onDrop example

The following illustrates the “drop” side of a Drag&Drop Copy operation between two TreeView objects (see the drag( ) example). The Target’s onDrop expects cType to contain the class name “TreeView”, and cName to contain the name of a text file produced by the Source TreeView’s streamChildren( ) method. If the parameters are correct, the event calls loadChildren( ) to repopulate the Target TreeView from the text file.

If the drop fails and there is an onLeftMouseUp event handler, it is explicitly called.

function TREEVIEW1_onDrop(nLeft, nTop, cType, cName)

   local lReturn

   lReturn = false             // Initialize return value

   if cType == this.className        // Validate first parameter

     if file( cName )           // Validate second parameter

       try                // Trap potential errors

         this.loadChildren( cName )     // Process

         delete file (cName)        // Clean up

         lReturn = true          // Return success

       catch ( Exception e )

         msgBox( e.message, "Copy failed" ) // Some error, no drop

       endTry

     endIf

   endIf

   if not lReturn

     if type( “this.onLeftMouseUp“ ) == “FP” // Test for mouse Up event handler

       this.onLeftMouseUp( )         // “Fire” if present

     endIf

   endIf

 return lReturn