standalone/003_simple_text.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 <oglplus/ext/EXT_direct_state_access/matrix.hpp>

#include <vector>

class TextExample
 : public oglplus::StandaloneExample
{
private:
    oglplus::Context gl;
    oglplus::ARB_compatibility glc;
    oglplus::NV_path_rendering pr;
    oglplus::EXT_direct_state_access dsa;
    oglplus::DSAModelviewMatrixEXT modelview;
    oglplus::DSAProjectionMatrixEXT projection;

    const oglplus::String text;
    oglplus::PathArrayNV text_path;
    std::vector<GLubyte> glyph_indices;

    static std::vector<GLubyte> make_glyph_indices(void)
    {
        const GLubyte indices[7] = {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x00};
        return std::vector<GLubyte>(indices, indices+7);
    }

    std::vector<GLfloat> glyph_spacings;
public:
    TextExample(int /*argc*/, const char** /*argv*/)
     : text("OpenGL")
     , text_path(text.size())
     , glyph_indices(make_glyph_indices())
     , glyph_spacings(glyph_indices.size())
    {
        using namespace oglplus;

        GLfloat font_scale = 64;

        text_path.Glyphs(
            PathNVFontTarget::Standard,
            "Sans",
            PathNVFontStyle::Bold,
            text,
            PathNVMissingGlyph::Use,
            ~0,
            font_scale
        );

        text_path.GetSpacing(
            PathNVListMode::AccumAdjacentPairs,
            glyph_indices,
            1.0f, 1.0f,
            PathNVTransformType::TranslateX,
            glyph_spacings
        );

        glyph_spacings.insert(glyph_spacings.begin(), 0);
        glyph_spacings.pop_back();
        glyph_indices.pop_back();

        GLfloat text_left = glyph_spacings.front();
        GLfloat text_right = glyph_spacings.back();

        GLfloat font_min_max[2];

        text_path.GetMetricRange(
            PathNVMetricQuery::FontYMinBounds|
            PathNVMetricQuery::FontYMaxBounds,
            1, 0,
            font_min_max
        );

        projection.Ortho(
            text_left -10,
            text_right+10,
            font_min_max[0],
            font_min_max[1],
            -1.0,
            +1.0
        );
        modelview.LoadIdentity();

        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 Reshape(void)
    {
        using namespace oglplus;

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

    void Render(void)
    {
        using namespace oglplus;

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

        glc.Color(0.2, 0.2, 1.0);

        text_path.StencilFillInstanced(
            glyph_indices,
            PathNVFillMode::CountUp,
            0xFF,
            PathNVTransformType::TranslateX,
            glyph_spacings
        );
        text_path.CoverFillInstanced(
            glyph_indices,
            PathNVFillCoverMode::BoundingBoxOfBoundingBoxes,
            PathNVTransformType::TranslateX,
            glyph_spacings
        );

        glc.Color(0.0, 0.0, 0.0);

        text_path.StencilStrokeInstanced(
            glyph_indices,
            1, ~0,
            PathNVTransformType::TranslateX,
            glyph_spacings
        );
        text_path.CoverStrokeInstanced(
            glyph_indices,
            PathNVStrokeCoverMode::ConvexHull,
            PathNVTransformType::TranslateX,
            glyph_spacings
        );
    }
};

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