Selection Box with Scaling Canvas

Unity Engine
,
1

I can’t figure out what I’m doing wrong here. I’m just trying to get my selection box to follow the mouse position. Which works fine, until the canvas is scaled up or down based on screen size. Here’s a code snippet where the selection box (visual) is being manipulated.

private void Update()
{
   if (isSelecting)
   {
      currentSelectionPos = Mouse.current.position.ReadValue();

      float width = currentSelectionPos.x - selectionStartPos.x;
      float height = currentSelectionPos.y - selectionStartPos.y;

      selectionBox.rectTransform.sizeDelta = new Vector2(Mathf.Abs(width), Mathf.Abs(height));
      selectionBox.rectTransform.anchoredPosition = selectionStartPos + new Vector2(width / 2, height / 2 );
   }
}

Here’s a couple of shots of the UI set up.

NOTE - I’ve already tried dividing the anchored position by the Canvas.scaleFactor. Didn’t help. Also tried dividing it by the Canvas.rectTransform.scale.x (or y…it doesn’t matter). Also didn’t help. The box is always offset from where it should be whenever the canvas scale is changed.

2

As with all things Unity… I figured it out shortly after I posted this. :sweat_smile: The Image - Selection Box was a child of a Panel that wasn’t set to stretch with the Canvas. Also… I had to make THIS change to the code.

private void Update()
{
   if (isSelecting)
   {
      currentSelectionPos = Mouse.current.position.ReadValue();

      float width = currentSelectionPos.x - selectionStartPos.x;
      float height = currentSelectionPos.y - selectionStartPos.y;

      selectionBox.rectTransform.sizeDelta = new Vector2(Mathf.Abs(width), Mathf.Abs(height)) / canvas.scaleFactor;
      selectionBox.rectTransform.anchoredPosition = (selectionStartPos + new Vector2(width / 2, height / 2)) / canvas.scaleFactor;
   }
}
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