Calculate item progress from time estimates

if(wi.type.id==='workpackage'){
    var all =  ( wi.getRemainingEstimate()!=null ? wi.getRemainingEstimate().getHours() : 0 )  
    		+  ( wi.getTimeSpent()!=null ? wi.getTimeSpent().getHours() : 0 );
    var done = ( wi.getTimeSpent()!=null ? wi.getTimeSpent().getHours() : 0 );
    
    if(wi.getResolution()!=null){
      task.progress = 1;
    }else if(all==0){
      task.progress = 0;
    }else{
      task.progress = done / all;
    }    
    
    var progressString =  ( wi.getTimeSpent()!=null ? wi.getTimeSpent() : "0h" )  
    	+ " |  " 
        + ( wi.getRemainingEstimate()!=null ? wi.getRemainingEstimate() : "0h"  )  
        + "  (" +  Math.round(task.progress*100) + " %)";
    task.getFields().put("progressString", progressString);
}

Notes:

1. The script above calculates the  progress only for work items  of type workpackage. You shall change the item type on line 1 or completely remove the IF statement.
2. On line 14 we prepare a text, that we later can show on the gantt, see bellow.
3. You can adjust the line 2 based on your preference - if the progress shall be calculated as timeSpent/initialEstimate , or as proposed above timeSpent / (remainingEstimate + timeSpent)

Disable the progress drag

As we are calculating the progress automatically we need to disable progress drag.

Add following line into Widget Properties > Advanced > Gantt Config Script

  gantt.config.drag_progress = false;

Show the progress in the Gantt

You may want to show the progress information in the gantt:

To do so add following fragment into Widget Properties > Advanced > Gantt Config Script

  gantt.config.drag_progress = false;
  gantt.templates.rightside_text = function(start, end, task){
        return "<b><img src='" + task.fields.statusIcon + "'/> " + task.fields.statusName + "</b> " 
        	+ (task.progress !=null ? task.fields.progressString : "");
  };