TerrainOverlay.h

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/* Copyright (C) 2012 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/>.
 */

/*
 * System for representing tile-based information on top of the
 * terrain.
 */

#ifndef INCLUDED_TERRAINOVERLAY
#define INCLUDED_TERRAINOVERLAY

#include "lib/ogl.h"

struct CColor;
class CTerrain;
class CSimContext;

/**
 * Common interface for terrain-tile-based and texture-based debug overlays.
 *
 * An overlay object will be rendered for as long as it is allocated
 * (it is automatically registered/deregistered by constructor/destructor).
 */
class ITerrainOverlay
{
    NONCOPYABLE(ITerrainOverlay);

public:
    virtual ~ITerrainOverlay();

    virtual void RenderBeforeWater() { }

    virtual void RenderAfterWater() { }

    /**
     * Draw all ITerrainOverlay objects that exist
     * and that should be drawn before water.
     */
    static void RenderOverlaysBeforeWater();

    /**
     * Draw all ITerrainOverlay objects that exist
     * and that should be drawn after water.
     */
    static void RenderOverlaysAfterWater();

protected:
    ITerrainOverlay(int priority);
};

/**
 * Base class for (relatively) simple drawing of
 * data onto terrain tiles, intended for debugging purposes and for the Atlas
 * editor (hence not trying to be very efficient).
 *
 * To start drawing a terrain overlay, first create a subclass of TerrainOverlay.
 * Override the method GetTileExtents if you want to change the range over which
 * it is drawn.
 * Override ProcessTile to do your processing for each tile, which should call
 * RenderTile and RenderTileOutline as appropriate.
 */
class TerrainOverlay : public ITerrainOverlay
{
protected:
    /**
     * Construct the object and register it with the global
     * list of terrain overlays.
     * <p>
     * The priority parameter controls the order in which overlays are drawn,
     * if several exist - they are processed in order of increasing priority,
     * so later ones draw on top of earlier ones.
     * Most should use the default of 100. Numbers from 200 are used
     * by Atlas.
     *
     * @param priority  controls the order of drawing
     */
    TerrainOverlay(const CSimContext& simContext, int priority = 100);

    /**
     * Override to perform processing at the start of the overlay rendering,
     * before the ProcessTile calls
     */
    virtual void StartRender();

    /**
     * Override to perform processing at the end of the overlay rendering,
     * after the ProcessTile calls
     */
    virtual void EndRender();

    /**
     * Override to limit the range over which ProcessTile will
     * be called. Defaults to the size of the map.
     *
     * @param min_i_inclusive  [output] smallest <i>i</i> coordinate, in tile-space units
     * (1 unit per tile, <i>+i</i> is world-space <i>+x</i> and game-space East)
     * @param min_j_inclusive  [output] smallest <i>j</i> coordinate
     * (<i>+j</i> is world-space <i>+z</i> and game-space North)
     * @param max_i_inclusive  [output] largest <i>i</i> coordinate
     * @param max_j_inclusive  [output] largest <i>j</i> coordinate
     */
    virtual void GetTileExtents(ssize_t& min_i_inclusive, ssize_t& min_j_inclusive,
                                ssize_t& max_i_inclusive, ssize_t& max_j_inclusive);

    /**
     * Override to perform processing of each tile. Typically calls
     * RenderTile and/or RenderTileOutline.
     *
     * @param i  <i>i</i> coordinate of tile being processed
     * @param j  <i>j</i> coordinate of tile being processed
     */
    virtual void ProcessTile(ssize_t i, ssize_t j) = 0;

    /**
     * Draw a filled quad on top of the current tile.
     *
     * @param colour  colour to draw. May be transparent (alpha &lt; 1)
     * @param draw_hidden  true if hidden tiles (i.e. those behind other tiles)
     * should be drawn
     */
    void RenderTile(const CColor& colour, bool draw_hidden);

    /**
     * Draw a filled quad on top of the given tile.
     */
    void RenderTile(const CColor& colour, bool draw_hidden, ssize_t i, ssize_t j);

    /**
     * Draw an outlined quad on top of the current tile.
     *
     * @param colour  colour to draw. May be transparent (alpha &lt; 1)
     * @param line_width  width of lines in pixels. 1 is a sensible value
     * @param draw_hidden  true if hidden tiles (i.e. those behind other tiles)
     * should be drawn
     */
    void RenderTileOutline(const CColor& colour, int line_width, bool draw_hidden);

    /**
     * Draw an outlined quad on top of the given tile.
     */
    void RenderTileOutline(const CColor& colour, int line_width, bool draw_hidden, ssize_t i, ssize_t j);
    
private:
    // Process all tiles
    virtual void RenderBeforeWater();

    // Temporary storage of tile coordinates, so ProcessTile doesn't need to
    // pass it to RenderTile/etc (and doesn't have a chance to get it wrong)
    ssize_t m_i, m_j;

    CTerrain* m_Terrain;
};

/**
 * Base class for texture-based terrain overlays, with an arbitrary number of
 * texels per terrain tile, intended for debugging purposes.
 * Subclasses must implement BuildTextureRGBA which will be called each frame.
 */
class TerrainTextureOverlay : public ITerrainOverlay
{
public:
    TerrainTextureOverlay(float texelsPerTile, int priority = 100);

    virtual ~TerrainTextureOverlay();

protected:
    /**
     * Called each frame to generate the texture to render on the terrain.
     * @p data is w*h*4 bytes, where w and h are the terrain size multiplied
     * by texelsPerTile. @p data defaults to fully transparent, and should
     * be filled with data in RGBA order.
     */
    virtual void BuildTextureRGBA(u8* data, size_t w, size_t h) = 0;

private:
    void RenderAfterWater();

    float m_TexelsPerTile;
    GLuint m_Texture;
    GLsizei m_TextureW, m_TextureH;
};

#endif // INCLUDED_TERRAINOVERLAY