Enhance the UserFontFace example

	* examples/text/user-font.cc: enhanced the UserFontFace example quite a bit so
	that it shows a few different virtual functions and actually draws different
	sized boxes for different characters

1 files changed, 94 insertions, 18 deletions

diff --git a/examples/text/user-font.cc b/examples/text/user-font.cc
index 8e5dae9..7836f5b 100644
--- a/examples/text/user-font.cc
+++ b/examples/text/user-font.cc
@@ -1,36 +1,98 @@
 #include <cairomm/cairomm.h>
 #include <iostream>
+#include <map>
 
 const double HEIGHT = 200.0;
 const double WIDTH = 400.0;
 const double FONT_SIZE = 64.0;
 const double TEXT_ORIGIN_Y = (HEIGHT / 2.0) + (FONT_SIZE / 2.0);
 const double TEXT_ORIGIN_X = 50.0;  // arbitrary
+const double GLYPH_SPACING = 0.1;
+
+struct GlyphBounds
+{
+  unsigned long glyph;
+  double width;
+  double height;
+};
+
+// an array that stores the bounds of the glyphs that we're going to draw
+static const GlyphBounds glyphs[] =
+{
+  { 'c', 0.45, 0.5 },
+  { 'a', 0.45, 0.5 },
+  { 'i', 0.2, 0.75 },
+  { 'r', 0.4, 0.5 },
+  { 'o', 0.44, 0.5 },
+  { 'm', 0.75, 0.5 },
+  { '!', 0.2, 0.75 }
+};
 
 // A *very* simple font that just draws a box for every glyph
 class BoxFontFace : public Cairo::UserFontFace
 {
 public:
+  // Derived user font classes should have a factory method to create an object
+  // and return it with a RefPtr
   static Cairo::RefPtr<BoxFontFace> create()
   {
     return Cairo::RefPtr<BoxFontFace>(new BoxFontFace());
   }
 
   virtual Cairo::ErrorStatus
-    render_glyph(const Cairo::RefPtr<Cairo::ScaledFont>& /*scaled_font*/,
-                 unsigned long glyph,
-                 const Cairo::RefPtr<Cairo::Context>& cr,
-                 Cairo::TextExtents& /*metrics*/)
+    init(const Cairo::RefPtr<Cairo::ScaledFont>& /*scaled_font*/,
+         const Cairo::RefPtr<Cairo::Context>& /*cr*/,
+         Cairo::FontExtents &extents)
   {
-    std::cout << "Rendering glyph " << glyph << std::endl;
-    cr->set_line_width(0.05);
-    // FIXME: is the negative Y value correct?
-    cr->rectangle(0.0, 0.0, 1.0, -1.0);
-    cr->stroke();
+    double max = 0;
+    for (unsigned int i = 0; i < sizeof (glyphs) / sizeof (GlyphBounds); ++i) {
+      if (glyphs[i].width > max)
+        max = glyphs[i].width;
+    }
+    // add some spacing between characters
+    max += GLYPH_SPACING;
+    extents.max_x_advance = max;
+    return CAIRO_STATUS_SUCCESS;
+  }
+
+  virtual Cairo::ErrorStatus
+  unicode_to_glyph (const Cairo::RefPtr<Cairo::ScaledFont>& /*scaled_font*/,
+                    unsigned long unicode, unsigned long& glyph)
+  {
+    glyph = 0;
+    // yes this is a stupid an ineffienct way to do this but we only have a few
+    // glyphs and this is just demonstration code
+    for (unsigned int i = 0; i < sizeof (glyphs) / sizeof (GlyphBounds); ++i) {
+      if (glyphs[i].glyph == unicode) {
+        // glyph 0 is often a special glyph-not-found value, so offset it by 1
+        glyph = i+1;
+        break;
+      }
+    }
+    return CAIRO_STATUS_SUCCESS;
+  }
+
+  virtual Cairo::ErrorStatus
+  render_glyph(const Cairo::RefPtr<Cairo::ScaledFont>& /*scaled_font*/,
+               unsigned long glyph,
+               const Cairo::RefPtr<Cairo::Context>& cr,
+               Cairo::TextExtents& metrics)
+  {
+    // check that the glyph is in our table
+    if (glyph >= 1 && glyph <= sizeof(glyphs)/sizeof(GlyphBounds)) {
+      cr->set_line_width(0.05);
+      // Need a negative Y value since the text origin is at the bottom left point
+      // and cairo's positive Y axis is down and we want to draw up
+      cr->rectangle(0.0, 0.0, glyphs[glyph-1].width, -glyphs[glyph-1].height);
+      cr->stroke();
+      metrics.x_advance = glyphs[glyph-1].width + GLYPH_SPACING;
+    }
     return CAIRO_STATUS_SUCCESS;
   }
 
 protected:
+  // FontFace is a ref-counted object, so the constructor should be protected so
+  // it is not created without a refptr to manage it.  See the create() method
   BoxFontFace() : UserFontFace() { }
 };
 
@@ -51,16 +113,30 @@ int main(int, char**)
   // draw the text
   cr->move_to(TEXT_ORIGIN_X, TEXT_ORIGIN_Y);
   cr->set_source_rgb(0.8, 0.2, 0.2);
+  Cairo::RefPtr<BoxFontFace> font = BoxFontFace::create();
+  cr->set_font_face(font);
+  cr->set_font_size(FONT_SIZE);
+  cr->show_text("cairomm!");
 
-  // this scope block is simply to test that the user font can still be
-  // drawn even after the UserFont wrapper object has been de-referenced
-  {
-    Cairo::RefPtr<BoxFontFace> font = BoxFontFace::create();
-    cr->set_font_face(font);
-  }
-
+  // Now show it with the toy text API to demonstrate how the glyphs match up
+  cr->move_to(TEXT_ORIGIN_X, TEXT_ORIGIN_Y);
+  cr->set_source_rgba(0.2, 0.2, 0.2, 0.3);
+  Cairo::RefPtr<Cairo::ToyFontFace> toy_font =
+    Cairo::ToyFontFace::create("Bitstream Charter",
+                               Cairo::FONT_SLANT_NORMAL,
+                               Cairo::FONT_WEIGHT_BOLD);
+  cr->set_font_face(toy_font);
   cr->set_font_size(FONT_SIZE);
   cr->show_text("cairomm!");
-  surface->write_to_png("user-font.png");
-  return 0;
+
+  const char* filename = "user-font.png";
+  try {
+    surface->write_to_png(filename);
+    std::cout << "Wrote Image " << filename << std::endl;
+    return 0;
+  } catch (const std::exception& e)
+  {
+    std::cout << "** Unable to write Image " << filename << std::endl;
+    return 1;
+  }
 }