1 files changed, 47 insertions, 0 deletions
diff --git a/layout/generic/ColumnUtils.cpp b/layout/generic/ColumnUtils.cpp
new file mode 100644
index 0000000000..6f1f54824f
--- /dev/null
+++ b/layout/generic/ColumnUtils.cpp
@@ -0,0 +1,47 @@
+/* -*- 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/. */
+
+/* A namespace class for static muti-column utilities. */
+
+#include "mozilla/ColumnUtils.h"
+
+#include <algorithm>
+
+#include "nsContainerFrame.h"
+#include "nsLayoutUtils.h"
+
+namespace mozilla {
+
+/* static */
+nscoord ColumnUtils::GetColumnGap(const nsContainerFrame* aFrame,
+                                  nscoord aPercentageBasis) {
+  const auto& columnGap = aFrame->StylePosition()->mColumnGap;
+  if (columnGap.IsNormal()) {
+    return aFrame->StyleFont()->mFont.size.ToAppUnits();
+  }
+  return nsLayoutUtils::ResolveGapToLength(columnGap, aPercentageBasis);
+}
+
+/* static */
+nscoord ColumnUtils::ClampUsedColumnWidth(const Length& aColumnWidth) {
+  // Per spec, used values will be clamped to a minimum of 1px.
+  return std::max(CSSPixel::ToAppUnits(1), aColumnWidth.ToAppUnits());
+}
+
+/* static */
+nscoord ColumnUtils::IntrinsicISize(uint32_t aColCount, nscoord aColGap,
+                                    nscoord aColISize) {
+  MOZ_ASSERT(aColCount > 0, "Cannot compute with zero columns!");
+
+  // Column box's inline-size times number of columns (n), plus n-1 column gaps.
+  nscoord iSize = aColISize * aColCount + aColGap * (aColCount - 1);
+
+  // The multiplication above can make 'iSize' negative (integer overflow),
+  // so use std::max to protect against that.
+  return std::max(iSize, aColISize);
+}
+
+}  // namespace mozilla