Subpixel Layout And Rendering

Gecko does subpixel layout and rounds coordinates to device pixels for rendering.

He's right that in some sense, when you have to render a CSS layout to a screen with discrete pixels, all the options are imperfect and browsers are choosing different imperfect options. However I think we need to explain the big picture a little better.

Gecko intentionally supports subpixel layout because for high resolution output devices, especially printers but also high-DPI screens that will become more common, one CSS "px" should be mapped to many device pixels, so you can in fact do sub-CSS-pixel rendering. For those devices, rounding layout units to CSS pixels is actually throwing away information and giving you a strictly worse layout than Gecko will give. For example, try printing in FF3 beta. You should see that in the printout (or generated PDF), no rounding has occurred and each child DIV looks identical.

Because this is important and we don't want layout to vary unnecessarily across devices, we do subpixel layout on all devices. When we have to draw to a regular-DPI screen, we then have to round the edges of drawn objects to the nearest screen pixel. This explains the results. Note that our approach of rounding at drawing time is optimal for avoiding gross layout changes due to rounding; it limits the impact of rounding to moving object edges by one pixel in some direction. It avoids gross layout changes like IE moving a DIV to the next line, or Safari leaving a 2px strip vacant at the end of the line. Thus I believe our approach is better than the alternatives in important ways.

The preceding paragraph is actually a slight oversimplification. We do have to do some rounding during layout simply due to the fact that computer arithmetic has limited precision. So during layout we round measurements to the nearest 1/60th of a CSS pixel. This number was chosen so that common fractions of a CSS pixel can be represented exactly. Note that rounding to 1/60th of a CSS pixel is far more benign than rounding to CSS pixels; 1/60th of a CSS pixel is approximately 1/5760th of an inch, not something most people are going to worry about!

In practice, we have seen very few Web compatibility issues caused by this scheme. Web authors should just not worry about the rounding, and should not attempt to round coordinates themselves. The new getBoundingClientRect and getClientRects APIs in FF3 can return fractional coordinates, just go with the flow. Feel free to position elements at those fractional boundaries, it will be lined up visually. If you insist on consistent rendering down to the pixel, then the only way to go is to specify px values for everything, including line-heights, and avoid percentage units. Or better still, use SVG. Or a PNG.

Flex in a week (47 video tutorial)

• Video 01 - Comparing Flash, Flex, FP and AIR
• Video 02 - Introducing Flex Builder
• Video 03 - Flex Builder Workspace and Project
• Video 04 - Using Pre-Built Flex Controls
• Video 05 - Understanding MXML
• Video 06 - Binding Data Between Controls
• Video 07 - Handling User Events
• Video 08 - Introducing the Event Object
• Video 09 - Adding Event Listeners with AS3
• Video 10 - Retrieving data via HTTPService
• Video 11 - Displaying Data in the DataGrid
• Video 12 - Working with Containers
• Video 13 - Creating Custom MXML Components
• Video 14 - Implementing Value Object Classes
• Video 15 - Creating Custom Events
• Video 16 - Creating Custom Event Classes
• Video 17 - Customizing Item Renderers
• Video 18 - Exploring Flex Builder Tips
• Video 19 - Validating Data
• Video 20 - Passing Data to Server with RemoteObject
• Video 21 - Formatting Data
• Video 22 - Dragging Data Between List Components
• Video 23 - Filtering XML with E4X
• Video 24 - Deploying Flex and AIR Applications
• Video 25 - Implementing Navigator Containers
• Video 26 - Embedding Images
• Video 27 - Embedding Fonts
• Video 28 - Creating Constraint-Based Layouts
• Video 29 - Applying Styles to MXML Components
• Video 30 - Skinning Components with Adobe CS3
• Video 31 - Creating View States
• Video 32 - Animating - Behaviors and Transitions
• Video 33 - Drawing Shapes with the Drawing API
• Video 34 - Skinning Components Programmatically
• Video 35 - Extending Components
• Video 48 - Reducing file size
• Video 40 - Building runtime shared libraries
• Video 36 - Flash timer mechanism
• Video 37 - Custom Flash graphics in comp
• Video 38 - Using and animating filters
• Video 39 - Creating SWC files
• Video 41 - Splitting your app into modules
• Video 42 - Communicating over local connections
• Video 43 - Using shared objects
• Video 44 - Embedding video in your application
• Video 46 - Localization using resource bundles
• Video 45 - Controlling video using Ajax
• Video 47 - Integrating Flex with PHP using XML

Add Copy To / Move To to the Windows Explorer Right Click Menu

A hidden functionality in Windows allows you to right click on a file, select Copy To Folder or Move To Folder, and the move to box will pop up and let you choose a location to either copy or move the file or folder to.

Here's the quick registry hack to get this working. As usual, back up your registry just in case. You will want to browse down to this key:

HKEY_CLASSES_ROOT\AllFilesystemObjects\shellex\ContextMenuHandlers

Once you are at that key, right click and choose the New Key option:

Now you will double-click on the (Default) value and enter the following:

{C2FBB630-2971-11D1-A18C-00C04FD75D13}

Click OK and continue.

If you want to enable Move To, you will repeat the same steps, except creating a new key named Move To, and using this value:

{C2FBB631-2971-11D1-A18C-00C04FD75D13}

Now when you right click on a file or folder, you should see the following options:

Let's click Copy To Folder just to see what happens….

And that's it. Useful!

Open PCs (WIN XP) protected by passwords.

1. Power on the PC.
2. Press CTRL+ALT+DEL
3. Press CTRL+ALT+DEL, again
   
4. Type in the user name field the word "Administrator"
5. Leave the password field empty.

That's all !!

.SO extension

• Extension: .so
• Type: Unix Shared Library
• Category: Development
• Mime type: application/octet-stream
• Description: SO file is an Unix Shared Library (Shared Object). A shared library is a library of functions or classes (for C/C++ programmers) that are compiled, linked, and stored separately from the clients (applications) that use them. The UNIX equivalent of a DLL file in Windows is a Shared Library (SO) file.
  

Kerberos

Kerberos is a computer network authentication protocol, which allows individuals communicating over a non-secure network to prove their identity to one another in a secure manner. It is also a suite of free software published by Massachusetts Institute of Technology (MIT) that implements this protocol. Its designers aimed primarily at a client-server model, and it provides mutual authentication — both the user and the server verify each other's identity. Kerberos protocol messages are protected against eavesdropping and replay attacks.

Kerberos builds on symmetric key cryptography and requires a trusted third party. Extensions to Kerberos can provide for the use of public-key cryptography during certain phases of authentication.


Description

Kerberos uses as its basis the Needham-Schroeder protocol. It makes use of a trusted third party, termed a key distribution center (KDC), which consists of two logically separate parts: an Authentication Server (AS) and a Ticket Granting Server (TGS). Kerberos works on the basis of "tickets" which serve to prove the identity of users.

The KDC maintains a database of secret keys; each entity on the network — whether a client or a server — shares a secret key known only to itself and to the KDC. Knowledge of this key serves to prove an entity's identity. For communication between two entities, the KDC generates a session key which they can use to secure their interactions.


Protocol

The security of the protocol relies heavily on participants maintaining loosely synchronized time and on short-lived assertions of authenticity called Kerberos tickets.

What follows is a simplified description of the protocol. The following abbreviations will be used:

• AS = Authentication Server
• TGS = Ticket Granting Server
• SS = Service Server
• TGT = Ticket Granting Ticket
  

Briefly, the client authenticates to AS using a long-term shared secret and receives a ticket from the AS. Later the client can use this ticket to get additional tickets for SS without resorting to using the shared secret. These tickets can be used to prove authentication to SS.

In more detail:

User Client-based Logon Steps:

1. A user enters a username and password on the client machine.
2. The client performs a one-way function (Hash mostly) on the entered password, and this becomes the secret key of the client/user.
   

Client Authentication Steps:

1. The client sends a cleartext message to the AS requesting services on behalf of the user. Sample message: "User XYZ would like to request services". Note: Neither the secret key nor the password is sent to the AS.
2. The AS checks to see if the client is in its database. If it is, the AS sends back the following two messages to the client:
• Message A: Client/TGS Session Key encrypted using the secret key of the client/user.
• Message B: Ticket-Granting Ticket (which includes the client ID, client network address, ticket validity period, and the client/TGS session key) encrypted using the secret key of the TGS.
3. Once the client receives messages A and B, it decrypts message A to obtain the Client/TGS Session Key. This session key is used for further communications with TGS.
   (Note: The client cannot decrypt Message B, as it is encrypted using TGS's secret key.)
   At this point, the client has enough information to authenticate itself to the TGS.
   

Client Service Authorization Steps:

1. When requesting services, the client sends the following two messages to the TGS:
• Message C: Composed of the Ticket-Granting Ticket from message B and the ID of the requested service.
• Message D: Authenticator (which is composed of the client ID and the timestamp), encrypted using the Client/TGS Session Key.
2. Upon receiving messages C and D, the TGS retrieves message B out of message C. It decrypts message B using the TGS secret key. This gives it the "client/TGS session key". Using this key, the TGS decrypts message D (Authenticator) and sends the following two messages to the client:
• Message E: Client-to-server ticket (which includes the client ID, client network address, validity period and Client/Server Session Key) encrypted using the service's secret key.
• Message F: Client/server session key encrypted with the Client/TGS Session Key.
  

Client Service Request Steps:

1. Upon receiving messages E and F from TGS, the client has enough information to authenticate itself to the SS. The client connects to the SS and sends the following two messages:
• Message E from the previous step (the client-to-server ticket, encrypted using service's secret key).
• Message G: a new Authenticator, which includes the client ID, timestamp and is encrypted using client/server session key.
2. The SS decrypts the ticket using its own secret key to retrieve the Client/Server Session Key. Using the sessions key, SS decrypts the Authenticator and sends the following message to the client to confirm its true identity and willingness to serve the client:
• Message H: the timestamp found in client's Authenticator plus 1, encrypted using the Client/Server Session Key.
3. The client decrypts the confirmation using the Client/Server Session Key and checks whether the timestamp is correctly updated. If so, then the client can trust the server and can start issuing service requests to the server.
4. The server provides the requested services to the client.
   

Drawbacks

• Single point of failure: It requires continuous availability of a central server. When the Kerberos server is down, no one can log in. This can be mitigated by using multiple Kerberos servers and fallback authentication mechanisms.
• Kerberos requires the clocks of the involved hosts to be synchronized. The tickets have a time availability period and if the host clock is not synchronized with the Kerberos server clock, the authentication will fail. The default configuration requires that clock times are no more than 10 minutes apart. In practice Network Time Protocol daemons are usually used to keep the host clocks synchronized.
• The administration protocol is not standardized and differs between server implementations. Password changes are described in RFC 3244.
• Since the secret keys for all users are stored on the central server, a compromise of that server will compromise all users' secret keys.
• A compromised client will compromise the user's password
  

Shared secret

In cryptography, a shared secret is a piece of data only known to the parties involved in a secure communication. The shared secret can be a password, a passphrase, a big number or an array of randomly chosen bytes.

The shared secret is either shared beforehand between the communicating parties, in which case it can also be called a pre-shared key. Or it is created at the start of the communication session by using a key-agreement protocol, for-instance using public-key cryptography such as Diffie-Hellman or using symmetric-key cryptography such as Kerberos.

The shared secret can be used for authentication (for instance when logging in to a remote system) using methods such as challenge-response or it can be fed to a key derivation function to produce one or more keys to use for encryption and/or MACing of messages.

To make unique session and message keys the shared secret is usually combined with an initialization vector (IV).

Passphrase

A passphrase is a sequence of words or other text used to control access to a computer system, program or data. A passphrase is similar to a password in usage, but is generally longer for added security. Passphrases are often used to control both access to, and operation of, cryptographic programs and systems. Passphrases are particularly applicable to systems that use the passphrase as an encryption key.

Compared to passwords

Passphrases differ from passwords. A password is usually short — six to ten characters. Such passwords may be adequate for various applications (if frequently changed, if chosen using an appropriate policy, if not found in dictionaries, if sufficiently random, and/or if the system prevents online guessing, etc.) such as:

• Logging onto computer systems
• Negotiating keys in an interactive setting (e.g. using password-authenticated key agreement)
• Enabling a smart-card or PIN for an ATM card (e.g. where the password data (hopefully) cannot be extracted)
  

But passwords are typically not safe to use as keys for standalone security systems (e.g., encryption systems) that expose data to enable offline password guessing by an attacker. Passphrases are generally stronger, and a clearly better choice in these cases. First, they usually are (and always should be) much longer — 20 to 30 characters or more is typical, making some kinds of brute force attacks entirely impractical. Second, if well chosen, they will not be found in any 'phrase or quote dictionary', so such dictionary attacks will be almost impossible. Third, they can be so structured as to be more easily memorable than passwords without being written down, reducing that risk as well. Most applications will allow for spaces which is recommended because the use of spaces will increase the brain’s ability to remember the passphrase. They can be, thus, considerably more 'secure'.

Passphrase selection

Typical advice about choosing a passphrase includes suggestions that it should be:

• Long enough to be hard to guess (eg, automatically by a search program, as from a list of famous phrases). * Not a famous quotation from literature, holy books, et cetera
• Hard to guess by intuition -- even by someone who knows the user well
• Easy to remember and type accurately
• For better security, any easily memorable encoding at your own level can be applied.

Advanced JavaScript by Douglas Crockford

Douglas Crockford teaches "Advanced JavaScript."
This course is broken into three clips;
Slides: http://yuiblog.com/assets/crockford/advancedjavascript.zip

Douglas Crockford: "Advanced JavaScript" (1 of 3)

Douglas Crockford: "Advanced JavaScript" (2 of 3)

Douglas Crockford: "Advanced JavaScript" (3 of 3)

int VS Integer

Newbies are often confused by the difference between int and Integer.

To properly understand the difference, you should read an introductory textbook on Java. I will make a small stab at answering here.

Everything I say here applies analogously to char and Character, short and Short, long and Long, float and Float, double and Double.

Definitions

An int is a primitive. It is not an Object. An int is a high performance, streamlined beast for calculating numbers in the range -2,147,483,648 [-2³¹] aka Integer.MIN_VALUE to +2,147,483,647 [2 ³¹-1] aka Integer.MAX_VALUE. An int is a bare bones 32-bit chunk of information. int variables are mutable. Unless you mark them final, you can change their value at any time.

An Integer, is a Object that contains a single int field. An Integer is much bulkier than an int. It is sort like a Fedex box to contain the int. Integers are immutable. If you want to affect the value of a Integer variable, the only way is to create a new Integer object and discard the old one.

Which is better?

That is like asking which is better a volley ball or a volleyball in a Fedex box. It depends what you want to do with it.

ability	unboxed int	boxed Integer
Calculate with it, + - * / % ^ etc.	yes	no
Pass it as a parameter	yes	yes
return it as a value	yes	yes
Use methods on it from java.lang.Integer	no	yes
Store it in a Vector or other Collection	no	yes
Use it as a HashMap key	no	yes
serialize it	no	yes
send it by itself over RMI	no	yes
send it as part of another Object over RMI	yes	yes
pass it as a generic object to a TableCellRenderer. You may pass a variety of different types via the same paramter.	no	yes
Allow for a null value that means there is no value.	no	yes

Converting

Fortunately it is easy to convert back and forth between int and Integer.

// to int i from Integer ii
int i = ii.intValue();

// to Integer ii from int i
Integer ii = new Integer( i );

Starting with Java 1.5, with boxing and unboxing, the compiler will sometimes automatically do the conversions to and from int and Integer for you so you can treat int and Integer as if they were almost the same thing.

Why Both?

Why are there both int and Integer? For speed. ints, without any Object packaging are compact and fast. Would it not have been easier if there were only one of sort of creature that could do everything and have the compiler automatically figure out when the packaging was needed and when not? The Eiffel language designers thought so, and the Java designers are gradually coming around to the same conclusion.

Unable to start debugging on the web server

Problem :
debugging your ASP.NET code you receive a message box :
"Error while trying to run project: Unable to start debugging on the web server. You do not have permission to debug the application. The URL for this project is in the Internet zone. Click Help for more information"

Solution :
01. Open Internet Explorer.
02. Point to "Tools" in IE main Menu Bar.
03. Select "Internet Options".
04. Switch to "Security" Tab.
05. Click on "Internet" (The Globe Icon, by the way it's the default ).
06. Click on "Custom Level" in the bottom.
07. Scroll down to "User Authentication" section.
08. Select "Automatic logon with current username and password".
09. Click "Ok" .
10. Click another "Ok".

This should solve the issue !!
Don't forget ..... enjoy your problems !!!!