Visualforce and Lightning Componets: how to get the Lightning-Icon Name on a VF-Page (or LC) for any custom object?

Question

Assume there is a custom object elfBCQuote__c having an Tab and an Icon assigned during object creation via Setup.

Now I am on a VF-Page and have only the objects name elfBCQuote__c as string. Is there any way to get the correct lightning icon name of that given object?

I need to identify that icon:

I need get something like custom/custom41 or custom:custom41 to dereference the SVG from SLDS in my own VF-comoponents. VF, JS or APEX solutions or even ideas are welcome!

Annex 1

I'm also interested of getting the same inside my lightning-components. Solution via markup, js-controller, apex-controller or otherwise are all welcome!

Annex 2

Actually I was able to do it for an <apex:relatedList> but my solution is such an evil hack, that I'm not going to post it here... But @saleforce: we need this urgently. So this question stays still open. However the result (believe it or not it's a visualforce page) looks like this:

Answer 1

I came across something which could do the trick. But that's a bit ugly...

In fact, you can get the different tabs used in an app and each icon url related to theses tabs.

Finally, by checking if the tab is related to the sobject you're searching for, you're able to return the icon name by removing the other parts of the icon url.

Here's my class:

public class IconsUtil {
    private static final String LIGHTNING_ICON_EXT = '.svg';

    private Map<String, String> iconsNamesBySObjectNames;

    public IconsUtil(){
        this.iconsNamesBySObjectNames = new Map<String, String>();

        //we loop through each application
        for(Schema.DescribeTabSetResult tsr : Schema.describeTabs()) { 
            //that's the current selected application
            if(tsr.isSelected()){
                //we loop through each tab
                for(Schema.DescribeTabResult tabResult : tsr.getTabs()){
                    //there are different icons related to this tab. Some for the vf version, some for Lightning. And also depending on the icon size.
                    for(Schema.DescribeIconResult iconResult : tabResult.getIcons()){
                        String iconUrl = iconResult.getUrl();
                        if(iconUrl.endsWith(LIGHTNING_ICON_EXT)){
                            //Unfortunately, that's the whole url. So we extract the end without the extension
                            this.iconsNamesBySObjectNames.put(tabResult.getSobjectName(), iconUrl.substringAfterLast('/').substringBefore(LIGHTNING_ICON_EXT));
                            break;
                        }
                    }    
                }
                break;
            }
        }
    }

    public String getBySObjectName(String sobjectName){
        return this.iconsNamesBySObjectNames.get(sobjectName);
    }
}

Here's how to use it:

IconsUtil iconsUtil = new IconsUtil();
String iconName = iconsUtil.getBySObjectName('MyCustomObject__c');

Answer 2

I tried above solution but is was not working for all the objects. For some custom objects above solution was returning blank values. So I tried using ui-api.

Here is code for that

        HttpRequest req = new HttpRequest();
        req.setEndpoint(orgUrl+'/services/data/v43.0/ui-api/object-info/'+objectName);
        req.setHeader('Content-type','application/json; charset=UTF-8');
        req.setHeader('Accept','application/json');
        req.setMethod('GET');
        req.setHeader('Authorization', 'OAuth ' + sessionId);        
        Http http = new Http();
        HTTPResponse res = http.send(req);
        String response = res.getBody();
        if(res.getStatus() != 'OK'){
            throw new ApplicationException(res.getStatus());
        }
        Map<String,object> apiResponse =(Map<String,Object>)JSON.deserializeUntyped(response);
        Map<String,object> themeInfo = (Map<String,object>)apiResponse.get('themeInfo');
        String objectIcon;
        if(themeInfo != null){
        String iconUrl = (String)themeInfo.get('iconUrl');
        if(String.isNotBlank(iconUrl)){
            List<String> urlList = iconUrl.split('/');
            if(urlList.size() > 2){
                String iconSvg = urlList[urlList.size() - 1];
                String iconName = iconSvg.substringBeforeLast('_');
                objectIcon = urlList[urlList.size() - 2]+ ':' + iconName;
            }
        }
    return objectIcon;

ui-api returns theme info object in which it contains a iconUrl key. We can retrieve iconName from that url.