[Solved] HTMLPlaceHolder within RadDocking display problems

[Keylight]

I am having problems with using the HTMLPlaceHolder control with the RadDocking control.  I have placed the HTMLPlaceHolder control as the content of a RadPane and experience several different problems sporadically, but frequently, when I move the pane around (e.g. click and drag, dock and undock, etc).  The problems include:

1. HTML content not displaying, i.e. I see all white in the HTMLPlaceHolderControl as if there is no content.  This occurs in several docking states, but more often when the panes are docked at the root compass.
2. Overlap issues between multiple panes (see overlap_error.jpg).  Sometimes I can see the contents of one pane within another pane if one of the panes is docked and the other is undocked.
3. An error pops-up (see attached popup_error_msg.jpg) that reads: "Error: 'RadHtmlPlaceholderJS' is undefined".  When I hit Debug, I get sent to this script: "if(RadHtmlPlaceholderJS && RadHtmlPlaceholderJS.RAD_HP_12772dc77db54349861c88209a913634) delete RadHtmlPlaceholderJS.RAD_HP_12772dc77db54349861c88209a913634"  Note: In my example below, this error seems to occur more often when I only have the RadPane with header = "#1" present, i.e. comment out the RadPane with header = "#2", launch application, then move pane #1 around.
4. In the example below, in pane #2: if I navigate to another page in the HTMLPlaceHolder (e.g. by clicking on a link), then click and drag pane #2 around, the page will reset to the original page specified by the SourceUrl.  I expect that it should remain on the page that I navigated to.

This occurs with a brand new Silverlight 4 solution (standard two projects: Silverlight application project and the hosting website project) created with VS 2010.

Here is my XAML:

<UserControl
    xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
    xmlns:radDock="clr-namespace:Telerik.Windows.Controls;assembly=Telerik.Windows.Controls.Docking"
    x:Class="HTMLPlaceholderTest.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    d:DesignHeight="300" d:DesignWidth="400">
    <radDock:RadDocking>
        <radDock:RadDocking.DocumentHost>
            <radDock:RadSplitContainer>
                <radDock:RadPaneGroup>
                    <radDock:RadPane Header="#1">
                        <telerik:RadHtmlPlaceholder x:Name="MyHTMLPlaceHolder" />
                    </radDock:RadPane>
                    <radDock:RadPane Header="#2">
                        <telerik:RadHtmlPlaceholder SourceUrl="http://www.google.com" />
                    </radDock:RadPane>
                </radDock:RadPaneGroup>
            </radDock:RadSplitContainer>
        </radDock:RadDocking.DocumentHost>
    </radDock:RadDocking>

</UserControl>

And here is the code-behind:

Partial Public Class MainPage
    Inherits UserControl

    Public Sub New()
        InitializeComponent()
        MyHTMLPlaceHolder.HtmlSource = "<b>Some HTML text</b>"
    End Sub

End Class

[Miroslav]

Hello Keylight,

The HtmlPlaceholder displays html pages / content in an IFrame which floats over the Silverlight plugin.

More advanced clipping scenarios like having panes overlapping are unfortunately not supported.

On to your questions:
1. In which browser does this happen? I tried refreshing / restarting the your example multiple times but the pages did load.
2. Yes, this is a known limitation.
3. This is a bug and should be fixed in the latest internal builds of the Q2 and will be available with the coming SP.
4. I have logged this as a bug, you can vote for it here:

http://www.telerik.com/support/pits.aspx#/public/silverlight/2893

Depending on your needs, you may find alternative approaches useful as well:
- for displaying simple formatted HTML I can suggest using the RadRichTextBox.
- in OOB applications the WebBrowserBrush displays html which integrates natively in Silverlight's layout.

Regards,
Miroslav
the Telerik team

[Keylight]

Re: 1. In which browser does this happen? I tried refreshing / restarting the your example multiple times but the pages did load.

Internet Explorer 8 (version 8.0.7600.16385).  I've also attached an image (htmlcontentnotdisplaying.jpg) that shows the problem I am encountering.

[Miroslav]

Hello Keylight,

Thank you for the details and the screenshot!

Yes, I confirmed that this indeed happens. I have logged it as a bug here:

http://www.telerik.com/support/pits.aspx#/public/silverlight/2932

Your Telerik Points have been updated for your feedback.

All the best,
Miroslav
the Telerik team

[Brian Nguyen]

We need this fix asap! We use RadHtmlPlaceHolder's in RadTabItems to display BING ajax html maps and prior to latest Q2 relase everything was working. Now, when switching between tabs we lose our html layer - it is completely removed from the DOM when switching to a new tab.

[Miroslav]

Hi Brian Nguyen,

This behavior of the HtmlPlaceholder was actually a fix for a memory leak where the Html IFrame will be kept in memory when it is no longer needed.

We discussed this and agreed that there may be cases like yours where keeping the page is desirable.

We will add a new property KeepContentInMemory which you will be able  to set to true to enable this.

The change will appear with the SP 1 release next week.

Thank you for your feedback!

Best wishes,
Miroslav
the Telerik team

[B]

Hi,

We have similar issues, with a radDocking pane in autohide mode this will get the RadHtmlPlacehold over it, see screenshot.

Regards,

Bayram

[Petar Mladenov]

Hi B,

 Could you please elaborate more on your scenario , any sample or just your XAML will be highly appreciated ? This way we would be better able to investigate this and advice you. Thank you in advance. 

Kind regards,
Petar Mladenov
the Telerik team