[Webkit-unassigned] [Bug 270955] New: Canvas rendering issue in Safari causing delayed rendering compared to Chrome

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=270955

            Bug ID: 270955
           Summary: Canvas rendering issue in Safari causing delayed
                    rendering compared to Chrome
           Product: WebKit
           Version: Safari 17
          Hardware: Mac (Apple Silicon)
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebGL
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: ksardana at adobe.com
                CC: dino at apple.com, kbr at google.com, kkinnunen at apple.com

Created attachment 470359

  --> https://bugs.webkit.org/attachment.cgi?id=470359&action=review

Sample App where this issue can be replicated.

I am encountering an issue with canvas rendering in Safari, where my drawing application, functioning smoothly on Chrome, exhibits delayed rendering behavior in Safari. Specifically, when clicking a button to draw a triangle on the canvas, it often requires multiple clicks (sometimes 3-4) to render the triangle as expected.

Observations:

Adding glFinish() after glDrawArrays resolves the issue, while glFlush() does not.
Confirmed that the main thread is not blocked during the rendering process through logging.
Attempted to call emscripten_webgl_commit_frame() after glDrawArrays at regular intervals, but the issue persists. The function consistently returns EMSCRIPTEN_RESULT_SUCCESS.


Steps to Reproduce:

Open the drawing application in Safari.
Click the button to draw a triangle on the canvas.
Observe that the triangle does not render on the first click and may require multiple clicks for rendering.

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