api.CanvasRenderingContext2D.globalAlpha - Doesn't work after safari 16.x and also 17.x version

[KKHKO]

What type of issue is this?

Browser bug (a bug with a feature that may impact site compatibility)

What information was incorrect, unhelpful, or incomplete?

<style> #canvas { border: 1px solid black; } </style>

<script>
    
    const canvas = document.getElementById("canvas");
    const ctx = canvas.getContext("2d");

    
    ctx.fillStyle = "red";
    ctx.fillRect(50, 50, 200, 200);

    
    ctx.globalCompositeOperation = "destination-in";
	ctx.fillRect(50, 50, 200, 200);
    ctx.globalAlpha = 0.5;
    // 绘制目标形状（圆形）
    ctx.fillStyle = "blue";
    ctx.beginPath();
    ctx.arc(200, 200, 100, 0, Math.PI * 2);
    ctx.closePath();
    ctx.fill();
</script>

What browsers does this problem apply to, if applicable?

Safari

What did you expect to see?

The transparency of image doesn't work on safari

Did you test this? If so, how?

Yes, deployed my code and show it on safari

Can you link to any release notes, bugs, pull requests, or MDN pages related to this?

No response

Do you have anything more you want to share?

I am not sure exact safari version.

MDN URL

https://developer.mozilla.org/zh-CN/docs/Web/API/CanvasRenderingContext2D/globalAlpha

MDN metadata

MDN page report details

• Query: api.CanvasRenderingContext2D.globalAlpha
• Report started: 2024-03-15T03:49:59.009Z

[queengooborg]

The example on MDN works on both Chrome and Safari exactly the same, but I can confirm your code renders differently on both browsers.

(Top: Chrome, bottom: Safari)

Once I take away the ctx.globalCompositeOperation = "destination-in"; line, however, both browsers render identically.

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I don't know how we would track this in BCD, but this isn't an issue that globalAlpha isn't supported. In the meantime, I'd recommend reporting the bug to WebKit.