Prevent ToolTip position from resetting too often

Author: govert

Source/ExcelDna.IntelliSense/ToolTipForm.cs

@@ -16,24 +16,26 @@ class ToolTipForm  : Form
         FormattedText _text;
         System.ComponentModel.IContainer components;
         Win32Window _owner;
+        // Help Link
+        Rectangle _linkClientRect;
+        bool _linkActive;
+        string _linkAddress;
+        // Mouse Capture information for moving        
+        bool _captured = false;
+        Point _mouseDownScreenLocation;
+        Point _mouseDownFormLocation;
         // We keep track of this, else Visibility seems to confuse things...
         int _left;
         int _top;
+        int _showLeft;
+        int _showTop;
         // Various graphics object cached
         Brush _textBrush;
         Brush _linkBrush;
         Pen _borderPen;
         Pen _borderLightPen;
         Dictionary<FontStyle, Font> _fonts;
         ToolTip tipDna;
-        // Help Link
-        Rectangle _linkClientRect;
-        bool _linkActive;
-        string _linkAddress;
-        // Mouse Capture information for moving        
-        bool _captured = false;
-        Point _mouseDownScreenLocation;
-        Point _mouseDownFormLocation;
 
         public ToolTipForm(IntPtr hwndOwner)
         {
@@ -108,27 +110,36 @@ void ShowToolTip()
         public void ShowToolTip(FormattedText text, int left, int top)
         {
             _text = text;
-            _left = left;
-            _top = top;
+            if (left != _showLeft || top != _showTop)
+            {
+                // Update the start position and the current position
+                _left = left;
+                _top = top;
+                _showLeft = _left;
+                _showTop = _top;
+            }
             if (!Visible)
             {
-                Debug.Print($"Showing ToolTipForm: {_text.ToString()}");
+                Debug.Print($"ShowToolTip - Showing ToolTipForm: {_text.ToString()}");
                 // Make sure we're in the right position before we're first shown
                 SetBounds(_left, _top, 0, 0);
                 ShowToolTip();
             }
             else
             {
-                Debug.Print($"Invalidating ToolTipForm: {_text.ToString()}");
+                Debug.Print($"ShowToolTip - Invalidating ToolTipForm: {_text.ToString()}");
                 Invalidate();
             }
         }
 
 
         public void MoveToolTip(int left, int top)
         {
+            // We might consider checking the new position against earlier mouse movements
             _left = left;
             _top = top;
+            _showLeft = _left;
+            _showTop = _top;
             Invalidate();
         }