Making an RTS selection box

I'm trying to draw a rectangle on the screen when the player left clicks and drags. This code detects the left click but freezes when it enters the while loop:

if (Input.GetMouseButtonDown(0))
{
Debug.Log("clicked the left mouse button");
startClick = Input.mousePosition;
while (Input.GetMouseButtonDown(0))
{
selectionBox = new Rect(startClick.x, startClick.y, startClick.x + 100, startClick.y + 100);
Graphics.DrawTexture(selectionBox, selectionTexture);
}


}

 

Input is only updated once per frame. So you have created an infinite loop.

You could make it a coroutine. Or you could set a bool that you clear when the mouse is released and change your while to an if.

 

GetMouseButtonDown - the first frame when the mouse button is pressed (setup and create the rect)
GetMouseButton - every frame where the mouse button is held down (update the rect, i.e. where you should be doing what you are trying to use a while for, DONT use a while, it updates every frame and you don't want to work within a frame, but over all the frames the user holds down the button).
GetMouseButtonUp - the frame when the mouse button is released (remove rect, hand selection stuff etc.)

there are probably better approaches, but this appears to be what you were attempting, just needs the start, middle, end. not the start, start, start, start, start... ad infinitum

 

Code (csharp):

1.  
2. private Vector3 firstClick;
3. private bool selecting = false;
4.  
5. void Update () {
6.   if (Input.GetMouseButtonDown(0))
7.   {
8.     firstClick = MousePosInWorld();
9.     selecting = true;
10.   }
11.  
12.   if (Input.GetMouseButtonUp(0))
13.   {
14.     selecting = false;
15.   }
16.  
17.   if (selecting)
18.   {
19.     Debug.DrawLine(firstClick, MousePosInWorld());
20.   }
21. }
22.  
23. Vector3 MousePosInWorld()
24. {
25.   return Camera.main.ScreenToWorldPoint(Input.mousePosition);
26. }
27.