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Dynamically setting initial map view and scale

The following script allows us to set the initial x, y and scale attributes of a map using the MapGuide Ajax Viewer. It expects the values to be passed to the script as querystring parameters, e.g.

​http://localhost/mapguide/set_intial_view.php?x=507700&y=186000&scale=400000

It works by taking a copy of the WebLayout stored in the Library repository and changing the <CenterX/>, <CenterY/> and <Scale/> elements. The updated XML is written into the Session and is used as the target when the page is ultimately redirected.

This code could easily be converted to C# (or whatever).

Things to note

• A side-effect of the code is that it facilitates anonymous connections
• The parameter-checking could be made a little more robust *cough*
• The $wl variable should be changed to reflect the relevant WebLayout identifier

The code

<?php

//
// Vital includes.
//
$viewerDir = "mapviewerphp\\";
include $viewerDir . "constants.php";
include $viewerDir . "common.php";

//
// Check and get the required parameters.
//
if (!isset($_REQUEST["x"]) || !isset($_REQUEST["y"]) || !isset($_REQUEST["scale"])) {
        echo "<Error>One or more of the required arguments is missing.</Error>";
        exit;
}

$x = $_REQUEST["x"];
$y = $_REQUEST["y"];
$scale = $_REQUEST["scale"];

//
// Usual initialisation step.
//
InitializeWebTier();

//
// Obtain a new session ID for this anonymous user, use it to set up
// a new site connection and use that to create a resource service.
//
$site = new MgSite();
$site->Open(new MgUserInformation("Anonymous", ""));

$sessionId = $site->CreateSession();

$siteConnection = new MgSiteConnection();
$siteConnection->Open(new MgUserInformation($sessionId));

$resourceService = $siteConnection->CreateService(MgServiceType::ResourceService);

//
// Read the web layout into an XML DOM document object.
//
$wl = "Library://WebPID/WebPID_SDF_Static.WebLayout"; // TODO Constant!
$wlResourceId = new MgResourceIdentifier($wl);
$wlReader = $resourceService->GetResourceContent($wlResourceId);
$wlXml = $wlReader->ToString();
$wlDomDoc = DOMDocument::loadXML($wlXml); 

//
// Now, update the initial x, y and scale values with the desired values.
//
$nodeCenterX = $wlDomDoc->getElementsByTagName("CenterX")->item(0);
$nodeCenterX->nodeValue = "$x";

$nodeCenterY = $wlDomDoc->getElementsByTagName("CenterY")->item(0);
$nodeCenterY->nodeValue = "$y";

$nodeScale = $wlDomDoc->getElementsByTagName("Scale")->item(0);
$nodeScale->nodeValue = "$scale";

//
// Prepare the updated XML to be written out to the session.
//
$updatedXml = $wlDomDoc->saveXML();
$byteSource = new MgByteSource($updatedXml, strlen($updatedXml));

//
// Create a web layout in the session to hold the updated version
// from the library.
//
$sessionMapName = $wlResourceId->GetName();
$sessionWebLayout = "Session:$sessionId//$sessionMapName.WebLayout";
$sessionResourceId = new MgResourceIdentifier($sessionWebLayout);

//
// Write the updated web layout to the session.
//
$resourceService->SetResource($sessionResourceId, $byteSource->GetReader(), null);

//
// Redirect to the Ajax viewer pointing at the map at the desired coordinates.
//
$redirectTo = "mapguide/mapviewerajax/?SESSION=$sessionId&WEBLAYOUT=$sessionWebLayout";
$host = $_SERVER["HTTP_HOST"];
$url = "http://$host/$redirectTo";

//
// Redirect!
//
header("Location: $url");
exit;

?>

See also

To reposition a MapGuide map at a given x, y and scale using JavaScript, take a look at the ZoomToView() API function.