diff --git a/SourceGen/RuntimeData/Apple/VisHiRes.cs b/SourceGen/RuntimeData/Apple/VisHiRes.cs
index 0f7cef3..51b5b05 100644
--- a/SourceGen/RuntimeData/Apple/VisHiRes.cs
+++ b/SourceGen/RuntimeData/Apple/VisHiRes.cs
@@ -198,7 +198,7 @@ namespace RuntimeData.Apple {
                 return null;
             }
 
-            int lastOffset = offset + itemByteWidth * itemHeight - 1;
+            int lastOffset = offset + itemByteWidth * itemHeight * count - 1;
             if (lastOffset >= mFileData.Length) {
                 mAppRef.ReportError("Bitmap runs off end of file (last offset +" +
                     lastOffset.ToString("x6") + ")");
diff --git a/SourceGen/WpfGui/EditVisualization.xaml b/SourceGen/WpfGui/EditVisualization.xaml
index 1041a11..00e201a 100644
--- a/SourceGen/WpfGui/EditVisualization.xaml
+++ b/SourceGen/WpfGui/EditVisualization.xaml
@@ -23,8 +23,9 @@ limitations under the License.
         xmlns:local="clr-namespace:SourceGen.WpfGui"
         mc:Ignorable="d"
         Title="Edit Visualization"
-        Width="460" SizeToContent="Height" ResizeMode="NoResize"
+        SizeToContent="WidthAndHeight" ResizeMode="CanResizeWithGrip"
         ShowInTaskbar="False" WindowStartupLocation="CenterOwner"
+        Loaded="Window_Loaded"
         Closed="Window_Closed">
 
     <Window.Resources>
@@ -91,7 +92,7 @@ limitations under the License.
     <Grid Margin="8">
         <Grid.RowDefinitions>
             <RowDefinition Height="Auto"/>
-            <RowDefinition Height="Auto"/>
+            <RowDefinition Height="*"/>
             <RowDefinition Height="Auto"/>
             <RowDefinition Height="Auto"/>
         </Grid.RowDefinitions>
@@ -110,30 +111,30 @@ limitations under the License.
 
             <TextBlock Grid.Column="0" Grid.Row="0" HorizontalAlignment="Right" Margin="0,3,4,0"
                        Text="Visualizer:"/>
-            <ComboBox Name="visComboBox" Grid.Column="1" Grid.Row="0" Margin="0,0,0,4"
+            <ComboBox Name="visComboBox" Grid.Column="1" Grid.Row="0" Width="250" Margin="0,0,0,4"
+                      HorizontalAlignment="Left"
                       ItemsSource="{Binding VisualizationList}" DisplayMemberPath="VisDescriptor.UiName"
                       SelectionChanged="VisComboBox_SelectionChanged"/>
 
             <TextBlock Grid.Column="0" Grid.Row="1" HorizontalAlignment="Right" Margin="0,0,4,0"
                        Text="Tag:" Foreground="{Binding TagLabelBrush}"/>
-            <TextBox Grid.Column="1" Grid.Row="1" Margin="0,1,0,0"
+            <TextBox Grid.Column="1" Grid.Row="1" Width="250" Margin="0,1,0,0" HorizontalAlignment="Left"
                      Text="{Binding TagString, UpdateSourceTrigger=PropertyChanged}"
                      FontFamily="{StaticResource GeneralMonoFont}"/>
 
             <TextBlock Grid.Column="1" Grid.Row="2" Text="• Must be unique, 2+ chars"/>
 
-            <TextBlock Grid.Column="0" Grid.Row="3" Grid.ColumnSpan="2" Margin="0,20,0,4" Text="Preview:"/>
+            <TextBlock Grid.Column="0" Grid.Row="3" Grid.ColumnSpan="2" Margin="0,10,0,4" Text="Preview:"/>
         </Grid>
 
-        <Border Grid.Row="1" BorderThickness="1" HorizontalAlignment="Center"
+        <Border Grid.Row="1" BorderThickness="1" HorizontalAlignment="Stretch"
                 BorderBrush="{DynamicResource {x:Static SystemColors.WindowFrameBrushKey}}"
                 Background="{StaticResource CheckerBackground}">
-            <Image Name="previewImage" Width="320" Height="320" Source="/Res/RedX.png"
+            <Image Name="previewImage" Width="400" Height="400" Source="/Res/RedX.png"
                    RenderOptions.BitmapScalingMode="NearestNeighbor"/>
-            <!--<Button Width="400" Height="400" Content="Test"/>-->
         </Border>
 
-        <Grid Grid.Row="2">
+        <Grid Grid.Row="2" HorizontalAlignment="Left">
             <Grid.RowDefinitions>
                 <RowDefinition Height="Auto"/>
                 <RowDefinition Height="Auto"/>
@@ -148,7 +149,7 @@ limitations under the License.
             <TextBlock Grid.Row="1" Text="Parameters:" Margin="0,0,0,4"/>
 
             <!-- generated controls are placed here -->
-            <ItemsControl Grid.Row="2"
+            <ItemsControl Grid.Row="2" Width="400"
                 ItemsSource="{Binding ParameterList}"
                 ItemTemplateSelector="{StaticResource ParameterTemplateSelector}">
             </ItemsControl>
diff --git a/SourceGen/WpfGui/EditVisualization.xaml.cs b/SourceGen/WpfGui/EditVisualization.xaml.cs
index 115ba22..3a1841b 100644
--- a/SourceGen/WpfGui/EditVisualization.xaml.cs
+++ b/SourceGen/WpfGui/EditVisualization.xaml.cs
@@ -40,6 +40,7 @@ namespace SourceGen.WpfGui {
         private Formatter mFormatter;
         private int mSetOffset;
         private Visualization mOrigVis;
+        private string mOrigTag;
 
         private Brush mDefaultLabelColor = SystemColors.WindowTextBrush;
         private Brush mErrorLabelColor = Brushes.Red;
@@ -167,6 +168,7 @@ namespace SourceGen.WpfGui {
             mFormatter = formatter;
             mSetOffset = setOffset;
             mOrigVis = vis;
+            mOrigTag = vis.Tag;
 
             mScriptSupport = new ScriptSupport(this);
             mProject.PrepareScripts(mScriptSupport);
@@ -251,6 +253,24 @@ namespace SourceGen.WpfGui {
             }
         }
 
+        private void Window_Loaded(object sender, RoutedEventArgs e) {
+            // https://stackoverflow.com/a/31407415/294248
+            // After the window's size has been established to minimally wrap the elements,
+            // we set the minimum width to the current width, and un-freeze the preview image
+            // control so it changes size with the window.  This allows the window to resize
+            // without clipping any of the controls.
+            //
+            // This isn't quite right of course -- if the user changes the combo box setting
+            // the number of parameter controls will change -- but that just means the preview
+            // window will shrink or grow.  So long as this isn't taken to extremes we won't
+            // clip controls.
+            ClearValue(SizeToContentProperty);
+            SetValue(MinWidthProperty, this.Width);
+            SetValue(MinHeightProperty, this.Height);
+            previewImage.ClearValue(WidthProperty);
+            previewImage.ClearValue(HeightProperty);
+        }
+
         private void Window_Closed(object sender, EventArgs e) {
             mProject.UnprepareScripts();
         }
@@ -406,6 +426,7 @@ namespace SourceGen.WpfGui {
                         // Report the last message we got as an error.
                         PluginErrMessage = LastPluginMessage;
                     }
+                    IsValid = false;
                 } else {
                     previewImage.Source = Visualization.ConvertToBitmapSource(vis2d);
                 }
@@ -413,8 +434,15 @@ namespace SourceGen.WpfGui {
 
             string trimTag = Visualization.TrimAndValidateTag(TagString, out bool tagOk);
             Visualization match = FindVisualizationByTag(trimTag);
-            if (match != null && match != mOrigVis) {
+            if (match != null && trimTag != mOrigTag) {
                 // Another vis already has this tag.
+                //
+                // TODO: this is wrong.  If I edit the set, edit a Vis, change it's tag, then
+                // immediately edit it again, I can't change the tag back to what it originally
+                // was, because the original version of the Vis is in the VisSet and I no longer
+                // have a way to know that that Vis and this Vis are the same.  To make this work
+                // correctly we need to track renames, which I think we may want to do later on
+                // for animations, so not dealing with this yet.
                 tagOk = false;
             }
             if (!tagOk) {