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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/xhtml;charset=UTF-8"/>
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<title>cairomm: user-font.cc</title>
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<script type="text/javascript" src="jquery.js"></script>
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<body>
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cairomm
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    1.0
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  • Main Page
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  • Namespaces
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  • Classes
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  • Examples
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    user-font.cc
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    A relatively simple example of using Cairo::UserFontFace
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    #include <cairomm/cairomm.h>
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    #include <iostream>
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    #include <map>
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    const double HEIGHT = 200.0;
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    const double WIDTH = 400.0;
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    const double FONT_SIZE = 64.0;
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    const double TEXT_ORIGIN_Y = (HEIGHT / 2.0) + (FONT_SIZE / 2.0);
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    const double TEXT_ORIGIN_X = 50.0;  // arbitrary
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    const double GLYPH_SPACING = 0.1;
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    struct GlyphBounds
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    {
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      unsigned long glyph;
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      double width;
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      double height;
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    };
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    // an array that stores the bounds of the glyphs that we're going to draw
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    static const GlyphBounds glyphs[] =
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    {
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      { 'c', 0.45, 0.5 },
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      { 'a', 0.45, 0.5 },
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      { 'i', 0.2, 0.75 },
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      { 'r', 0.4, 0.5 },
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      { 'o', 0.44, 0.5 },
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      { 'm', 0.75, 0.5 },
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      { '!', 0.2, 0.75 }
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    };
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    // A *very* simple font that just draws a box for every glyph
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    class BoxFontFace : public Cairo::UserFontFace
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    {
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    public:
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      // Derived user font classes should have a factory method to create an object
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      // and return it with a RefPtr
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      static Cairo::RefPtr<BoxFontFace> create()
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      {
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        return Cairo::RefPtr<BoxFontFace>(new BoxFontFace());
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      }
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      Cairo::ErrorStatus
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        init(const Cairo::RefPtr<Cairo::ScaledFont>& /*scaled_font*/,
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             const Cairo::RefPtr<Cairo::Context>& /*cr*/,
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             Cairo::FontExtents &extents) override
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      {
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        double max = 0;
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        for (unsigned int i = 0; i < sizeof (glyphs) / sizeof (GlyphBounds); ++i) {
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          if (glyphs[i].width > max)
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            max = glyphs[i].width;
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        }
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        // add some spacing between characters
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        max += GLYPH_SPACING;
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        extents.max_x_advance = max;
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        return CAIRO_STATUS_SUCCESS;
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      }
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      Cairo::ErrorStatus
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      unicode_to_glyph (const Cairo::RefPtr<Cairo::ScaledFont>& /*scaled_font*/,
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                        unsigned long unicode, unsigned long& glyph) override
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      {
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        glyph = 0;
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        // yes this is a stupid an ineffienct way to do this but we only have a few
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        // glyphs and this is just demonstration code
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        for (unsigned int i = 0; i < sizeof (glyphs) / sizeof (GlyphBounds); ++i) {
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          if (glyphs[i].glyph == unicode) {
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            // glyph 0 is often a special glyph-not-found value, so offset it by 1
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            glyph = i+1;
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            break;
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          }
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        }
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        return CAIRO_STATUS_SUCCESS;
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      }
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      Cairo::ErrorStatus
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      render_glyph(const Cairo::RefPtr<Cairo::ScaledFont>& /*scaled_font*/,
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                   unsigned long glyph,
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                   const Cairo::RefPtr<Cairo::Context>& cr,
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                   Cairo::TextExtents& metrics) override
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      {
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        // check that the glyph is in our table
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        if (glyph >= 1 && glyph <= sizeof(glyphs)/sizeof(GlyphBounds)) {
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          cr->set_line_width(0.05);
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          // Need a negative Y value since the text origin is at the bottom left point
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          // and cairo's positive Y axis is down and we want to draw up
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          cr->rectangle(0.0, 0.0, glyphs[glyph-1].width, -glyphs[glyph-1].height);
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          cr->stroke();
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          metrics.x_advance = glyphs[glyph-1].width + GLYPH_SPACING;
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        }
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        return CAIRO_STATUS_SUCCESS;
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      }
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    protected:
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      // FontFace is a ref-counted object, so the constructor should be protected so
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      // it is not created without a refptr to manage it.  See the create() method
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      BoxFontFace() : UserFontFace() { }
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    };
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    int main(int, char**)
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    {
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      auto surface =
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        Cairo::ImageSurface::create(Cairo::FORMAT_ARGB32, WIDTH, HEIGHT);
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      auto cr = Cairo::Context::create(surface);
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      // fill background in white
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      cr->set_source_rgb(1.0, 1.0, 1.0);
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      cr->paint();
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      // draw a little dot at the point where text will be drawn
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      cr->arc(TEXT_ORIGIN_X, TEXT_ORIGIN_Y, FONT_SIZE / 4.0, 0, 2*M_PI);
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      cr->set_source_rgba(0.0, 1.0, 0.0, 0.5);
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      cr->fill();
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      // draw the text
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      cr->move_to(TEXT_ORIGIN_X, TEXT_ORIGIN_Y);
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      cr->set_source_rgb(0.8, 0.2, 0.2);
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      auto font = BoxFontFace::create();
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      cr->set_font_face(font);
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      cr->set_font_size(FONT_SIZE);
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      cr->show_text("cairomm!");
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      // Now show it with the toy text API to demonstrate how the glyphs match up
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      cr->move_to(TEXT_ORIGIN_X, TEXT_ORIGIN_Y);
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      cr->set_source_rgba(0.2, 0.2, 0.2, 0.3);
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      auto toy_font =
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        Cairo::ToyFontFace::create("Bitstream Charter",
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                                   Cairo::FONT_SLANT_NORMAL,
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                                   Cairo::FONT_WEIGHT_BOLD);
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      cr->set_font_face(toy_font);
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      cr->set_font_size(FONT_SIZE);
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      cr->show_text("cairomm!");
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      const char* filename = "user-font.png";
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      try {
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        surface->write_to_png(filename);
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        std::cout << "Wrote Image " << filename << std::endl;
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        return 0;
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      } catch (const std::exception& e)
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      {
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        std::cout << "** Unable to write Image " << filename << std::endl;
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        return 1;
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      }
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    }
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    <address class="footer"><small>
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    Generated on Mon Sep 21 2015 21:56:36 for cairomm by  
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    doxygen
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     1.8.9.1
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    </small></address>
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    </body>
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    </html>

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