Move points across a map without leaving a symbol trail

Summary

When you animate point features in ArcView using Avenue, a trail of symbols may be left along the path. This document discusses how to animate point feature without leaving a trail and without the need to refresh the entire screen; only the area where the point is moving gets refreshed.

The example scripts below assume you have an editab;le point theme with only one feature in a view titled View1. The point theme must be the first active theme in the view.

Procedure

1. Open a new script.
   
   
   A. Activate the Project window.
   B. Click the Scripts icon.
   C. Click New.
   
   
2. Paste the following code into the new script.
   
   

   Code:
   '-- Sample Script #1  "Sscript1"
   '
   '-- Get the view, display, theme, editable FTab, and shape field
   theView = av.FindDoc("View1")
   theDisplay = theView.GetDisplay
   theTheme = theView.getactivethemes.Get(0)
   theFTab = theTheme.GetFTab
   theFTab.SetEditable(true)
   shpFld = theFTab.FindField("Shape")
   '
   '-- Get the current point location
   pt = theFTab.ReturnValue(shpFld,0)
   '
   '-- Make a rectangle that surrounds the current point's marker symbol
   
   '-- You may need to adjust these numbers
   origExt = Rect.Make((pt.GetX - 2) @ (pt.GetY - 2), 4@4)
   '
   '-- Increment the location of the poiont.
   '-- In this case the point is moved 1.4 coverage units to the Northeast
   pt = pt + (1@1)  '1 unit north, 1 unit east = 1.4 units northeast
   '
   '-- Give the theme's FTab this new point location
   theFTab.SetValue(shpFld,0,pt)
   '
   '-- Stop editing the FTab and write it to disk
   theFTab.SetEditable(false)
   theFTab.Flush
   '
   '-- Make a rectangle that surrounds the new point's marker symbol
   
   '-- You may need to adjust these numbers
   newExt = Rect.Make((pt.GetX - 2) @ (pt.GetY - 2), 4@4)
   '
   '-- Calculate the portion of the view you want to re-draw
   
   '-- Do a union of the original point's symbol extent with the new point's symbol
   invRect = origExt.UnionWith(newRect)
   '
   '-- Re-draw the view only within the re-draw area
   theDisplay.InvalidateRect(invExt)
   '
   '-- Wait 2 seconds and run Script2
   av.delayedrun("Script2",nil,2)
   '
   '-- End of Script1 

   
   
3. Make sure the name of the script window is Script1.
   
   
   A. Select Properties from the Script menu.
   B. Type in a new name in the Name field.
   C. Click OK.
   
   
4. Open a new script.
5. Paste the following code into the second new script.
   
   

   Code:
   '-- Sample Script #2  "Sscript2"
   '
   '-- Run Script1
   av.Run("Script1",nil)
   '
   '-- End of Script2

   
   
   
6. Make sure the name of the second script window is Script2.
7. Compile both scripts.
8. Run Script1.