CodeSchool courses on JavaScript Frameworks

CodeSchool is a great site for introductory programming courses. With all guides and practice exercises available right within the browser, it is a hassle-free way to start learning. The design of the site is also very pleasing which enhances the overall experience.

Recently, CodeSchool offered a free weekend pass to all their content. I took the opportunity to brush up my skills on the new version of Angular and also quickly went through the React course.

codeschool-angular-2

Course Link: Accelerating through Angular 2

 

codeschool-react

Course Link: Powering Up with React

 

Run MySql without installation

I had to run MySql database without installation and it took a little bit of effort to make it work. Here are the steps I performed for running MySql without going through installation (noinstall):

  1. Download Zip Archive (Community Edition) from http://dev.mysql.com/downloads/mysql/
  2. Unzip the archive and go to the bin folder.
  3. Initialize MySql database: Run the following on Command Prompt (cmd) while being in the bin folder. This creates data folder with database files.
    mysqld --initialize
  4. Start server with unrestricted access to the full database.
    mysqld --console --skip-grant-tables
  5. Reset password for root user
    • Run mysql.exe (MySql client) from the bin folder. This will take you to a prompt (mysql>).
    • Tell the server to load the grant tables so that account management statements work (They are not loaded due –skip-grant-tables parameter to server).
      mysql> FLUSH PRIVILEGES;
    • 
      

      On mysql prompt (mysql>), run the following queries to reset the root password (one of the following will work depending on your version)

      • ALTER USER 'root'@'localhost' IDENTIFIED BY 'MyNewPass';
      • SET PASSWORD FOR 'root'@'localhost' = PASSWORD('MyNewPass');
      • UPDATE mysql.user SET authentication_string = PASSWORD('MyNewPass') WHERE User = 'root' AND Host = 'localhost';
        FLUSH PRIVILEGES;
  6. Restart server in normal mode.
    mysqld --console
  7. Connect using client
    mysql -u root -p

    Enter the password (MyNewPass) when prompted

  8. Execute your queries on mysql prompt (mysql>).

Please note that this works for version 5.7, but may or may not apply to other versions.

 

In order to connect to MySql from the application, download the relevant connector from MySql Connectors. For instance, JDBC driver (connector) for connecting from Java application is available at Connector/J.

Mind Mate: Mind Mapping on Windows 7 and 8

(for background on Mind Mate, click here)

I have been developing Mind Mate on Windows 10 machine, so wasn’t sure how it is going to behave on earlier versions of OS. Today, I tested it on Windows 7 and 8 using VMs made available by Microsoft.

Mind Mate worked perfectly on Windows 8 but encountered few issues on Windows 7 related to Windows Ribbon Control. These issues are:

– Images in PNG format are not displayed in the ribbon. Seems like Ribbon control on Win7 only supports BMP, that too generated in a certain version of BMP specification. I found that only PixelFormer knows how to generate the right BMP file for Windows 7 Ribbon control.

– Controls don’t layout properly after initial launch, it requires resizing the main window once, then it starts working fine.

– Non true type fonts are not supported.

These issues are resolved in the new Build. Download it from here and give it a go.

Developed Mind Mapping software–codenamed ‘Mind Mate’

Mind Map is a graphical way of representing concepts and ideas. It starts with the main idea at the center with branches going into details.

Personally I use it for all my notes taking, to do lists, managing project information etc. Probably it goes beyond what normal usage of the term Mind Map implies but I found many people using Mind Mapping software in the same way. The appeal of Mind Mapping software, in the regard, is the ability to handle the depth of information. Due to outlining you focus on the level of information you want, dig deeper into a topic or zoom out to the headlines with ease.

FreeMind and XMind are the most popular software out there. Personally I prefer FreeMind as it is more suitable to the usage style I described above. XMind is more focused towards presentation, rather than daily usage for notes taking. Unfortunately, FreeMind is a not being developed very actively.

Since last couple of years I have been developing my own Mind Mapping software on Github. It started just as a pastime and somehow I managed to put in some hours week after week. It have been a fun ride and a very good learning experience. I switched to it for my daily use for few months now. Today i prepared a installer for MindMate to make it more accessible. Please download it and give it a short. I will wait for your feedback.

It would be my pleasure if you are interested in contributing to the project in any role. It could be as developer, document writer, tester or just providing feedback as a user.

Download Windows Installer or Portable Zip from here: MindMate

(MindMate only supports Windows 10 for now, will test and build it for earlier version soon)

Review: Pixar in a box Tutorial by Khan Academy

Pixar is a box’ is an excellent tutorial at Khan Academy developed in collaboration with Pixar Animation Studios. It is about some of the Math concepts that we learn in school and how they apply to making animated movies. The content is meant for secondary school students (and above Smile).

Tutorial sketches a broad outline of the pipeline for producing animation, with each lesson digging deeper into a particular concept and its Mathematics.

1- Environment Modeling talks about representing curves (parabolic curves) using three points, rather than equations. It is more intuitive to work with three control points while designing and animating curves. This knowledge about curves is applied to create grass blade. A lot of grass blades are put together with randomness and animation offsets to create a natural looking grass field.

2- Character Modeling describes how polygons are used to start modeling shapes and subdivision algorithm is used to smoothen out the edges. 2D sketch of Human hand is designed using this technique without much effort. The crux of the lesson is the mathematics of subdivision and its application in 2D and 3D.

3- Animation lesson explains the role of Bezier curve in representing animation. A realistic bouncing ball animation is created in hands-on exercise.

4- Crowds are created by joining a number of parts in various combinations.  Lesson explores the concepts of permutations and apply it to calculating the number of possible combinations.

5- Sets & Staging deals with placing characters in the environment. Environment contains various objects which are placed around in the scene after scaling and rotating them as required. The lesson explains the mathematics behind these geometric transformations.

6- Rendering is a particularly exciting lesson which brings out the complexity of the whole process. While rendering we have to determine the color of each pixel in a frame taking into account all the light sources, camera position, all objects in the scene and how each object reflects or refracts light. This is done by casting rays out of the light sources and bouncing them off various surfaces. Diffuse and Specular properties of a surface determine how light will be reflected by it.

‘‘Pixar in a box’ is highly recommended as a fun way to learn.

Pixar in a box

Developed a basic, light-weight library for scheduling tasks in C# .Net

Source code can be found at GitHub

TaskSchedular

TaskScheduler is a simple and efficient C# .Net library that runs given tasks at the specified date and time.

  • Efficient : There is no polling. Only runs when a task is due. This is achieved though AutoResetEvent.
  • Simple : Merely 8 KB in size. Pretty easy to use but addresses limited number of use cases.

Background

.Net Framework comes with various Timer classes which give us the ability to run a task periodically.

Apart from Timers which run periodically, we don’t have any class which executes tasks at a given time. A usual work around is to use Timer of a second or so (based on your need), then keep checking if any task is due in timer’s event and execute the task when due. In order to be more resource friendly, TaskSchedular takes a different approach instead of continuous polling for task due date.

How TaskScheduler Works

It runs in it’s own thread and doesn’t consume any CPU resouces till a task is due. This is acheived through Wait Handle (AutoResetEvent). All scheduled tasks are executed in the same thread, which means:

  • tasks are not running in GUI thread so any code which is related to GUI should be invoked on the GUI thread. See this blog post for running code in GUI thread using Control.Invoke.
  • tasks are never executed in parallel as there is only one thread. This has following upshots:
    • saves us from thread synhronization issues within tasks.
    • this library might not the the right one for you if you need more parallelism. In such a case, check out alternatives like Quartz.NET and FluentScheduler.

Usage

Starting TaskScheduler
var schedular = new TaskSchedular.TaskSchedular();
schedular.Start();
Adding task
schedular.AddTask(new TaskSchedular.Task()
    {
        StartTime = DateTime.Now.AddSeconds(30),
        TaskAction = () =>
        {
            // do some work here
            System.Threading.Thread.Sleep(300);
        },
        Recurrance = TimeSpan.FromSeconds(30)
    });

Note: TaskSchedular is has a tolerance of 1 second by default, that is, if a task is due within a second, it will execute it right away.

Book Review: Operational Decision Management for Dummies

ODM for Dummies BookBusiness rules and validations related to an automated Business Process are generally hidden deep within the application source code and configuration settings. They are not openly accessible, easily to change or review. They might be duplicated several times across the source code.

Operational Decision Management (ODM) systems try to remedy this situation by providing a central repository for business rules. This repository acts as a single source of truth for users as well as systems. Rules are generally specified in the form of Decision Tables or Trees.

ODM complements BPM (Business Process Management) systems well, as BPM is also metadata driven with a focus on business process workflows and SOA (Serice Oriented Architecture) for integration.

Operational Decision Management for Dummies is a free booklet sponsored by IBM which provides a nice and quick definition of ODM systems. It is recommended for anyone interested in understanding what ODM is, what are its use cases and potential pay offs.

You can also check out this article for some concrete examples on how operational decisions (business rules) are automated by any ODM system.

MouseHover event in Windows Forms .Net – Generating it repeatedly

MouseHover Event

When mouse is stationary for some time over a Windows Forms control, Mouse Hover event is generated. This event is generated only once during mouse’s stay and movement over a control. If mouse leaves and re-enters the control, system again starts tracking for Mouse Hover and will generate the event accordingly.

A common use of Mouse Hover event is to display tool tip.

Following code attaches MouseHover handler to a control.

myControl.MouseHover += myControl_MouseHover;

The handler just logs that event is generated.

void myControl_MouseHover(object sender, EventArgs e)
{
    System.Diagnostics.Debug.WriteLine(
        "MouseHover event generated");
}

Generating Mouse Hover event repeatedly

In some scenarios, it could be desirable to generate Mouse Hover event repeatedly inside a control, whenever mouse becomes stationary. For instance, this could be useful if you have a user-drawn control and want to generate Mouse Hover events for individual user-drawn components. To achieve this, we need to reset the Hover event every time it is generated. This can be done by calling TrackMouseEvent method in MouseMove event.

Adding MouseMove event handler…

myControl.MouseMove += myControl_MouseMove;

Calling TrackMouseEvent to reset tracking of Hover event:

void myControl_MouseMove(object sender, MouseEventArgs e)
{
    const uint HOVER_DEFAULT = 0xFFFFFFFF;
    TRACKMOUSEEVENT trackMouseEvent = 
        new TRACKMOUSEEVENT(TMEFlags.TME_HOVER, this.Handle, HOVER_DEFAULT);
    TrackMouseEvent(ref trackMouseEvent);
}

As TrackMouseEvent is a native method, we need to define it using DllImport along with the TRACKMOUSEEVENT structure.

[System.Runtime.InteropServices.DllImport("user32.dll")]
static extern int TrackMouseEvent(ref TRACKMOUSEEVENT lpEventTrack);

[System.Runtime.InteropServices.StructLayout(System.Runtime.InteropServices.LayoutKind.Sequential)]
public struct TRACKMOUSEEVENT
{
    public Int32 cbSize;    // using Int32 instead of UInt32 is safe here, and this avoids casting the result  of Marshal.SizeOf()
    [System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.U4)]
    public TMEFlags dwFlags;
    public IntPtr hWnd;
    public UInt32 dwHoverTime;

    public TRACKMOUSEEVENT(TMEFlags dwFlags, IntPtr hWnd, UInt32 dwHoverTime)
    {
        this.cbSize = System.Runtime.InteropServices.Marshal.SizeOf(typeof(TRACKMOUSEEVENT));
        this.dwFlags = dwFlags;
        this.hWnd = hWnd;
        this.dwHoverTime = dwHoverTime;
    }
}


/// <summary>
/// The services requested. This member can be a combination of the following values.
/// </summary>
/// <seealso cref="http://msdn.microsoft.com/en-us/library/ms645604%28v=vs.85%29.aspx"/>
[Flags]
public enum TMEFlags : uint
{
    /// <summary>
    /// The caller wants to cancel a prior tracking request. The caller should also specify the type of tracking that it wants to cancel. For example, to cancel hover tracking, the caller must pass the TME_CANCEL and TME_HOVER flags.
    /// </summary>
    TME_CANCEL = 0x80000000,
    /// <summary>
    /// The caller wants hover notification. Notification is delivered as a WM_MOUSEHOVER message.
    /// If the caller requests hover tracking while hover tracking is already active, the hover timer will be reset.
    /// This flag is ignored if the mouse pointer is not over the specified window or area.
    /// </summary>
    TME_HOVER = 0x00000001,
    /// <summary>
    /// The caller wants leave notification. Notification is delivered as a WM_MOUSELEAVE message. If the mouse is not over the specified window or area, a leave notification is generated immediately and no further tracking is performed.
    /// </summary>
    TME_LEAVE = 0x00000002,
    /// <summary>
    /// The caller wants hover and leave notification for the nonclient areas. Notification is delivered as WM_NCMOUSEHOVER and WM_NCMOUSELEAVE messages.
    /// </summary>
    TME_NONCLIENT = 0x00000010,
    /// <summary>
    /// The function fills in the structure instead of treating it as a tracking request. The structure is filled such that had that structure been passed to TrackMouseEvent, it would generate the current tracking. The only anomaly is that the hover time-out returned is always the actual time-out and not HOVER_DEFAULT, if HOVER_DEFAULT was specified during the original TrackMouseEvent request.
    /// </summary>
    TME_QUERY = 0x40000000,
}

Above ensures that Hover event is generated whenever mouse stays still for sometime, and not only once after mouse enters the control.

Book Review: Threading in C# by Joseph Albahari

Threading is a complex subject, it is easy to get yourself entangled in threads which don’t behave as you expect them to. There are many constructs and approaches to synchronize threads or achieve parallelism, each with its own quirks and advantages. There are good old threads, there are thread pools, task parallelism, Parallel class, Async methods and Timers. Then there are a myriad ways of synchronizing thread like locks, spin locks, mutex, semaphores, event wait handles, concurrent collections, Synchronization attribute, Memory Barriers, Interlocked class, Monitor’s Wait/Pulse and Reader Writer Lock . To make sense of it all,  Threading in C# by Joseph Albahari is thorough reference on the subject. It is available online, free of charge in hypertext format which makes it particularly useful as a reference.

csianThreading in C# is also there as a chapter in somewhat abridged form in author’s book ‘C# in a Nutshell‘.