[Answered]How to instantly draw rect in editor GUI for 2D tilemapper

I have written a custom editor script that displays a sprite map texture on the inspector and I am attempting to have this tool allow the user to click and drag over portions of the sprite map he wants to use for an object to speed up the level creation for my 2D game.

As such I have the editorGUI draw a rect over the texture. My problem is that I want it to draw during a mouse drag event yet it will only draw the rectangle 2-3 seconds after I let go of the button.

I created a portion of the script that drew a rectangle of increasing size that reset itself and even that had large latency problems. But I started quickly clicking on the editor in a gray area and it started drawing the aforementioned growing rectangle every time I clicked. I am unsure how to interpret this behavior.

Here is how my script currently gets the coordinates:

         private void DrawCropAreaGUI() {
             //Cache the event
             Event evt = Event.current;
 
             switch(evt.type){
                 case EventType.MouseDown:
                 case EventType.MouseDrag:
                 case EventType.MouseUp:
                     //If the click is outside of the sprite sheet
                     if(!spriteSheetRect.Contains( evt.mousePosition ))
                         break;
 
                     //We're working with the initial click
                     if(evt.type == EventType.MouseDown) {
                         mouseDown = evt.mousePosition;
                     }
 
                     //We haven't finished yet we're just drawing the outline
                     if(evt.type == EventType.MouseDrag || evt.type == EventType.MouseUp) {
                         int left, top, right, bottom; //The extents of our rectangle of selection
                         //The drag is moving to the left
                         if(mouseDown.x > evt.mousePosition.x){
                             left = (int)evt.mousePosition.x;
                             right = (int)mouseDown.x;
                         }
                         //The drag is moving to the right
                         else{
                             left = (int)mouseDown.x;
                             right = (int)evt.mousePosition.x;
                         }
                         //The drag is moving up
                         if(mouseDown.y > evt.mousePosition.y){
                             top = (int)evt.mousePosition.y;
                             bottom = (int)mouseDown.y;
                         }
                         //The drag is going down
                         else{
                             top = (int)mouseDown.y;
                             bottom = (int)evt.mousePosition.y;
                         } 
 
                         selectionRect = new Rect( left, top , right - left, bottom - top );
                     }
                     break;
 
             }
         }

Then this is the OnInspectorGUI function:

         public override void OnInspectorGUI() {
             //Grab the attributes from the object
             m_Object.Update();
             
             //Overall settings label
             GUILayout.Label("Selection Settings", EditorStyles.boldLabel);
             
             //Set up the fields
             EditorGUILayout.PropertyField( t_width );
             EditorGUILayout.PropertyField( t_height );
 
             //If the width value is less than 0
             if(t_width.intValue < 0)
                 //We can't select less than 0 pixels
                 t_width.intValue = 0;
             //If the height value is less than 0
             if(t_height.intValue < 0)
                 //We can't select less than 0 pixels
                 t_height.intValue = 0;
 
             //The sprite map label
             GUILayout.Label( "Sprite Map", EditorStyles.boldLabel );
             Color c = new Color(200, 200, 0, 0.5f);
            
             if(t_texture.objectReferenceValue != null) {
                 spriteSheetRect = GUILayoutUtility.GetRect( 0.0f, 100.0f, GUILayout.ExpandWidth( true ), GUILayout.ExpandHeight(true) );
                 DrawCropAreaGUI();
                 //Draw our texturefor the user to eselect from
                 EditorGUI.DrawTextureTransparent(spriteSheetRect , (Texture2D) t_texture.objectReferenceValue );
                 Debug.Log( "spriteshseet " + spriteSheetRect + " selection " + selectionRect );     
                 EditorGUI.DrawRect( selectionRect, c );
                  //ShadowAndOutline.DrawOutline( selectionRect, "", new GUIStyle(), Color.red, Color.gray, 10 );
             }
             DropAreaGUI();
             //Apply the attributes to the object once done 
             m_Object.ApplyModifiedProperties();
            
         }