LayoutTests/fast/scrolling/scrolling-apis-subpixel.html - Issue 610423004: Preserve fractional scroll offset for JS scrolling API

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Issue 610423004: Preserve fractional scroll offset for JS scrolling API (Closed) Base URL: https://chromium.googlesource.com/chromium/blink.git@master

Patch Set: Created 6 years, 2 months ago

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1 <!DOCTYPE html>	1 <!DOCTYPE html>

2 <style>	2 <style>

3 .spacer {	3 .spacer {

4 height: 1000px;	4 height: 1000px;

5 width: 1000px;	5 width: 1000px;

6 }	6 }

7 #scroller, body {	7 #scroller, body {

8 height: 100px;	8 height: 100px;

9 width: 100px;	9 width: 100px;

10 overflow: scroll;	10 overflow: scroll;

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21 </body>	21 </body>

22	22

23 <script src="../../resources/js-test.js"></script>	23 <script src="../../resources/js-test.js"></script>

24 <script>	24 <script>

25	25

26 description("Verifies that scrolling APIs support fractional offsets.");	26 description("Verifies that scrolling APIs support fractional offsets.");

27 // Note we current support fractional scrolling only for the special case of	27 // Note we current support fractional scrolling only for the special case of

28 // browser zoom. When http://crbug.com/414283 is fixed, we should test	28 // browser zoom. When http://crbug.com/414283 is fixed, we should test

29 // other cases like device scale.	29 // other cases like device scale.

30	30

	31 var floatPrecision = 0.01;
	Rick Byers 2014/10/02 21:44:05 How close is this in practice? Eg. would 0.0001 a How close is this in practice? Eg. would 0.0001 also work? I'm worried that there may be web page bugs if we're off by a non-trivial amount. I believe we have some cases where we convert from double to LayoutUnit and back to double again (which could be responsible for differences of ~0.01) - those probably need to be considered bugs and fixed to consistently use double. Yufeng Shen (Slow to review) 2014/10/02 23:34:34 Yes. Element::setScrollLeft() has a conversion fro Show quoted text On 2014/10/02 21:44:05, Rick Byers wrote: > How close is this in practice? Eg. would 0.0001 also work? > > I'm worried that there may be web page bugs if we're off by a non-trivial > amount. I believe we have some cases where we convert from double to LayoutUnit > and back to double again (which could be responsible for differences of ~0.01) - > those probably need to be considered bugs and fixed to consistently use double. Yes. Element::setScrollLeft() has a conversion from float to LayoutUnit LayoutUnit::fromFloatRound() which adds about ~0.003. So that's why I have to put the precision so large, e.g. if you call setScrollLeft(4.2) and read it back, it would be something like 4.203. I am leaving a FIXME here to make the floatPrecision smaller. Rick Byers 2014/10/03 16:42:46 Ok. Ideally we'll even be able to go back to shou Show quoted text On 2014/10/02 23:34:34, Yufeng Shen wrote: > On 2014/10/02 21:44:05, Rick Byers wrote: > > How close is this in practice? Eg. would 0.0001 also work? > > > > I'm worried that there may be web page bugs if we're off by a non-trivial > > amount. I believe we have some cases where we convert from double to > LayoutUnit > > and back to double again (which could be responsible for differences of ~0.01) > - > > those probably need to be considered bugs and fixed to consistently use > double. > > Yes. Element::setScrollLeft() has a conversion from float to LayoutUnit > LayoutUnit::fromFloatRound() which adds about ~0.003. So that's why I have to > put the precision so large, e.g. if you call setScrollLeft(4.2) and > read it back, it would be something like 4.203. > > I am leaving a FIXME here to make the floatPrecision smaller. Ok. Ideally we'll even be able to go back to shouldBeEqualToNumber (if all we're doing is reading the exact double we stored, there should be no numerics issues).
	32

31 function testScroll(scrollOffset) {	33 function testScroll(scrollOffset) {

32	34

33 debug('Scrolling DIV with scrollTop/scrollLeft');	35 debug('Scrolling DIV with scrollTop/scrollLeft');

34 scroller.scrollTop = scrollOffset;	36 scroller.scrollTop = scrollOffset;

35 shouldBeEqualToNumber('scroller.scrollTop', scrollOffset);	37 shouldBeCloseTo('scroller.scrollTop', scrollOffset, floatPrecision);

36 scroller.scrollLeft = scrollOffset;	38 scroller.scrollLeft = scrollOffset;

37 shouldBeEqualToNumber('scroller.scrollLeft', scrollOffset);	39 shouldBeCloseTo('scroller.scrollLeft', scrollOffset, floatPrecision);

38	40

39 // Note that the body element is a special case - we don't attempt to	41 // Note that the body element is a special case - we don't attempt to

40 // test it here as it's semantics are in flux (http://goo.gl/BFHtMR).	42 // test it here as it's semantics are in flux (http://goo.gl/BFHtMR).

41	43

42 debug('Scrolling the document with window.scroll');	44 debug('Scrolling the document with window.scroll');

43 window.scroll(0,0);	45 window.scroll(0,0);

44 scrollOffset++;	46 scrollOffset++;

45 window.scroll(scrollOffset, scrollOffset);	47 window.scroll(scrollOffset, scrollOffset);

46 shouldBeEqualToNumber('window.scrollY', scrollOffset);	48 shouldBeCloseTo('window.scrollY', scrollOffset, floatPrecision);

47 shouldBeEqualToNumber('window.scrollX', scrollOffset);	49 shouldBeCloseTo('window.scrollX', scrollOffset, floatPrecision);

48	50

49 debug('Scrolling the document with window.scrollTo');	51 debug('Scrolling the document with window.scrollTo');

50 window.scroll(0,0);	52 window.scroll(0,0);

51 window.scrollTo(scrollOffset, scrollOffset);	53 window.scrollTo(scrollOffset, scrollOffset);

52 shouldBeEqualToNumber('window.pageYOffset', scrollOffset);	54 shouldBeCloseTo('window.pageYOffset', scrollOffset, floatPrecision);

53 shouldBeEqualToNumber('window.pageXOffset', scrollOffset);	55 shouldBeCloseTo('window.pageXOffset', scrollOffset, floatPrecision);

54	56

55 debug('Scrolling the document with window.scrollBy');	57 debug('Scrolling the document with window.scrollBy');

56 window.scroll(1,1);	58 window.scroll(1,1);

57 window.scrollBy(scrollOffset - 1, scrollOffset - 1);	59 window.scrollBy(scrollOffset - 1, scrollOffset - 1);

58 shouldBeEqualToNumber('window.scrollY', scrollOffset);	60 shouldBeCloseTo('window.scrollY', scrollOffset, floatPrecision);

59 shouldBeEqualToNumber('window.scrollX', scrollOffset);	61 shouldBeCloseTo('window.scrollX', scrollOffset, floatPrecision);

60	62

61 debug('');	63 debug('');

62 }	64 }

63	65

64 function testPageZoom(zoom) {	66 function testPageZoom(zoom) {

65 debug('---- Testing page zoom = ' + zoom + ' ----');	67 debug('---- Testing page zoom = ' + zoom + ' ----');

66 eventSender.setPageZoomFactor(zoom);	68 eventSender.setPageZoomFactor(zoom);

67 testScroll(4);	69 testScroll(4);

68 testScroll(4.5);	70 testScroll(4.5);

69 }	71 }

70	72

	73 testScroll(4.2);

71 testPageZoom(2);	74 testPageZoom(2);

72 </script>	75 </script>

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