HDD.
I tried switching to other port and it worked. I simply ignored it by thinking that my HDD cable might be loose.
Now I bought a new USB drive and to get it detected, I have to insert and detach it multiple times. And as usual, I suspected the new USB drive, as my Mac is brand new. And planned to replace my USB drive.
Now my HDD came back to  my mind. And also my earlier laptop, in which few KEYS went unresponsive due to accumulated charges.
By little researching I found that I'm not alone. The solution that worked for me was "Resetting SMC"
Here is the procedure I followed:
  • Shut down the Mac and connect the power cable
  • Hold down Shift+Control+Option+Power concurrently for a few seconds.
  • When the light on the power adapter blinks or changes colors you’ll know SMC reset is complete
  • Release all keys at the same time
  • Now boot your Mac as usual.

Now I'm happy that I don't have to replace any of my devices.

Tuesday, May 31, 2016



It's been almost two years I've been using HSQLDB in one of my client-critical application.
When I was given the task of working on this application (which was already in production), main challenge was to reduce latency and also to make it flexible enough to accommodate any future use-cases.

Without going into to much details, here's my use-case:
  • Application receives data from multiple sources
  • Parse data from each source and extract required data
  • Aggregate this extracted data and find best candidate which satisfies certain rules

One simplest solution is to join data from all sources by having a (for-)loop, one each for a source and apply rules inside inner-most loop. As number of data sources increases, so does the latency.
HSQLDB came to my rescue. I used in-memory variant, as the data is non more required, once a candidate is found.

Data extracted from each source is stored into DB (from here on, DB => in-memory HSQLDB), wherein we have one table each for a data source.

Here come the best part.
Now all my rules for computation are mere SQL queries. Instead of going through the code, one can easily understand the rules by looking at this SQL queries.
By adding proper indices, which can be done by simple annotations, we can perform any complex query in almost no time (subject to the size of data).
It also comes with one more added benefit, flexibility. We can add/modify rules with almost no effort.

HSQLDB has a huge community and all your queries, if any, would have been already answered.

Please share your comments/queries below.
Will add samples and mocks, if required.