Xaml file code

===============

<Window x:Class="CustomizableFloatingPane.Window1"

    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

    Title="Customizing Floating Window" 

        xmlns:igDock="http://infragistics.com/DockManager">

    <Grid>

        <igDock:XamDockManager Name="xamDockManager1">

            <igDock:XamDockManager.Resources>

                <Style TargetType="{x:Type igDock:PaneToolWindow}" x:Key="style">

                    <Setter Property="BorderBrush" Value="Gray"/>

                    <Setter Property="BorderThickness" Value="2"/>

                    <Setter Property="Background" Value="GhostWhite"/>

                    <Setter Property="Template">

                        <Setter.Value>

                            <ControlTemplate TargetType="{x:Type igDock:PaneToolWindow}">

                                <Border Background="{TemplateBinding Background}"

                                        BorderBrush="{TemplateBinding BorderBrush}"

                                        BorderThickness="{TemplateBinding BorderThickness}">

                                    <Grid>

                                        <Grid.RowDefinitions>

                                            <RowDefinition Height="Auto" />

                                            <RowDefinition/>

                                        </Grid.RowDefinitions>

                                        <DockPanel Grid.Row="0" >

                                            <Button DockPanel.Dock="Right" Click="Button_Click">X</Button>

                                            <ContentPresenter Content="{TemplateBinding Title}" />

                                        </DockPanel>

                                        <ContentPresenter Content="{TemplateBinding Content}" 

                                                          Grid.Row="1"/>

                                    </Grid>

                                </Border>

                            </ControlTemplate>

                        </Setter.Value>

                    </Setter>

                </Style>

            </igDock:XamDockManager.Resources>

            <igDock:XamDockManager.Panes>

                <igDock:SplitPane>

                    <igDock:ContentPane Header="Conten Pane 1">

                        <TextBlock>Testing Content</TextBlock>

                    </igDock:ContentPane>

                </igDock:SplitPane>

                <igDock:SplitPane >

                    <igDock:ContentPane Header="Conten Pane 2">

                        <TextBlock>Testing Content</TextBlock>

                    </igDock:ContentPane>

                </igDock:SplitPane>

            </igDock:XamDockManager.Panes>

        </igDock:XamDockManager>

    </Grid>

</Window>

I used that snippet and the content shows up. The window bounces around but that's because you're moving the window (in the mousemove handler you added) and then the dockmanager dragging logic is moving the window. You need to either let the dockmanager do the dragging or you need to mark the events handled and you perform whatever dragging your going to do.

BTW the code using GetAncestorFromType to get the PaneToolWindow isn't needed when you're hooking events of the PaneToolWindow itself - you could just use the sender. Actually GetAncestorFromType won't work anyway since the e.OriginalSource could be the PaneToolWindow itself.

I would also recommend taking our template for the ToolWindow (provided in the DefaultStyles directory) and use that as a starting point for creating a custom template.