I've got a Canvas that I'm setting the Background property to a VisualBrush consisting of an Image. I'm data binding the Canvas' Width and Height to the Images' Width and Height. Here's the XAML:
<Canvas x:Name="imageCanvas" ClipToBounds="True" Width="{Binding ActualWidth, ElementName=dataImage}" Height="{Binding ActualHeight, ElementName=dataImage}"
Loaded="imageCanvas_Loaded" MouseMove="imageCanvas_MouseMove">
<Canvas.Background>
<VisualBrush Stretch="Uniform">
<VisualBrush.Visual>
<Image x:Name="dataImage" ClipToBounds="True" RenderOptions.BitmapScalingMode="HighQuality" Stretch="Uniform" Source="{Binding DataImage, Mode=OneWay}" LayoutTransform="{Binding DataImageLayoutTransform, Mode=OneWay}"/>
</VisualBrush.Visual>
</VisualBrush>
</Canvas.Background>
</Canvas>
Note that Image is using a LayoutTransform. I'm using this to stretch the width of the image. If I disable the LayoutTransform binding and run I get the following (properly) rendered output:
However, when I add the LayoutTransform to stretch the width of the image by a factor of 6, the image looks stretched correctly but it is too small i.e. it is not filling the Canvas uniformly:
I suspect this may have something to do with binding the Canvas Height/Width to the image height width, but it's not clear what the exact problem is. Can anyone provide some insight? Thank you in advance.
I have a ListBox inside a DockPanel. I want to find out what should be the size of the ListBox so it doesn't have the scroll bar. I use ListBox.DesiredSize but actually DesiredSize is equal to ListBox.ActualWidth / Height and the ListBox has scrollbar because there are more items that can fit its height.
How to get real desired size ?
If you want to get rid of scrollbar in Listbox instead of creating static height in wpf application, you can disable scrollbar property.
In XAML:
<ListBox ScrollViewer.HorizontalScrollBarVisibility="Disabled" />
<ListBox ScrollViewer.VerticalScrollBarVisibility="Disabled" />
In C#:
myListBox.SetValue(ScrollViewer.HorizontalScrollBarVisibilityProperty, ScrollBarVisibility.Disabled);
myListBox.SetValue(ScrollViewer.VerticalScrollBarVisibilityProperty, ScrollBarVisibility.Disabled);
You can disable the scrollbar
Or else
VerticalScrollBarVisibility="Auto"
and set any height for Listbox scroll bar will be visible only content reaches its max Listbox height.
Or
Try this to achieve the desired height by binding the ListBox height property to the ActualHeight of the LayoutRoot Grid via the XAML below:
<Grid x:Name="LayoutRoot" Background="LightGray">
<Grid.ColumnDefinitions>
<ColumnDefinition Width=".24*"/>
<ColumnDefinition Width=".73*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height=".9*"/>
<RowDefinition Height=".1*"/>
</Grid.RowDefinitions>
<ListBox Name="Subdivisions" SelectedItem="{Binding SelectedSubdivisionViewModel}" ItemsSource="{Binding Path=Subdivisions}" Grid.IsSharedSizeScope="True" Height="{Binding ElementName=LayoutRoot, Path=ActualHeight}" >
The important bit being:
Height="{Binding ElementName=LayoutRoot, Path=ActualHeight}"
Also achievable via ancestor type:
Height="{Binding Path=ActualHeight, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Grid}}}"
Its my working code you can change it from grid to Dockpanel.
How to get real desired size ?
The desired size of the ListBox is calculated automatically if you don't explicitly set its Height or VerticalAlignment property and avoid putting it in a Panel that measures its children with an infinite space such as a StackPanel.
The desired size of the ListBox itself is however not the same as the aggregated size of all ListBoxItem containers. In fact, there is no easy way to calculate this height exactly since not all containers are generated up front provided that you haven't disabled the UI virtualization of the ListBox.
The easiest workaround/solution would probably be to get the height of the first container once the ListBox has been loaded and then multiply this value with the actual number of items, e.g.:
<ListBox x:Name="lb" Loaded="lb_Loaded">
<ListBoxItem>1</ListBoxItem>
<ListBoxItem>2</ListBoxItem>
<ListBoxItem>3</ListBoxItem>
</ListBox>
private void lb_Loaded(object sender, RoutedEventArgs e)
{
ListBoxItem lbi = lb.ItemContainerGenerator.ContainerFromIndex(0) as ListBoxItem;
if (lbi != null)
{
lb.Height = lbi.ActualHeight * lb.Items.Count + /* add some offset */ 5;
}
}
I am having trouble getting the height of a scrollviewer to adjust to whatever the height is of a tabitem.
XAML:
<TabItem header="Item">
<ScrollViewer Height={Binding ActualHeight, RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=TabItem}}>
<Grid>
.
.
.
</Grid>
</ScrollViewer>
</TabItem>
When I do this the scrollviewer is only about 50 pixels high. The content inside displays fine. The viewing area height is limited.
I tried this.
<TabItem header="Item" x:Name="itemname">
<ScrollViewer Height="{Binding ElementName="itemname", Path=ViewportHeight}">
The scrollviewer is not limited but when the content inside the
scrollviewer grows it goes beyond the viewing area and the scrollbar
deos not work.
I have used the first (FindAncestor) example with a StackPanel and it works. Not sure why it won't with a TabItem.
Why not use the HorizontalAlignment / VerticalAlignment properties?
<ScrollViewer HorizontalAlignment="Stretch" VerticalAlignment="Stretech">
I have learned that if the height of a grid row, where the ScrollViewer resides, is set as Auto, the vertical scroll bar will not take effect since the actual size of the ScrollViewer can be larger than the height in sight. So in order to make the scroll bar work, I should set the height to either a fixed number or star height
However, I now have this requirement, that I have two different views reside in two grid rows, and I have a toggle button to switch between these two views: when one view is shown, the other one is hidden/disappeared. So I have defined two rows, both heights are set as Auto. And I bind the visibility of the view in each row to a boolean property from my ViewModel (one is converted from True to Visible and the other from True to Collapsed. The idea is when one view's visibility is Collapsed, the height of the grid row/view will be changed to 0 automatically.
The view show/hidden is working fine. However, in one view I have a ScrollViewer, which as I mentioned doesn't work when the row height is set as Auto. Can anybody tell me how I can fulfill such requirement while still having the ScrollViewer working automatically`? I guess I can set the height in code-behind. But since I am using MVVM, it would require extra communication/notification. Is there a more straightforward way to do that?
In MVVM, the way that worked for me was to bind the height of the ScrollViewer to the ActualHeight of the parent control (which is always of type UIElement).
ActualHeight is a read-only property which is only set after the control has been drawn onto the screen. It may change if the window is resized.
<StackPanel>
<ScrollViewer Height="{Binding Path=ActualHeight,
RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UIElement}}">
<TextBlock Text=Hello"/>
</ScrollViewer>
</StackPanel>
But what if the parent control has an infinite height?
If the parent control has an infinite height, then we have a bigger problem. We have to keep setting the height of all parents, until we hit a control with a non-infinite height.
Snoop is absolutely invaluable for this:
If the "Height" for any XAML element is 0 or NaN, you can set it to something using one of:
Height="{Binding Path=ActualHeight, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UIElement}}"
VerticalAlignment="Stretch"
Height="Auto"
Hint: Use VerticalAlignment="Stretch" if you are a child of a Grid with a <RowDefinition Height="*">, and the Binding RelativeSource... elsewhere if that doesn't work.
If you're interested, here is all of my previous attempts to fix this issue:
Appendix A: Previous Attempt 1
Can also use this:
Height="{Binding Path=ActualHeight, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=StackPanel}}"
Appendix B: Previous Attempt 2
Useful info: see Auto Height in combination with MaxHeight.
If nothing seems to work, it's probably because the ActualHeight of the parent is either 0 (so nothing is visible) or huge (so the scrollviewer never needs to appear). This is more of a problem if there are deeply nested grids, with a scrollviewer right at the bottom.
Use Snoop to find the ActualHeight of the parent StackPanel. In properties, filter by the word "Actual", which brings back ActualHeight and ActualWidth.
If ActualHeight is zero, give it a minimum height using MinHeight, so we can at least see something.
If ActualHeight is so huge that it goes off the edge of the screen (i.e. 16,000), give it a reasonable maximum height using MaxHeight, so the scrollbars will appear.
Once the scrollbars are appearing, then we can clean it up further:
Bind the Height of the StackPanel or Grid to the ActualHeight of the parent.
Finally, put a ScrollViewer inside this StackPanel.
Appendix C: Previous Attempt 3
It turns out that this can sometimes fail:
Height="{Binding Path=ActualHeight, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=StackPanel}}"
The reason? It the binding fails, the height will be zero and nothing will be seen. The binding can fail if we are binding to an element which is not accessible. The binding will fail if we are going up the visual tree, then down to a leaf node (e.g. up to the parent grid, then down to the ActualHeight of a row attached to that grid). This is why binding to the ActualWidth of a RowDefinition simply won't work.
Appendix D: Previous Attempt 4
I ended up getting this working by making sure that Height=Auto for all of the parent elements from us to the first <Grid> element in the UserControl.
Change Height from Auto to *, if you can.
Example:
<Window x:Class="WpfApplication3.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="200" Width="525">
<StackPanel Orientation="Horizontal" Background="LightGray">
<Grid Width="100">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<ScrollViewer VerticalScrollBarVisibility="Auto" x:Name="_scroll1">
<Border Height="300" Background="Red" />
</ScrollViewer>
<TextBlock Text="{Binding ElementName=_scroll1, Path=ActualHeight}" Grid.Row="1"/>
</Grid>
<Grid Width="100">
<Grid.RowDefinitions>
<RowDefinition Height="*" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<ScrollViewer VerticalScrollBarVisibility="Auto" x:Name="_scroll2">
<Border Height="300" Background="Green" />
</ScrollViewer>
<TextBlock Text="{Binding ElementName=_scroll2, Path=ActualHeight}" Grid.Row="1"/>
</Grid>
</StackPanel>
</Window>
I've had similar problem, taking me hours to figure out the solution. What solved it was using a Dockpanel as parent container instead of a StackPanel. Just specify all children to dock to top if the functionality should be similar to vertical stackpanel. Consider using LastChildFill="False" in the Dock XAML which is'n default.
So instead of:
<StackPanel Orientation="Horizontal">
<Textbox>SomeTextBox</Textbox>
<Scrollviewer/>
</StackPanel>
Try:
<DockPanel LastChildFill="False">
<Textbox DockPanel.Dock="Top">SomeTextBox</Textbox>
<Scrollviewer DockPanel.Dock="Top"/>
</DockPanel>
You can either set a fix height on your ScrollViewer but then you have to consider that the second row of your grid will have that height too since row's first child will be the ScrollViewer and row's height is auto, or you bind the height of ScrollViewer to another control in your layout. We don't know how your layout looks alike.
At the end if you don't like neither of both just set the row's height to * as swiszcz suggested or hack wpf write your own custom panel that will be able to layout everything possible in every parallel universe or something like that. :)
What I discover is that you have to put your ScrollViewer within a container that has Height=Auto or you get his parent Heigh Actual Size and apply it to that container.
In my case I have UserControl like
<Grid Margin="0,0,0,0" Padding="0,2,0,0">
<ScrollViewer Height="Auto" ZoomMode="Disabled" IsVerticalScrollChainingEnabled="True" VerticalAlignment="Top"
HorizontalScrollMode="Enabled" HorizontalScrollBarVisibility="Disabled"
VerticalScrollMode="Enabled" VerticalScrollBarVisibility="Visible">
<ListView ItemsSource="{x:Bind PersonalDB.View, Mode=OneWay}" x:Name="DeviceList"
ScrollViewer.VerticalScrollBarVisibility="Hidden"
ItemTemplate="{StaticResource ContactListViewTemplate}"
SelectionMode="Single"
ShowsScrollingPlaceholders="False"
Grid.Row="1"
Grid.ColumnSpan="2"
VerticalAlignment="Stretch"
BorderThickness="0,0,0,0"
BorderBrush="DimGray">
<ListView.ItemsPanel>
<ItemsPanelTemplate>
<ItemsStackPanel AreStickyGroupHeadersEnabled="False" />
</ItemsPanelTemplate>
</ListView.ItemsPanel>
<ListView.GroupStyle>
<GroupStyle>
<GroupStyle.HeaderTemplate>
<DataTemplate x:DataType="local1:GroupInfoList">
<TextBlock Text="{x:Bind Key}"
Style="{ThemeResource TitleTextBlockStyle}"/>
</DataTemplate>
</GroupStyle.HeaderTemplate>
</GroupStyle>
</ListView.GroupStyle>
</ListView>
</ScrollViewer>
</Grid>
And I add it dinamically to ContentControl which is within a Page.
<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}" Margin="0,0,12,0">
<Grid.RowDefinitions>
<RowDefinition Height="70" />
<RowDefinition Height="*" MinHeight="200" />
</Grid.RowDefinitions>
<Grid Grid.Row="1" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" >
<ContentControl x:Name="UIControlContainer" />
</Grid>
</Grid>
Notice that Heigh of the Row is *
When I populate ContentControl I use this code in Loaded event
UIControlContainer.Content = new UIDeviceSelection() {
VerticalAlignment = VerticalAlignment.Stretch,
HorizontalAlignment = HorizontalAlignment.Stretch,
Height = UIControlContainer.ActualHeight,
Width = UIControlContainer.ActualWidth
};
And also when ContentControl changes its size you have to update size of the UserControl.
UIControlContainer.SizeChanged += UIControlContainer_SizeChanged;
private void UIControlContainer_SizeChanged(object sender, SizeChangedEventArgs e)
{
if (UIControlContainer.Content != null)
{
if (UIControlContainer.Content is UserControl)
{
(UIControlContainer.Content as UserControl).Height = UIControlContainer.ActualHeight;
(UIControlContainer.Content as UserControl).Width = UIControlContainer.ActualWidth;
}
}
}
Enjoy!
P.S. Acctually I did it for UWP.
Since the canvas requires a Top/Left for placement, if you want to center something, is adding a grid at the proper Canvas.Top with HorizontalAlignment="Center" the best way to do it, or is there a better way?
This snip is a 150X300 canvas, with some content centered in a grid ....
<Canvas Width="150" Height="300">
<Grid Canvas.Top="75" Width="106" HorizontalAlignment="Center">
{whatever you want centered}
</Grid>
</Canvas>
Guy's solution works, but you may have to tweak z-order and visibility if you're juggling hit testing.
Another alternative is having the Grid inside the Canvas (as you've specified in your XAML) with the Height/Width set to (or bound to) the Height/Width of the Canvas. Then setting HorizontalAlignment/VerticalAlignment to Center for the contents of your Grid.
I'm not sure if this will meet your exact requirement, but if you put both the canvas and the content inside a grid as peers, it will get you a centered result:
<Grid>
<Canvas Width="150" Height="300"/>
<Button HorizontalAlignment="Center" VerticalAlignment="Center" Width="106" Content="Click"/>
</Grid>