M E R Goulding Software Development

This week I had a report of an application locking up while executing the shell function. Actually it was executing shell(“ipconfig /all”) in my modification of Ken Ray’s GetMACAddress function to return the machine’s LAN ip.

System administrators tend to like to turn things off so normal human beings can’t make a mess of their nice machines. One thing they can do is set a Windows registry entry to disable cmd.exe for the user. So by checking HKEY_CURRENT_USER\Software\Policies\Microsoft\Windows\System\DisableCMD”=dword:1 we can find out if cmd.exe is disabled for the current user. What this does is when cmd.exe is run it opens the console but all you get is a blocked by admin message and no command prompt. If Bill would just change this so it stopped cmd.exe from launching at all then we wouldn’t have such a problem. LiveCode is therefore able to run cmd.exe and just sits there waiting for it to terminate but it never does.

So I wrote a safer shell function to check for this situation and also possible execution errors from hash rules and renaming of cmd.exe etc. If the registry setting is there it will attempt to execute the command directly using process commands rather than via shell.

function safeShell pCommand
   -- assume the shellCommand has been set appropriately
   set the hideConsoleWindows to true
   set the itemDel to "\"
   if item -1 of the shellCommand is "cmd.exe" AND \ 
          charToNum(queryRegistry("HKEY_CURRENT_USER\Software\Policies\Microsoft\Windows\System\DisableCMD")) = 1 then
      -- don't use cmd.exe because shell() won't return
      -- don't revert to command.com because there seems to be a problem in the engine
      return executeProcess(pCommand)
   else
      try
         -- still check for empty if your are expecting a result
         -- because there's no execution error on os x
         return shell(pCommand)
      catch e
         -- execution error on windows shellCommand doesn't exist
         -- hopefully this catches hash rule blocks
         return "Error executing command"
      end try
   end if
end safeShell

function executeProcess pProcess,pElevate
   local tReturn
   if pElevate then
      open elevated process pProcess for text read
   else
      open process pProcess for text read
   end if
   repeat forever
      # Loop until there are no more lines to read.
      read from process pProcess for 1 line
      if the result = "" or the result = "timed out" then
         -- something to add
         put it after tReturn
      else
         close process pProcess
         return tReturn
      end if
   end repeat
end executeProcess

I have a project where using a data grid form really simplifies things, however, it’s critical that the user can re-order the list in arbitrary way. To do this I needed to add drag and drop to the data grid.

First I wrote rolled my own:

There two main limitations with this code are that it will only work for a data grid form (not table) and only if the cache controls property is true.

local sDragImage,sControlIndexMap,sOriginalIndexes

on dragStart
   local tControl,tItem
   set the dragData["private"] to "dgDragIndex"&&the dgHilitedIndex of me
   put the dgDataControlOfIndex[the dgHilitedIndex of me] of me into tControl
   lock screen
   import snapshot from tControl
   put the long id of the last image into sDragImage
   set the visible of sDragImage to false
   set the dragImage to the short id of sDragImage
   put the dgIndexes of me into sOriginalIndexes
   delete variable sControlIndexMap
   repeat for each item tItem in the dgIndexes of me
      put tItem into sControlIndexMap[the dgDataControlOfIndex[tItem] of me]
   end repeat
   set the allowableDragActions to "move"
   pass dragStart
end dragStart

on dragMove pX,pY
   local tDragIndex,tNewIndexes,tOverIndex
   if word 1 of the dragData["private"] = "dgDragIndex" then
      unlock screen
      lock cursor -- refresh bug workaround on setting the dgIndexes the dragAction seems to get set to none
      put word 2 of the dragData["private"] into tDragIndex
      set the dragAction to "move"
      if pY > the bottom of me-20 then
         if item 2 of the dgVisibleLines of me <  the dgNumberOfLines of me or the scroll of me is not the dgFormattedHeight of me then 
            set the dgVscroll of me to min(the dgVscroll of me + 20, the dgFormattedHeight of me)
         end if
      else if  pY < the top of me+20 then
         if item 1 of the dgVisibleLines of me >  1 or the scroll of me is not 0 then 
            set the dgVscroll of me to max(the dgVscroll of me - 20,0)
         end if
      end if
      repeat with X=1 to the number of groups of group "dgList" of me
         if the visible of group X of group "dgList" and the short name of the owner of group X of group "dgList" is "dgList" then
            if (pY >= the top of group X of group "dgList" of me) and (pY < (the top of group X of group "dgList" of me+(the bottom of group X of group "dgList" of me-the top of group X of group "dgList" of me) div 2)) then
               -- place above index
               put sControlIndexMap[the long id of group X of group "dgList" of me] into tOverIndex
               --put "over"&&tOverIndex
               if tDragIndex = tOverIndex then 
                  put sOriginalIndexes into tNewIndexes
               else
                  put sOriginalIndexes into tNewIndexes
                  delete item itemOffset(tDragIndex,tNewIndexes) of tNewIndexes
                  put tDragIndex&"," before item itemOffset(tOverIndex,tNewIndexes) of tNewIndexes
               end if
               set the dgIndexes of me to tNewIndexes
               put tNewIndexes into sOriginalIndexes
            else if (pY <= the bottom of group X of group "dgList" of me) and (pY > (the top of group X of group "dgList" of me+(the bottom of group X of group "dgList" of me-the top of group X of group "dgList" of me) div 2)) then
               -- place below index
               put sControlIndexMap[the long id of group X of group "dgList" of me] into tOverIndex
               --put "over"&&tOverIndex
               if tDragIndex = tOverIndex then 
                  put sOriginalIndexes into tNewIndexes
               else
                  put sOriginalIndexes into tNewIndexes
                  delete item itemOffset(tDragIndex,tNewIndexes) of tNewIndexes
                  put ","&tDragIndex after item itemOffset(tOverIndex,tNewIndexes) of tNewIndexes
               end if
               set the dgIndexes of me to tNewIndexes
               put tNewIndexes into sOriginalIndexes
            end if
         end if
      end repeat
   end if
   pass dragMove
end dragMove

on dragEnd
   -- clean up
   if sDragImage <> "" then
      delete sDragImage
      put "" into sDragImage
   end if
   pass dragEnd
end dragEnd

Then I had a poke around the data grid behavior script and found undocumented support for drag and drop. So here’s the new script that does not have the limitations of the above and is obviously far less verbose:

on dragStart
   local tIndex
   if (the dgHeader of the target is empty) then
      put the dgIndex of the dgDataControl of the target into tIndex
      set the dgDragImageIndex of me to tIndex
      set the dragData["private"] to empty
      set the dgTrackDragReorder[tIndex] of me to true
   end if
end dragStart

on DragReorderDrop pOriginatingIndex, pStartLine, pDroppedOnLine
   if (pStartLine is not pDroppedOnLine) then
      SetLineOfIndex pOriginatingIndex, pDroppedOnLine
      send "RefreshList" to me in 0 secs
   end if
end DragReorderDrop

on dragMove
   set the dragaction to "move"
end dragMove