DYN-9829: Fix hidden resize grip in ScriptEditorWindow (#16756)

Author: ivaylo-matov

src/Libraries/PythonNodeModelsWpf/ScriptEditorWindow.xaml

@@ -13,7 +13,7 @@
                          Width="600"
                          MinWidth="500"
                          MinHeight="450"
-                         ResizeMode="CanResizeWithGrip"
+                         ResizeMode="CanResize"
                          Style="{DynamicResource DynamoWindowStyle}"
                          AllowsTransparency="True"
                          Background="Transparent"
@@ -455,6 +455,33 @@
                         </Grid>
                     </Border>
                 </Grid>
+                <Border x:Name="WindowResizeHandle"
+                        Grid.Row="4"
+                        HorizontalAlignment="Right"
+                        VerticalAlignment="Bottom"
+                        Width="11"
+                        Height="11"
+                        Margin="0 0 3 3"
+                        Cursor="SizeNWSE"
+                        Background="Transparent"
+                        MouseLeftButtonDown="WindowResizeHandle_OnMouseLeftButtonDown">
+                    <Canvas HorizontalAlignment="Right"
+                            VerticalAlignment="Bottom"
+                            Width="11"
+                            Height="11"
+                            Margin="0">
+                        <Rectangle Width="2" Height="2" Fill="#FFFFFF" Canvas.Left="9"/>
+                        <Rectangle Width="2" Height="2" Fill="#FFFFFF" Canvas.Left="9" Canvas.Top="3"/>
+                        <Rectangle Width="2" Height="2" Fill="#FFFFFF" Canvas.Left="9" Canvas.Top="6"/>
+                        <Rectangle Width="2" Height="2" Fill="#FFFFFF" Canvas.Left="9" Canvas.Top="9"/>
+                        <Rectangle Width="2" Height="2" Fill="#FFFFFF" Canvas.Left="6" Canvas.Top="3"/>
+                        <Rectangle Width="2" Height="2" Fill="#FFFFFF" Canvas.Left="6" Canvas.Top="6"/>
+                        <Rectangle Width="2" Height="2" Fill="#FFFFFF" Canvas.Left="6" Canvas.Top="9"/>
+                        <Rectangle Width="2" Height="2" Fill="#FFFFFF" Canvas.Left="3" Canvas.Top="6"/>
+                        <Rectangle Width="2" Height="2" Fill="#FFFFFF" Canvas.Left="3" Canvas.Top="9"/>
+                        <Rectangle Width="2" Height="2" Fill="#FFFFFF" Canvas.Top="9"/>
+                    </Canvas>
+                </Border>
             </Grid>
         </Border>
     </Grid>

src/Libraries/PythonNodeModelsWpf/ScriptEditorWindow.xaml.cs

@@ -3,9 +3,11 @@
 using System.Collections.Specialized;
 using System.ComponentModel;
 using System.Linq;
+using System.Runtime.InteropServices;
 using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Input;
+using System.Windows.Interop;
 using System.Windows.Media;
 using System.Xml;
 using Dynamo.Configuration;
@@ -50,6 +52,16 @@ public partial class ScriptEditorWindow : ModelessChildWindow
         // Reasonable max and min font size values for zooming limits
         private const double FONT_MAX_SIZE = 60d;
         private const double FONT_MIN_SIZE = 5d;
+        // Win32 system command and hit-test constants used for resizing
+        private const int WM_SYSCOMMAND = 0x0112;
+        private const int SC_SIZE = 0xF000;
+        private const int HTBOTTOMRIGHT = 0x0008;
+
+        /// <summary>
+        /// Sends a Win32 message to forward a system resize command when the custom resize grip is clicked
+        /// </summary>
+        [DllImport("user32.dll")]
+        private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam);
 
         private const double pythonZoomScalingSliderMaximum = 300d;
         private const double pythonZoomScalingSliderMinimum = 25d;
@@ -239,6 +251,7 @@ internal void DockWindow()
                 editor.IsModified = !IsSaved;
 
                 dynamoView.DockWindowInSideBar(this, NodeModel, titleBar);
+                WindowResizeHandle.Visibility = Visibility.Collapsed;
 
                 Analytics.TrackEvent(
                                Actions.Dock,
@@ -676,11 +689,13 @@ private void ToggleButtons(bool toggle)
             {
                 this.MaximizeButton.Visibility = Visibility.Collapsed;
                 this.NormalizeButton.Visibility = Visibility.Visible;
+                this.WindowResizeHandle.Visibility = Visibility.Collapsed;
             }
             else
             {
                 this.MaximizeButton.Visibility = Visibility.Visible;
                 this.NormalizeButton.Visibility = Visibility.Collapsed;
+                this.WindowResizeHandle.Visibility = Visibility.Visible;
             }
         }
 
@@ -796,6 +811,17 @@ private void EditText_OnPreviewKeyDown(object sender, KeyEventArgs e)
                 IsEnterHit = false;
             }
         }
-        #endregion
+
+        // Handles clicks on the custom resize grip and forwards them as a Win32 bottom-right resize command
+        private void WindowResizeHandle_OnMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
+        {
+            if (WindowState != WindowState.Normal)
+                return;
+
+            var helper = new WindowInteropHelper(this);
+            SendMessage(helper.Handle, WM_SYSCOMMAND, (IntPtr)(SC_SIZE + HTBOTTOMRIGHT), IntPtr.Zero);
+            e.Handled = true;
+        }
+        #endregion        
     }
 }