Add function to render a single unicode codepoint

src/font_renderer_alpha.h

@@ -137,6 +137,47 @@ public:
         x += x_delta / scale_x;
     }
 
+    template<class Rasterizer, class Scanline, class RenSolid>
+    void draw_codepoint(Rasterizer& ras, Scanline& sl, 
+        RenSolid& ren_solid, const color_type color,
+        int codepoint, double& x, double& y, double height)
+    {
+        const double scale_x = 100;
+
+        m_feng.height(height);
+        m_feng.width(height * scale_x);
+        m_feng.hinting(m_hinting);
+
+        // Represent the delta in x scaled by scale_x.
+        double x_delta = 0;
+        double start_x = x;
+
+        const agg::glyph_cache* glyph = m_fman.glyph(codepoint);
+        if(glyph)
+        {
+            if(m_kerning)
+            {
+                m_fman.add_kerning(&x_delta, &y);
+            }
+
+            m_fman.init_embedded_adaptors(glyph, 0, 0);
+            if(glyph->data_type == agg::glyph_data_outline)
+            {
+                double ty = m_hinting ? floor(y + 0.5) : y;
+                ras.reset();
+                m_mtx.reset();
+                m_mtx *= agg::trans_affine_scaling(1.0 / scale_x, 1);
+                m_mtx *= agg::trans_affine_translation(start_x + x_delta / scale_x, ty);
+                ras.add_path(m_trans);
+                ren_solid.color(color);
+                agg::render_scanlines(ras, sl, ren_solid);
+            }
+
+            y += glyph->advance_y;
+            x += (x_delta + glyph->advance_x) / scale_x;
+        }
+    }
+
     void clear(agg::rendering_buffer& ren_buf, const color_type color) {
         pixfmt_type pf(ren_buf);
         base_ren_type ren_base(pf);
@@ -161,4 +202,23 @@ public:
         renderer_solid ren_solid(ren_base);
         draw_text(ras, sl, ren_solid, text_color, text, x, y, text_size);
     }
+
+    void render_codepoint(agg::rendering_buffer& ren_buf,
+        const double text_size,
+        const color_type text_color,
+        double& x, double& y,
+        int codepoint)
+    {
+        if (!m_font_loaded) {
+            return;
+        }
+        agg::scanline_u8 sl;
+        agg::rasterizer_scanline_aa<> ras;
+        ras.clip_box(0, 0, ren_buf.width(), ren_buf.height());
+
+        agg::pixfmt_alpha8 pf(ren_buf);
+        base_ren_type ren_base(pf);
+        renderer_solid ren_solid(ren_base);
+        draw_codepoint(ras, sl, ren_solid, text_color, codepoint, x, y, text_size);
+    }
 };