Seems to be a bug in the 4.0.1 release that causing a resizing event to fire as a window is closed - this means that you have to close the window twice.
This appears when the text exceeds the width of the pop up causing it to wrap. In the attached example, the yellow highlighted text is too long for the window. Shorter texts that don't wrap don't seem to cause the issue.
This bug is repeatable in your demo code:
@page "/"
<h1>Hello, world!</h1>
Welcome to your new app.<br />
<TelerikButton OnClick="@SayHelloHandler" ThemeColor="@(ThemeConstants.Button.ThemeColor.Primary)">Say Hello</TelerikButton>
<br />
@helloString
<TelerikButton OnClick="@ButtonClicked" Title="Open Window">Open Window</TelerikButton>
<TelerikWindow @bind-Visible="@IsLearnMoreWindowVisible"
MaxHeight="90%"
MaxWidth="90%"
Modal="true"
Centered="true">
<WindowTitle>
<strong>Learn More: Something</strong>
</WindowTitle>
<WindowContent>
@(new MarkupString("
<p>What is the form called? Will appear in the Header to show the user what they are looking at. Any spaces in the name will be stripped during code generation for T-SQL.</p>"))
</WindowContent>
<WindowActions>
<WindowAction Name="Close" OnClick="@(() => IsLearnMoreWindowVisible = false)"></WindowAction>
</WindowActions>
</TelerikWindow>
@code {
MarkupString helloString;
bool IsLearnMoreWindowVisible = false;
void SayHelloHandler()
{
string msg = string.Format("Hello from <strong>Telerik Blazor</strong> at {0}.<br /> Now you can use C# to write front-end!", DateTime.Now);
helloString = new MarkupString(msg);
}
void ButtonClicked()
{
IsLearnMoreWindowVisible = true;
}
}