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+/* 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/. */
+
+#ifndef LAYOUT_BASE_BASELINE_H_
+#define LAYOUT_BASE_BASELINE_H_
+
+#include "nsCoord.h"
+#include "mozilla/WritingModes.h"
+
+class nsIFrame;
+
+namespace mozilla {
+
+// https://drafts.csswg.org/css-align-3/#baseline-sharing-group
+enum class BaselineSharingGroup : uint8_t {
+ // NOTE Used as an array index so must be 0 and 1.
+ First = 0,
+ Last = 1,
+};
+
+// Layout context under which the baseline is being exported to.
+enum class BaselineExportContext : uint8_t {
+ LineLayout = 0,
+ Other = 1,
+};
+
+class Baseline {
+ public:
+ /**
+ * Synthesize a first(last) inline-axis baseline in aWM based on aFrame's
+ * margin-box.
+ *
+ * An alphabetical baseline is at the end edge of aFrame's margin-box with
+ * respect to aWM's block-axis, and a central baseline is halfway between the
+ * start and end edges. (aWM tells which baseline to use.)
+ * https://drafts.csswg.org/css-align-3/#synthesize-baseline
+ *
+ * @note This works only when aFrame's writing-mode is parallel to aWM.
+ * @param aWM the writing-mode of the alignment context.
+ * @return an offset from aFrame's border-box start(end) edge in aWM's
+ * block-axis for a first(last) baseline, respectively.
+ */
+ static nscoord SynthesizeBOffsetFromMarginBox(const nsIFrame* aFrame,
+ WritingMode aWM,
+ BaselineSharingGroup);
+
+ /**
+ * Synthesize a first(last) inline-axis baseline in aWM based on aFrame's
+ * border-box.
+ *
+ * An alphabetical baseline is at the end edge of aFrame's border-box with
+ * respect to aWM's block-axis, and a central baseline is halfway between the
+ * start and end edges. (aWM tells which baseline to use.)
+ * https://drafts.csswg.org/css-align-3/#synthesize-baseline
+ *
+ * @param aWM the writing-mode of the alignment context.
+ * @return an offset from aFrame's border-box start(end) edge in aWM's
+ * block-axis for a first(last) baseline, respectively.
+ */
+ static nscoord SynthesizeBOffsetFromBorderBox(const nsIFrame* aFrame,
+ WritingMode aWM,
+ BaselineSharingGroup);
+
+ /**
+ * Synthesize a first(last) inline-axis baseline in aWM based on aFrame's
+ * content-box.
+ *
+ * An alphabetical baseline is at the end edge of aFrame's content-box with
+ * respect to aWM's block-axis, and a central baseline is halfway between the
+ * start and end edges. (aWM tells which baseline to use.)
+ * https://drafts.csswg.org/css-align-3/#synthesize-baseline
+ *
+ * @note This works only when aFrame's writing-mode is parallel to aWM.
+ * @param aWM the writing-mode of the alignment context.
+ * @return an offset from aFrame's border-box start(end) edge in aWM's
+ * block-axis for a first(last) baseline, respectively.
+ */
+ static nscoord SynthesizeBOffsetFromContentBox(const nsIFrame* aFrame,
+ WritingMode aWM,
+ BaselineSharingGroup);
+};
+
+} // namespace mozilla
+
+#endif // LAYOUT_BASE_BASELINE_H_