How do I define a Grid so that ithas the same width as it's parent StackPanel in WPF?


I'm building out the layout for a WPF application.

I have a Grid embedded in a StackPanel.
The grid is 2 Columns X 3 Rows.
What do I need to do to have the Grid fill the horizontal space of the StackPanel (During resizing as well).
I would like the grid to have the same width as the StackPanel.

jxbmaSoftware ConsultantAsked:
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you would calculate the new column width for each column by multiplying it with the stack panel width and dividing it by the current grid width.

pseudo code:

current_grid_width = sum(column_widths)
total_width = stack_panel_width
foreach column in grid do
     column_width = (column_width * total_width) / current_grid_width
     set column_width
redraw grid

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perhaps you have additionally to consider frame thickness of panel and/or grid.

It should already be doing that... Unless you're overriding or setting a specific size, a StackPanel will expand it's children.
Is the stackpanel horizontal or vertical orientation?
jxbmaSoftware ConsultantAuthor Commented:
Snarf001::> It is horizontal orientation
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jxbmaSoftware ConsultantAuthor Commented:
So, I googled around and found the following solution which was posted for Silverlight.
It sort of works.
<StackPanel Name="stackPanelClassifiers" Orientation="Horizontal" Background="cyan" Height="200" HorizontalAlignment="Stretch" VerticalAlignment="Top" Opacity=".8">
                <Grid Name="gridClassifierDisplay" VerticalAlignment="Stretch" Background="LightGoldenrodYellow" Width="{Binding ActualWidth, ElementName=stackPanelClassifiers}">

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It works when you scale up the window.
However, when you attempt to scale the window back smaller, the grid seems to maintain it's max size and not shrink it's width with the downsizing?


Can you give a little background on what else is going to be happening?
If you're trying to stretch the with, I'm a little confused as to why you're using a horizontal StackPanel, since it's intended to have more items put in beside it.
Are you going to be having more elements?  And if so, what do you want to happen then?
And, FYI, the reason you're getting the behavior above, is because that's technically how a StackPanel is designed to respond.  It grows to whatever width it requires to display it's children.

So binding the Grid to the width works fine to increase the grid width, but as soon as that happens, the StackPanel has now grown to accommodate the Grid's width.
When you shrink the window, the StackPanel thinks the Grid is still that wide, so it isn't going to shrink itself again.

As I said, couple more details and we can get it down.  There's so many different handy containers in WPF, I'm sure there's a simple fix for what you need, just need a bit more detail on what that is.
jxbmaSoftware ConsultantAuthor Commented:
OK. Finally figure out what does the trick:
           <StackPanel Name="stackPanelClassifiers" Orientation="Vertical" Background="cyan" Height="200" HorizontalAlignment="Stretch" VerticalAlignment="Top" Opacity=".8">
                <Grid Name="gridClassifierDisplay" VerticalAlignment="Stretch" Background="LightGoldenrodYellow" 
                      Width="{Binding ElementName=stackPanelClassifiers, Path=ActualWidth}"
                      Height="{Binding ElementName=stackPanelClassifiers, Path=ActualHeight}" >

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Can anyone explain why this should only work with Orientation set to "Vertical?"
It doesn't actually.  You still have the same underlying problem, the height isn't going to stretch properly, and will overflow.
When StackPanel is set to Horizontal, it will horizontally stack any and all items that are put into it, and grow as needed.
Vertically, same difference.
When you set the alignments to stretch, they'll natively take up the corresponding space required, but StackPanel will still grow as needed.

Hate to keep pushing the point... but I'm really not sure that's the container you should actually be using.
Happy to shoot more info if you want to give some more detail.
A bit more context for you, maybe that will help.
There's quite a few different container elements available in WPF; A grid natively will stretch it's children to it's bounds, while letting you specify columns and rows and corresponding widths.
Canvas is absolute positioning.
WrapPanel will tile items in order more like HTML flow.

A Stackpanel, in horizontal mode for example, has the sole exclusive purpose of making sure that MULTIPLE children will always be on after the other on a horizontal line, no matter their height and width.

By doing what you have in there, and binding the width and height, you've basically explicitly said "don't do what the stack panel is intended for".  If you add another child element to it, the Grid you have is bound to the stackpanel's height and width, so will never resize properly.

In the case you have above, the same effect you're looking for would have been accomplished just as easily, without any of the bindings, using another Grid as the parent container:

    <Grid Name="stackPanelClassifiers" Background="cyan" Height="200" VerticalAlignment="Top" Opacity=".8">
        <Grid Name="gridClassifierDisplay" Background="LightGoldenrodYellow" >

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jxbmaSoftware ConsultantAuthor Commented:
I have a StackPanel --> Grid --> Image.

 1) I would like the image to fill the available space in the grid (stretch/scale?)

 2) I would like the grid to fill the available space in the StackPanel

 I assign the image's source dynamically at runtime.
 The image dimensions are 640 X 480.
 I would like the image centered in the grid, but filling the width/height of the grid.

 Here is a snippet of XAML that I am using:
            <StackPanel Name="stackPanelImage" Orientation="Vertical" VerticalAlignment="Stretch" HorizontalAlignment="Stretch">
                <Grid Name="imageDisplayGrid" VerticalAlignment="Stretch" >
                    <Image Name="imageDisplay" Width="auto" HorizontalAlignment="Center" VerticalAlignment="Center"  Height="auto" Visibility="Hidden" Stretch="Uniform"/>

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A little background about the application.
The application takes frame by frame captures from a PC camera/library and the intent is to display it within the
panel/grid scheme that I have above.

With a frame rate of 15 frames per second, the solution has to be performant.


Okay, so you're not every going to be adding more children, just replacing the current image.
If so, StackPanel is simply the wrong choice.

If you have just a grid, it will do what you need.
Default behavior of a grid is to fill, and default behavior of an image in a grid is to uniformly stretch to fill the space.
Just this, with no other parameters or scaling specifications should do exactly what you want:

            <Image />

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