/*****************************************************************************
 * Copyright (c) 2014-2025 OpenRCT2 developers
 *
 * For a complete list of all authors, please refer to contributors.md
 * Interested in contributing? Visit https://github.com/OpenRCT2/OpenRCT2
 *
 * OpenRCT2 is licensed under the GNU General Public License version 3.
 *****************************************************************************/

#ifndef DISABLE_OPENGL

    #include "../DrawingEngineFactory.hpp"
    #include "ApplyPaletteShader.h"
    #include "DrawCommands.h"
    #include "DrawLineShader.h"
    #include "DrawRectShader.h"
    #include "GLSLTypes.h"
    #include "OpenGLAPI.h"
    #include "OpenGLFramebuffer.h"
    #include "SwapFramebuffer.h"
    #include "TextureCache.h"
    #include "TransparencyDepth.h"

    #include <SDL.h>
    #include <algorithm>
    #include <cassert>
    #include <cmath>
    #include <openrct2-ui/interface/Window.h>
    #include <openrct2/config/Config.h>
    #include <openrct2/core/Console.hpp>
    #include <openrct2/drawing/Drawing.h>
    #include <openrct2/drawing/IDrawingContext.h>
    #include <openrct2/drawing/IDrawingEngine.h>
    #include <openrct2/drawing/LightFX.h>
    #include <openrct2/drawing/Weather.h>
    #include <openrct2/interface/Screenshot.h>
    #include <openrct2/ui/UiContext.h>
    #include <openrct2/world/Climate.h>

using namespace OpenRCT2;
using namespace OpenRCT2::Drawing;
using namespace OpenRCT2::Ui;

struct OpenGLVersion
{
    GLint Major;
    GLint Minor;
};

constexpr OpenGLVersion kOpenGLMinimumRequiredVersion = { 3, 3 };

constexpr uint8_t kCSInside = 0b0000;
constexpr uint8_t kCSLeft = 0b0001;
constexpr uint8_t kCSRight = 0b0010;
constexpr uint8_t kCSTop = 0b0100;
constexpr uint8_t kCSBottom = 0b1000;

class OpenGLDrawingEngine;

class OpenGLDrawingContext final : public IDrawingContext
{
private:
    OpenGLDrawingEngine& _engine;
    std::unique_ptr<ApplyTransparencyShader> _applyTransparencyShader;
    std::unique_ptr<DrawLineShader> _drawLineShader;
    std::unique_ptr<DrawRectShader> _drawRectShader;
    std::unique_ptr<SwapFramebuffer> _swapFramebuffer;

    std::unique_ptr<TextureCache> _textureCache;

    int32_t _drawCount = 0;

    #ifndef NO_TTF
    uint32_t _ttfGlId = 0;
    #endif

    struct
    {
        LineCommandBatch lines;
        RectCommandBatch rects;
        RectCommandBatch transparent;
    } _commandBuffers;

    static uint8_t ComputeOutCode(ScreenCoordsXY, ScreenCoordsXY, ScreenCoordsXY);
    static bool CohenSutherlandLineClip(ScreenLine&, const DrawPixelInfo&);
    [[nodiscard]] ScreenRect CalculateClipping(const DrawPixelInfo& dpi) const;

public:
    explicit OpenGLDrawingContext(OpenGLDrawingEngine& engine);
    ~OpenGLDrawingContext() override;

    TextureCache* GetTextureCache() const
    {
        return _textureCache.get();
    }
    const OpenGLFramebuffer& GetFinalFramebuffer() const
    {
        return _swapFramebuffer->GetFinalFramebuffer();
    }

    void Initialise();
    void Resize(int32_t width, int32_t height);
    void ResetPalette();
    void StartNewDraw();

    void Clear(DrawPixelInfo& dpi, uint8_t paletteIndex) override;
    void FillRect(DrawPixelInfo& dpi, uint32_t colour, int32_t x, int32_t y, int32_t w, int32_t h) override;
    void FilterRect(
        DrawPixelInfo& dpi, FilterPaletteID palette, int32_t left, int32_t top, int32_t right, int32_t bottom) override;
    void DrawLine(DrawPixelInfo& dpi, uint32_t colour, const ScreenLine& line) override;
    void DrawSprite(DrawPixelInfo& dpi, const ImageId imageId, int32_t x, int32_t y) override;
    void DrawSpriteRawMasked(
        DrawPixelInfo& dpi, int32_t x, int32_t y, const ImageId maskImage, const ImageId colourImage) override;
    void DrawSpriteSolid(DrawPixelInfo& dpi, const ImageId image, int32_t x, int32_t y, uint8_t colour) override;
    void DrawGlyph(DrawPixelInfo& dpi, const ImageId image, int32_t x, int32_t y, const PaletteMap& palette) override;
    void DrawTTFBitmap(
        DrawPixelInfo& dpi, TextDrawInfo* info, TTFSurface* surface, int32_t x, int32_t y, uint8_t hintingThreshold) override;

    void FlushCommandBuffers();

    void FlushLines();
    void FlushRectangles();
    void HandleTransparency();
};

class OpenGLWeatherDrawer final : public IWeatherDrawer
{
    OpenGLDrawingContext* _drawingContext;

public:
    explicit OpenGLWeatherDrawer(OpenGLDrawingContext* drawingContext)
        : _drawingContext(drawingContext)
    {
    }

    virtual void Draw(
        DrawPixelInfo& dpi, int32_t x, int32_t y, int32_t width, int32_t height, int32_t xStart, int32_t yStart,
        const uint8_t* weatherpattern) override
    {
        const uint8_t* pattern = weatherpattern;
        auto patternXSpace = *pattern++;
        auto patternYSpace = *pattern++;

        uint8_t patternStartXOffset = xStart % patternXSpace;
        uint8_t patternStartYOffset = yStart % patternYSpace;

        uint32_t pixelOffset = dpi.LineStride() * y + x;
        uint8_t patternYPos = patternStartYOffset % patternYSpace;

        for (; height != 0; height--)
        {
            auto patternX = pattern[patternYPos * 2];
            if (patternX != 0xFF)
            {
                uint32_t finalPixelOffset = width + pixelOffset;

                uint32_t xPixelOffset = pixelOffset;
                xPixelOffset += (static_cast<uint8_t>(patternX - patternStartXOffset)) % patternXSpace;

                auto patternPixel = pattern[patternYPos * 2 + 1];
                for (; xPixelOffset < finalPixelOffset; xPixelOffset += patternXSpace)
                {
                    int32_t pixelX = xPixelOffset % dpi.width;
                    int32_t pixelY = (xPixelOffset / dpi.width) % dpi.height;

                    _drawingContext->DrawLine(dpi, patternPixel, { { pixelX, pixelY }, { pixelX + 1, pixelY + 1 } });
                }
            }

            pixelOffset += dpi.LineStride();
            patternYPos++;
            patternYPos %= patternYSpace;
        }
    }
};

class OpenGLDrawingEngine final : public IDrawingEngine
{
private:
    std::shared_ptr<IUiContext> const _uiContext;
    SDL_Window* _window = nullptr;
    SDL_GLContext _context = nullptr;

    uint32_t _width = 0;
    uint32_t _height = 0;
    uint32_t _pitch = 0;
    size_t _bitsSize = 0;
    std::unique_ptr<uint8_t[]> _bits;

    DrawPixelInfo _bitsDPI = {};

    std::unique_ptr<OpenGLDrawingContext> _drawingContext;

    std::unique_ptr<ApplyPaletteShader> _applyPaletteShader;
    std::unique_ptr<OpenGLFramebuffer> _screenFramebuffer;
    std::unique_ptr<OpenGLFramebuffer> _scaleFramebuffer;
    std::unique_ptr<OpenGLFramebuffer> _smoothScaleFramebuffer;
    OpenGLWeatherDrawer _weatherDrawer;

public:
    SDL_Color Palette[256];
    vec4 GLPalette[256];

    explicit OpenGLDrawingEngine(const std::shared_ptr<IUiContext>& uiContext)
        : _uiContext(uiContext)
        , _drawingContext(std::make_unique<OpenGLDrawingContext>(*this))
        , _weatherDrawer(_drawingContext.get())
    {
        _window = static_cast<SDL_Window*>(_uiContext->GetWindow());
        _bitsDPI.DrawingEngine = this;
        LightFx::SetAvailable(false);
    }

    ~OpenGLDrawingEngine() override
    {
        SDL_GL_DeleteContext(_context);
    }

    void Initialise() override
    {
        OpenGLVersion requiredVersion = kOpenGLMinimumRequiredVersion;
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, requiredVersion.Major);
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, requiredVersion.Minor);

        _context = SDL_GL_CreateContext(_window);
        if (_context == nullptr)
        {
            char szRequiredVersion[32];
            snprintf(szRequiredVersion, 32, "OpenGL %d.%d", requiredVersion.Major, requiredVersion.Minor);
            throw std::runtime_error(std::string(szRequiredVersion) + std::string(" not available."));
        }
        SDL_GL_MakeCurrent(_window, _context);

        if (!OpenGLAPI::Initialise())
        {
            throw std::runtime_error("Unable to initialise OpenGL.");
        }

        _drawingContext->Initialise();

        _applyPaletteShader = std::make_unique<ApplyPaletteShader>();
    }

    void Resize(uint32_t width, uint32_t height) override
    {
        ConfigureBits(width, height, width);
        ConfigureCanvas();
        _drawingContext->Resize(width, height);
        _drawingContext->Clear(_bitsDPI, PALETTE_INDEX_10);
    }

    void SetPalette(const GamePalette& palette) override
    {
        for (int32_t i = 0; i < 256; i++)
        {
            SDL_Color colour;
            colour.r = palette[i].Red;
            colour.g = palette[i].Green;
            colour.b = palette[i].Blue;
            colour.a = i == 0 ? 0 : 255;

            Palette[i] = colour;
            GLPalette[i] = {
                colour.r / 255.0f,
                colour.g / 255.0f,
                colour.b / 255.0f,
                colour.a / 255.0f,
            };
        }

        _applyPaletteShader->Use();
        _applyPaletteShader->SetPalette(GLPalette);
        _drawingContext->ResetPalette();
    }

    void SetVSync(bool vsync) override
    {
        SDL_GL_SetSwapInterval(vsync);
    }

    void Invalidate(int32_t left, int32_t top, int32_t right, int32_t bottom) override
    {
    }

    void BeginDraw() override
    {
        assert(_screenFramebuffer != nullptr);

        _drawingContext->StartNewDraw();
    }

    void EndDraw() override
    {
        _drawingContext->FlushCommandBuffers();

        glDisable(GL_DEPTH_TEST);
        if (_scaleFramebuffer != nullptr)
        {
            // Render to intermediary RGB buffer for GL_LINEAR
            _scaleFramebuffer->Bind();
        }
        else
        {
            _screenFramebuffer->Bind();
        }

        _applyPaletteShader->Use();
        _applyPaletteShader->SetTexture(_drawingContext->GetFinalFramebuffer().GetTexture());
        _applyPaletteShader->Draw();

        if (_smoothScaleFramebuffer != nullptr)
        {
            _smoothScaleFramebuffer->Copy(*_scaleFramebuffer, GL_NEAREST);
            _screenFramebuffer->Copy(*_smoothScaleFramebuffer, GL_LINEAR);
        }
        else if (_scaleFramebuffer != nullptr)
        {
            _screenFramebuffer->Copy(*_scaleFramebuffer, GL_LINEAR);
        }

        CheckGLError();
        Display();
    }

    void PaintWindows() override
    {
        WindowUpdateAllViewports();
        WindowDrawAll(_bitsDPI, 0, 0, _width, _height);
    }

    void PaintWeather() override
    {
        DrawWeather(_bitsDPI, &_weatherDrawer);
    }

    std::string Screenshot() override
    {
        const OpenGLFramebuffer& framebuffer = _drawingContext->GetFinalFramebuffer();
        framebuffer.Bind();
        framebuffer.GetPixels(_bitsDPI);
        std::string result = ScreenshotDumpPNG(_bitsDPI);
        return result;
    }

    void CopyRect(int32_t x, int32_t y, int32_t width, int32_t height, int32_t dx, int32_t dy) override
    {
        // Not applicable for this engine
    }

    IDrawingContext* GetDrawingContext() override
    {
        return _drawingContext.get();
    }

    DrawPixelInfo* GetDrawingPixelInfo() override
    {
        return &_bitsDPI;
    }

    DrawingEngineFlags GetFlags() override
    {
        return {};
    }

    void InvalidateImage(uint32_t image) override
    {
        _drawingContext->GetTextureCache()->InvalidateImage(image);
    }

    DrawPixelInfo* GetDPI()
    {
        return &_bitsDPI;
    }

private:
    static OpenGLVersion GetOpenGLVersion()
    {
        CheckGLError(); // Clear Any Errors
        OpenGLVersion version = { 0, 0 };
        glGetIntegerv(GL_MAJOR_VERSION, &version.Major);
        if (glGetError() != GL_NO_ERROR)
            return { 0, 0 };
        glGetIntegerv(GL_MINOR_VERSION, &version.Minor);
        if (glGetError() != GL_NO_ERROR)
            return { 0, 0 };
        return version;
    }

    void ConfigureBits(uint32_t width, uint32_t height, uint32_t pitch)
    {
        size_t newBitsSize = pitch * height;

        auto newBits = std::make_unique<uint8_t[]>(newBitsSize);
        if (_bits == nullptr)
        {
            std::fill_n(newBits.get(), newBitsSize, 0);
        }
        else
        {
            if (_pitch == pitch)
            {
                std::copy_n(_bits.get(), std::min(_bitsSize, newBitsSize), newBits.get());
            }
            else
            {
                uint8_t* src = _bits.get();
                uint8_t* dst = newBits.get();

                uint32_t minWidth = std::min(_width, width);
                uint32_t minHeight = std::min(_height, height);
                for (uint32_t y = 0; y < minHeight; y++)
                {
                    std::copy_n(src, minWidth, dst);
                    if (pitch - minWidth > 0)
                    {
                        std::fill_n(dst + minWidth, pitch - minWidth, 0);
                    }
                    src += _pitch;
                    dst += pitch;
                }
            }
        }

        _bits = std::move(newBits);
        _bitsSize = newBitsSize;
        _width = width;
        _height = height;
        _pitch = pitch;

        DrawPixelInfo* dpi = &_bitsDPI;
        dpi->bits = _bits.get();
        dpi->x = 0;
        dpi->y = 0;
        dpi->width = width;
        dpi->height = height;
        dpi->pitch = _pitch - width;
    }

    void ConfigureCanvas()
    {
        // Re-create screen framebuffer
        _screenFramebuffer = std::make_unique<OpenGLFramebuffer>(_window);
        _smoothScaleFramebuffer.reset();
        _scaleFramebuffer.reset();
        if (GetContext()->GetUiContext()->GetScaleQuality() != ScaleQuality::NearestNeighbour)
        {
            _scaleFramebuffer = std::make_unique<OpenGLFramebuffer>(_width, _height, false, false);
        }
        if (GetContext()->GetUiContext()->GetScaleQuality() == ScaleQuality::SmoothNearestNeighbour)
        {
            uint32_t scale = std::ceil(Config::Get().general.WindowScale);
            _smoothScaleFramebuffer = std::make_unique<OpenGLFramebuffer>(_width * scale, _height * scale, false, false);
        }
    }

    void Display()
    {
        SDL_GL_SwapWindow(_window);
    }
};

std::unique_ptr<IDrawingEngine> OpenRCT2::Ui::CreateOpenGLDrawingEngine(const std::shared_ptr<IUiContext>& uiContext)
{
    return std::make_unique<OpenGLDrawingEngine>(uiContext);
}

OpenGLDrawingContext::OpenGLDrawingContext(OpenGLDrawingEngine& engine)
    : _engine(engine)
{
}

OpenGLDrawingContext::~OpenGLDrawingContext()
{
}

void OpenGLDrawingContext::Initialise()
{
    _textureCache = std::make_unique<TextureCache>();
    _applyTransparencyShader = std::make_unique<ApplyTransparencyShader>();
    _drawRectShader = std::make_unique<DrawRectShader>();
    _drawLineShader = std::make_unique<DrawLineShader>();
}

void OpenGLDrawingContext::Resize(int32_t width, int32_t height)
{
    _commandBuffers.lines.clear();
    _commandBuffers.rects.clear();

    _drawRectShader->Use();
    _drawRectShader->SetScreenSize(width, height);
    _drawLineShader->Use();
    _drawLineShader->SetScreenSize(width, height);

    // Re-create canvas framebuffer
    _swapFramebuffer = std::make_unique<SwapFramebuffer>(width, height);
}

void OpenGLDrawingContext::ResetPalette()
{
    // FlushCommandBuffers();
}

void OpenGLDrawingContext::StartNewDraw()
{
    _drawCount = 0;
    _swapFramebuffer->Clear();
}

void OpenGLDrawingContext::Clear(DrawPixelInfo& dpi, uint8_t paletteIndex)
{
    FillRect(dpi, paletteIndex, dpi.x, dpi.y, dpi.x + dpi.width, dpi.y + dpi.height);
}

void OpenGLDrawingContext::FillRect(
    DrawPixelInfo& dpi, uint32_t colour, int32_t left, int32_t top, int32_t right, int32_t bottom)
{
    const ScreenRect clip = CalculateClipping(dpi);

    left += clip.GetLeft() - dpi.x;
    top += clip.GetTop() - dpi.y;
    right += clip.GetLeft() - dpi.x;
    bottom += clip.GetTop() - dpi.y;

    DrawRectCommand& command = _commandBuffers.rects.allocate();

    command.clip = { clip.GetLeft(), clip.GetTop(), clip.GetRight(), clip.GetBottom() };
    command.texColourAtlas = 0;
    command.texColourBounds = { 0.0f, 0.0f, 0.0f, 0.0f };
    command.texMaskAtlas = 0;
    command.texMaskBounds = { 0.0f, 0.0f, 0.0f, 0.0f };
    command.palettes = { 0, 0, 0 };
    command.colour = colour & 0xFF;
    command.bounds = { left, top, right + 1, bottom + 1 };
    command.flags = DrawRectCommand::FLAG_NO_TEXTURE;
    command.depth = _drawCount++;
    command.zoom = 1.0f;

    if (colour & 0x1000000)
    {
        // cross-pattern
        command.flags |= DrawRectCommand::FLAG_CROSS_HATCH;
    }
    else if (colour & 0x2000000)
    {
        assert(false);
        // Should be FilterRect
    }
}

void OpenGLDrawingContext::FilterRect(
    DrawPixelInfo& dpi, FilterPaletteID palette, int32_t left, int32_t top, int32_t right, int32_t bottom)
{
    const ScreenRect clip = CalculateClipping(dpi);

    left += clip.GetLeft() - dpi.x;
    top += clip.GetTop() - dpi.y;
    right += clip.GetLeft() - dpi.x;
    bottom += clip.GetTop() - dpi.y;

    DrawRectCommand& command = _commandBuffers.transparent.allocate();

    command.clip = { clip.GetLeft(), clip.GetTop(), clip.GetRight(), clip.GetBottom() };
    command.texColourAtlas = 0;
    command.texColourBounds = { 0.0f, 0.0f, 0.0f, 0.0f };
    command.texMaskAtlas = 0;
    command.texMaskBounds = { 0.0f, 0.0f, 0.0f, 0.0f };
    command.palettes = { 0, 0, 0 };
    command.colour = TextureCache::PaletteToY(palette);
    command.bounds = { left, top, right + 1, bottom + 1 };
    command.flags = DrawRectCommand::FLAG_NO_TEXTURE;
    command.depth = _drawCount++;
    command.zoom = 1.0f;
}

// Compute the bit code for a point p relative to the clip rectangle defined by topLeft and bottomRight
uint8_t OpenGLDrawingContext::ComputeOutCode(
    const ScreenCoordsXY p, const ScreenCoordsXY topLeft, const ScreenCoordsXY bottomRight)
{
    uint8_t code = kCSInside;

    if (p.x < topLeft.x)
        code |= kCSLeft;
    else if (p.x > bottomRight.x)
        code |= kCSRight;
    if (p.y < topLeft.y)
        code |= kCSTop;
    else if (p.y > bottomRight.y)
        code |= kCSBottom;

    return code;
}

// Trims the line to be within the bounds of the dpi.
// based on: https://en.wikipedia.org/wiki/Cohen%E2%80%93Sutherland_algorithm
bool OpenGLDrawingContext::CohenSutherlandLineClip(ScreenLine& line, const DrawPixelInfo& dpi)
{
    ScreenCoordsXY topLeft = { dpi.x, dpi.y };
    ScreenCoordsXY bottomRight = { dpi.x + dpi.width - 1, dpi.y + dpi.height - 1 };
    uint8_t outcode1 = ComputeOutCode(line.Point1, topLeft, bottomRight);
    uint8_t outcode2 = ComputeOutCode(line.Point2, topLeft, bottomRight);

    while (true)
    {
        if (outcode1 == kCSInside && outcode2 == kCSInside)
        {
            // both points inside dpi
            return true;
        }
        if (outcode1 & outcode2)
        {
            // both points share an outside zone so both must be outside dpi
            return false;
        }

        // At least one endpoint is outside the clip rectangle; pick it.
        uint8_t outcodeOut = outcode2 > outcode1 ? outcode2 : outcode1;
        ScreenCoordsXY clipped;

        // clang-format off
        if (outcodeOut & kCSBottom)
        {
            clipped.x = line.Point1.x + (line.Point2.x - line.Point1.x) *
                (bottomRight.y - line.Point1.y) / (line.Point2.y - line.Point1.y);
            clipped.y = bottomRight.y;
        }
        else if (outcodeOut & kCSTop)
        {
            clipped.x = line.Point1.x + (line.Point2.x - line.Point1.x) *
                (topLeft.y - line.Point1.y) / (line.Point2.y - line.Point1.y);
            clipped.y = topLeft.y;
        }
        else if (outcodeOut & kCSRight)
        {
            clipped.y = line.Point1.y + (line.Point2.y - line.Point1.y) *
                (bottomRight.x - line.Point1.x) / (line.Point2.x - line.Point1.x);
            clipped.x = bottomRight.x;
        }
        else if (outcodeOut & kCSLeft)
        {
            clipped.y = line.Point1.y + (line.Point2.y - line.Point1.y) *
                (topLeft.x - line.Point1.x) / (line.Point2.x - line.Point1.x);
            clipped.x = topLeft.x;
        }
        // clang-format on

        if (outcodeOut == outcode1)
        {
            line.Point1 = clipped;
            outcode1 = ComputeOutCode(line.Point1, topLeft, bottomRight);
        }
        else
        {
            line.Point2 = clipped;
            outcode2 = ComputeOutCode(line.Point2, topLeft, bottomRight);
        }
    }
}

void OpenGLDrawingContext::DrawLine(DrawPixelInfo& dpi, uint32_t colour, const ScreenLine& line)
{
    const ZoomLevel zoom = dpi.zoom_level;
    ScreenLine trimmedLine = { { zoom.ApplyInversedTo(line.GetX1()), zoom.ApplyInversedTo(line.GetY1()) },
                               { zoom.ApplyInversedTo(line.GetX2()), zoom.ApplyInversedTo(line.GetY2()) } };
    if (!CohenSutherlandLineClip(trimmedLine, dpi))
        return;

    DrawLineCommand& command = _commandBuffers.lines.allocate();

    const ScreenRect clip = CalculateClipping(dpi);
    const int32_t x1 = trimmedLine.GetX1() - dpi.x + clip.GetLeft();
    const int32_t y1 = trimmedLine.GetY1() - dpi.y + clip.GetTop();
    const int32_t x2 = trimmedLine.GetX2() - dpi.x + clip.GetLeft();
    const int32_t y2 = trimmedLine.GetY2() - dpi.y + clip.GetTop();

    command.bounds = { x1, y1, x2, y2 };
    command.colour = colour & 0xFF;
    command.depth = _drawCount++;
}

static auto EuclideanRemainder(const auto a, const auto b)
{
    const auto r = a % b;
    return r >= 0 ? r : r + b;
};

void OpenGLDrawingContext::DrawSprite(DrawPixelInfo& dpi, const ImageId imageId, const int32_t x, const int32_t y)
{
    auto g1Element = GfxGetG1Element(imageId);
    if (g1Element == nullptr)
    {
        return;
    }

    if (dpi.zoom_level > ZoomLevel{ 0 })
    {
        if (g1Element->flags & G1_FLAG_HAS_ZOOM_SPRITE)
        {
            DrawPixelInfo zoomedDPI;
            zoomedDPI.bits = dpi.bits;
            zoomedDPI.x = dpi.x;
            zoomedDPI.y = dpi.y;
            zoomedDPI.height = dpi.height;
            zoomedDPI.width = dpi.width;
            zoomedDPI.pitch = dpi.pitch;
            zoomedDPI.zoom_level = dpi.zoom_level - 1;
            DrawSprite(zoomedDPI, imageId.WithIndex(imageId.GetIndex() - g1Element->zoomed_offset), x >> 1, y >> 1);
            return;
        }
        if (g1Element->flags & G1_FLAG_NO_ZOOM_DRAW)
        {
            return;
        }
    }

    auto texture = _textureCache->GetOrLoadImageTexture(imageId);

    int32_t left = x + g1Element->x_offset;
    int32_t top = y + g1Element->y_offset;

    int32_t xModifier = 0;
    int32_t yModifier = 0;
    int32_t widthModifier = 0;

    if (dpi.zoom_level > ZoomLevel{ 0 })
    {
        const int32_t interval = dpi.zoom_level.ApplyTo(1);

        xModifier = EuclideanRemainder(left, interval);
        xModifier = xModifier ? interval - xModifier : 0;
        yModifier = EuclideanRemainder(top, interval);
        widthModifier = EuclideanRemainder(left + g1Element->width, interval);
        widthModifier = widthModifier ? interval - widthModifier : 0;

        texture.coords.x += xModifier;
        texture.coords.y += (interval - 1) - yModifier;
    }

    left = dpi.zoom_level.ApplyInversedTo(left + xModifier);
    top = dpi.zoom_level.ApplyInversedTo(top);
    int32_t right = left + dpi.zoom_level.ApplyInversedTo(g1Element->width + widthModifier);
    int32_t bottom = top + dpi.zoom_level.ApplyInversedTo(g1Element->height + yModifier);

    const ScreenRect clip = CalculateClipping(dpi);
    left += clip.GetLeft() - dpi.x;
    top += clip.GetTop() - dpi.y;
    right += clip.GetLeft() - dpi.x;
    bottom += clip.GetTop() - dpi.y;

    const float zoom = dpi.zoom_level >= ZoomLevel{ 0 } ? static_cast<float>(dpi.zoom_level.ApplyTo(1))
                                                        : 1.0f / static_cast<float>(dpi.zoom_level.ApplyInversedTo(1));

    int paletteCount;
    ivec3 palettes{};
    bool special = false;
    if (imageId.HasSecondary())
    {
        palettes.x = TextureCache::PaletteToY(static_cast<FilterPaletteID>(imageId.GetPrimary()));
        palettes.y = TextureCache::PaletteToY(static_cast<FilterPaletteID>(imageId.GetSecondary()));
        if (!imageId.HasTertiary())
        {
            paletteCount = 2;
        }
        else
        {
            paletteCount = 3;
            palettes.z = TextureCache::PaletteToY(static_cast<FilterPaletteID>(imageId.GetTertiary()));
        }
    }
    else if (imageId.IsRemap() || imageId.IsBlended())
    {
        paletteCount = 1;
        FilterPaletteID palette = static_cast<FilterPaletteID>(imageId.GetRemap());
        palettes.x = TextureCache::PaletteToY(palette);
        if (palette == FilterPaletteID::PaletteWater)
        {
            special = true;
        }
    }
    else
    {
        paletteCount = 0;
    }

    if (special || imageId.IsBlended())
    {
        DrawRectCommand& command = _commandBuffers.transparent.allocate();

        command.clip = { clip.GetLeft(), clip.GetTop(), clip.GetRight(), clip.GetBottom() };
        command.texColourAtlas = texture.index;
        command.texColourBounds = texture.coords;
        command.texMaskAtlas = texture.index;
        command.texMaskBounds = texture.coords;
        command.palettes = palettes;
        command.colour = palettes.x - (special ? 1 : 0);
        command.bounds = { left, top, right, bottom };
        command.flags = special ? 0 : DrawRectCommand::FLAG_NO_TEXTURE | DrawRectCommand::FLAG_MASK;
        command.depth = _drawCount++;
        command.zoom = zoom;
    }
    else
    {
        DrawRectCommand& command = _commandBuffers.rects.allocate();

        command.clip = { clip.GetLeft(), clip.GetTop(), clip.GetRight(), clip.GetBottom() };
        command.texColourAtlas = texture.index;
        command.texColourBounds = texture.coords;
        command.texMaskAtlas = 0;
        command.texMaskBounds = { 0.0f, 0.0f, texture.coords.z, texture.coords.w };
        command.palettes = palettes;
        command.colour = 0;
        command.bounds = { left, top, right, bottom };
        command.flags = paletteCount;
        command.depth = _drawCount++;
        command.zoom = zoom;
    }
}

void OpenGLDrawingContext::DrawSpriteRawMasked(
    DrawPixelInfo& dpi, int32_t x, int32_t y, const ImageId maskImage, const ImageId colourImage)
{
    auto g1ElementMask = GfxGetG1Element(maskImage);
    auto g1ElementColour = GfxGetG1Element(colourImage);
    if (g1ElementMask == nullptr || g1ElementColour == nullptr)
    {
        return;
    }

    const auto textureMask = _textureCache->GetOrLoadImageTexture(maskImage);
    const auto textureColour = _textureCache->GetOrLoadImageTexture(colourImage);

    int32_t drawOffsetX = g1ElementMask->x_offset;
    int32_t drawOffsetY = g1ElementMask->y_offset;
    int32_t drawWidth = std::min(g1ElementMask->width, g1ElementColour->width);
    int32_t drawHeight = std::min(g1ElementMask->height, g1ElementColour->height);

    int32_t left = x + drawOffsetX;
    int32_t top = y + drawOffsetY;
    int32_t right = left + drawWidth;
    int32_t bottom = top + drawHeight;

    if (left > right)
    {
        std::swap(left, right);
    }
    if (top > bottom)
    {
        std::swap(top, bottom);
    }

    left = dpi.zoom_level.ApplyInversedTo(left);
    top = dpi.zoom_level.ApplyInversedTo(top);
    right = dpi.zoom_level.ApplyInversedTo(right);
    bottom = dpi.zoom_level.ApplyInversedTo(bottom);

    const ScreenRect clip = CalculateClipping(dpi);
    left += clip.GetLeft() - dpi.x;
    top += clip.GetTop() - dpi.y;
    right += clip.GetLeft() - dpi.x;
    bottom += clip.GetTop() - dpi.y;

    const float zoom = dpi.zoom_level >= ZoomLevel{ 0 } ? static_cast<float>(dpi.zoom_level.ApplyTo(1))
                                                        : 1.0f / static_cast<float>(dpi.zoom_level.ApplyInversedTo(1));

    DrawRectCommand& command = _commandBuffers.rects.allocate();

    command.clip = { clip.GetLeft(), clip.GetTop(), clip.GetRight(), clip.GetBottom() };
    command.texColourAtlas = textureColour.index;
    command.texColourBounds = textureColour.coords;
    command.texMaskAtlas = textureMask.index;
    command.texMaskBounds = textureMask.coords;
    command.palettes = { 0, 0, 0 };
    command.flags = DrawRectCommand::FLAG_MASK;
    command.colour = 0;
    command.bounds = { left, top, right, bottom };
    command.depth = _drawCount++;
    command.zoom = zoom;
}

void OpenGLDrawingContext::DrawSpriteSolid(DrawPixelInfo& dpi, const ImageId image, int32_t x, int32_t y, uint8_t colour)
{
    auto g1Element = GfxGetG1Element(image);
    if (g1Element == nullptr)
    {
        return;
    }

    const auto texture = _textureCache->GetOrLoadImageTexture(image);

    int32_t drawOffsetX = g1Element->x_offset;
    int32_t drawOffsetY = g1Element->y_offset;
    int32_t drawWidth = static_cast<uint16_t>(g1Element->width);
    int32_t drawHeight = static_cast<uint16_t>(g1Element->height);

    int32_t left = x + drawOffsetX;
    int32_t top = y + drawOffsetY;
    int32_t right = left + drawWidth;
    int32_t bottom = top + drawHeight;

    if (left > right)
    {
        std::swap(left, right);
    }
    if (top > bottom)
    {
        std::swap(top, bottom);
    }

    const ScreenRect clip = CalculateClipping(dpi);
    left += clip.GetLeft() - dpi.x;
    top += clip.GetTop() - dpi.y;
    right += clip.GetLeft() - dpi.x;
    bottom += clip.GetTop() - dpi.y;

    DrawRectCommand& command = _commandBuffers.rects.allocate();

    command.clip = { clip.GetLeft(), clip.GetTop(), clip.GetRight(), clip.GetBottom() };
    command.texColourAtlas = 0;
    command.texColourBounds = { 0.0f, 0.0f, 0.0f, 0.0f };
    command.texMaskAtlas = texture.index;
    command.texMaskBounds = texture.coords;
    command.palettes = { 0, 0, 0 };
    command.flags = DrawRectCommand::FLAG_NO_TEXTURE | DrawRectCommand::FLAG_MASK;
    command.colour = colour & 0xFF;
    command.bounds = { left, top, right, bottom };
    command.depth = _drawCount++;
    command.zoom = 1.0f;
}

void OpenGLDrawingContext::DrawGlyph(DrawPixelInfo& dpi, const ImageId image, int32_t x, int32_t y, const PaletteMap& palette)
{
    auto g1Element = GfxGetG1Element(image);
    if (g1Element == nullptr)
    {
        return;
    }

    const auto texture = _textureCache->GetOrLoadGlyphTexture(image, palette);

    int32_t left = x + g1Element->x_offset;
    int32_t top = y + g1Element->y_offset;
    int32_t right = left + static_cast<uint16_t>(g1Element->width);
    int32_t bottom = top + static_cast<uint16_t>(g1Element->height);

    if (left > right)
    {
        std::swap(left, right);
    }
    if (top > bottom)
    {
        std::swap(top, bottom);
    }

    left = dpi.zoom_level.ApplyInversedTo(left);
    top = dpi.zoom_level.ApplyInversedTo(top);
    right = dpi.zoom_level.ApplyInversedTo(right);
    bottom = dpi.zoom_level.ApplyInversedTo(bottom);

    const ScreenRect clip = CalculateClipping(dpi);
    left += clip.GetLeft() - dpi.x;
    top += clip.GetTop() - dpi.y;
    right += clip.GetLeft() - dpi.x;
    bottom += clip.GetTop() - dpi.y;

    const float zoom = dpi.zoom_level >= ZoomLevel{ 0 } ? static_cast<float>(dpi.zoom_level.ApplyTo(1))
                                                        : 1.0f / static_cast<float>(dpi.zoom_level.ApplyInversedTo(1));

    DrawRectCommand& command = _commandBuffers.rects.allocate();

    command.clip = { clip.GetLeft(), clip.GetTop(), clip.GetRight(), clip.GetBottom() };
    command.texColourAtlas = texture.index;
    command.texColourBounds = texture.coords;
    command.texMaskAtlas = 0;
    command.texMaskBounds = { 0.0f, 0.0f, 0.0f, 0.0f };
    command.palettes = { 0, 0, 0 };
    command.flags = 0;
    command.colour = 0;
    command.bounds = { left, top, right, bottom };
    command.depth = _drawCount++;
    command.zoom = zoom;
}

void OpenGLDrawingContext::DrawTTFBitmap(
    DrawPixelInfo& dpi, TextDrawInfo* info, TTFSurface* surface, int32_t x, int32_t y, uint8_t hintingThreshold)
{
    #ifndef NO_TTF
    auto baseId = static_cast<uint32_t>(0x7FFFF) - 1024;
    auto imageId = baseId + _ttfGlId;
    _engine.InvalidateImage(imageId);
    const auto texture = _textureCache->GetOrLoadBitmapTexture(imageId, surface->pixels, surface->w, surface->h);
    _ttfGlId++;
    if (_ttfGlId >= 1023)
    {
        _ttfGlId = 0;
    }

    int32_t drawOffsetX = 0;
    int32_t drawOffsetY = 0;
    int32_t drawWidth = static_cast<uint16_t>(surface->w);
    int32_t drawHeight = static_cast<uint16_t>(surface->h);

    int32_t left = x + drawOffsetX;
    int32_t top = y + drawOffsetY;
    int32_t right = left + drawWidth;
    int32_t bottom = top + drawHeight;

    if (left > right)
    {
        std::swap(left, right);
    }
    if (top > bottom)
    {
        std::swap(top, bottom);
    }

    const ScreenRect clip = CalculateClipping(dpi);
    left += clip.GetLeft() - dpi.x;
    top += clip.GetTop() - dpi.y;
    right += clip.GetLeft() - dpi.x;
    bottom += clip.GetTop() - dpi.y;

    if (info->flags & TEXT_DRAW_FLAG_OUTLINE)
    {
        std::array<ivec4, 4> boundsArr = { {
            { left + 1, top, right + 1, bottom },
            { left - 1, top, right - 1, bottom },
            { left, top + 1, right, bottom + 1 },
            { left, top - 1, right, bottom - 1 },
        } };
        for (auto b : boundsArr)
        {
            DrawRectCommand& command = _commandBuffers.rects.allocate();
            command.clip = { clip.GetLeft(), clip.GetTop(), clip.GetRight(), clip.GetBottom() };
            command.texColourAtlas = texture.index;
            command.texColourBounds = texture.coords;
            command.texMaskAtlas = 0;
            command.texMaskBounds = { 0.0f, 0.0f, 0.0f, 0.0f };
            command.palettes = { 0, 0, 0 };
            command.flags = DrawRectCommand::FLAG_TTF_TEXT;
            command.colour = info->palette[3];
            command.bounds = b;
            command.depth = _drawCount++;
            command.zoom = 1.0f;
        }
    }
    if (info->flags & TEXT_DRAW_FLAG_INSET)
    {
        DrawRectCommand& command = _commandBuffers.rects.allocate();
        command.clip = { clip.GetLeft(), clip.GetTop(), clip.GetRight(), clip.GetBottom() };
        command.texColourAtlas = texture.index;
        command.texColourBounds = texture.coords;
        command.texMaskAtlas = 0;
        command.texMaskBounds = { 0.0f, 0.0f, 0.0f, 0.0f };
        command.palettes = { 0, 0, 0 };
        command.flags = DrawRectCommand::FLAG_TTF_TEXT;
        command.colour = info->palette[3];
        command.bounds = { left + 1, top + 1, right + 1, bottom + 1 };
        command.depth = _drawCount++;
        command.zoom = 1.0f;
    }
    auto& cmdBuf = hintingThreshold > 0 ? _commandBuffers.transparent : _commandBuffers.rects;
    DrawRectCommand& command = cmdBuf.allocate();
    command.clip = { clip.GetLeft(), clip.GetTop(), clip.GetRight(), clip.GetBottom() };
    command.texColourAtlas = texture.index;
    command.texColourBounds = texture.coords;
    command.texMaskAtlas = 0;
    command.texMaskBounds = { 0.0f, 0.0f, 0.0f, 0.0f };
    command.palettes = { 0, 0, 0 };
    command.flags = DrawRectCommand::FLAG_TTF_TEXT | (hintingThreshold << 8);
    command.colour = info->palette[1];
    command.bounds = { left, top, right, bottom };
    command.depth = _drawCount++;
    command.zoom = 1.0f;
    #endif // NO_TTF
}

void OpenGLDrawingContext::FlushCommandBuffers()
{
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LESS);

    _swapFramebuffer->BindOpaque();
    _drawRectShader->Use();
    _drawRectShader->DisablePeeling();

    FlushLines();
    FlushRectangles();

    HandleTransparency();
}

void OpenGLDrawingContext::FlushLines()
{
    if (_commandBuffers.lines.empty())
        return;

    _drawLineShader->Use();
    _drawLineShader->DrawInstances(_commandBuffers.lines);

    _commandBuffers.lines.clear();
}

void OpenGLDrawingContext::FlushRectangles()
{
    if (_commandBuffers.rects.empty())
        return;

    OpenGLAPI::SetTexture(0, GL_TEXTURE_2D_ARRAY, _textureCache->GetAtlasesTexture());
    OpenGLAPI::SetTexture(1, GL_TEXTURE_2D, _textureCache->GetPaletteTexture());

    _drawRectShader->Use();
    _drawRectShader->SetInstances(_commandBuffers.rects);
    _drawRectShader->DrawInstances();

    _commandBuffers.rects.clear();
}

void OpenGLDrawingContext::HandleTransparency()
{
    if (_commandBuffers.transparent.empty())
    {
        return;
    }

    _drawRectShader->Use();
    _drawRectShader->SetInstances(_commandBuffers.transparent);

    int32_t max_depth = MaxTransparencyDepth(_commandBuffers.transparent);
    for (int32_t i = 0; i < max_depth; ++i)
    {
        _swapFramebuffer->BindTransparent();

        glEnable(GL_DEPTH_TEST);
        glDepthFunc(GL_GREATER);
        _drawRectShader->Use();

        if (i > 0)
        {
            _drawRectShader->EnablePeeling(_swapFramebuffer->GetBackDepthTexture());
        }

        OpenGLAPI::SetTexture(0, GL_TEXTURE_2D_ARRAY, _textureCache->GetAtlasesTexture());
        OpenGLAPI::SetTexture(1, GL_TEXTURE_2D, _textureCache->GetPaletteTexture());

        _drawRectShader->Use();
        _drawRectShader->DrawInstances();
        _swapFramebuffer->ApplyTransparency(
            *_applyTransparencyShader, _textureCache->GetPaletteTexture(), _textureCache->GetBlendPaletteTexture());
    }

    _commandBuffers.transparent.clear();
}

ScreenRect OpenGLDrawingContext::CalculateClipping(const DrawPixelInfo& dpi) const
{
    // mber: Calculating the screen coordinates by dividing the difference between pointers like this is a dirty hack.
    //       It's also quite slow. In future the drawing code needs to be refactored to avoid this somehow.
    const DrawPixelInfo* screenDPI = _engine.GetDPI();
    const int32_t bytesPerRow = screenDPI->LineStride();
    const int32_t bitsOffset = static_cast<int32_t>(dpi.bits - screenDPI->bits);
    #ifndef NDEBUG
    const ptrdiff_t bitsSize = static_cast<ptrdiff_t>(screenDPI->height) * static_cast<ptrdiff_t>(bytesPerRow);
    assert(static_cast<ptrdiff_t>(bitsOffset) < bitsSize && static_cast<ptrdiff_t>(bitsOffset) >= 0);
    #endif

    const int32_t left = bitsOffset % bytesPerRow;
    const int32_t top = bitsOffset / bytesPerRow;
    const int32_t right = left + dpi.width;
    const int32_t bottom = top + dpi.height;

    return { { left, top }, { right, bottom } };
}

#endif /* DISABLE_OPENGL */
