standalone/004_text_rendering.cpp

Shows usage of the NV_path_rendering extension for rendering textCopyright 2008-2014 Matus Chochlik. Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#include "glut_glew_example.hpp"

#include <oglplus/all.hpp>
#include <oglplus/ext/ARB_compatibility.hpp>
#include <oglplus/ext/NV_path_rendering.hpp>
#include <oglplus/ext/EXT_direct_state_access.hpp>

#include <vector>
#include <sstream>
#include <iomanip>

class TextExample
 : public oglplus::StandaloneExample
{
private:
    oglplus::Context gl;
    oglplus::ARB_compatibility glc;
    oglplus::NV_path_rendering npr;
    oglplus::EXT_direct_state_access dsa;

    oglplus::PathArrayNV text_glyphs;
    std::vector<GLfloat> glyph_spacings;

    GLfloat font_y_min, font_y_max, font_height;
public:
    TextExample(int /*argc*/, const char** /*argv*/)
     : text_glyphs(128)
    {
        using namespace oglplus;

        GLfloat font_scale = 48;

        text_glyphs.GlyphRange(
            PathNVFontTarget::Standard,
            "Sans",
            PathNVFontStyle::Bold,
            0, 128,
            PathNVMissingGlyph::Use,
            ~0,
            font_scale
        );

        GLfloat color_gen_coeffs[9] = {
            -0.6f, 0.0f, 0.8f,
             0.0f, 0.0f, 0.0f,
             0.5f, 0.0f, 0.5f
        };
        npr.ColorGen(
            PathNVColor::Primary,
            PathNVGenMode::ObjectBoundingBox,
            PathNVColorFormat::RGB,
            color_gen_coeffs
        );

        gl.ClearColor(1.0f, 1.0f, 1.0f, 0.0f);
        gl.ClearStencil(0);
        gl.StencilMask(~0);
        gl.StencilFunc(CompareFunction::NotEqual, 0, 0xFF);
        gl.StencilOp(
            StencilOperation::Keep,
            StencilOperation::Keep,
            StencilOperation::Zero
        );

        gl.Enable(Capability::StencilTest);
    }

    void RenderText(GLfloat x, GLfloat y, const oglplus::String& text)
    {
        using namespace oglplus;

        glyph_spacings.resize(text.size()+1);
        text_glyphs.GetSpacing(
            PathNVListMode::AccumAdjacentPairs,
            text,
            1.0f, 1.0f,
            PathNVTransformType::TranslateX,
            glyph_spacings
        );
        glyph_spacings.insert(glyph_spacings.begin(), 0);

        dsa.ModelviewMatrix()
            .LoadIdentity()
            .Translate(x, y, 0);

        text_glyphs.StencilFillInstanced(
            text,
            PathNVFillMode::CountUp,
            0xFF,
            PathNVTransformType::TranslateX,
            glyph_spacings
        );
        text_glyphs.CoverFillInstanced(
            text,
            PathNVFillCoverMode::BoundingBoxOfBoundingBoxes,
            PathNVTransformType::TranslateX,
            glyph_spacings
        );
    }

    void Render(void)
    {
        using namespace oglplus;

        gl.Clear().ColorBuffer().StencilBuffer();

        auto h = Height();
        int l = font_height / 2, i = 1;
        RenderText(l, h - font_height*i++, "NV_path_rendering");

        {
            std::stringstream s;
            s << "Frame no.: " << FrameNumber();
            RenderText(l, h - font_height*i++, s.str());
        }
        {
            std::stringstream s;
            s << std::fixed << std::setprecision(2);
            s << "Time: " << FrameTime() << " [s]";
            RenderText(l, h - font_height*i++, s.str());
        }
        {
            std::stringstream s;
            s << std::fixed << std::setprecision(2);
            s << "Average FPS: " << (FrameTime()>0.0 ? AverageFPS() : 0.0);
            RenderText(l, h - font_height*i++, s.str());
        }
        {
            std::stringstream s;
            s << std::fixed << std::setprecision(2);
            s << "Current FPS: " << (FrameDuration()>0.0 ? CurrentFPS() : 0.0);
            RenderText(l, h - font_height*i++, s.str());
        }
        {
            std::stringstream s;
            s << "Viewport: " << Width() << " x " << Height();
            RenderText(l, h - font_height*i++, s.str());
        }
        {
            std::stringstream s;
            s << std::fixed << std::setprecision(3);
            s << "Aspect ratio: " << Aspect();
            RenderText(l, h - font_height*i++, s.str());
        }
    }

    void Reshape(void)
    {
        using namespace oglplus;

        gl.Viewport(Width(), Height());

        dsa.ProjectionMatrix()
            .LoadIdentity()
            .Ortho(0, Width(), 0, Height(), -1, 1);

        GLfloat font_min_max[2];
        text_glyphs.GetMetricRange(
            PathNVMetricQuery::FontYMinBounds|
            PathNVMetricQuery::FontYMaxBounds,
            1, 0,
            font_min_max
        );
        font_y_min = font_min_max[0];
        font_y_max = font_min_max[1];
        font_height = font_y_max - font_y_min;
    }
};

int main(int argc, char* argv[])
{
    return oglplus::GlutGlewMain<TextExample>(
        "Example of text rendering with NV_path_rendering",
        argc, argv
    );
}