Renderer.h

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/* Copyright (C) 2023 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef INCLUDED_RENDERER
#define INCLUDED_RENDERER

#include "graphics/Camera.h"
#include "graphics/ShaderDefines.h"
#include "graphics/ShaderProgramPtr.h"
#include "ps/containers/Span.h"
#include "ps/Singleton.h"
#include "renderer/backend/IDeviceCommandContext.h"
#include "renderer/backend/IShaderProgram.h"
#include "renderer/RenderingOptions.h"
#include "renderer/Scene.h"

#include <memory>

class CDebugRenderer;
class CFontManager;
class CPostprocManager;
class CSceneRenderer;
class CShaderManager;
class CTextureManager;
class CTimeManager;

#define g_Renderer CRenderer::GetSingleton()

/**
 * Higher level interface on top of the whole frame rendering. It does know
 * what should be rendered and via which renderer but shouldn't know how to
 * render a particular area, like UI or scene.
 */
class CRenderer : public Singleton<CRenderer>
{
public:
    // stats class - per frame counts of number of draw calls, poly counts etc
    struct Stats
    {
        // set all stats to zero
        void Reset() { memset(this, 0, sizeof(*this)); }
        // number of draw calls per frame - total DrawElements + Begin/End immediate mode loops
        size_t m_DrawCalls;
        // number of terrain triangles drawn
        size_t m_TerrainTris;
        // number of water triangles drawn
        size_t m_WaterTris;
        // number of (non-transparent) model triangles drawn
        size_t m_ModelTris;
        // number of overlay triangles drawn
        size_t m_OverlayTris;
        // number of splat passes for alphamapping
        size_t m_BlendSplats;
        // number of particles
        size_t m_Particles;
    };

    enum class ScreenShotType
    {
        NONE,
        DEFAULT,
        BIG
    };

public:
    CRenderer();
    ~CRenderer();

    // open up the renderer: performs any necessary initialisation
    bool Open(int width, int height);

    // resize renderer view
    void Resize(int width, int height);

    // return view width
    int GetWidth() const { return m_Width; }
    // return view height
    int GetHeight() const { return m_Height; }

    void RenderFrame(bool needsPresent);

    // signal frame start
    void BeginFrame();
    // signal frame end
    void EndFrame();

    // trigger a reload of shaders (when parameters they depend on have changed)
    void MakeShadersDirty();

    // return stats accumulated for current frame
    Stats& GetStats() { return m_Stats; }

    CTextureManager& GetTextureManager();

    CShaderManager& GetShaderManager();

    CFontManager& GetFontManager();

    CTimeManager& GetTimeManager();

    CPostprocManager& GetPostprocManager();

    CSceneRenderer& GetSceneRenderer();

    CDebugRenderer& GetDebugRenderer();

    /**
     * Performs a complete frame without presenting to force loading all needed
     * resources. It's used for the first frame on a game start.
     * TODO: It might be better to preload resources without a complete frame
     * rendering.
     */
    void PreloadResourcesBeforeNextFrame();

    /**
     * Makes a screenshot on the next RenderFrame according of the given
     * screenshot type.
     */
    void MakeScreenShotOnNextFrame(ScreenShotType screenShotType);

    Renderer::Backend::IDeviceCommandContext* GetDeviceCommandContext();

    /**
     * Returns a cached vertex input layout. The renderer owns the layout to be
     * able to share it between different clients. As backend should have
     * as few different layouts as possible.
     * The function isn't cheap so it should be called as rarely as possible.
     * TODO: we need to make VertexArray less error prone by passing layout.
     */
    Renderer::Backend::IVertexInputLayout* GetVertexInputLayout(
        const PS::span<const Renderer::Backend::SVertexAttributeFormat> attributes);

protected:
    friend class CPatchRData;
    friend class CDecalRData;
    friend class HWLightingModelRenderer;
    friend class ShaderModelVertexRenderer;
    friend class InstancingModelRenderer;
    friend class CRenderingOptions;

    bool ShouldRender() const;

    void RenderFrameImpl(const bool renderGUI, const bool renderLogger);
    void RenderFrame2D(const bool renderGUI, const bool renderLogger);
    void RenderScreenShot(const bool needsPresent);
    void RenderBigScreenShot(const bool needsPresent);

    // SetRenderPath: Select the preferred render path.
    // This may only be called before Open(), because the layout of vertex arrays and other
    // data may depend on the chosen render path.
    void SetRenderPath(RenderPath rp);

    void ReloadShaders();

    // Private data that is not needed by inline functions.
    class Internals;
    std::unique_ptr<Internals> m;
    // view width
    int m_Width = 0;
    // view height
    int m_Height = 0;

    // per-frame renderer stats
    Stats m_Stats;

    bool m_ShouldPreloadResourcesBeforeNextFrame = false;

    ScreenShotType m_ScreenShotType = ScreenShotType::NONE;
};

#endif // INCLUDED_RENDERER