Wpf: Check if _child is null in TemplatedAdorner.MeasureOverride

[JohanLarsson]

No null check here is weird given that there is a null check here

From reference source:

        /// <summary>
        /// Measure adorner.
        /// </summary>
        protected override Size MeasureOverride(Size constraint)
        {
            Debug.Assert(_child != null, "_child should not be null");

            if (ReferenceElement != null && AdornedElement != null &&
                AdornedElement.IsMeasureValid &&
                !DoubleUtil.AreClose(ReferenceElement.DesiredSize, AdornedElement.DesiredSize)
                )
            {
                ReferenceElement.InvalidateMeasure();
            }

            (_child).Measure(new Size(Double.PositiveInfinity, Double.PositiveInfinity));

            return (_child).DesiredSize;
        }



        /// <summary>
        ///     Default control arrangement is to only arrange
        ///     the first visual child. No transforms will be applied.
        /// </summary>
        protected override Size ArrangeOverride(Size size)
        {
            Size finalSize;

            finalSize = base.ArrangeOverride(size);

            if (_child != null)
            {
                    _child.Arrange(new Rect(new Point(), finalSize));
            }
            return finalSize;
        }

Did a search and did not find TemplatedAdorner in the repo.

Repro:
Resize the window with the below markup:

<DataGrid ItemsSource="{Binding People}">
    <DataGrid.RowStyle>
        <Style TargetType="DataGridRow">
            <Setter Property="adorners:Info.Template">
                <Setter.Value>
                    <ControlTemplate>
                        <Border BorderBrush="HotPink"
                                BorderThickness="3">
                            <AdornedElementPlaceholder />
                        </Border>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </DataGrid.RowStyle>
</DataGrid>

[stevenbrix]

@JohanLarsson the source code for PresentationFramework hasn't been opened yet. Once the infrastructure is ready to do so, this looks like something that could be fixed.

[JohanLarsson]

Ok, np, just wrote the issue as a reminder.

[ghost]

I would like to take this as a first issue.

[karelz]

Great @daniel-loudon, thanks!
I just sent you collaborator invite - that way we can assign the issue to you (assigning temporarily to myself). Ping me when you accept the invitation.
Let us know if you need any help.

[karelz]

Oh, wait. I just read the thread and it seems the code is not open-sourced yet - is that right @stevenbrix? In that case, we should not mark the issue as up-for-grabs as it is not ready for contributors yet.
Can you please confirm?

[stevenbrix]

@karelz that's correct, i'll remove up-for-grabs. @daniel-loudon, it's yours when the source is available!

[karelz]

In general: I recommend to use up-for-grabs only for actionable issues (i.e. the code is open-sourced already). Or we could mark them 'blocked' if we do not want to retriage them once we open source more WPF code.

[karelz]

@stevenbrix @vatsan-madhavan is the code open-sourced now? If yes, we can add the up-for-grabs again ;) ... I bet there are few community members who will be interested in helping out :)

[stevenbrix]

@karelz unfortunately not yet. we don't have exact dates yet, but we should be able to start getting to this soon.