It has been a few weeks since we have had any new information on this and it looks like it is resolved. Thus, I am marking this one as "Declined" because it does not look to be a bug in the component but an app configuration issue.

Regards,
Marin Bratanov
Progress Telerik

Hi Guy,

This seems to work for me and my best guess is that the order of the CSS rules in your app is different - the custom rules come before built-in rules from our Themes. If this is the case you need to simply make the selectors a little heavier.

I am attaching here a short video that shows how the snippet from the docs works as expected for me, and I am adding here an example with heavier selectors for you to try.

If this does not help you move forward, please share with me a simple runnable example that shows the problem so I can investigate.

<TelerikWindow Class="MyClass" Visible="true">
    <WindowTitle>
        <strong>The Title</strong>
    </WindowTitle>
    <WindowContent>
        This is my window <strong>popup</strong> content.
    </WindowContent>
</TelerikWindow>

<style>
    div.k-window.MyClass { /* targets the entire popup element */
        border: 5px solid red;
    }

        div.k-window.MyClass .k-window-content { /* targets the content element */
            background: yellow;
        }

        div.k-window.MyClass .k-window-title { /* targets the title container */
            color: blue;
        }

        div.k-window.MyClass .k-window-titlebar { /* targets the entire titlebar */
            background: gold;
        }
</style>

Regards,
Marin Bratanov
Progress Telerik