Question

This is more of a why doesn’t this work question. I obviously must be missing something because I cannot for the life of me figure out why calculating the width and height values give me the same static value that I started with. But when I substitute hardcoded values it works just fine. So obviously my calculations are bad but I cannot seem to figure out why. Can anyone help? If you need more info please ask.

 if(objectList[selectedIndex].Selected == true)
 {
      //The width would be mouselocationx - objectlocationx
      //The height would be mouselocationy - objectlocationy
      //Off set the position so it doesnt snap to mouse location
      //WHY THE *%$!! DOESNT THIS WORK!!?!?!?!?!?!?
      //int width = e.X - objectList[selectedIndex].X;
      //int height = e.Y - objectList[selectedIndex].Y;
      //Why is this so hard??
      //Point location = objectList[selectedIndex].Location;
      //location.X = e.X - (e.X - objectList[selectedIndex].Location.X);
      //location.Y = e.Y - (e.Y - objectList[selectedIndex].Location.Y);
      objectList[selectedIndex].X = e.Location.X - 12;
      objectList[selectedIndex].Y = e.Location.Y - 12;
      objectLocationXLabel.Text = "OBJX: " + objectList[selectedIndex].X.ToString();
      objectLocationYLabel.Text = "OBJY: " + objectList[selectedIndex].Y.ToString();
      panel1.Invalidate();
   }

Answer 1

It’s not at all clear what you want to do. But there are at least two issues with your commented code:

location.X = e.X - (e.X - objectList[selectedIndex].Location.X);

is equivalent to

location.X = objectList[selectedIndex].Location.X;

Point is a value type. So when you do this:

Point location = objectList[selectedIndex].Location;
location.X = ...;

location is modified, but not objectList[selectedIndex].Location.

Edit in response to comment: I think you must determine the offset in the MouseDown event, store it in a member and use it in MouseMove.