How to fix the tiny scrollbar thumb

[jschroedl]

This is an answer, not a question. I was frustrated by the default size of the scrollbar thumb being tiny when there is a large amount of content to scroll. It's way too small.

I found the following discussion: and the answer there works for the WPF UI case as well:
MinHeight on ScrollBar Thumb?

In my copy of ScrollBar.xaml, I have added the Double value like below. I chose 52 which gives a minimum thumb size of 26 because that matches Word and Edge minimum thumb sizing.

    <ControlTemplate x:Key="UiVerticalScrollBar" TargetType="{x:Type ScrollBar}">
         . . . 
            <Track
                x:Name="PART_Track"
                Grid.Row="1"
                Width="6"
                IsDirectionReversed="True">
                <Track.Resources>
                    <!-- Thumb's minimum height is half of this metric -->
                    <!-- Using 52 (26) to match Word and Edge.         -->
                    <system:Double x:Key="{x:Static SystemParameters.VerticalScrollBarButtonHeightKey}">52</system:Double>
                </Track.Resources>
                <Track.DecreaseRepeatButton>
                    <RepeatButton Command="ScrollBar.PageUpCommand" Style="{StaticResource UiScrollBarPageButton}" />
                </Track.DecreaseRepeatButton>
                <Track.Thumb>
                    <Thumb
                        Margin="0"
                        Padding="0"
                        Style="{StaticResource UiScrollBarThumb}" />
                </Track.Thumb>
                <Track.IncreaseRepeatButton>
                    <RepeatButton Command="ScrollBar.PageDownCommand" Style="{StaticResource UiScrollBarPageButton}" />
                </Track.IncreaseRepeatButton>
            </Track>

Hope this helps others. It would be nice if this were configurable or even settable via an attached property but that's an exercise for the reader.