[[TOC]]

== Introduction ==
HTML and !JavaScript have become the predominate rendering technologies on the web.  Used for everything from web browsing to mobile phone applications.  HTMLGfx attempts to bring HTML rendering technologies into the BOINC graphics and screensaver environment.

By providing precompiled binaries the barrier to entry is greatly reduced allowing projects to deploy customized graphics for their applications. All projects would need to supply is the HTML/CSS/JavaScript required to display something about what is going on with the currently executing job.

In theory, volunteers could even get in on the act and create graphics for whatever applications suit their interests and share them with the community.  It is conceivable that projects may even hold yearly competitions to include a volunteers graphics bundle to be deployed with the project's application.

'''NOTE:''' HTMLGfx is only supported on Windows at this time.

References: [GraphicsApi Making graphics applications for BOINC]

== System Overview ==
HTMLGfx leverages existing operating system dependent libraries for rendering HTML.  By leveraging the operating systems HTML renderer HTMLGfx will be able to support whatever the latest technologies the operating systems browser supports.

== Design Considerations ==

=== General Constraints ===
Known security related issues:
 * [http://developer.mozilla.org/en-US/docs/Web/Security/Same-origin_policy Same Origin Policy]
 * [http://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS HTTP Access Control (CORS)]

Known browser utilization issues (on Windows):
 * [http://msdn.microsoft.com/en-us/library/ie/ee330730(v=vs.85).aspx#browser_emulation Internet Explorer Browser Feature Emulation][[BR]]
   NOTE: Unless the registry is set-up, your application will act as Internet Explorer 7.0

Differences when compared to current wxWidgets wxWebView implementation (on Windows):
 * Prevent new browser windows from being spawned by javascript.[[BR]]
   NOTE: Implements [http://msdn.microsoft.com/en-us/library/aa768283(v=vs.85).aspx DWebBrowserEvents2]
 * Prevent !JavaScript errors from displaying in a dialog.[[BR]]
   NOTE: Implements [http://msdn.microsoft.com/en-us/library/windows/desktop/ms683797(v=vs.85).aspx IOleCommandTarget]
 * Prevent !ShowHelp/!ShowMessage UI elements from being displayed.[[BR]]
   NOTE: Implements [http://msdn.microsoft.com/en-us/library/aa770041(v=vs.85).aspx IDocHostShowUI]
 * Writes all HTML/!JavaScript errors to standard log file.[[BR]]
   NOTE: Implements [http://msdn.microsoft.com/en-us/library/jj126732(v=vs.85).aspx IDeveloperConsoleMessageReceiver]

=== Goals and Guidelines ===
Top level goals are:
 * Projects should only need to create HTML/CSS/!JavaScript to have a fully functional graphics application.
 * Projects should be able to use their favorite browser to debug their graphics application.

== Detailed System Design ==

=== HTML Window ===
This component is responsible for creating the main frame window used for hosting the web browser 
control as well as creating the web browser control itself.

As part of the normal operations of the window, it should update which URL the web browser control is
displaying as state changes are detected.

It supports whatever requirements are described for BOINC graphics applications.

Reference: [GraphicsApi#Graphicsapps Making graphics applications for BOINC]

=== HTTP Server ===
This component serves up content from the slot directory running the application.  It should only be
bound to the loopback adapter and should not provide a default document nor a directory listing
when queried.  It should only serve up files that are contained within the slot directory structure.

=== HTTP Server RPCs ===

==== Embedded Static Content ====
The following files are embedded within the executable:
|| Namespace              || Contents ||
|| /api/static/index.html || [http://boinc.berkeley.edu/gitweb/?p=boinc-v2.git;a=blob;f=samples/gfx_html/templates/index.html;hb=master index.html] ||
|| /api/static/boinc.png  || [http://boinc.berkeley.edu/gitweb/?p=boinc-v2.git;a=blob;f=samples/gfx_html/templates/boinc.png;hb=master boinc.png] ||
|| /api/static/boinc.js   || [http://boinc.berkeley.edu/gitweb/?p=boinc-v2.git;a=blob;f=samples/gfx_html/templates/boinc.js;hb=master boinc.js] ||

==== Retrieve init_data.xml ====
Returns the contents of the init_data.xml file.

|| Namespace:  || /api/getInitData ||
|| Parameters: || None ||
|| Returns:    || XmlDocument ||

==== Retrieve graphics_status.xml ====
Returns the contents of the graphics_status.xml file and in addition the Vboxwrapper WebAPI and Remote 
Desktop port information.

|| Namespace:  || /api/getGraphicsStatus ||
|| Parameters: || None ||
|| Returns:    || XmlDocument ||

==== Reset reread_init_data_file flag ====
Resets the internal flag notifying the HTML application it needs to read the init_data.xml file.  This
flag is published as part of the /api/getGraphicsStatus API.

|| Namespace:  || /api/resetReadFlag ||
|| Parameters: || None ||
|| Returns:    || XmlDocument ||

==== Calling RPCs ====
Here is some prototype code for calling the described RPCs:
{{{
function createRequest {
    var xmlHttp = null;
    var XMLHttpFactories = [
        function () { return new XMLHttpRequest() },
        function () { return new ActiveXObject('Msxml2.XMLHTTP') },
        function () { return new ActiveXObject('Msxml3.XMLHTTP') },
        function () { return new ActiveXObject('Microsoft.XMLHTTP') }
    ];

    for (var i = 0; i < XMLHttpFactories.length; i++) {
        try {
            xmlHttp = XMLHttpFactories[i]();
        } catch (e) {
            continue;
        }
        break;
    }
    return xmlHttp;
}

function sendRequest(url) {
    var req = createRequest();
    var response = null;
    req.open('GET', url, false);
    req.send();
    response = req.responseXML;
    req = null;
    return response;
}

var xmlDocument = sendRequest('/api/getInitData');

}}}

=== State URL Selection Process ===
URL selection works by the following process:
{{{
    switch_to_url = default_url

    if ((status.abort_request or status.quit_request or status.no_heartbeat) and (exiting_url not empty))
        switch_to_url = exiting_url
    else if (status.suspended and (suspended_url not empty))
        switch_to_url = suspended_url
    else if (status.network_suspended and (network_suspended_url not empty))
        switch_to_url = network_suspended_url
    else if (running_url not empty)
        switch_to_url = running_url

    if ((is_vbox_job && webapi_port) && (switch_to_url is empty))
        switch_to_url  = "http://localhost:" + webapi_port + "/";

    if (switch_to_url is empty)
        switch_to_url  = "http://localhost:" + webserver_port + "/api/static/index.html";
}}}

=== Configuration File ===
The graphics description file has the logical name of '''boinc_graphics.xml'''
(its physical name should include a version number and other info).
It has following structure:

{{{
<boinc_graphics>
    [ <default_url>filename</default_url> ]
    [ <running_url>filename</running_url> ]
    [ <suspended_url>filename</suspended_url> ]
    [ <network_suspended_url>filename</network_suspended_url> ]
    [ <exiting_url>filename</exiting_url> ]
</boinc_graphics>
}}}
Optional elements:
 '''default_url'''::
    document to display if no state specific URL is defined.
 '''running_url'''::
    document to display while the task is running.
 '''suspended_url'''::
    document to display while the task is suspended.
 '''network_suspended_url'''::
    document to display while the network is suspended.
 '''exiting_url'''::
    document to display before the task exits in 5 seconds or less.

=== Graphics Status File ===
It is read once a second and is generally managed via the worker applications via
the boinc_write_graphics_status() BOINC API.

Reference: [BasicApi#GraphicsStatus graphics_status.xml]

=== Vboxwrapper WebAPI Port ===

Reference: [VboxApps#WebAPIstatefile vbox_webapi.xml]

=== Vboxwrapper Remote Desktop Port ===

Reference: [VboxApps#RemoteDesktopstatefile vbox_remote_desktop.xml]

== Example HTML Page ==

Here is a link to a working HTML page that is embedded within the HTMLGfx app in case the boinc_graphics.xml file is missing.

Reference: [http://boinc.berkeley.edu/gitweb/?p=boinc-v2.git;a=tree;f=samples/gfx_html/templates;hb=master HTML Source Files]

== Precompiled Binaries ==

On Windows:
 * x64: [http://boinc.berkeley.edu/dl/htmlgfx_26155_windows_x86_64.zip htmlgfx_26155_windows_x86_64.zip]
 * x86: [http://boinc.berkeley.edu/dl/htmlgfx_26155_windows_intelx86.zip htmlgfx_26155_windows_intelx86.zip]