While we get the final Chronon 3 build ready, lets talk about some of the UI stuff in Chronon 3. Although this release is mainly focused on insane performance improvements, we have taken some time to improve the Chronon Debugger too.

Per Thread Time

Up till Chronon 2, we only had a single global timeline to represent all events.

With Chronon 3, we are introducing ‘Per Thread Time’, which gives each thread its own timeline, facilitating in must easier and faster debugging.

Timeline View

The Timeline View has always been one of the most critical views in the Chronon Debugger UI. It does the fundamental job of telling you whether you just jumped forward/backward in the execution of your program. Without it, you would be ‘lost in time’. The Timeline view also allows to save Time Bookmarks.

Time Progress Bars

The biggest UI change you will notice is that instead of having a single bar showing progress through time, we have 2 bars.

One shows ‘global time’, which tells you how far you are down the execution of the entire program. This is conceptually similar to the single bar that used to be present in Chronon 2.

The bar below that shows you how far you are down the execution of the current thread.

Time Bookmarks

Time Bookmarks now save time as ‘current thread time’ instead of ‘global time’

Conclusion

Per Thread Time is a feature that many users have wanted and is extremely useful.

A lot of times, in a large recording, you can have many, many threads that were created and destroyed throughout the course of the program, and you really want to know whether the code you are debugging in the current thread, are you close to the end of that thread or in the middle. A good example is when debugging uncaught exceptions, since when you are near an uncaught exception, the ‘current thread’ bar will be almost full.

With that said, we are just packaging things up for the final release. Stay tuned to our twitter feed to hear about the release as soon as it is available! 

A lot of people come up to me with this peeve:

The Step Forward button in Chronon, when it reaches the end of a method, doesn’t perform an automatic ‘step out’ like your regular debugger. Instead you have to click the ‘Step Out’ button manually.

The Problem

The reason we don’t have the ‘Step Forward’ button automatically do a ‘Step Out’ is apparently due to the presence of the ‘Step Backward’ button.

Consider this scenario:

1. Stepping forward at the end of a method Steps Out of it.
2. Now when the user presses the Step Backward button:
   1. Should we go back inside the method we came out of, or
   2. Should we ‘step back’ in the current method we just stepped out to.

The undefined semantic of the Step Back button in this case could cause confusion to the user if we took either of those choices, but the user expected the another.

Our Solution

We wanted to keep the semantic of the ‘Step Back’ button to do exactly the opposite of what the ‘Step Forward’ button does.

So in this case, to keep that semantics of Step Back intact, we limited the Step Back and Step Forward to only step inside a single method call and requiring the user to press the ‘Step Out’ button explicitly.

Mitigation

Although considering all the advantages Chronon offers over a regular debugger or logging, pressing the Step Out button is hardly an inconvenience, we made it even easier with the introduction of Keyboard Shortcuts.

The peeves that developers mentioned were really related to the fluidity and smoothness of the debugging experience when you only have to keep track of pressing a single button.

Keeping this in mind, if you use keyboard shortcuts for stepping within Chronon, the Step Out button is only a key away. Also you will notice the speed and fluidity when stepping using keyboard shortcuts is far, far smoother than using a regular debugger since we are not executing any code. Thus stepping over say a method that contains the bulk of your program’s execution in Chronon would happen instantly compared to a regular debugger where you would notice pauses.

Conclusion

I think the above post does a good job explaining the rational behind the behavior of the Step Forward button. The keyboard shortcuts introduced recently in Chronon do a good job of keeping the fluidity of the debugging experience and you will find the experience butter-smooth compared to using a regular debugger even with the extra hassle of pressing a different key for step out.

When we were developing Chronon and started using it ourselves, we realized something very intriguing. You see, the various views of Chronon allow you to step not only forward and backward but to any random point in time. For example, using the Variable History view, you can instantly jump to when a variable became ‘null’ or use one of the powerful filters in method history view to jump directly to a particular call of a method.

The problem

Since you are not just stepping forward, it is easy to get lost in time.

For example:

1. How does one event relate to the other, did it happen before or after the other?
2. Did I just jump forward or backward when I clicked in the variable history view?
3. If I did jump backward/forward, by how much did I jump?
4. Where am I in the execution of my program? Am I near the end of my program/ middle or end?

The Solution

Imagine you are a real world time traveler. What is the most important tool in your arsenal?

A clock.

We needed some sort of a clock inside Chronon to solve all the above issues.
Thus we invented the concept of ‘time’.

Time inside Chronon

‘Time’ inside Chronon does not stand for real-world clock time. After all how precisely can you really measure the time interval between say 2 variable assignments, and even if you could looking at the system clock each time your program executed an instruction, would result in a huge performance drain.

 

Thus ‘time’ in Chronon is merely an application wide counter. It has no relation to clock time. Its sole purpose is to give an ordering to events recorded in a program.

The only thing you know when you look at a time value is:

An event at say time 5 occurred after any event at time < 5, ie 4,3,… and before any event > 5, ie 6,7…

 

It is not guaranteed that the next time value after 5 would be 6 (though it is in 99% of cases), it could be 7,8 or any time > 5.

All you know about time values is that they are ascending in order, thus putting an ordering on events in your application.

 

Thus all the views in Chronon, like the Variable History, Method History, Thrown Exceptions, etc have a time value so you can see how the events in each relate to the other.

 

Timeline View

The ‘Timeline View’ was added to quite literally serve the role of a clock inside Chronon.

• It literally shows the current time value.
• The progress bar gives you an idea of how far down the execution of the program you are.
  See the bar completely fill up, well you are near the end, if its almost empty, you are near the beginning.
• We also added ‘time bookmarks’ in this view which act as a checkpoint mechanism for anything interesting you might want to return to in the future.

Consider the following  piece of code:

class B extends A {  //constructor  B()  {        this.field1 = "asdf";  }}void foo(){   B b =  new B();}

Note that the constructor of class B does not contain an explicit call to super()

In a traditional debugger, if you put a breakpoint on the line

B b = new B();

and ‘stepped into’ the call to new B(), you would be taken directly inside B(), with no chance to look at the super constructor of class A. The only way out of this would be to

1. Go back and explicitly place a breakpoint inside A()
2. Reproduce the bug (if it is at all possible at this point).
3. Start debugging all over again….
4. … only to have this happen again accidentally for the constructor of another class.

Step to Super

To deal with the issue of an explicit call to super() not being present, in Chronon we added a ‘Step to Super‘ button in the Stack view.
This button is active only when you are inside a constructor and clicking it takes you directly to the constructor of the superclass of that method.

The screenshots above show this in action.