From 1aea07a33fa0002c09a446969857a8fd98430773 Mon Sep 17 00:00:00 2001
From: Andres Riofrio <riofrios@gmail.com>
Date: Fri, 17 May 2013 09:52:05 -0700
Subject: [PATCH] Read typographic hints from Pango for text decorations

---
 weasyprint/draw.py | 23 +++++++++++++++++------
 weasyprint/text.py | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+), 6 deletions(-)

diff --git a/weasyprint/draw.py b/weasyprint/draw.py
index 02862d73..369a2e68 100644
--- a/weasyprint/draw.py
+++ b/weasyprint/draw.py
@@ -666,28 +666,39 @@ def draw_text(context, textbox, enable_hinting):
     context.set_source_rgba(*textbox.style.color)
     show_first_line(context, textbox.pango_layout, enable_hinting)
     values = textbox.style.text_decoration
+
+    metrics = textbox.pango_layout.get_font_metrics()
+    thickness = textbox.style.font_size / 18
+    if enable_hinting and thickness < 1:
+        thickness = 1
+
     if 'overline' in values:
         draw_text_decoration(
             context, textbox,
-            textbox.baseline - 0.15 * textbox.style.font_size,
+            textbox.baseline - metrics.ascent + thickness / 2,
+            thickness,
             enable_hinting)
     elif 'underline' in values:
         draw_text_decoration(
             context, textbox,
-            textbox.baseline + 0.15 * textbox.style.font_size,
+            textbox.baseline - metrics.underline_position + thickness / 2,
+            thickness,
             enable_hinting)
     elif 'line-through' in values:
-        draw_text_decoration(context, textbox, textbox.height * 0.5,
-                             enable_hinting)
+        draw_text_decoration(
+            context, textbox,
+            textbox.baseline - metrics.strikethrough_position,
+            thickness,
+            enable_hinting)
 
 
-def draw_text_decoration(context, textbox, offset_y, enable_hinting):
+def draw_text_decoration(context, textbox, offset_y, thickness, enable_hinting):
     """Draw text-decoration of ``textbox`` to a ``cairo.Context``."""
     with stacked(context):
         if enable_hinting:
             context.set_antialias(cairo.ANTIALIAS_NONE)
         context.set_source_rgba(*textbox.style.color)
-        context.set_line_width(1)  # TODO: make this proportional to font_size?
+        context.set_line_width(thickness)
         context.move_to(textbox.position_x, textbox.position_y + offset_y)
         context.rel_line_to(textbox.width, 0)
         context.stroke()
diff --git a/weasyprint/text.py b/weasyprint/text.py
index 7552d56e..a918460c 100644
--- a/weasyprint/text.py
+++ b/weasyprint/text.py
@@ -65,6 +65,9 @@ ffi.cdef('''
     typedef void* gpointer;
     typedef ... cairo_t;
     typedef ... PangoLayout;
+    typedef ... PangoContext;
+    typedef ... PangoFontMetrics;
+    typedef ... PangoLanguage;
     typedef ... PangoFontDescription;
     typedef ... PangoLayoutIter;
     typedef ... PangoAttrList;
@@ -151,6 +154,27 @@ ffi.cdef('''
         PangoLayoutLine *line,
         PangoRectangle *ink_rect, PangoRectangle *logical_rect);
 
+    PangoContext *      pango_layout_get_context    (PangoLayout *layout);
+    PangoFontMetrics *  pango_context_get_metrics   (PangoContext *context,
+                                                     const PangoFontDescription *desc,
+                                                     PangoLanguage *language);
+
+    void    pango_font_metrics_unref            (PangoFontMetrics *metrics);
+    int     pango_font_metrics_get_ascent       (PangoFontMetrics *metrics);
+    int     pango_font_metrics_get_descent      (PangoFontMetrics *metrics);
+    int     pango_font_metrics_get_approximate_char_width
+                                                (PangoFontMetrics *metrics);
+    int     pango_font_metrics_get_approximate_digit_width
+                                                (PangoFontMetrics *metrics);
+    int     pango_font_metrics_get_underline_thickness
+                                                (PangoFontMetrics *metrics);
+    int     pango_font_metrics_get_underline_position
+                                                (PangoFontMetrics *metrics);
+    int     pango_font_metrics_get_strikethrough_thickness
+                                                (PangoFontMetrics *metrics);
+    int     pango_font_metrics_get_strikethrough_position
+                                                (PangoFontMetrics *metrics);
+
     void pango_cairo_update_layout (cairo_t *cr, PangoLayout *layout);
     void pango_cairo_show_layout_line (cairo_t *cr, PangoLayoutLine *line);
 
@@ -286,6 +310,28 @@ class Layout(object):
         self.text_bytes = bytestring
         pango.pango_layout_set_text(self.layout, text, -1)
 
+    def get_font_metrics(self):
+        context = pango.pango_layout_get_context(self.layout)
+        return FontMetrics(context, self.font)
+
+
+class FontMetrics(object):
+    def __init__(self, context, font):
+        self.metrics = ffi.gc(
+                pango.pango_context_get_metrics(context, font, ffi.NULL),
+                pango.pango_font_metrics_unref)
+
+    def __dir__(self):
+        return ['ascent', 'descent',
+                'approximate_char_width', 'approximate_digit_width',
+                'underline_thickness', 'underline_position',
+                'strikethrough_thickness', 'strikethrough_position']
+
+    def __getattr__(self, key):
+        if key in dir(self):
+            return units_to_double(
+                getattr(pango, 'pango_font_metrics_get_' + key)(self.metrics))
+    
 
 def create_layout(text, style, hinting, max_width):
     """Return an opaque Pango layout with default Pango line-breaks.