Tile Editor tile selection
 

Can anyone explain to me clearly as to exactly how you would go about selecting a group of tiles in a GuiDrawingPanel using the onMouseDragged event.
I just want the maths and code aspect of this, nothing fancy. Also, before you direct me to an example of a tile editor doing this, I've already searched the forums and can't make sense out of any of them.

1. onMouseDown: Determine the tile the mouse is currently over and use it as your top-left reference point.
2. onMouseDragged: Determine the tile the mouse is currently over and use it as your bottom-right reference point.
3. onMouseUp: Do whatever with your selection.

I believe:

tile_x = mouse_x - (mouse_x % tile_width);
tile_y = mouse_y - (mouse_y % tile_height);

Will get you the top-left x and y of the tile your mouse is currently over.

% is for modulus which basically gives you the remainder from dividing a number. I.e: 20 % 16 equals 4.

Thanks!
One thing that I can't seem to do is get the mouse position on the tileset image according to the positioning of the screen the GuiDrawingPanel is at.
Any idea?

You should be able to get the mouse x and y from params[1] and params[2].

onMouseDown(keymodifier,mousescreenx,mousescreeny, clickcount)
onMouseDragged(keymodifier,mousescreenx,mousescree ny)
onMouseUp(keymodifier,mousescreenx,mousescreeny)