Updates to FormItem label and A11y (#395)

* feat: 1. add AccessKey support for form item.
2. Support label positioning for different content height.
3. polish demo.

* feat: add a transparent background for label.

demo/Ursa.Demo/Pages/FormDemo.axaml

@@ -13,59 +13,42 @@
     x:DataType="vm:FormDemoViewModel"
     mc:Ignorable="d">
     <ScrollViewer>
-        <StackPanel>
-            <Grid RowDefinitions="Auto, Auto" ColumnDefinitions="Auto, Auto">
-                <TextBlock Grid.Row="0" Grid.Column="0" Text="Label Position" VerticalAlignment="Center"></TextBlock>
-                <TextBlock Grid.Row="1" Grid.Column="0" Text="Label Alignment" VerticalAlignment="Center"></TextBlock>
-                <u:EnumSelector Grid.Row="0" Grid.Column="1"
-                    Name="position"
-                    EnumType="common:Position"
-                    Value="{x:Static common:Position.Top}" />
-                <u:EnumSelector Grid.Row="1" Grid.Column="1"
-                    Name="alignment"
-                    EnumType="HorizontalAlignment"
-                    Value="{x:Static HorizontalAlignment.Left}" />
-            </Grid>
-            <u:Form
-                DataContext="{Binding Model}"
-                LabelAlignment="{Binding #alignment.Value}"
-                LabelPosition="{Binding #position.Value}"
-                LabelWidth="*">
-                <u:FormGroup Header="Information">
-                    <TextBox
-                        Width="300"
-                        u:FormItem.IsRequired="True"
-                        u:FormItem.Label="Name"
-                        Text="{Binding Name}" />
-                    <TextBox
-                        Width="300"
-                        u:FormItem.Label="Email"
-                        Text="{Binding Email}" />
-                    <u:NumericDoubleUpDown Value="{Binding Number}" u:FormItem.Label="Number" Width="300"/>
+        <StackPanel HorizontalAlignment="Left" Margin="24  0 0 0 ">
+            <u:Divider Content="Simple Form"/>
+            <u:Form LabelPosition="Left" LabelWidth="*">
+                <TextBox Width="300" u:FormItem.Label="Name" />
+                <TextBox Width="300" u:FormItem.Label="Email" />
+                <TextBox Width="300" u:FormItem.Label="Message" Classes="TextArea"/>
+            </u:Form>
+            <u:Divider Content="Form accessibility"/>
+            <u:Form LabelPosition="Left" LabelWidth="*">
+                <TextBox Width="300" u:FormItem.Label="_Name" />
+                <TextBox Width="300" u:FormItem.Label="_Email" />
+                <TextBox Width="300" u:FormItem.Label="_Message" Classes="TextArea"/>
+            </u:Form>
+            <u:Divider Content="Label on top"/>
+            <u:Form LabelPosition="Top" LabelWidth="*">
+                <TextBox Width="300" u:FormItem.Label="Name" />
+                <TextBox Width="300" u:FormItem.Label="Email" />
+            </u:Form>
+            <u:Divider Content="FormGroup"/>
+            <u:Form LabelPosition="Left" LabelWidth="*">
+                <u:FormGroup Header="Basic Information">
+                    <TextBox Width="300" u:FormItem.Label="Name" />
+                    <TextBox Width="300" u:FormItem.Label="Email" />
                 </u:FormGroup>
-                <u:FormItem Label="Please select a Date">
-                    <CalendarDatePicker SelectedDate="{Binding Date}" />
-                </u:FormItem>
-                
-                <u:FormGroup Header="Education">
-                    <TextBox
-                        HorizontalAlignment="Stretch"
-                        u:FormItem.IsRequired="True"
-                        u:FormItem.Label="Name"
-                        Text="{Binding Name}" />
-                    <TextBox
-                        HorizontalAlignment="Stretch"
-                        u:FormItem.Label="Email"
-                        u:FormItem.IsRequired="True"
-                        Text="{Binding Email}" />
+                <u:FormGroup Header="Education Information">
+                    <TextBox Width="300" u:FormItem.Label="Collage" />
+                    <u:FormItem Label="Study Time">
+                        <u:DateRangePicker Width="300"></u:DateRangePicker>
+                    </u:FormItem>
                 </u:FormGroup>
-                <u:FormItem Label="Click to Submit">
-                    <Button Content="Button With Label" />
-                </u:FormItem>
-                <CheckBox Content="I Agree User Agreement" u:FormItem.NoLabel="True"></CheckBox>
-                <u:FormItem NoLabel="True">
-                    <Button HorizontalAlignment="Left" Content="No Label" />
-                </u:FormItem>
+                <Button Content="Submit" Theme="{DynamicResource SolidButton}" u:FormItem.NoLabel="True" HorizontalAlignment="Stretch"/>
+            </u:Form>
+            <u:Divider Content="MVVM setup and validation" />
+            <u:Form LabelPosition="Left" LabelWidth="*" DataContext="{Binding Model}">
+                <TextBox Width="300" u:FormItem.Label="Name" Text="{Binding  Name}"/>
+                <TextBox Width="300" u:FormItem.Label="Email" Text="{Binding Email}" />
             </u:Form>
         </StackPanel>
     </ScrollViewer>

src/Ursa.Themes.Semi/Controls/Form.axaml

@@ -1,24 +1,30 @@
 <ResourceDictionary
     xmlns="https://github.com/avaloniaui"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-    xmlns:u="https://irihi.tech/ursa">
+    xmlns:u="https://irihi.tech/ursa"
+    xmlns:converters="clr-namespace:Ursa.Themes.Semi.Converters">
     <!--  Add Resources Here  -->
-    <ControlTheme x:Key="{x:Type u:Form}" TargetType="u:Form">
-        <Setter Property="Grid.IsSharedSizeScope" Value="False" />
+    <ControlTheme x:Key="{x:Type u:Form}"
+                  TargetType="u:Form">
+        <Setter Property="Grid.IsSharedSizeScope"
+                Value="False" />
         <Setter Property="HorizontalAlignment" Value="Left" />
         <Setter Property="Template">
             <ControlTemplate TargetType="u:Form">
                 <DataValidationErrors>
-                    <ItemsPresenter ItemsPanel="{TemplateBinding ItemsPanel}" />
+                    <ItemsPresenter
+                        ItemsPanel="{TemplateBinding ItemsPanel}" />
                 </DataValidationErrors>
             </ControlTemplate>
         </Setter>
         <Style Selector="^:fixed-width">
-            <Setter Property="Grid.IsSharedSizeScope" Value="True" />
+            <Setter Property="Grid.IsSharedSizeScope"
+                    Value="True" />
         </Style>
     </ControlTheme>
 
-    <ControlTheme x:Key="{x:Type u:FormGroup}" TargetType="u:FormGroup">
+    <ControlTheme x:Key="{x:Type u:FormGroup}"
+                  TargetType="u:FormGroup">
         <Setter Property="Template">
             <ControlTemplate TargetType="u:FormGroup">
                 <StackPanel>
@@ -32,15 +38,17 @@
                         Height="1"
                         Margin="0,8"
                         HorizontalAlignment="Stretch"
-                        IsVisible="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=Header, Converter={x:Static ObjectConverters.IsNotNull}}" 
-                        Fill="{DynamicResource SemiColorBorder}" />
-                    <ItemsPresenter ItemsPanel="{TemplateBinding ItemsPanel}" />
+                        Fill="{DynamicResource SemiColorBorder}"
+                        IsVisible="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=Header, Converter={x:Static ObjectConverters.IsNotNull}}" />
+                    <ItemsPresenter
+                        ItemsPanel="{TemplateBinding ItemsPanel}" />
                 </StackPanel>
             </ControlTemplate>
         </Setter>
     </ControlTheme>
 
-    <ControlTheme x:Key="{x:Type u:FormItem}" TargetType="u:FormItem">
+    <ControlTheme x:Key="{x:Type u:FormItem}"
+                  TargetType="u:FormItem">
         <Setter Property="Margin" Value="0 8" />
         <Setter Property="Template">
             <ControlTemplate TargetType="u:FormItem">
@@ -50,13 +58,19 @@
                         Margin="0,0,0,4"
                         HorizontalAlignment="{TemplateBinding LabelAlignment}"
                         Orientation="Horizontal">
-                        <ContentPresenter Content="{TemplateBinding Label}" FontWeight="{DynamicResource TextBlockTitleFontWeight}" />
+                        <Label
+                            Content="{TemplateBinding Label}"
+                            Background="Transparent"
+                            FontWeight="{DynamicResource TextBlockTitleFontWeight}"
+                            Target="{Binding #PART_ContentPresenter.Content}" />
                         <TextBlock
                             Foreground="{DynamicResource SemiRed6}"
                             IsVisible="{TemplateBinding IsRequired}"
                             Text="*" />
                     </StackPanel>
-                    <ContentPresenter Content="{TemplateBinding Content}" />
+                    <ContentPresenter
+                        Name="PART_ContentPresenter"
+                        Content="{TemplateBinding Content}" />
                 </StackPanel>
             </ControlTemplate>
         </Setter>
@@ -65,7 +79,8 @@
                 <ControlTemplate TargetType="u:FormItem">
                     <Grid RowDefinitions="*, *">
                         <Grid.ColumnDefinitions>
-                            <ColumnDefinition Width="Auto" SharedSizeGroup="Label" />
+                            <ColumnDefinition Width="Auto"
+                                SharedSizeGroup="Label" />
                             <ColumnDefinition Width="*" />
                         </Grid.ColumnDefinitions>
                         <Border
@@ -74,10 +89,16 @@
                             Width="{TemplateBinding LabelWidth}">
                             <StackPanel
                                 Name="PART_LabelPanel"
-                                Margin="8,8,8,0"
+                                Margin="{Binding #PART_Label.Bounds.Height, Converter={x:Static converters:FormContentHeightToMarginConverter.Instance}}"
                                 HorizontalAlignment="{TemplateBinding LabelAlignment}"
+                                VerticalAlignment="{Binding #PART_ContentPresenter.Bounds.Height, Converter={x:Static converters:FormContentHeightToAlignmentConverter.Instance}}"
                                 Orientation="Horizontal">
-                                <ContentPresenter Content="{TemplateBinding Label}" FontWeight="{DynamicResource TextBlockTitleFontWeight}" />
+                                <Label
+                                    Name="PART_Label"
+                                    Content="{TemplateBinding Label}"
+                                    Background="Transparent"
+                                    FontWeight="{DynamicResource TextBlockTitleFontWeight}"
+                                    Target="{Binding #PART_ContentPresenter.Content}" />
                                 <TextBlock
                                     Foreground="{DynamicResource SemiRed6}"
                                     IsVisible="{TemplateBinding IsRequired}"
@@ -85,8 +106,11 @@
                             </StackPanel>
                         </Border>
                         <ContentPresenter
+                            Name="PART_ContentPresenter"
                             Grid.Row="0"
                             Grid.Column="1"
+                            VerticalAlignment="Stretch"
+                            VerticalContentAlignment="Center"
                             Content="{TemplateBinding Content}" />
                     </Grid>
                 </ControlTemplate>
@@ -95,9 +119,10 @@
         <Style Selector="^:no-label">
             <Setter Property="Template">
                 <ControlTemplate TargetType="u:FormItem">
-                    <ContentPresenter Content="{TemplateBinding Content}" />
+                    <ContentPresenter
+                        Content="{TemplateBinding Content}" />
                 </ControlTemplate>
             </Setter>
         </Style>
     </ControlTheme>
-</ResourceDictionary>
+</ResourceDictionary>

src/Ursa.Themes.Semi/Converters/FormContentHeightToAlignmentConverter.cs

@@ -0,0 +1,36 @@
+using System.Globalization;
+using Avalonia.Controls;
+using Avalonia.Data.Converters;
+using Avalonia.Layout;
+
+namespace Ursa.Themes.Semi.Converters;
+
+public class FormContentHeightToAlignmentConverter: IValueConverter
+{
+    public static FormContentHeightToAlignmentConverter Instance = new(32);
+    public double Threshold { get; set; }
+
+    public FormContentHeightToAlignmentConverter()
+    {
+        Threshold = 32;
+    }
+    
+    // ReSharper disable once ConvertToPrimaryConstructor
+    // Justification: need to keep the default constructor for XAML
+    public FormContentHeightToAlignmentConverter(double threshold)
+    {
+        Threshold = threshold;
+    }
+    
+    
+    public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+    {
+        if(value is not double d) return VerticalAlignment.Center;
+        return d > Threshold ? VerticalAlignment.Top : VerticalAlignment.Center;
+    }
+
+    public object? ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+    {
+        throw new NotImplementedException();
+    }
+}

src/Ursa.Themes.Semi/Converters/FormContentHeightToMarginConverter.cs

@@ -0,0 +1,34 @@
+using System.Globalization;
+using Avalonia;
+using Avalonia.Data.Converters;
+
+namespace Ursa.Themes.Semi.Converters;
+
+public class FormContentHeightToMarginConverter: IValueConverter
+{
+    public static FormContentHeightToMarginConverter Instance = new();
+    public double Threshold { get; set; }
+
+    public FormContentHeightToMarginConverter()
+    {
+        Threshold = 32;
+    }
+    
+    // ReSharper disable once ConvertToPrimaryConstructor
+    // Justification: need to keep the default constructor for XAML
+    public FormContentHeightToMarginConverter(double threshold)
+    {
+        Threshold = threshold;
+    }
+    
+    public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+    {
+        if(value is not double d) return new Thickness(0);
+        return d > Threshold ? new Thickness(0, 8, 8, 0) : new Thickness(0, 0, 8, 0);
+    }
+
+    public object? ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+    {
+        throw new NotImplementedException();
+    }
+}