HTML Application: Difference between revisions

Revision as of 04:45, 12 May 2015

Revision as of 12:13, 20 May 2015

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An '''HTML Application''' ('''HTA''') is a [[Microsoft Windows]] program whose source code consists of [[HTML]], [[Dynamic HTML]], and one or more scripting languages supported by [[Internet Explorer]], such as [[VBScript]] or [[JScript]]. The HTML is used to generate the user interface, and the scripting language is used for the program logic. An HTA executes without the constraints of the internet browser security model; in fact, it executes as a "fully trusted" application.

The usual file extension of an HTA is <code>.hta</code>.

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== Uses ==

HTAs give the developer the features of HTML together with the advantages of scripting languages. They are popular with Microsoft system administrators who use them for system administration from prototypes to "full-scale" applications, especially where flexibility and speed of development are critical.<ref>[https://msdn.microsoft.com/en-us/library/ms536496(v=vs.85).aspx ''Introduction to HTML Applications (HTAs)''], in MSDN Library</ref>

HTA is also a way of developing offline application. Such offline application usually includes a master HTA file, and bunch of html / js /css files.

== Disadvantages ==

Beside the advantage of programming applications in Internet environment [[programming languages]], which can usually be easier, due to the use of [[markup languages]] to build a [[User interface|UI]] (like [[XAML]], which was later presented by Microsoft as a part of [[Windows Presentation Foundation|WPF]]), there are a few disadvantages of the current standard of HTA:

* Only the main page of the project has the [[Filename extension|extension]] HTA, which means that only it can be modified with the properties of a GUI form.

* Opening new windows can be done only by [[JavaScript]] (and it might open it using the web browser). Linking to another page will open it in the same window.

* The engine of HTA files (mshta.exe) is completely dependent on [[Internet Explorer]]. In [[Windows Vista]], for the first time, the user can [[Removal of Internet Explorer|remove Internet Explorer]] from Windows, which will cause a serious bug for the engine of HTA files.

* Using [[server-side]] scripting languages isn't a built-in option, and can only be done by running a local server at the moment the HTA file is opened.

* HTA files can't be compiled. The only solution that was found for that is to compress all of the files of the project to an [[Self-extracting archive|SFX]] package. Another disadvantage of compiling an HTA is the fact that files inside the project can't be modified (modifying files usually can be done by [[server-side]] scripting languages, although the HTA engine has a permission to write files).

* HTA files are only correctly supported by IE6 to IE9 with their handful <HTA:Application> tag. As Microsoft has officially stopped their support for HTAs, these applications might never become HTML5 compliant.

* At the time of writing (2015), IE11 still supports HTA although with some minor features turned off. When people start a new project with HTA, it's important to find out whether Microsoft will dump it in the coming IE versions.

==Environment==

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[[File:HTA-Hello World example.png|thumb|300x300px|Screenshot of an example window produced by <code>mshta.exe</code>]]

An HTA is executed using the program <code>mshta.exe</code>, or, alternatively, double-clicking on the file. This program is typically installed whenalong with Internet Explorer is installed. <code>mshta.exe</code> executes the HTA by instantiating the Internet Explorer rendering engine (mshtml) as well as any required language engines (such as vbscript.dll).

An HTA is treated like any executable file with extension [[EXE|<code>.exe</code>]]. When executed via mshta.exe (or if the file icon is double-clicked), it runs immediately. When executed remotely via the browser, the user is asked once, before the HTA is downloaded, whether or not to save or run the application; if saved, it can simply be run on demand after that.<ref>[https://msdn.microsoft.com/en-us/library/ms536496(v=vs.85).aspx ''Why Use HTAs''], in MSDN Library, Introduction to HTML Applications</ref>

By default, HTAs are rendered as per "standards-mode content in IE7 Standards mode and quirks mode content in IE5 (Quirks) mode", but this can be altered using <code>X-UA-Compatible</code> headers.<ref>[https://msdn.microsoft.com/en-us/library/ms536496%28v=vs.85%29.aspx#Compatibility] Introduction to HTML Applications (HTAs) - Compatibility</ref>

* The engine of HTA filesengine (mshta.exe) is completely dependent on [[Internet Explorer]]. InStarting from [[Windows Vista]], for the first time, thea user can [[Removal of Internet Explorer|remove Internet Explorer]] from Windows, which will causemake athe serious bug for theHTA engine ofto HTAstop filesworking.

HTAs are fully supported in Internet Explorer from versions 5 to 9. Further versions, such as 10 and 11, still support HTAs though with some minor features turned off.{{fact}}

===Security considerations===

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On the other hand, an HTA runs as a fully trusted application and therefore has more privileges than a normal HTML file; for example, an HTA can create, edit and remove files and [[Windows Registry|registry]] entries. Although HTAs run in this 'trusted' environment, querying [[Active Directory]] can be subject to Internet Explorer Zone logic and associated error messages.

==FunctionalityDevelopment==

To customize the appearance of an HTA, aan new (optional) tag <code>hta:application</code> was introduced to the <code>HEAD</code> section. This tag exposes a set of attributes that enable control of border style, the program icon, etc., and provide information such as the argument (commandline) used to launch the HTA.<ref>[https://msdn.microsoft.com/en-us/library/aa360681(v=VS.85).aspx ''HTA:APPLICATION Object''], in MSDN Library, the complete specification of the tag <code>hta:application</code></ref> Otherwise, an HTA has the same format as an HTML page.

Otherwise, an HTA has the same format as an HTML page.

==Development tools==

Any text editor can be used to create an HTA. Editors with special features for developing HTML applications may be obtained from Microsoft<ref>[http://www.microsoft.com/downloads/details.aspx?FamilyId=231D8143-F21B-4707-B583-AE7B9152E6D9&displaylang=en ''HTA Helpomatic'']</ref> or from third-party sources.<ref>[http://www.htaedit.com/ ''HTAEdit, an editor for HTAs with a built-in debugger'']</ref>

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*[[Firefox OS]]

*[[PhoneGap]]

*[[XUL]] and [[XULRunner]] - a language and environment for Mozilla cross-platform applications that resembleresembles the mechanism of HTML Applications.

==References==