How do you account for Canvas Scaler match width or height mode set to 0.5 when trying to get the mouse click coordinates in canvas space?

Questions & Answers
1

Hi,
Short description
My image doesn’t go where I click. Here’s a video: https://youtu.be/u-xWNVt2LJM

Detailed description
I am trying to put a small white image in the position the mouse clicks. In the following setup:

Setup
Canvas - Render Mode: ScreenSpace - Overlay
Pixel perfect ticked
Canvas Scaler - UI Scale Mode: Scale Width or Height
Reference resolution: 1920x1080
Screen Match Mode: Match Width Or Height
Match: 0.5
Reference Pixels Per Unit: 100

I have an image attached to the canvas as child, anchored to the bottom left.

I have the following method I use to change Input.mousePosition to canvas space position that I apply to my image.

Vector2 UnscalePosition(Vector2 vec)
{
Vector2 referenceResolution = canvasScaler.referenceResolution;
Vector2 currentResolution = new Vector2(Screen.width, Screen.height);

    float widthRatio = currentResolution.x / referenceResolution.x;
    float heightRatio = currentResolution.y / referenceResolution.y;

    float ratio = Mathf.Lerp(heightRatio, widthRatio, canvasScaler.matchWidthOrHeight);

    return vec / ratio;
}

…

        Vector2 startPos = UnscalePosition(Input.mousePosition);
        mousePosImg.anchoredPosition = startPos;

It places the image correctly where I click when the aspect ratio is 16:10 or 16:9 (very close to the reference resolution), but it doesn’t when the height is very large and the width is very small (i.e. 300x900).
Unity has a strange explanation to what happens when matchWidthOrHeight is 0.5: Unity - Scripting API: UI.CanvasScaler.matchWidthOrHeight

How do you correctly bring Input.mousePosition in canvas space in this context?

2

I only needed to divide Input.mousePosition by canvas.scaleFactor. :slight_smile: