- From: <bugzilla@jessica.w3.org>
- Date: Fri, 18 Feb 2011 18:06:28 +0000
- To: public-html-bugzilla@w3.org
http://www.w3.org/Bugs/Public/show_bug.cgi?id=12123 Summary: File Streaming Product: HTML WG Version: unspecified Platform: PC OS/Version: Linux Status: NEW Severity: normal Priority: P2 Component: HTML5 spec (editor: Ian Hickson) AssignedTo: ian@hixie.ch ReportedBy: jackalmage@gmail.com QAContact: public-html-bugzilla@w3.org CC: mike@w3.org, public-html-wg-issue-tracking@w3.org, public-html@w3.org (This bug was split out from <http://www.w3.org/Bugs/Public/show_bug.cgi?id=11796>.) 4) File tag <file></file> and FILE STREAMING -------------------------------------------------------- This is the most important suggestion. Currently, server side technologies exist for dynamically generating content that can be displayed in browsers. E.g. images The problem here is no client side technology is available to support dynamic content generation. For better understanding, I will start with a problem statement PROBLEM --------------- I have a PHP script that dynamically generates a chart in form of a GIF image. I can point the SRC attribute of an image tag to this PHP script but there is no standard way for the browser to handle this, so while one browser will reject the image because it does not recognise ".php" as an image extension, another browser will ask the user if they want to save the file (download it). In PHP, there is an extension called GD that can be used to dynamically generate images at runtime, however to send this image to the browser, the image first has to be saved to a file on the server (this has an overhead), then an image tag is sent to the browser with the SRC attribute set to the location of the image file. This places restrictions on the use of dynamically generated files. It is important to note that dynamically generated files are not only limited to images, flash, PDF and other files can also be generated dynamically. Currently only static files are supported. SOLUTION --------------- The file tag is an attempt to provide a solution to this problem. The file tag provides a standard way for dynamically generated content to be sent to the client directly (streamed). Description : A file tag is a container for dynamically generated and streamed files. A file tag is a generic container that can host any type of file. The server side script first sends a mime-type header to inform client of the kind of file client should be expecting / will be receiving. Files are displayed through the use of plugins or inbuilt browser capabilities. Although there are special tags to handle various file types (<img>, <audio>, <video>), having one tag that is file type independent and relies mostly on plugins to display files removes to necessity to add file streaming support to each tag that hosts files. How It Works I add a file tag to my HTML page and set the "SRC" to a PHP script or any server side script. This script is called and it first sends a mime type header followed by dynamically generated content. Browser uses mime type to be able to display file. Browser might have native capacity to display file or it may have a plugin installed which it uses to display file. Where the browser does not have a plugin installed that can display file and a native capacity to display file, the user is informed that browser cannot display file and is given the option of saving file to disk to open later with an appropriate program. Also, dynamically generated content can also be streamed inbetween the file tag. I.E. Instead of setting the "SRC" attribute to a server side script, the server side script can simply echo the beginning file tag <file>, echo the mime type header, echo the dynamically generated content and then echo the closing tag </file> . It works either way. The file object created from a file tag exposes certain methods and properties - ispluginused (boolean property) : is true if a plugin is currently used to display the contents of file tag. - getplugin() : a method called to get a reference to plugin object if object exposes it self to javascript. returns the plugin object on success and false on failure - Load($url) : Current file content is unloaded and new content is loaded by calling server side script pointed to by $url - Refresh() : Reloads content from current url. DEFINITION OF TERMS --------------------------------- 1 )Static files : are files saved on the server which are sent to the client upon request. Static files are usually generated using 3rd party software and are then saved on the server. They are hardly changed after being saved on the server. And a change will require human interaction. 2 )Streamed files : are files that are generated dynamically by server side scripts and streamed (sent) directly to the client (browser). They are not normally saved to the server although they can be. APPLICATION / BENEFITS ------------------------------------- A PHP script that dynamically generates an image or PDF file can send it to the browser in a standard way without having to save it to disk on the server. The client will also understand and be able to display file. The file tag does not introduce any new file type, it is just a standard way for the browser to receive streamed files. PHP EXAMPLE --------------------- <?php $image = imagecreatefrompng("images/picture.png"); // image is fetched from file because this is an illustration of file tag not dynamic image generation echo "<file>"; echo "mime-type:image/png"; imagepng($image); echo "</file>"; imagedestroy($image); ?> OR // image.php <?php $image = imagecreatefrompng("images/picture.png"); echo "mime-type:image/png"; imagepng($image); imagedestroy($image); ?> // image.html (part) <file src="image.php"></file> -- Configure bugmail: http://www.w3.org/Bugs/Public/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are the QA contact for the bug.
Received on Friday, 18 February 2011 18:06:30 UTC