Commit a57cdd05 authored by David Shin's avatar David Shin
Browse files

Bug 1800907 - Do not `UnionRect` empty rects in `OverflowAreas::Union*`. r=jwatt 

Previously, when current overflow area has one axis at zero size, calling
`OverflowAreas::Union*` with a rect with both axes at zero would overwrite
the axis with non-zero size.

Differential Revision: https://phabricator.services.mozilla.com/D162245
parent 0515d6a0

layout/generic/ReflowOutput.cpp

+24 −3
Original line number Diff line number Diff line
@@ -11,6 +11,19 @@ 


namespace mozilla {



static bool IsValidOverflowRect(const nsRect& aRect) {

  // `IsEmpty` in the context of `nsRect` means "width OR height is zero."

  // However, in the context of overflow, the rect having one axis as zero is

  // NOT considered empty.

  if (MOZ_LIKELY(!aRect.IsEmpty())) {

    return true;

  }



  // Be defensive and consider rects with any negative size as invalid.

  return !aRect.IsEqualEdges(nsRect()) && aRect.Width() >= 0 &&

         aRect.Height() >= 0;

}



/* static */

nsRect OverflowAreas::GetOverflowClipRect(const nsRect& aRectToClip,

                                          const nsRect& aBounds,
@@ -40,12 +53,20 @@ void OverflowAreas::ApplyOverflowClippingOnRect(nsRect& aOverflowRect, 
}



void OverflowAreas::UnionWith(const OverflowAreas& aOther) {

  if (IsValidOverflowRect(aOther.InkOverflow())) {

    InkOverflow().UnionRect(InkOverflow(), aOther.InkOverflow());

  }

  if (IsValidOverflowRect(aOther.ScrollableOverflow())) {

    ScrollableOverflow().UnionRect(ScrollableOverflow(),

                                   aOther.ScrollableOverflow());

  }

}



void OverflowAreas::UnionAllWith(const nsRect& aRect) {

  if (!IsValidOverflowRect(aRect)) {

    // Same as `UnionWith()` - avoid losing information.

    return;

  }

  InkOverflow().UnionRect(InkOverflow(), aRect);

  ScrollableOverflow().UnionRect(ScrollableOverflow(), aRect);

}

testing/web-platform/tests/css/css-overflow/scrollable-overflow-zero-one-axis.html

0 → 100644
+59 −0
Original line number Diff line number Diff line 
<!DOCTYPE html>

<meta charset="utf-8">

<title>CSS Overflow: Scroll Length Calculated Correctly When One Axis Has Zero Length</title>

<link rel="author" title="David Shin" href="mailto:dshin@mozilla.com">

<link rel="author" title="Mozilla" href="http://www.mozilla.org/">

<link rel="help" href="https://drafts.csswg.org/css-overflow-3/#scrollable">

<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1800907">

<style>

.scroll {

  overflow: scroll;

}



.zero-h {

  width: 100px;

  height: 0px;

}



.zero-w {

  width: 0;

  height: 100px;

}



.flex-row {

  display: flex;

}



.flex-col {

  display: flex;

  flex-direction: column;

}



.grid {

  display: grid;

}

</style>

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

<script src="/resources/check-layout-th.js"></script>

<body onload="checkLayout('.scroll')">

<div class="scroll zero-h" data-expected-scroll-height="100">

  <div class="zero-w"></div>

</div>

<div class="scroll zero-w" data-expected-scroll-width="100">

  <div class="zero-h"></div>

</div>



<div class="scroll zero-h flex-row" data-expected-scroll-height="100">

  <div class="zero-w"></div>

</div>

<div class="scroll zero-w flex-col" data-expected-scroll-width="100">

  <div class="zero-h"></div>

</div>



<div class="scroll zero-h grid" data-expected-scroll-height="100">

  <div class="zero-w"></div>

</div>

<div class="scroll zero-w grid" data-expected-scroll-width="100">

  <div class="zero-h"></div>

</div>