/* -*- 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 nsCSSRenderingGradients_h__

#define nsCSSRenderingGradients_h__

#include "nsLayoutUtils.h"

#include "nsStyleStruct.h"

#include "Units.h"

#include "mozilla/Maybe.h"

#include "mozilla/gfx/2D.h"

namespace mozilla {

namespace layers {

class StackingContextHelper;

} // namespace layers

namespace wr {

class DisplayListBuilder;

} // namespace wr

// A resolved color stop, with a specific position along the gradient line and

// a color.

struct ColorStop

{

  ColorStop()

    : mPosition(0)

    , mIsMidpoint(false)

  {

  }

  ColorStop(double aPosition, bool aIsMidPoint, const gfx::Color& aColor)

    : mPosition(aPosition)

    , mIsMidpoint(aIsMidPoint)

    , mColor(aColor)

  {

  }

  double mPosition; // along the gradient line; 0=start, 1=end

  bool mIsMidpoint;

  gfx::Color mColor;

};

class nsCSSGradientRenderer final

{

public:

  /**

   * Prepare a nsCSSGradientRenderer for a gradient for an element.

   * aIntrinsicSize - the size of the source gradient.

   */

  static nsCSSGradientRenderer Create(nsPresContext* aPresContext,

                                      ComputedStyle* aComputedStyle,

                                      nsStyleGradient* aGradient,

                                      const nsSize& aIntrinsiceSize);

  /**

   * Draw the gradient to aContext

   * aDest - where the first tile of gradient is

   * aFill - the area to be filled with tiles of aDest

   * aSrc - the area of the gradient that will fill aDest

   * aRepeatSize - the distance from the origin of a tile

   *               to the next origin of a tile

   * aDirtyRect - pixels outside of this area may be skipped

   */

  void Paint(gfxContext& aContext,

             const nsRect& aDest,

             const nsRect& aFill,

             const nsSize& aRepeatSize,

             const mozilla::CSSIntRect& aSrc,

             const nsRect& aDirtyRect,

             float aOpacity = 1.0);

  /**

   * Collect the gradient parameters

   */

  void BuildWebRenderParameters(float aOpacity,

                                wr::ExtendMode& aMode,

                                nsTArray<wr::GradientStop>& aStops,

                                LayoutDevicePoint& aLineStart,

                                LayoutDevicePoint& aLineEnd,

                                LayoutDeviceSize& aGradientRadius);

  /**

   * Build display items for the gradient

   * aLayer - the layer to make this display item relative to

   * aDest - where the first tile of gradient is

   * aFill - the area to be filled with tiles of aDest

   * aRepeatSize - the distance from the origin of a tile

   *               to the next origin of a tile

   * aSrc - the area of the gradient that will fill aDest

   */

  void BuildWebRenderDisplayItems(wr::DisplayListBuilder& aBuilder,

                                  const layers::StackingContextHelper& aSc,

                                  const nsRect& aDest,

                                  const nsRect& aFill,

                                  const nsSize& aRepeatSize,

                                  const mozilla::CSSIntRect& aSrc,

                                  bool aIsBackfaceVisible,

                                  float aOpacity = 1.0);

private:

  nsCSSGradientRenderer()

    : mPresContext(nullptr)

    , mGradient(nullptr)

    , mRadiusX(0.0)

    , mRadiusY(0.0)

  {

  }

  /**

   * Attempts to paint the tiles for a gradient by painting it once to an

   * offscreen surface and then painting that offscreen surface with

   * ExtendMode::Repeat to cover all tiles.

   *

   * Returns false if the optimization wasn't able to be used, in which case

   * a fallback should be used.

   */

  bool TryPaintTilesWithExtendMode(gfxContext& aContext,

                                   gfxPattern* aGradientPattern,

                                   nscoord aXStart,

                                   nscoord aYStart,

                                   const gfxRect& aDirtyAreaToFill,

                                   const nsRect& aDest,

                                   const nsSize& aRepeatSize,

                                   bool aForceRepeatToCoverTiles);

  nsPresContext* mPresContext;

  nsStyleGradient* mGradient;

  nsTArray<ColorStop> mStops;

  gfxPoint mLineStart, mLineEnd;

  double mRadiusX, mRadiusY;

};

} // namespace mozilla

#endif /* nsCSSRenderingGradients_h__ */