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Get reference to existing OpenSeadragon Viewer

I need to add an overlay to an existing OpenSeadragon viewer object which isn't created by my code, but elsewhere in the application.
I have got to a point where I know that the viewer has been created as I can access the various html elements that are created via jQuery. However I can't work out if there's any way to create a viewer from an existing reference.
I've tried using the id of the viewer div in:
var viewer = OpenSeadragon(id: "open-seadragon-viewer-id");
but this doesn't seem to work.
Is there any way to do this or can you only get the viewer within the code that initialised it?

Here's one crazy thought... you could monkey-patch some portion of OSD in order to grab the viewer...
var viewer;
var originalIsOpen = OpenSeadragon.Viewer.prototype.isOpen;
OpenSeadragon.Viewer.prototype.isOpen = function() {
// Now we know the viewer!
viewer = this;
// Reinstate the original, since we only need to run our version once
OpenSeadragon.Viewer.prototype.isOpen = originalIsOpen;
// Call the original
return originalIsOpen.call(this);
}
It's kind of tacky, but should work. Note this assumes there is only one viewer on the page... if there are more than one, the same principle could work but you would need to keep track of an array of viewers.
BTW, I'm using isOpen, because it's simple and it gets called every frame. Other functions could work as well.
EDIT: fixed code so we are using the prototype. I still haven't actually tested this code so there may still be bugs!

This solution does not directly answer the question, as it relies on your own code creating the OpenSeaDragon object. It is an implementation of #iangilman's mention of storing the viewer in a global variable. However others may find it useful. (Note that passing a global variable to a function requires a workaround - see Passing a global variable to a function)
The code demonstrates how to use the same OpenSeaDragon object to display different pictures.
var viewer3=null; //global variable
var newURL1='image/imageToDisplay1.png';
var newURL2='image/imageToDisplay2.png';
var elementID='myID';
//the loadScan function will display the picture using openSeaDragon and can be called as many times as you want.
loadScan("viewer3",newURL1,elementID);
loadScan("viewer3",newURL2,elementID);
//the actual function
function loadScan(theViewer,newURL,theID) {
//if object has already been created, then just change the image
if (window[theViewer]!=null) {
window[theViewer].open({
type: 'image',
url: newURL
});
} else {
//create a new OpenSeadragon object
window[theViewer] = OpenSeadragon({
prefixUrl: "/myapp/vendor/openseadragon/images/",
id: theID,
defaultZoomLevel: 1,
tileSources: {
url: newURL,
type: 'image'
}
});
}
}

VS Code MarkdownString Won't Display Links

I've been working on a custom extension for Visual Studio Code recently and am trying to show a link to the user when hovering over a specific phrase but it hasn't been working. The hover shows up but the link isn't "actionable".
My extension is registering a HoverProvider and is returning a new Hover object which contains a string with a link inside of it like so:
return new vscode.Hover({language: 'markdown', value: '[test-link](https://www.google.com)'});
I've tried switching the language between "markdown" and "HTML", but in either case, although the link was in the correct format, it was never actionable. I suspect this is because the value being fed in as a parameter to the Hover constructor is a MarkdownString which has the following note:
Note that markdown strings will be sanitized - that means html will be
escaped.
I could've sworn I've seen this feature elsewhere in VS Code like in a package.json file where a link to a repository was shown when hovering over a dependency name, but I can't seem to find a working example.
Here's an example of what the hover looks like:
Is there any way to get this feature working?

This is working for me:
let disposable1 = vscode.languages.registerHoverProvider('javascript', {
provideHover(document, position, token) {
const word = document.getText(document.getWordRangeAtPosition(position));
const searchOptions = {
query: word
};
const contents = new vscode.MarkdownString(`[test-link](https://www.google.com)`);
contents.isTrusted = true;
return new vscode.Hover(contents);
}
});
Note that new Hover() has this signature:
new Hover(contents: MarkdownString | MarkedString | Array<MarkdownString | MarkedString>, range?: Range): Hover
See Hover api reference.
You were trying to give it an object (with a language key).
With vscode v1.61 this will also work within the provider:
const contents = new vscode.MarkdownString(`[test-link](https://www.google.com)`);
contents.appendMarkdown("<a href='https://www.google.com'>test-link2</a>");
contents.supportHtml = true;
contents.isTrusted = true;
return new vscode.Hover(contents);
See https://stackoverflow.com/a/67954180/836330 for more on newly supported html tags.

I can't access my current element

This is an instance of Rappid Toolkit which uses jointJS for building visual tools as for web development. http://i.stack.imgur.com/6XSis.png
In this toolkit you can make a graph which can become a website.
My problem is the following one:
In every single element of this graph there is a box below it with:x,y,width,height,angle.
I want to change this information of this boxcontent and to display some info from this element but the code in which I have to add my snippet is the following(var Halo is the var for my element in the graph):
var halo = new joint.ui.Halo({
cellView: cellView,
boxContent: function(cellView) {
return"Here I want to display my box content info instead of x,y,width,height, angle";
}
}).render();
If I try to add my code inside it to access in JSON format my current element info my full code is:
var halo = new joint.ui.Halo({
cellView: cellView,
boxContent: function(cellView) {
// Drawing
var selectedObjectDataText = JSON.stringify(this.cellView.toJSON());
var selectedObjectDataJSON = JSON.parse(selectedObjectDataText);
return(selectedObjectDataJSON[0].wi_name);
}
}).render();
where wi_name is the name of my element but in the first line I can't access the specific element of my graph.
var selectedObjectDataText = JSON.stringify(this.cellView.toJSON());
Is there any global way to access my halo(my graph element) since this.cellView.toJSON() doesn't work?
I tried this.model.toJSON() this.cellView.model.toJSON() etc with no result

Note that JointJS links and elements are Backbone Models (linkView and elementView are Backbone Views).
To get the current value of an attribute use get() method.
boxContent: function(cellView) {
return cellView.model.get('wi_name');
}
Alternatively you can use prop(), that can return also nested properties of a model.
boxContent: function(cellView) {
return cellView.model.prop('wi_name');
}

It worked for var selectedObjectDataText = JSON.stringify(cellView.model.toJSON());
Thank you all for your support.

Cannot set WFS filter the second time

Here is my scenario. The page loads and the map loads with an empty vector layer. So its there, but has no features. Then the user clicks a button and a CQL filter loads features according to the CQL settings.
My methodology to implement this. I set an empty vector layer, no loader or strategy. The button the user clicks for the first time calls a "initialization " function (=firstTimeOnly()) that:
sets a loader and a strategy to the vector layer
now that a loader exists, calls another "filtering" function (=changeFilter()) that
resets the loader's cql filter and loads features
now the "filtering" function gets attached to the button and called
with every click. The "initialization" function served its purpose
and detaches itself from the button.
Here is my code
<button id= "magicButton", onclick="firstTimeOnly()">Click me</button>
//set globals to use them
var cqlFilter = "name='testpoint9'";
var urlTemplate = 'http://localhost:5550/geoserver/mymap/wfs?service=WFS&version=1.0.0&request=GetFeature&typeName=mymap:layerName&CQL_FILTER={{CQLFILTER}}&outputFormat=application/json';
var loader = function (extent) {
var url = urlTemplate.replace('{{CQLFILTER}}', cqlFilter);
$.ajax(url, {
type: 'GET',
success: function(response) {
var res = response;
var geojsonFormat = new ol.format.GeoJSON();
sourceVector.addFeatures(geojsonFormat.readFeatures(response));
}
})
};
var strategy = new ol.loadingstrategy.tile(ol.tilegrid.createXYZ({maxZoom: 20}));
//empty vector source
var sourceVector = new ol.source.Vector({});
function changeFilter() {
//remove all, set cql and reload
var featsToRemove = layerVector.getSource().getFeatures();
for (var f=0;f<featsToRemove.length;f++)
{
layerVector.getSource().removeFeature(featsToRemove[f]);
}
cqlFilter = "name LIKE 'p'";
sourceVector.clear(true);
}
layerVector = new ol.layer.Vector({
source: sourceVector,
style:styleFunction
});
function firstTimeOnly() {
sourceVector.set('loader', loader);
sourceVector.set('strategy', strategy);
changeFilter();
document.getElementById("magicButton").removeEventListener("click", firstTimeOnly, false);
document.getElementById("magicButton").addEventListener("click", changeFilter, false);
}
This is based to erilem's code for cql filter resetting and if I use just his code works fine. But if I want to start with an empty layer and edit it as the above, I get nothing. My code gives no errors. But, if I click the button I get nothing.
Please advide me how to fix this. Or maybe its an overkill and you suggest something smarter.
Thanks
UPDATE
If I put
console.log("loader "+sourceVector.get('loader'));
at the end of the changeFilter I get the loader function. So, I guess the first time I click the button, the firstTimeOnly actually sets a loader and calls changeFilter. So, the loader is there, but does not work? Any help?

Without getting into potential issues with Openlayers the issue I see is that removeEventListener only works for removing listeners that were set with addEventListener. Since you bound the onclick declaratively in the HTML the way to unbind it would be by doing document.getElementById("magicButton").onclick = null.
That said I would change your example so that somewhere in your code you set the event listener using addEventListener.
Example:
function firstTimeOnly() {
sourceVector.set('loader', loader);
sourceVector.set('strategy', strategy);
changeFilter();
document.getElementById("magicButton").removeEventListener("click", firstTimeOnly, false);
document.getElementById("magicButton").addEventListener("click", changeFilter, false);
}
document.getElementById("magicButton").addEventListener("click", firstTimeOnly, false);
And get rid of the onclick in the HTML.
Also consider caching the reference to magicButton so that you don't have to be constantly calling getElementById.
var magicButton = document.getElementById("magicButton");

What is the best practice for maintain a menu after a page reload? I have this custom code which feels wrong

I have a custom Menu which loads a new MVC View for each click as I want.
I load the new View by setting window.location.href. To make it work I have to set the baseURL (the name of the website) each time. To Store the state of the menu I use URL's querystring.
My concerns is in the use of:
'/WebConsole53/' // hardcode baseurl i have to apply each time manually
Setting window.location.href to load the new View from JavaScript // Is this the best way or should I use some URL/Html helpers instead?
I store the state of the selected menuItem in the querystring ("menu") // Is it more common to store that kind in Session/Cookie?
Any thoughts, corrections and suggestions would be much appriciated - thanks.
_Layout.cshtml
var controller = $self.data('webconsole-controller');
var action = $self.data('webconsole-action');
var menu = "?menu=" + $self.attr('id');
var relUrl = controller + "/" + action + menu;
var url = urlHelper.getUrl(relUrl);
window.location.href = url;
UrlHelper.js
var urlHelper = function () {
var getBaseUrl = '/WebConsole53/',
buildUrl = function(relUrl) {
return getBaseUrl + relUrl;
};
var getUrl = function(relUrl) { // relUrl format: 'controller/action'
return buildUrl(relUrl);
};
return {
getUrl: getUrl
};
}();
I Use MVC 5.

You can save this problem using Route. Through the route you know exactly where you are located in you application.
_Layout.cshtml is definetely not the place to have this javascript. Maybe you are missing some MVC concepts, I would recommend you to read a bit more about routes and routelinks
I hope this helps you a bit: RouteLinks in MVC

'/WebConsole53/' // hardcode baseurl I have to apply each time manually
sometimes you need to access your root from javascript where you don't have access to server-side code (eg #Html). While refactoring may be the best option you can get around this by storing the baseurl once, using server-side code, eg in _layout.cshtml:
<head>
<script type="text/javascript">
var basePath = '#Url.Content("~")'; // includes trailing /
</script>
... load other scripts after the above ...
</head>
you can then reference this everywhere and it will always be valid even if you move the base / migrate to test/live.
Setting window.location.href to load the new View from JavaScript // Is this the best way or should I use some URL/Html helpers instead?
Depends on your requirements - you could use $.ajax (or shortcuts $.get or $.load) to load PartialViews into specific areas on your page. There's plenty of examples on SO for this and the jquery api help.
Or just use <a> anchors or #Html.ActionLink as already suggested. Without needing menu= (see next) you don't need to control all your links.
I store the state of the selected menuItem in the querystring ("menu") // Is it more common to store that kind in Session/Cookie?
If you change the page, then you could query the current url to find which menu item points to it and highlight that one (ie set the menu dynamically rather than store it).
This would also cover the case where you user enters the url directly without the menu= part ... or where your forget to add this... not that that would happen :)
Additional: You can specify which layout to use in your view by specifying the Layout at the top of the view, eg:
#{
Layout = "~/Views/Shared/AltLayout.cshtml";
}
(which is also one of the options when you right click Views and Add View in visual studio)
Without this, MVC uses a configuration-by-convention and looks at Views/_ViewStart.cshtml which specifies the default _layout.cshtml.
If you don't want a layout at all, then just return PartialView(); instead