Issue #1230 - Part 1: Fix Back-computing percentages for intrinsic sizing in Layout CSS-Grid

List of relevant patches applied:

1398537 part 2 - [css-multicol] Implement percentages for 'column-gap' (Gecko part).

1434478 part 1 - [css-grid] Stop back-computing percentage grid gaps when the percentage basis is indefinite. Treat them as zero sized instead.

1434478 part 2 - Stop back-computing percentage padding/margin when the percentage basis is indefinite. Treat them as zero sized instead.

1434478 part 3 - Remove IntrinsicISizeOffsetData::hPctPadding/hPctMargin members since they are now unused.

1434478 part 4 - Factor out constants like NS_UNCONSTRAINEDSIZE so they can be used in headers without needing nsIFrame.h (idempotent patch).

1434478 part 5 - Create nsLayoutUtils::ResolveToLength for resolving CSS <length-percentage> (idempotent patch).

1434478 part 6 - Propagate a percentage basis to nsIFrame::IntrinsicISizeOffsets for resolving padding/margin.

This is needed only for CSS Grid since in other cases we're only using IntrinsicISizeOffsets in the inline-axis and the percentage basis is always indefinite for *intrinsic sizing*. When calculating the intrinsic size of grid items in the grid container's block axis however, we do have a definite size for the grid area in the inline-axis and it should be used per: https://drafts.csswg.org/css-grid/#algo-overview "2. Next, the track sizing algorithm resolves the sizes of the grid rows, using the grid column sizes calculated in the previous step." (Percentage padding/margin for grid items is always resolved against the grid area's inline-size nowadays.)

1 files changed, 31 insertions, 0 deletions

diff --git a/layout/base/LayoutConstants.h b/layout/base/LayoutConstants.h
new file mode 100644
index 000000000..cd6e1c3f5
--- /dev/null
+++ b/layout/base/LayoutConstants.h
@@ -0,0 +1,31 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* constants used throughout the Layout module */
+
+#ifndef LayoutConstants_h___
+#define LayoutConstants_h___
+
+#include "nsSize.h"  // for NS_MAXSIZE
+
+/**
+ * Constant used to indicate an unconstrained size.
+ */
+#define NS_UNCONSTRAINEDSIZE NS_MAXSIZE
+
+// NOTE: There are assumptions all over that these have the same value,
+//       namely NS_UNCONSTRAINEDSIZE.
+#define NS_INTRINSICSIZE    NS_UNCONSTRAINEDSIZE
+#define NS_AUTOHEIGHT       NS_UNCONSTRAINEDSIZE
+#define NS_AUTOOFFSET       NS_UNCONSTRAINEDSIZE
+
+// +1 is to avoid clamped huge margin values being processed as auto margins
+#define NS_AUTOMARGIN       (NS_UNCONSTRAINEDSIZE + 1)
+
+#define NS_INTRINSIC_WIDTH_UNKNOWN nscoord_MIN
+
+
+#endif // LayoutConstants_h___