nsMathMLmfracFrame.h

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/* -*- 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/. */

#ifndef nsMathMLmfracFrame_h___

#define nsMathMLmfracFrame_h___

#include "mozilla/Attributes.h"

#include "nsMathMLContainerFrame.h"

namespace mozilla {

class PresShell;

}  // namespace mozilla

//

// <mfrac> -- form a fraction from two subexpressions

//

/*

The MathML REC describes:

The <mfrac> element is used for fractions. It can also be used to mark up

fraction-like objects such as binomial coefficients and Legendre symbols.

The syntax for <mfrac> is:

  <mfrac> numerator denominator </mfrac>

Attributes of <mfrac>:

     Name                      values                     default

  linethickness  number [ v-unit ] | thin | medium | thick  1

E.g.,

linethickness=2 actually means that linethickness=2*DEFAULT_THICKNESS

(DEFAULT_THICKNESS is not specified by MathML, see below.)

The linethickness attribute indicates the thickness of the horizontal

"fraction bar", or "rule", typically used to render fractions. A fraction

with linethickness="0" renders without the bar, and might be used within

binomial coefficients. A linethickness greater than one might be used with

nested fractions.

In general, the value of linethickness can be a number, as a multiplier

of the default thickness of the fraction bar (the default thickness is

not specified by MathML), or a number with a unit of vertical length (see

Section 2.3.3), or one of the keywords medium (same as 1), thin (thinner

than 1, otherwise up to the renderer), or thick (thicker than 1, otherwise

up to the renderer).

The <mfrac> element sets displaystyle to "false", or if it was already

false increments scriptlevel by 1, within numerator and denominator.

These attributes are inherited by every element from its rendering

environment, but can be set explicitly only on the <mstyle>

element.

*/

class nsMathMLmfracFrame final : public nsMathMLContainerFrame {

 public:

  NS_DECL_FRAMEARENA_HELPERS(nsMathMLmfracFrame)

  friend nsIFrame* NS_NewMathMLmfracFrame(mozilla::PresShell* aPresShell,

                                          ComputedStyle* aStyle);

  eMathMLFrameType GetMathMLFrameType() override;

  nsresult Place(DrawTarget* aDrawTarget, const PlaceFlags& aFlags,

                 ReflowOutput& aDesiredSize) override;

  void BuildDisplayList(nsDisplayListBuilder* aBuilder,

                        const nsDisplayListSet& aLists) override;

  nsresult AttributeChanged(int32_t aNameSpaceID, nsAtom* aAttribute,

                            int32_t aModType) override;

  NS_IMETHOD

  TransmitAutomaticData() override;

  // override the base method so that we can deal with the fraction line

  nscoord FixInterFrameSpacing(ReflowOutput& aDesiredSize) override;

  // helper to translate the thickness attribute into a usable form

  nscoord CalcLineThickness(nsPresContext* aPresContext,

                            ComputedStyle* aComputedStyle,

                            nsString& aThicknessAttribute, nscoord onePixel,

                            nscoord aDefaultRuleThickness,

                            float aFontSizeInflation);

  uint8_t ScriptIncrement(nsIFrame* aFrame) override;

 protected:

  explicit nsMathMLmfracFrame(ComputedStyle* aStyle,

                              nsPresContext* aPresContext)

      : nsMathMLContainerFrame(aStyle, aPresContext, kClassID),

        mSlashChar(nullptr),

        mLineThickness(0) {}

  virtual ~nsMathMLmfracFrame();

  bool IsMathContentBoxHorizontallyCentered() const final { return true; }

  // Display a slash

  void DisplaySlash(nsDisplayListBuilder* aBuilder, const nsRect& aRect,

                    nscoord aThickness, const nsDisplayListSet& aLists);

  nsRect mLineRect;

  nsMathMLChar* mSlashChar;

  nscoord mLineThickness;

};

#endif /* nsMathMLmfracFrame_h___ */