Bug 1879770 Part 2 - Add a helper to query intrinsic scrollbar-gutter size for subgrid. r=emilio

See https://bugzilla.mozilla.org/show_bug.cgi?id=1879770#c2 for an analysis. Differential Revision: https://phabricator.services.mozilla.com/D201893
2024-03-04 14:30:23 +00:00 · 2024-03-04 14:30:23 +00:00 · a591467fd5
--- a/layout/generic/nsGfxScrollFrame.cpp
+++ b/layout/generic/nsGfxScrollFrame.cpp
@ -1173,9 +1173,15 @@ void nsHTMLScrollFrame::PlaceScrollArea(ScrollReflowInput& aState,
 }

 nscoord nsHTMLScrollFrame::IntrinsicScrollbarGutterSizeAtInlineEdges() const {
-  const bool isVerticalWM = GetWritingMode().IsVertical();
+  const auto wm = GetWritingMode();
+  const LogicalMargin gutter(wm, IntrinsicScrollbarGutterSize());
+  return gutter.IStartEnd(wm);
+}
+
+nsMargin nsHTMLScrollFrame::IntrinsicScrollbarGutterSize() const {
  if (PresContext()->UseOverlayScrollbars()) {
-    return 0;
+    // Overlay scrollbars do not consume space per spec.
+    return {};
  }

  const auto* styleForScrollbar = nsLayoutUtils::StyleForScrollbar(this);
@ -1183,28 +1189,30 @@ nscoord nsHTMLScrollFrame::IntrinsicScrollbarGutterSizeAtInlineEdges() const {
      styleForScrollbar->StyleUIReset()->ScrollbarWidth();
  if (styleScrollbarWidth == StyleScrollbarWidth::None) {
    // Scrollbar shouldn't appear at all with "scrollbar-width: none".
-    return 0;
+    return {};
  }

  const auto& styleScrollbarGutter =
      styleForScrollbar->StyleDisplay()->mScrollbarGutter;
-  ScrollStyles ss = GetScrollStyles();
-  const StyleOverflow& inlineEndStyleOverflow =
-      isVerticalWM ? ss.mHorizontal : ss.mVertical;
-
-  // Return the scrollbar-gutter size only if we have "overflow:scroll" or
-  // non-auto "scrollbar-gutter", so early-return here if the conditions aren't
-  // satisfied.
-  if (inlineEndStyleOverflow != StyleOverflow::Scroll &&
-      styleScrollbarGutter == StyleScrollbarGutter::AUTO) {
-    return 0;
+  nsMargin gutter =
+      ComputeStableScrollbarGutter(styleScrollbarWidth, styleScrollbarGutter);
+  if (gutter.LeftRight() == 0 || gutter.TopBottom() == 0) {
+    // If there is no stable scrollbar-gutter at vertical or horizontal
+    // dimension, check if a scrollbar is always shown at that dimension.
+    ScrollStyles scrollStyles = GetScrollStyles();
+    const nscoord scrollbarSize =
+        GetNonOverlayScrollbarSize(PresContext(), styleScrollbarWidth);
+    if (gutter.LeftRight() == 0 &&
+        scrollStyles.mVertical == StyleOverflow::Scroll) {
+      (IsScrollbarOnRight() ? gutter.right : gutter.left) = scrollbarSize;
+    }
+    if (gutter.TopBottom() == 0 &&
+        scrollStyles.mHorizontal == StyleOverflow::Scroll) {
+      // The horizontal scrollbar is always at the bottom side.
+      gutter.bottom = scrollbarSize;
+    }
  }
-
-  const nscoord scrollbarSize =
-      GetNonOverlayScrollbarSize(PresContext(), styleScrollbarWidth);
-  const auto bothEdges =
-      bool(styleScrollbarGutter & StyleScrollbarGutter::BOTH_EDGES);
-  return bothEdges ? scrollbarSize * 2 : scrollbarSize;
+  return gutter;
 }

 nsMargin nsHTMLScrollFrame::ComputeStableScrollbarGutter(
--- a/layout/generic/nsGfxScrollFrame.h
+++ b/layout/generic/nsGfxScrollFrame.h
@ -112,6 +112,12 @@ class nsHTMLScrollFrame : public nsContainerFrame,
  // scrollbar that scrolls in the block axis).
  nscoord IntrinsicScrollbarGutterSizeAtInlineEdges() const;

+  // Return the size of space created by scrollbar-gutter or actual scrollbars,
+  // assuming that the content is *not* overflowing the container. In other
+  // words, this space is created by stable scrollbar-gutter or by scrollbars
+  // due to "overflow: scroll".
+  nsMargin IntrinsicScrollbarGutterSize() const;
+
  // Compute stable scrollbar-gutter from scrollbar-width and scrollbar-gutter
  // properties.
  //
--- a/layout/generic/nsGridContainerFrame.cpp
+++ b/layout/generic/nsGridContainerFrame.cpp
@ -28,6 +28,7 @@
 #include "nsCSSFrameConstructor.h"
 #include "nsDisplayList.h"
 #include "nsFieldSetFrame.h"
+#include "nsGfxScrollFrame.h"
 #include "nsHashKeys.h"
 #include "nsIFrameInlines.h"  // for nsIFrame::GetLogicalNormalPosition (don't remove)
 #include "nsLayoutUtils.h"
@ -3685,7 +3686,8 @@ static Subgrid* SubgridComputeMarginBorderPadding(
      sz.ComputedLogicalMargin(cbWM) + sz.ComputedLogicalBorderPadding(cbWM);

  if (aGridItem.mFrame != subgridFrame) {
-    nsIScrollableFrame* scrollFrame = aGridItem.mFrame->GetScrollTargetFrame();
+    nsHTMLScrollFrame* scrollFrame =
+        do_QueryFrame(aGridItem.mFrame->GetScrollTargetFrame());
    if (scrollFrame) {
      MOZ_ASSERT(
          sz.ComputedLogicalMargin(cbWM) == LogicalMargin(cbWM) &&
@ -3699,7 +3701,7 @@ static Subgrid* SubgridComputeMarginBorderPadding(
          szScrollFrame.ComputedLogicalMargin(cbWM) +
          szScrollFrame.ComputedLogicalBorder(cbWM);

-      nsMargin ssz = scrollFrame->GetActualScrollbarSizes();
+      nsMargin ssz = scrollFrame->IntrinsicScrollbarGutterSize();
      subgrid->mMarginBorderPadding += LogicalMargin(cbWM, ssz);
    }

--- a/testing/web-platform/meta/css/css-grid/subgrid/scrollbar-gutter-002.html.ini
+++ b/testing/web-platform/meta/css/css-grid/subgrid/scrollbar-gutter-002.html.ini
@ -0,0 +1,3 @@
+[scrollbar-gutter-002.html]
+  fuzzy:
+    if os == "mac": maxDifference=6-6;totalPixels=240-240
--- a/testing/web-platform/tests/css/css-grid/subgrid/scrollbar-gutter-001-ref.html
+++ b/testing/web-platform/tests/css/css-grid/subgrid/scrollbar-gutter-001-ref.html
@ -0,0 +1,68 @@
+<!DOCTYPE HTML>
+<meta charset="utf-8">
+<title>CSS Grid Reference: Subgrids with 'overflow' and/or 'scrollbar-gutter'</title>
+<link rel="author" title="Ting-Yu Lin" href="mailto:tlin@mozilla.com">
+<link rel="author" title="Mozilla" href="https://www.mozilla.org/">
+
+<style>
+:root {
+  overflow: scroll; /* Required to reproduce the bug on Firefox */
+}
+.grid {
+  display: inline-block;
+  inline-size: 75px;
+  border: 5px solid blue;
+  vertical-align: top;
+}
+.subgrid {
+  block-size: 75px;
+}
+.item {
+  inline-size: 50px;
+  block-size: 50px;
+  background: green;
+}
+fieldset {
+  margin: 0;
+  padding: 0;
+  border: 0;
+}
+</style>
+
+<p>All the following subgrid scroll container shouldn't have any scrollbars.</p>
+
+<p>Testcase 1: subgrid with 'overflow: scroll'</p>
+<div class="grid">
+  <div class="subgrid" style="overflow: scroll;">
+    <div class="item"></div>
+  </div>
+</div>
+<div class="grid" style="writing-mode: vertical-rl;">
+  <div class="subgrid" style="overflow: scroll;">
+    <div class="item"></div>
+  </div>
+</div>
+
+<p>Testcase 2: subgrid with 'overflow: auto' and 'scrollbar-gutter: stable'</p>
+<div class="grid">
+  <div class="subgrid" style="overflow: auto; scrollbar-gutter: stable;">
+    <div class="item"></div>
+  </div>
+</div>
+<div class="grid" style="writing-mode: vertical-rl;">
+  <div class="subgrid" style="overflow: auto; scrollbar-gutter: stable;">
+    <div class="item"></div>
+  </div>
+</div>
+
+<p>Testcase 3: subgrid with 'overflow: hidden' and 'scrollbar-gutter: stable'</p>
+<div class="grid">
+  <div class="subgrid" style="overflow: hidden; scrollbar-gutter: stable;">
+    <div class="item"></div>
+  </div>
+</div>
+<div class="grid" style="writing-mode: vertical-rl;">
+  <div class="subgrid" style="overflow: hidden; scrollbar-gutter: stable;">
+    <div class="item"></div>
+  </div>
+</div>
--- a/testing/web-platform/tests/css/css-grid/subgrid/scrollbar-gutter-001.html
+++ b/testing/web-platform/tests/css/css-grid/subgrid/scrollbar-gutter-001.html
@ -0,0 +1,68 @@
+<!DOCTYPE HTML>
+<meta charset="utf-8">
+<title>CSS Grid Test: Subgrids with 'overflow' and/or 'scrollbar-gutter'</title>
+<link rel="author" title="Ting-Yu Lin" href="mailto:tlin@mozilla.com">
+<link rel="author" title="Mozilla" href="https://www.mozilla.org/">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1879770">
+<link rel="help" href="https://drafts.csswg.org/css-grid-2/#subgrid-item-contribution">
+<link rel="match" href="scrollbar-gutter-001-ref.html">
+
+<style>
+:root {
+  overflow: scroll; /* Required to reproduce the bug on Firefox */
+}
+.grid {
+  inline-size: 75px;
+  display: inline-grid;
+  border: 5px solid blue;
+  vertical-align: top;
+}
+.subgrid {
+  block-size: 75px;
+  display: grid;
+  grid: auto / subgrid;
+}
+.item {
+  inline-size: 50px;
+  block-size: 50px;
+  background: green;
+}
+</style>
+
+<p>All the following subgrid scroll container shouldn't have any scrollbars.</p>
+
+<p>Testcase 1: subgrid with 'overflow: scroll'</p>
+<div class="grid">
+  <div class="subgrid" style="overflow: scroll;">
+    <div class="item"></div>
+  </div>
+</div>
+<div class="grid" style="writing-mode: vertical-rl;">
+  <div class="subgrid" style="overflow: scroll;">
+    <div class="item"></div>
+  </div>
+</div>
+
+<p>Testcase 2: subgrid with 'overflow: auto' and 'scrollbar-gutter: stable'</p>
+<div class="grid">
+  <div class="subgrid" style="overflow: auto; scrollbar-gutter: stable;">
+    <div class="item"></div>
+  </div>
+</div>
+<div class="grid" style="writing-mode: vertical-rl;">
+  <div class="subgrid" style="overflow: auto; scrollbar-gutter: stable;">
+    <div class="item"></div>
+  </div>
+</div>
+
+<p>Testcase 3: subgrid with 'overflow: hidden' and 'scrollbar-gutter: stable'</p>
+<div class="grid">
+  <div class="subgrid" style="overflow: hidden; scrollbar-gutter: stable;">
+    <div class="item"></div>
+  </div>
+</div>
+<div class="grid" style="writing-mode: vertical-rl;">
+  <div class="subgrid" style="overflow: hidden; scrollbar-gutter: stable;">
+    <div class="item"></div>
+  </div>
+</div>
--- a/testing/web-platform/tests/css/css-grid/subgrid/scrollbar-gutter-002.html
+++ b/testing/web-platform/tests/css/css-grid/subgrid/scrollbar-gutter-002.html
@ -0,0 +1,73 @@
+<!DOCTYPE HTML>
+<meta charset="utf-8">
+<title>CSS Grid Test: Fieldset subgrids with 'overflow' and/or 'scrollbar-gutter'</title>
+<link rel="author" title="Ting-Yu Lin" href="mailto:tlin@mozilla.com">
+<link rel="author" title="Mozilla" href="https://www.mozilla.org/">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1879770">
+<link rel="help" href="https://drafts.csswg.org/css-grid-2/#subgrid-item-contribution">
+<link rel="match" href="scrollbar-gutter-001-ref.html">
+
+<style>
+:root {
+  overflow: scroll; /* Required to reproduce the bug on Firefox */
+}
+.grid {
+  inline-size: 75px;
+  display: inline-grid;
+  border: 5px solid blue;
+  vertical-align: top;
+}
+.subgrid {
+  block-size: 75px;
+  display: grid;
+  grid: auto / subgrid;
+}
+.item {
+  inline-size: 50px;
+  block-size: 50px;
+  background: green;
+}
+fieldset {
+  margin: 0;
+  padding: 0;
+  border: 0;
+}
+</style>
+
+<p>All the following subgrid scroll container shouldn't have any scrollbars.</p>
+
+<p>Testcase 1: subgrid with 'overflow: scroll'</p>
+<div class="grid">
+  <fieldset class="subgrid" style="overflow: scroll;">
+    <div class="item"></div>
+  </fieldset>
+</div>
+<div class="grid" style="writing-mode: vertical-rl;">
+  <fieldset class="subgrid" style="overflow: scroll;">
+    <div class="item"></div>
+  </fieldset>
+</div>
+
+<p>Testcase 2: subgrid with 'overflow: auto' and 'scrollbar-gutter: stable'</p>
+<div class="grid">
+  <fieldset class="subgrid" style="overflow: auto; scrollbar-gutter: stable;">
+    <div class="item"></div>
+  </fieldset>
+</div>
+<div class="grid" style="writing-mode: vertical-rl;">
+  <fieldset class="subgrid" style="overflow: auto; scrollbar-gutter: stable;">
+    <div class="item"></div>
+  </fieldset>
+</div>
+
+<p>Testcase 3: subgrid with 'overflow: hidden' and 'scrollbar-gutter: stable'</p>
+<div class="grid">
+  <fieldset class="subgrid" style="overflow: hidden; scrollbar-gutter: stable;">
+    <div class="item"></div>
+  </fieldset>
+</div>
+<div class="grid" style="writing-mode: vertical-rl;">
+  <fieldset class="subgrid" style="overflow: hidden; scrollbar-gutter: stable;">
+    <div class="item"></div>
+  </fieldset>
+</div>