The title of the SlidingPane is truncated in IE8 - http://screencast.com/t/yiJCR8DRp

Workaround:

        .rspSlideContainer td.rspSlideTitleContainer div.rspSlideTitle
        {
            width: 100% !important;
        }

Hovering the tab of a SlidingPane will render the pane only the first time, after the second hovering only the title of the SlidingPane will be rendered. The issue is reproducible both in enabled and disabled ClickToOpen, in IE8.

Video: http://screencast.com/t/jFhmqoJR

If the title of a SlidingPane is more than 22px it gets truncated in vertically oriented Splitter. The issue is reproducible in IE11 and IE8 here:
http://demos.telerik.com/aspnet-ajax/splitter/examples/sp_firstlook/defaultcs.aspx

When all Splitter's RadPanes have height configured in pixels, the control cannot be resized with the browser even if its width is set to 100%.

Steps to reproduce:
1. Run the following code and try to resize the width of the browser:
        <telerik:RadSplitter ID="VisualSplitter" runat="server" Orientation="Horizontal" Height="600px" Width="100%">
            <telerik:RadPane ID="TNPane" runat="server" Height="200" BackColor="WhiteSmoke" ContentUrl="Grid.aspx">
            </telerik:RadPane>
            <telerik:RadPane ID="ICPane" runat="server" Height="400" Scrolling="None" BackColor="Red" >
            </telerik:RadPane>
        </telerik:RadSplitter>


Temporary workaround:
Set the sum of all RadPanes' height as height of the Splitter and remain one RadPane's height not configured (the Splitter will calculate it on its own):
        <telerik:RadSplitter ID="VisualSplitter" runat="server" Orientation="Horizontal" _Height="600px" Width="100%">
            <telerik:RadPane ID="TNPane" runat="server" Height="200" BackColor="WhiteSmoke" ContentUrl="Grid.aspx">
            </telerik:RadPane>
            <telerik:RadPane ID="ICPane" runat="server" Scrolling="None" BackColor="Red" >
            </telerik:RadPane>
        </telerik:RadSplitter>

The client events of RazSlidingZone are not triggered properly when the zone is placed in a nested Splitter. For example, when a Sliding pane is docked the triggered events are ClientDocking (2 times) and ClientUndocking (1 time) instead of one time ClientDocking.


Code to reproduce the problem:
Note: Removing the decked pane of the parent splitter leads to proper behavior.

        <telerik:RadSplitter ID="MainSplitter" runat="Server" Width="100%" Height="100%">
            <telerik:RadPane ID="ViewerDocumentsPane" runat="Server">
                <telerik:RadSlidingZone ID="ViewerDocumentsSlidingZone" runat="Server"
                    DockedPaneId="ViewerDocumentsSlidingPane">
                    <telerik:RadSlidingPane ID="ViewerDocumentsSlidingPane" runat="Server" Title="Lef pane">
                    </telerik:RadSlidingPane>
                </telerik:RadSlidingZone>
            </telerik:RadPane>

            <telerik:RadPane ID="ViewerMainContainerPane" runat="Server">
                <telerik:RadSplitter ID="ViewerMainContainerSplitter" runat="Server"
                    Orientation="Horizontal">
                    <telerik:RadPane ID="ViewerInvalidSignaturePane" runat="Server">
                    </telerik:RadPane>

                    <telerik:RadPane ID="ViewerDocumentInfoPane" runat="Server" Height="22px">
                        <telerik:RadSlidingZone ID="ViewerDocInfoSlidingZone" Height="22px"
                            SlideDirection="Top"
                            runat="Server" DockedPaneId="ViewerDocInfoPane">
                            <telerik:RadSlidingPane Title="slidingPane"
                                ID="ViewerDocInfoPane" runat="Server"
                                OnClientDocking="OnClientDocking"
                                OnClientUndocking="OnClientUndocking">
                            </telerik:RadSlidingPane>
                        </telerik:RadSlidingZone>
                    </telerik:RadPane>

                </telerik:RadSplitter>
            </telerik:RadPane>

            <telerik:RadPane ID="ViewerDocumentDetails" runat="Server">
            </telerik:RadPane>
        </telerik:RadSplitter>

        <script>
            function OnClientDocking(sender, eventArgs) {
                console.log("OnClientDocking");
            }

            function OnClientUndocking(sender, eventArgs) {
                console.log("OnClientUndocking");
            }
        </script>

The print preview resulted by the Splitter's print() method appears blank in Chrome in case there are CSS files passed as an argument to method.

Steps to reproduce:
1. Open http://demos.telerik.com/aspnet-ajax/splitter/examples/printpane/defaultcs.aspx in Chrome
2. Click in the "Print LeftPane" button


Result: An empty print-preview window is shown.

Visual regressions in RadSplitter:

    [Lightweight] [IE-all] [All-Skins]  vertical sliding panes tab text is upside down now: https://www.screencast.com/t/GhdIru4Od2sU
    [Classic] [all-browsers] [BlackMetroTouch,MetroTouch] - missing SlidingPane icons - https://www.screencast.com/t/qc18E9vU7MSF
    [Classic] [all-browsers] [Metro, MetroTouch] - missing backgrounds in the entire splitter: https://www.screencast.com/t/MBjdwph1wcW
    [Classic] [all-browsers] [All-Skins] - missing active sliding pane effect (expected: https://www.screencast.com/t/lFAnFdyzwNRU , actual: https://www.screencast.com/t/jyDdWJHIa10 )
    [Classic] [all-browsers] [Silk] - missing sliding pane header background: https://www.screencast.com/t/Nrk33Jokvuao

Workaround is to use the Lightweight RenderMode as is affected in the least, or roll back to R3 2016 SP2

When RadSplitter is declared in a page with no Doctype the RadSlidingPane stops responding in IE and the layout looks broken when docking/undocking.

The scroll position of the radPanes is not pesisted after a postback (even if the PersistScrollPosition property of the Pane is set to "true").

When a RadPanelBar (having have more than 1 level of nested items) is nested inside a SlidingPane, it cannot be scrolled after expanding in iOS.

When the content of a RadPane is set through its ContentURL property, the RadPane cannot be scrolled in order to how its full content in IPAD.

The issue could be reproduced here: http://demos.telerik.com/aspnet-ajax/splitter/examples/externalcontentloading/defaultcs.aspx

The border size of the RadPanes is always inherited by their parent Splitter's BorderSize, ragardless of the value set to the Splitter's PanesBorderSize property.

When a Sliding pane have to be resized over a RadPane, containing a heavy weight object (Silverlight, PDF, Flash, etc.) its size is not calculated properly.

The HTML5 related changes in the RadSplitter have specific selectors that influence the content inside.

When a Tab of a Vertically oriented Splitter have both title and icon, its height is not calculated properly (the height of the icon is not taken into account). The issue is reproducible in Chrome.

Screenshot: http://screencast.com/t/0aaMryaShXZe

The border of the splitbar disappears on hover. The issue is reproducible in IE - http://screencast.com/t/QfaZIZirSZfB

When a RadPane with not configured fixed size is locked its size is not calculated properly (and the size of all its sibling free-sized panes).The issue can be reproduced with the following code in Firefox (both in horizontally or vertically oriented Splitter):

    <telerik:RadSplitter ID="TestSplitter" runat="server" Width="100%" Height="100%"
        Orientation="Horizontal">
        <telerik:RadPane ID="RadPane1" runat="server"
            Locked="true">
        </telerik:RadPane>
        <telerik:RadPane ID="RadPane2" runat="server">
        </telerik:RadPane>
        <telerik:RadPane ID="RadPane3" runat="server">
        </telerik:RadPane>
    </telerik:RadSplitter>

These overrides can be used as a temporary workaround:

        Telerik.Web.UI.SplitterPaneBase.prototype.get_height = function () {
            return this._height === "" ? 0 : parseInt(this._height);
        }
        Telerik.Web.UI.SplitterPaneBase.prototype.get_width = function () {
            return this._width === "" ? 0 : parseInt(this._width);
        }

The height of a  free-sized RadPane is not calculated properly on layout mode change in Android devices. The issue is reproducible in Firefox for Android.

A JavaScript error is thrown when a Splitbar is dragged in IE11 Edge mode and resolution 2560x1080. The issue is reproducible only when the ScriptManager's EnableScriptCombine property is set to False.

Temporary workaround: Set the RadScriptManager's EnableScriptCombine property to "True"