/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-

 * 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 GFX_GLYPHEXTENTS_H

#define GFX_GLYPHEXTENTS_H

#include "gfxFont.h"

#include "gfxRect.h"

#include "nsTHashtable.h"

#include "nsHashKeys.h"

#include "nsTArray.h"

#include "mozilla/MemoryReporting.h"

class gfxContext;

namespace mozilla {

namespace gfx {

class DrawTarget;

} // namespace gfx

} // namespace mozilla

/**

 * This stores glyph bounds information for a particular gfxFont, at

 * a particular appunits-per-dev-pixel ratio (because the compressed glyph

 * width array is stored in appunits).

 * 

 * We store a hashtable from glyph IDs to float bounding rects. For the

 * common case where the glyph has no horizontal left bearing, and no

 * y overflow above the font ascent or below the font descent, and tight

 * bounding boxes are not required, we avoid storing the glyph ID in the hashtable

 * and instead consult an array of 16-bit glyph XMost values (in appunits).

 * This array always has an entry for the font's space glyph --- the width is

 * assumed to be zero.

 */

class gfxGlyphExtents {

    typedef mozilla::gfx::DrawTarget DrawTarget;

public:

    explicit gfxGlyphExtents(int32_t aAppUnitsPerDevUnit) :

        mAppUnitsPerDevUnit(aAppUnitsPerDevUnit) {

        MOZ_COUNT_CTOR(gfxGlyphExtents);

    }

    ~gfxGlyphExtents();

    enum { INVALID_WIDTH = 0xFFFF };

    void NotifyGlyphsChanged() {

        mTightGlyphExtents.Clear();

    }

    // returns INVALID_WIDTH => not a contained glyph

    // Otherwise the glyph has no before-bearing or vertical bearings,

    // and the result is its width measured from the baseline origin, in

    // appunits.

    uint16_t GetContainedGlyphWidthAppUnits(uint32_t aGlyphID) const {

        return mContainedGlyphWidths.Get(aGlyphID);

    }

    bool IsGlyphKnown(uint32_t aGlyphID) const {

        return mContainedGlyphWidths.Get(aGlyphID) != INVALID_WIDTH ||

            mTightGlyphExtents.GetEntry(aGlyphID) != nullptr;

    }

    bool IsGlyphKnownWithTightExtents(uint32_t aGlyphID) const {

        return mTightGlyphExtents.GetEntry(aGlyphID) != nullptr;

    }

    // Get glyph extents; a rectangle relative to the left baseline origin

    // Returns true on success. Can fail on OOM or when aContext is null

    // and extents were not (successfully) prefetched.

    bool GetTightGlyphExtentsAppUnits(gfxFont* aFont,

            DrawTarget* aDrawTarget, uint32_t aGlyphID, gfxRect* aExtents);

    void SetContainedGlyphWidthAppUnits(uint32_t aGlyphID, uint16_t aWidth) {

        mContainedGlyphWidths.Set(aGlyphID, aWidth);

    }

    void SetTightGlyphExtents(uint32_t aGlyphID, const gfxRect& aExtentsAppUnits);

    int32_t GetAppUnitsPerDevUnit() { return mAppUnitsPerDevUnit; }

    size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;

    size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;

private:

    class HashEntry : public nsUint32HashKey {

    public:

        // When constructing a new entry in the hashtable, we'll leave this

        // blank. The caller of Put() will fill this in.

        explicit HashEntry(KeyTypePointer aPtr)

          : nsUint32HashKey(aPtr)

          , x(0.0)

          , y(0.0)

          , width(0.0)

          , height(0.0) {}

        HashEntry(HashEntry&& aOther)

            : nsUint32HashKey(std::move(aOther))

            , x(aOther.x)

            , y(aOther.y)

            , width(aOther.width)

            , height(aOther.height) {

        }

        float x, y, width, height;

    };

    enum { BLOCK_SIZE_BITS = 7, BLOCK_SIZE = 1 << BLOCK_SIZE_BITS }; // 128-glyph blocks

    class GlyphWidths {

    public:

        void Set(uint32_t aIndex, uint16_t aValue);

        uint16_t Get(uint32_t aIndex) const {

            uint32_t block = aIndex >> BLOCK_SIZE_BITS;

            if (block >= mBlocks.Length())

                return INVALID_WIDTH;

            uintptr_t bits = mBlocks[block];

            if (!bits)

                return INVALID_WIDTH;

            uint32_t indexInBlock = aIndex & (BLOCK_SIZE - 1);

            if (bits & 0x1) {

                if (GetGlyphOffset(bits) != indexInBlock)

                    return INVALID_WIDTH;

                return GetWidth(bits);

            }

            uint16_t *widths = reinterpret_cast<uint16_t *>(bits);

            return widths[indexInBlock];

        }

        uint32_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;

        ~GlyphWidths();

    private:

        static uint32_t GetGlyphOffset(uintptr_t aBits) {

            NS_ASSERTION(aBits & 0x1, "This is really a pointer...");

            return (aBits >> 1) & ((1 << BLOCK_SIZE_BITS) - 1);

        }

        static uint32_t GetWidth(uintptr_t aBits) {

            NS_ASSERTION(aBits & 0x1, "This is really a pointer...");

            return aBits >> (1 + BLOCK_SIZE_BITS);

        }

        static uintptr_t MakeSingle(uint32_t aGlyphOffset, uint16_t aWidth) {

            return (aWidth << (1 + BLOCK_SIZE_BITS)) + (aGlyphOffset << 1) + 1;

        }

        nsTArray<uintptr_t> mBlocks;

    };

    GlyphWidths             mContainedGlyphWidths;

    nsTHashtable<HashEntry> mTightGlyphExtents;

    int32_t                 mAppUnitsPerDevUnit;

private:

    // not implemented:

    gfxGlyphExtents(const gfxGlyphExtents& aOther) = delete;

    gfxGlyphExtents& operator=(const gfxGlyphExtents& aOther) = delete;

};

#endif