159608 2016-07-10 03:52:43 -0700 preserveDrawingBuffer=true wrongly double-buffers on current iOS h/w 2020-05-08 16:03:37 -0700 1 1 1 Unclassified WebKit WebGL Other iPhone / iPad iOS 9.2 RESOLVED WONTFIX InRadar P2 Normal --- 183151 1 reuben.scratton dino dino gman kbr oldest_to_newest 1209531 0 reuben.scratton 2016-07-10 03:52:43 -0700 [F.A.O. Dean Jackson] Using preserveDrawingBuffer=true on iOS wrongly expects that rendering is done to two alternating backbuffers, i.e. normal double-buffering. As far as I can tell other WebGL implementations treat preserveDrawingBuffer=true as rendering to a single backbuffer which is then copied to the front buffer rather than swapped. Here is a simple demo of preserveDrawingBuffer=true written by Gregg Tavares: http://greggman.com/downloads/examples/webgl/lessons/resources/webgl-preservedrawingbuffer-true.html This demo looks fine on all desktop browsers and Android but flickers dreadfully on mobile Safari on iOS 9.x and 8.x because of the unexpected double-buffering. I reported the issue to Gregg and he advised me to report it here, marked for the attention of Dean. 1210334 1 283491 gman 2016-07-12 23:12:52 -0700 Created attachment 283491 webgl preservedrawingbuffer issue ios safari demonstration Can also go here https://jsfiddle.net/greggman/boffbn3k/ 1210336 2 gman 2016-07-12 23:18:12 -0700 I don't remember if I'm supposed to report this stuff but I also filed it as an apple bug 27317599 Also the conformance test fails on iOS https://www.khronos.org/registry/webgl/sdk/tests/conformance/context/context-attribute-preserve-drawing-buffer.html?webglVersion=1&quiet=0 1220601 3 reuben.scratton 2016-08-16 15:21:57 -0700 *crickets* 1221422 4 dino 2016-08-19 12:13:54 -0700 <rdar://problem/27317599> 1650767 5 kbr 2020-05-08 14:31:17 -0700 This bug might be fixed with the fix for Bug 183151, or it might have been fixed since it was filed. 1650814 6 dino 2020-05-08 16:01:44 -0700 This doesn't reproduce on current tip-of-tree iOS, but I think that's because we're now using the same compositing/back-buffer approach as macOS (now that both are using ANGLE). 1650816 7 kbr 2020-05-08 16:03:30 -0700 Great. Thanks Dean for confirming. It looked to me like the antialias:true path for preserveDrawingBuffer:true was working correctly, and that's what this test case uses. Closing as WontFix - no longer reproducible. 283491 2016-07-12 23:12:52 -0700 2016-07-12 23:12:52 -0700 webgl preservedrawingbuffer issue ios safari demonstration safari-webgl-preservedrawingbuffer-issue.html text/html 956 gman PHN0eWxlPgpib2R5IHsgbWFyZ2luOiAwOyB9CmNhbnZhcyB7IHdpZHRoOiAxMDB2dzsgaGVpZ2h0 OiAxMDB2aDsgfQo8L3N0eWxlPgo8Ym9keT4KPGNhbnZhcz48L2NhbnZhcz4KPC9ib2R5Pgo8c2Ny aXB0Pgp2YXIgY2FudmFzID0gZG9jdW1lbnQucXVlcnlTZWxlY3RvcigiY2FudmFzIik7CnZhciBn bCA9IGNhbnZhcy5nZXRDb250ZXh0KCJ3ZWJnbCIsIHsgcHJlc2VydmVEcmF3aW5nQnVmZmVyOiB0 cnVlIH0pOwoKZnVuY3Rpb24gcihtYXgpIHsKICByZXR1cm4gTWF0aC5yYW5kb20oKSAqIG1heCB8 IDA7Cn0KCmZ1bmN0aW9uIHJmKCkgewogIHJldHVybiBNYXRoLnJhbmRvbSgpICogMC41ICsgMC41 Owp9CgpmdW5jdGlvbiByZXNpemUoZ2wpIHsKICB2YXIgY2FudmFzID0gZ2wuY2FudmFzOwogIHZh ciB3aWR0aCA9IGNhbnZhcy5jbGllbnRXaWR0aDsKICB2YXIgaGVpZ2h0ID0gY2FudmFzLmNsaWVu dEhlaWdodDsKICBpZiAoY2FudmFzLndpZHRoICE9IHdpZHRoIHx8IGNhbnZhcy5oZWlnaHQgIT0g aGVpZ2h0KSB7CiAgICBjYW52YXMud2lkdGggPSB3aWR0aDsKICAgIGNhbnZhcy5oZWlnaHQgPSBo ZWlnaHQ7CiAgICBnbC52aWV3cG9ydCgwLCAwLCB3aWR0aCwgaGVpZ2h0KTsKICB9Cn0KCmZ1bmN0 aW9uIHJlbmRlcigpIHsKICByZXNpemUoZ2wpOwogIGdsLmVuYWJsZShnbC5TQ0lTU09SX1RFU1Qp OwoKICB2YXIgdyA9IGNhbnZhcy53aWR0aDsKICB2YXIgaCA9IGNhbnZhcy5oZWlnaHQ7CiAgdmFy IHggPSByKHcpOwogIHZhciB5ID0gcihoKTsKICBnbC5zY2lzc29yKHgsIHksIHIodyAtIHgpLCBy KGggLSB5KSk7CiAgZ2wuY2xlYXJDb2xvcihyZigpLCByZigpLCByZigpLCAxKTsKICBnbC5jbGVh cihnbC5DT0xPUl9CVUZGRVJfQklUKTsKICByZXF1ZXN0QW5pbWF0aW9uRnJhbWUocmVuZGVyKTsK fQpyZXF1ZXN0QW5pbWF0aW9uRnJhbWUocmVuZGVyKTsKPC9zY3JpcHQ+Cgo=