OverlayRenderer.h

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/* Copyright (C) 2022 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_OVERLAYRENDERER
#define INCLUDED_OVERLAYRENDERER

#include "graphics/ShaderProgram.h"
#include "renderer/backend/IDeviceCommandContext.h"

struct SOverlayLine;
struct SOverlayTexturedLine;
struct SOverlaySprite;
struct SOverlayQuad;
struct SOverlaySphere;
class CCamera;

struct OverlayRendererInternals;

/**
 * Class OverlayRenderer: Render various bits of data that overlay the
 * game world (selection circles, health bars, etc).
 */
class OverlayRenderer
{
    NONCOPYABLE(OverlayRenderer);

public:
    OverlayRenderer();
    ~OverlayRenderer();

    /**
     * Performs one-time initialization. Called by CRenderer::Open after graphics
     * capabilities and the shader path have been determined.
     */
    void Initialize();

    /**
     * Add a line overlay for rendering in this frame.
     * @param overlay Must be non-null. The pointed-to object must remain valid at least
     *                until the end of the frame.
     */
    void Submit(SOverlayLine* overlay);

    /**
     * Add a textured line overlay for rendering in this frame.
     * @param overlay Must be non-null. The pointed-to object must remain valid at least
     *                until the end of the frame.
     */
    void Submit(SOverlayTexturedLine* overlay);

    /**
     * Add a sprite overlay for rendering in this frame.
     * @param overlay Must be non-null. The pointed-to object must remain valid at least
     *                until the end of the frame.
     */
    void Submit(SOverlaySprite* overlay);

    /**
     * Add a textured quad overlay for rendering in this frame.
     * @param overlay Must be non-null. The pointed-to object must remain valid at least
     *                until the end of the frame.
     */
    void Submit(SOverlayQuad* overlay);

    /**
     * Add a sphere overlay for rendering in this frame.
     * @param overlay Must be non-null. The pointed-to object must remain valid at least
     *                until the end of the frame.
     */
    void Submit(SOverlaySphere* overlay);

    /**
     * Prepare internal data structures for rendering.
     * Must be called after all Submit calls for a frame, and before
     * uploading data.
     */
    void PrepareForRendering();

    /**
     * Upload prepared data to backend.
     * Must be called after preparing, and before any rendering calls.
     */
    void Upload(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext);

    /**
     * Reset the list of submitted overlays.
     */
    void EndFrame();

    /**
     * Render all the submitted overlays that are embedded in the world
     * (i.e. rendered behind other objects in the normal 3D way)
     * and should be drawn before water (i.e. may be visible under the water)
     */
    void RenderOverlaysBeforeWater(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext);

    /**
     * Render all the submitted overlays that are embedded in the world
     * (i.e. rendered behind other objects in the normal 3D way)
     * and should be drawn after water (i.e. may be visible on top of the water)
     */
    void RenderOverlaysAfterWater(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext);

    /**
     * Render all the submitted overlays that should appear on top of everything
     * in the world.
     * @param viewCamera camera to be used for billboard computations
     */
    void RenderForegroundOverlays(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext,
        const CCamera& viewCamera);

    /// Small vertical offset of overlays from terrain to prevent visual glitches
    static const float OVERLAY_VOFFSET;

private:

    /**
     * Helper method; renders all overlay lines currently registered in the internals. Batch-
     * renders textured overlay lines batched according to their visibility status by delegating
     * to RenderTexturedOverlayLines(IShaderProgram, bool).
     */
    void RenderTexturedOverlayLines(Renderer::Backend::IDeviceCommandContext* deviceCommandContext);

    /**
     * Helper method; renders those overlay lines currently registered in the internals (i.e.
     * in m->texlines) for which the 'always visible' flag equals @p alwaysVisible. Used for
     * batch rendering the overlay lines according to their alwaysVisible status, as this
     * requires a separate shader to be used.
     */
    void RenderTexturedOverlayLines(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext,
        Renderer::Backend::IShaderProgram* shader, bool alwaysVisible);

    /**
     * Helper method; batch-renders all registered quad overlays, batched by their texture for effiency.
     */
    void RenderQuadOverlays(Renderer::Backend::IDeviceCommandContext* deviceCommandContext);

    /**
     * Helper method; batch-renders all sphere quad overlays.
     */
     void RenderSphereOverlays(Renderer::Backend::IDeviceCommandContext* deviceCommandContext);

private:
    OverlayRendererInternals* m;
};

#endif // INCLUDED_OVERLAYRENDERER