wpf "Half the Whitespace" Design principle Demonstration of the problem and the solution

Example

For example, imagine a screen with 3 sections, laid out like this:

The blue box might be given a margin of 4,4,0,0. The green box might be given a margin of 4,4,4,0. The purple box margin would be 4,4,4,4. Here's the XAML: (I'm using a grid to achieve the layout; but this design principle applies regardless of how you choose to achieve the layout):

<UserControl x:Class="WpfApplication5.UserControl1HardCoded"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="3*"/>
        <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>
    <Grid.RowDefinitions>
        <RowDefinition Height="2*"/>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>

    <Border Grid.Column="0" Grid.Row="0" Margin="4,4,0,0" Background="DodgerBlue" BorderBrush="DarkBlue" BorderThickness="5"/>
    <Border Grid.Column="1" Grid.Row="0" Margin="4,4,4,0" Background="Green" BorderBrush="DarkGreen" BorderThickness="5"/>
    <Border Grid.Column="0" Grid.ColumnSpan="2" Grid.Row="1" Margin="4,4,4,4" Background="MediumPurple" BorderBrush="Purple" BorderThickness="5"/>
</Grid>
</UserControl>

Now imagine that we want to change the layout, to put the green box on the left of the blue box. Should be simple, shouldn’t it? Except that when we move that box, we now need to tinker with the margins. Either we can change the blue box’s margins to 0,4,4,0; or we could change blue to 4,4,4,0 and green to 4,4,0,0. Here's the XAML:

<UserControl x:Class="WpfApplication5.UserControl2HardCoded"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="3*"/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="2*"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>

        <Border Grid.Column="1" Grid.Row="0" Margin="4,4,4,0" Background="DodgerBlue" BorderBrush="DarkBlue" BorderThickness="5"/>
        <Border Grid.Column="0" Grid.Row="0" Margin="4,4,0,0" Background="Green" BorderBrush="DarkGreen" BorderThickness="5"/>
        <Border Grid.Column="0" Grid.ColumnSpan="2" Grid.Row="1" Margin="4,4,4,4" Background="MediumPurple" BorderBrush="Purple" BorderThickness="5"/>
    </Grid>
</UserControl>

Now let’s put the purple box at the top. So blue’s margins become 4,0,4,4; green becomes 4,0,0,4.

<UserControl x:Class="WpfApplication5.UserControl3HardCoded"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="3*"/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
            <RowDefinition Height="2*"/>
        </Grid.RowDefinitions>

        <Border Grid.Column="1" Grid.Row="1" Margin="4,0,4,4" Background="DodgerBlue" BorderBrush="DarkBlue" BorderThickness="5"/>
        <Border Grid.Column="0" Grid.Row="1" Margin="4,0,0,4" Background="Green" BorderBrush="DarkGreen" BorderThickness="5"/>
        <Border Grid.Column="0" Grid.ColumnSpan="2" Grid.Row="0" Margin="4,4,4,4" Background="MediumPurple" BorderBrush="Purple" BorderThickness="5"/>
    </Grid>
</UserControl>

Wouldn’t it be nice if we could move things around so that we didn’t need to adjust these values at all. This can be achieved by just thinking about the whitespace in a different way. Rather than allocating all the whitespace to one control or the other, imagine half the whitespace being allocated to each box: (my drawing is not quite to scale - the dotted lines should be half-way between the edge of the box and its neighbour).

So the blue box has margins of 2,2,2,2; the green box has margins of 2,2,2,2; the purple box has margins of 2,2,2,2. And the container in which they are housed is given a padding (not margin) of 2,2,2,2. Here's the XAML:

<UserControl x:Class="WpfApplication5.UserControl1HalfTheWhitespace"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300"
             Padding="2,2,2,2">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="3*"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="2*"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>

        <Border Grid.Column="0" Grid.Row="0" Margin="2,2,2,2" Background="DodgerBlue" BorderBrush="DarkBlue" BorderThickness="5"/>
        <Border Grid.Column="1" Grid.Row="0" Margin="2,2,2,2" Background="Green" BorderBrush="DarkGreen" BorderThickness="5"/>
        <Border Grid.Column="0" Grid.ColumnSpan="2" Grid.Row="1" Margin="2,2,2,2" Background="MediumPurple" BorderBrush="Purple" BorderThickness="5"/>
    </Grid>
</UserControl>

Now let’s try moving the boxes around, the same way as before...Let’s put the green box on the left of the blue box. OK, done. And there was no need to change any padding or margins. Here's the XAML:

<UserControl x:Class="WpfApplication5.UserControl2HalfTheWhitespace"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300"
             Padding="2,2,2,2">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="3*"/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="2*"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>

        <Border Grid.Column="1" Grid.Row="0" Margin="2,2,2,2" Background="DodgerBlue" BorderBrush="DarkBlue" BorderThickness="5"/>
        <Border Grid.Column="0" Grid.Row="0" Margin="2,2,2,2" Background="Green" BorderBrush="DarkGreen" BorderThickness="5"/>
        <Border Grid.Column="0" Grid.ColumnSpan="2" Grid.Row="1" Margin="2,2,2,2" Background="MediumPurple" BorderBrush="Purple" BorderThickness="5"/>
    </Grid>
</UserControl>

Now let’s put the purple box at the top. OK, done. And there was no need to change any padding or margins. Here's the XAML:

<UserControl x:Class="WpfApplication5.UserControl3HalfTheWhitespace"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300"
             Padding="2,2,2,2">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="3*"/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
            <RowDefinition Height="2*"/>
        </Grid.RowDefinitions>

        <Border Grid.Column="1" Grid.Row="1" Margin="2,2,2,2" Background="DodgerBlue" BorderBrush="DarkBlue" BorderThickness="5"/>
        <Border Grid.Column="0" Grid.Row="1" Margin="2,2,2,2" Background="Green" BorderBrush="DarkGreen" BorderThickness="5"/>
        <Border Grid.Column="0" Grid.ColumnSpan="2" Grid.Row="0" Margin="2,2,2,2" Background="MediumPurple" BorderBrush="Purple" BorderThickness="5"/>
    </Grid>
</UserControl>