How UniformGrid work with infinite size

Question

For example we have a ListBox with a UnidormGrid like a ListBoxPanel.

    <ListBox>
        <ListBox.ItemsPanel>
            <ItemsPanelTemplate>
                <UniformGrid Columns="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=ListBox}, Path=Items.Count}"></UniformGrid>
                <!--<cntr:StackGrid Orientation="Horizontal" Direction="Normal"/>-->
            </ItemsPanelTemplate>
        </ListBox.ItemsPanel>
        <Button>1</Button>
        <Button>2</Button>
        <Button>3</Button>
        <Button>4</Button>
    </ListBox>

ListBox will give a infinite size to UniformGrid, but there is no any errors. UniformGrid will use only a visible size. How it do that? It will help me in bulding my own panel.

P.S. I know, that i can to disable ScrollView in ListBox and my panel will get a visible size.

You may read the [Panels Overview](http://msdn.microsoft.com/en-us/library/ms754152.aspx) article on MSDN. It has a section about custom panels. — Clemens, Sep 04 '14 at 06:08
There is no information about how to work with infinite size. — Nodon, Sep 04 '14 at 06:27
From the remarks section in [UIElement.Measure](http://msdn.microsoft.com/en-us/library/system.windows.uielement.measure.aspx) and also [UIElement.Arrange](http://msdn.microsoft.com/en-us/library/system.windows.uielement.arrange.aspx): *availableSize can be any number from zero to infinity*. It is not an error, but simply means that the size to which the Panel can layout its children is not constrained. You simply have to deal with it. You must however not return an infinite size from MeasureOverride or ArrangeOverride. — Clemens, Sep 04 '14 at 06:47
Just a note: it doesn't make much sense to bind the UniformGrid's Columns property to the item count of the ListBox. Instead you could just set `Rows="1"`. — Clemens, Sep 04 '14 at 07:33

score 1 · Accepted Answer · answered Sep 04 '14 at 07:09

As far as I know, the UniformGrid derives its cell size by the largest child it is displaying. It breaks the content to a new line when either its width or height is exceeded, according to the Orientation property. By default, it is set to Horizontal.

Which leads me to your question: why do you think that it has an infinite width? Sure, the ListBox contains a ScrollViewer in its default control template, but in my opinion it only provides vertical infinite space for the panel (horizontally, it is constrained to the width of the list box), which allows breaks for the default uniform grid to happen.

If you have any further questions, please feel free to ask.

How UniformGrid work with infinite size

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