OpenSceneGraph/include/osgText/Text

/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield
 *
 * This library is open source and may be redistributed and/or modified under
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 *
 * This library 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
 * OpenSceneGraph Public License for more details.
*/

#ifndef OSGTEXT_TEXT
#define OSGTEXT_TEXT 1


#include <osg/Drawable>
#include <osg/Quat>

#include <osgText/TextBase>
#include <osgText/Font>

namespace osgText {

class OSGTEXT_EXPORT Text : public osgText::TextBase
{
public:

    Text();
    Text(const Text& text,const osg::CopyOp& copyop=osg::CopyOp::SHALLOW_COPY);

    virtual osg::Object* cloneType() const { return new Text(); }
    virtual osg::Object* clone(const osg::CopyOp& copyop) const { return new Text(*this,copyop); }
    virtual bool isSameKindAs(const osg::Object* obj) const { return dynamic_cast<const Text*>(obj)!=NULL; }
    virtual const char* className() const { return "Text"; }
    virtual const char* libraryName() const { return "osgText"; }

    virtual void setFont(Font* font=0) { setFont(osg::ref_ptr<Font>(font)); };

    /** Set the Font to use to render the text.*/
    virtual void setFont(osg::ref_ptr<Font> font);

    /** Set the font, loaded from the specified front file, to use to render the text,
      * setFont("") sets the use of the default font.
      * See the osgText::readFontFile function for how the font file will be located. */
    virtual void setFont(const std::string& fontfile) { TextBase::setFont(fontfile); }

    /**
     * Turns off writing to the depth buffer when rendering text. This only affects text
     * with no backdrop or text using the DELAYED_DEPTH_WRITES implementation, since
     * the other backdrop implementations are really only useful for backwards
     * compatibility and are not worth updating to utilize this flag.
     */
    void setEnableDepthWrites(bool enable) { _enableDepthWrites = enable; }
    bool getEnableDepthWrites() const { return _enableDepthWrites; }


    enum BackdropType
    {
        DROP_SHADOW_BOTTOM_RIGHT = 0,  // usually the type of shadow you see
        DROP_SHADOW_CENTER_RIGHT,
        DROP_SHADOW_TOP_RIGHT,
        DROP_SHADOW_BOTTOM_CENTER,
        DROP_SHADOW_TOP_CENTER,
        DROP_SHADOW_BOTTOM_LEFT,
        DROP_SHADOW_CENTER_LEFT,
        DROP_SHADOW_TOP_LEFT,
        OUTLINE,
        NONE
    };

    enum BackdropImplementation
    {
        /* POLYGON_OFFSET:
         * This uses glPolygonOffset to draw the text multiple times to
         * create the drop-shadow and outline effects. glPolygonOffset
         * is used to prevent z-fighting of the overlapping text.
         * This probably should have been the best option, but all the ATI
         * cards we have encountered so far have serious problems with this.
         * We see little white holes/artifacts in the rendered glyph textures
         * which move around depending on the viewing angle. For moving text,
         * the moving holes give an extremely unpleasant flickering effect.
         * Pumping up the "units" parameter in glPolygonOffset can minimize
         * this problem, but two other bad side-effects occur if you do this.
         * First, high values will cause problems with clipping, particularly
         * when there are objects behind the text. The drop-shadows or outline
         * may be culled because their computed offset is behind the object or
         * z-far plane. Second, there is an additional problem associated with
         * the Z-slope. High values can make large chunks of the backdrop
         * suddenly disappear. This can be reduced by the "factor" parameter.
         * Making the "factor" value small, can help, but experimentally, we've
         * found that it creates a new, different kind of z-fighting problem.
         * So there is no perfect solution. With units, you trade off the 'holes'
         * for the large-section clipping.
         * Experimentally, we have found units values from 150-512 to be tolerable
         * to acceptable with respect to the 'holes'. A factor of .1 seems to
         * bring down the large clipping problem without creating a new z-fighting
         * problem.
         * (You can experiment with these numbers by playing with the
         * osg:PolygonOffset multipliers which this backend tries to respect.)
         *
         * If ATI ever fixes their cards/drivers, then this might become the
         * best option.*/
        POLYGON_OFFSET = 0,

        /* NO_DEPTH_BUFFER
         * Instead of using glPolygonOffset to prevent z-fighting, this mode
         * just disables the depth buffer when rendering the text. This allows
         * the text to be rendered without any z-fighting. The downside to this
         * mode is that render order begins to matter and the text will not
         * necessarily correctly appear above or behind other objects in the
         * scene based on depth values.
         * This mode is best for text that only needs to be ontop and
         * not obscured by any objects.*/
        NO_DEPTH_BUFFER,

        /* DEPTH_RANGE
         * This mode is inspired by Paul Martz's OpenGL FAQ, item 13.050.
         * This uses glDepthRange as a substitute for glPolygonOffset.
         * Strangely, experiments on ATI cards seem to produce cleaner results
         * than when using glPolygonOffset. The trade-off for this is that the
         * backdrop still may be placed too far back and might be culled by objects
         * directly behind the object or by the far z-plane. If ATI ever fixes
         * the glPolygonOffset problem, polygon offset is probably a slightly
         * better solution because you can use smaller offsets. But with the
         * current ATI problem, this option may be preferable.*/
        DEPTH_RANGE,
        /* STENCIL_BUFFER
         * (Assuming the backend is written correctly,) the Stencil Buffer is
         * the most "correct" and reliable way of producing backdrop text.
         * The stencil buffer is a multipass system that allows writing to the
         * same z-values without needing to resort to offsets. This implementation
         * should not have any of the problems associated with the 3 previous
         * implementations. But the trade-off for this mode is that without
         * hardware acceleration for the stencil buffer, rendering will be
         * extremely slow. (There is also potentially more overhead for this
         * algorithm so it could be slower than the other implementations.
         * Benchmarking would be required to determine if the speed differences
         * are significant on your particular hardware.) This mode is best for
         * when quality is important and stencil buffer hardware acceleration
         * is available.*/
        STENCIL_BUFFER,

        /* DELAYED_DEPTH_WRITES
         * This mode renders all text with depth writes turned off, then
         * again with depth writes on, but with the color buffer disabled.
         * This should render text accurately for all graphics cards. The
         * only downside is the additional pass to render to the depth
         * buffer. But if you don't need the depth buffer updated for
         * your, this extra pass can be disabled by calling
         * enableDepthWrites(false).*/
        DELAYED_DEPTH_WRITES
    };

    /**
     * BackdropType gives you a background shadow text behind your regular
     * text. This helps give text extra contrast which can be useful when
     * placing text against noisy backgrounds.
     * The color of the background shadow text is specified by setBackdropColor().
     * DROP_SHADOW_BOTTOM_RIGHT will draw backdrop text to the right and down of
     * the normal text. Other DROW_SHADOW_* modes do the same for their repective directions.
     * OUTLINE will draw backdrop text so that it appears the text has an outline
     * or border around the normal text. This mode is particularly useful against
     * really noisy backgrounds that may put text on top of things that have
     * all types of colors which you don't have control over.
     * Some real world examples of this general technique in use that I know of
     * are Google Earth, Sid Meier's Pirates (2004 Remake), and Star Control 2 (PC 1993).
     * The default is NONE.
     */
    void setBackdropType(BackdropType type);

    BackdropType getBackdropType() const { return _backdropType; }

    /**
     * Sets the amount text is offset to create the backdrop/shadow effect.
     * Set the value too high and for example, in OUTLINE mode you will get a "Brady Bunch"
     * effect where you see duplicates of the text in a 3x3 grid.
     * Set the value too small and you won't see anything.
     * The values represent percentages. 1.0 means 100% so a value of 1.0
     * in DROW_SHADOW_LEFT_CENTER mode would cause each glyph to be echoed
     * next to it self. So the letter 'e' might look like 'ee'.
     * Good values tend to be in the 0.03 to 0.10 range (but will be subject
     * to your specific font and display characteristics).
     * Note that the text bounding boxes are updated to include backdrop offsets.
     * However, other metric information such as getCharacterHeight() are unaffected
     * by this. This means that individual glyph spacing (kerning?) are unchanged
     * even when this mode is used.
     * The default is 0.07 (7% offset).
     */
    void setBackdropOffset(float offset = 0.07f);
    /**
     * This overloaded version lets you specify the offset for the horizontal
     * and vertical components separately.
     */
    void setBackdropOffset(float horizontal, float vertical);

    float getBackdropHorizontalOffset() const { return _backdropHorizontalOffset; }

    float getBackdropVerticalOffset() const { return _backdropVerticalOffset; }

    /**
     * This specifies the color of the backdrop text.
     * The default is black.
     */
    void setBackdropColor(const osg::Vec4& color);

    const osg::Vec4& getBackdropColor() const { return _backdropColor; }

    /**
     * This specifies the underlying backdrop rendering implementation.
     * Unfortunately, at this time, there is no "perfect" rendering solution
     * so this function is provided to let you 'pick your poison'. Each
     * implementation has trade-offs. See BackdropImplementation enum
     * docs for details.*/
     void setBackdropImplementation(BackdropImplementation implementation);

     BackdropImplementation getBackdropImplementation() const { return _backdropImplementation; }



    enum ColorGradientMode
    {
        SOLID = 0, // a.k.a. ColorGradients off
        PER_CHARACTER,
        OVERALL
    };

    /**
     * This sets different types of text coloring modes.
     * When the coloring mode is not set to SOLID, the
     * colors specified in setColorGradientCorners() determine
     * the colors for the text.
     * When the gradient mode is OVERALL, the coloring scheme
     * attempts to approximate the effect as if the entire text box/region
     * were a single polygon and you had applied colors to each of the four
     * corners with GL_SMOOTH enabled. In this mode, OpenGL interpolates
     * the colors across the polygon, and this is what OVERALL tries to
     * emulate. This can be used to give nice embellishments on things
     * like logos and names.
     * PER_CHARACTER is similar to OVERALL except that it applies the
     * color interpolation to the four corners of each character instead
     * of across the overall text box.
     * The default is SOLID (a.k.a. off).
     */
    void setColorGradientMode(ColorGradientMode mode);

    ColorGradientMode getColorGradientMode() const { return _colorGradientMode; }

    /**
     * Used only for gradient mode, let's you specify the colors of the 4 corners.
     * If ColorGradients are off, these values are ignored (and the value from setColor()
     * is the only one that is relevant.
     */
    void setColorGradientCorners(const osg::Vec4& topLeft, const osg::Vec4& bottomLeft, const osg::Vec4& bottomRight, const osg::Vec4& topRight);

    const osg::Vec4& getColorGradientTopLeft() const { return _colorGradientTopLeft; }
    const osg::Vec4& getColorGradientBottomLeft() const { return _colorGradientBottomLeft; }
    const osg::Vec4& getColorGradientBottomRight() const { return _colorGradientBottomRight; }
    const osg::Vec4& getColorGradientTopRight() const { return _colorGradientTopRight; }



    /** Draw the text.*/
    virtual void drawImplementation(osg::RenderInfo& renderInfo) const;

    /** return false, osgText::Text does not support accept(AttributeFunctor&).*/
    virtual bool supports(const osg::Drawable::AttributeFunctor&) const { return false; }

    /** return true, osgText::Text does support accept(ConstAttributeFunctor&).*/
    virtual bool supports(const osg::Drawable::ConstAttributeFunctor&) const { return true; }

    /** accept an ConstAttributeFunctor and call its methods to tell it about the internal attributes that this Drawable has.*/
    virtual void accept(osg::Drawable::ConstAttributeFunctor& af) const;

    /** return true, osgText::Text does support accept(PrimitiveFunctor&) .*/
    virtual bool supports(const osg::PrimitiveFunctor&) const { return true; }

    /** accept a PrimtiveFunctor and call its methods to tell it about the internal primitives that this Drawable has.*/
    virtual void accept(osg::PrimitiveFunctor& pf) const;


    /** Resize any per context GLObject buffers to specified size. */
    virtual void resizeGLObjectBuffers(unsigned int maxSize);

    /** If State is non-zero, this function releases OpenGL objects for
      * the specified graphics context. Otherwise, releases OpenGL objexts
      * for all graphics contexts. */
    virtual void releaseGLObjects(osg::State* state=0) const;

public:


    // internal structures, variable and methods used for rendering of characters.
    struct OSGTEXT_EXPORT GlyphQuads
    {
        typedef std::vector<Glyph*> Glyphs;

        Glyphs                          _glyphs;
        Primitives                      _primitives;

        GlyphQuads();
        GlyphQuads(const GlyphQuads& gq);

        void initGlyphQuads();
        void initGPUBufferObjects();

        void setupPrimitives(Text::BackdropType backdropType);

        Glyphs& getGlyphs() { return _glyphs; }
        const Glyphs& getGlyphs() const { return _glyphs; }

        /** Resize any per context GLObject buffers to specified size. */
        void resizeGLObjectBuffers(unsigned int maxSize);

        /** If State is non-zero, this function releases OpenGL objects for
        * the specified graphics context. Otherwise, releases OpenGL objexts
        * for all graphics contexts. */
        void releaseGLObjects(osg::State* state=0) const;

    private:

        GlyphQuads& operator = (const GlyphQuads&) { return *this; }
    };

    typedef std::map<osg::ref_ptr<GlyphTexture>,GlyphQuads> TextureGlyphQuadMap;

    /** Direct Access to GlyphQuads */
    const GlyphQuads* getGlyphQuads(GlyphTexture* texture) const
    {
        TextureGlyphQuadMap::const_iterator itGlyphQuad = _textureGlyphQuadMap.find(texture);
        if (itGlyphQuad == _textureGlyphQuadMap.end()) return NULL;

        return &itGlyphQuad->second;
    }

    const TextureGlyphQuadMap& getTextureGlyphQuadMap() const
    {
        return _textureGlyphQuadMap;
    }

    void addGlyphQuad(Glyph* glyph, const osg::Vec2& minc, const osg::Vec2& maxc, const osg::Vec2& mintc, const osg::Vec2& maxtc);

protected:

    virtual ~Text();

    Font* getActiveFont();
    const Font* getActiveFont() const;

    String::iterator computeLastCharacterOnLine(osg::Vec2& cursor, String::iterator first,String::iterator last);

    // members which have public access.

    // iternal map used for rendering. Set up by the computeGlyphRepresentation() method.
    TextureGlyphQuadMap            _textureGlyphQuadMap;

    void computeGlyphRepresentation();

    // internal caches of the positioning of the text.

    bool computeAverageGlyphWidthAndHeight(float& avg_width, float& avg_height) const;

    virtual void computePositionsImplementation();

    void computeBackdropPositions();
    void computeBackdropBoundingBox();
    void computeBoundingBoxMargin();

    void computeColorGradients();
    void computeColorGradientsOverall();
    void computeColorGradientsPerCharacter();

    void drawImplementation(osg::State& state, const osg::Vec4& colorMultiplier) const;
    void drawForegroundText(osg::State& state, const GlyphQuads& glyphquad, const osg::Vec4& colorMultiplier) const;
    void drawTextWithBackdrop(osg::State& state, const osg::Vec4& colorMultiplier) const;
    void renderOnlyForegroundText(osg::State& state, const osg::Vec4& colorMultiplier) const;
    void renderWithPolygonOffset(osg::State& state, const osg::Vec4& colorMultiplier) const;
    void renderWithNoDepthBuffer(osg::State& state, const osg::Vec4& colorMultiplier) const;
    void renderWithDepthRange(osg::State& state, const osg::Vec4& colorMultiplier) const;
    void renderWithStencilBuffer(osg::State& state, const osg::Vec4& colorMultiplier) const;
    void renderWithDelayedDepthWrites(osg::State& state, const osg::Vec4& colorMultiplier) const;

    bool _enableDepthWrites;

    BackdropType _backdropType;
    BackdropImplementation _backdropImplementation;

    float _backdropHorizontalOffset;
    float _backdropVerticalOffset;
    osg::Vec4 _backdropColor;

    ColorGradientMode _colorGradientMode;
    osg::Vec4 _colorGradientTopLeft;
    osg::Vec4 _colorGradientBottomLeft;
    osg::Vec4 _colorGradientBottomRight;
    osg::Vec4 _colorGradientTopRight;


    // Helper function for color interpolation
    float bilinearInterpolate(float x1, float x2, float y1, float y2, float x, float y, float q11, float q12, float q21, float q22) const;
};

}


#endif