Add underline and strikethrough position and thickness metrics.

Thu May 27 15:32:03 2004  Owen Taylor  <otaylor@redhat.com>

        * pango/pango-font.h pango/fonts.c: Add underline and
        strikethrough position and thickness metrics.

        * pango/pangofc-font.c: Implement underline and strikethrough
        position and thickness metrics.

        * pango/pango-fontset.c (pango_fontset_real_get_metrics):
        Initialize metrics from the metrics of the first font
        in the fontset.

4 files changed, 179 insertions, 0 deletions

diff --git a/pango/fonts.c b/pango/fonts.c
index aaa8c812..6535f7a9 100644
--- a/pango/fonts.c
+++ b/pango/fonts.c
@@ -1288,6 +1288,76 @@ pango_font_metrics_get_approximate_digit_width (PangoFontMetrics *metrics)
   return metrics->approximate_digit_width;
 }
 
+/**
+ * pango_font_metrics_get_underline_position:
+ * @metrics: a #PangoFontMetrics structure
+ * 
+ * Gets the suggested position to draw the underline.
+ * The value returned is the distance <emphasis>above</emphasis> the
+ * baseline of the top of the underline. Since most fonts have
+ * underline positions beneath the baseline, this value is typically
+ * negative.
+ * 
+ * Return value: the suggested underline position, in Pango units.
+ **/
+int
+pango_font_metrics_get_underline_position (PangoFontMetrics *metrics)
+{
+  g_return_val_if_fail (metrics != NULL, 0);
+
+  return metrics->underline_position;
+}
+
+/**
+ * pango_font_metrics_get_underline_thickness:
+ * @metrics: a #PangoFontMetrics structure
+ * 
+ * Gets the suggested thickness to draw for the underline.
+ * 
+ * Return value: the suggested underline thickness, in Pango units.
+ **/
+int
+pango_font_metrics_get_underline_thickness (PangoFontMetrics *metrics)
+{
+  g_return_val_if_fail (metrics != NULL, 0);
+
+  return metrics->underline_thickness;
+}
+
+/**
+ * pango_font_metrics_get_strikethrough_position:
+ * @metrics: a #PangoFontMetrics structure
+ * 
+ * Gets the suggested position to draw the strikethrough.
+ * The value returned is the distance <emphasis>above</emphasis> the
+ * baseline of the top of the strikethrough.
+ * 
+ * Return value: the suggested strikethrough position, in Pango units.
+ **/
+int
+pango_font_metrics_get_strikethrough_position (PangoFontMetrics *metrics)
+{
+  g_return_val_if_fail (metrics != NULL, 0);
+
+  return metrics->strikethrough_position;
+}
+
+/**
+ * pango_font_metrics_get_strikethrough_thickness:
+ * @metrics: a #PangoFontMetrics structure
+ * 
+ * Gets the suggested thickness to draw for the strikethrough.
+ * 
+ * Return value: the suggested strikethrough thickness, in Pango units.
+ **/
+int
+pango_font_metrics_get_strikethrough_thickness (PangoFontMetrics *metrics)
+{
+  g_return_val_if_fail (metrics != NULL, 0);
+
+  return metrics->strikethrough_thickness;
+}
+
 /*
  * PangoFontFamily
  */
diff --git a/pango/pango-font.h b/pango/pango-font.h
index 56b3b72f..ebe1fc87 100644
--- a/pango/pango-font.h
+++ b/pango/pango-font.h
@@ -159,6 +159,10 @@ int               pango_font_metrics_get_ascent                  (PangoFontMetri
 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_position      (PangoFontMetrics *metrics);
+int               pango_font_metrics_get_underline_thickness     (PangoFontMetrics *metrics);
+int               pango_font_metrics_get_strikethrough_position  (PangoFontMetrics *metrics);
+int               pango_font_metrics_get_strikethrough_thickness (PangoFontMetrics *metrics);
 
 #ifdef PANGO_ENABLE_BACKEND
 
@@ -172,6 +176,10 @@ struct _PangoFontMetrics
   int descent;
   int approximate_char_width;
   int approximate_digit_width;
+  int underline_position;
+  int underline_thickness;
+  int strikethrough_position;
+  int strikethrough_thickness;
 };
 
 #endif /* PANGO_ENABLE_BACKEND */
diff --git a/pango/pango-fontset.c b/pango/pango-fontset.c
index e3f38920..d4aaf351 100644
--- a/pango/pango-fontset.c
+++ b/pango/pango-fontset.c
@@ -100,6 +100,29 @@ pango_fontset_foreach (PangoFontset           *fontset,
   PANGO_FONTSET_GET_CLASS (fontset)->foreach (fontset, func, data);
 }
 
+static gboolean
+get_first_metrics_foreach (PangoFontset  *fontset,
+			   PangoFont     *font,
+			   gpointer       data)
+{
+  PangoFontMetrics *fontset_metrics = data;
+  PangoLanguage *language = PANGO_FONTSET_GET_CLASS (fontset)->get_language (fontset);
+  PangoFontMetrics *font_metrics = pango_font_get_metrics (font, language);
+  guint save_ref_count;
+
+  /* Initialize the fontset metrics to metrics of the first font in the
+   * fontset; saving the refcount and restoring it is a bit of hack but avoids
+   * having to update this code for each metrics addition.
+   */
+  save_ref_count = fontset_metrics->ref_count;
+  *fontset_metrics = *font_metrics;
+  fontset_metrics->ref_count = save_ref_count;
+
+  pango_font_metrics_unref (font_metrics);
+
+  return TRUE;			/* Stops iteration */
+}
+
 static PangoFontMetrics *
 pango_fontset_real_get_metrics (PangoFontset  *fontset)
 {
@@ -118,6 +141,9 @@ pango_fontset_real_get_metrics (PangoFontset  *fontset)
   metrics = pango_font_metrics_new ();
   fonts_seen = g_hash_table_new_full (NULL, NULL, g_object_unref, NULL);
 
+  /* Initialize the metrics from the first font in the fontset */
+  pango_fontset_foreach (fontset, get_first_metrics_foreach, metrics);
+
   p = sample_str;
   while (*p)
     {
diff --git a/pango/pangofc-font.c b/pango/pangofc-font.c
index 18530ded..de43513d 100644
--- a/pango/pangofc-font.c
+++ b/pango/pangofc-font.c
@@ -26,6 +26,8 @@
 #include "pango-modules.h"
 #include "pango-utils.h"
 
+#include FT_TRUETYPE_TABLES_H
+
 #define PANGO_SCALE_26_6 (PANGO_SCALE / (1<<6))
 #define PANGO_PIXELS_26_6(d)				\
   (((d) >= 0) ?						\
@@ -209,6 +211,28 @@ pango_fc_font_get_coverage (PangoFont     *font,
 					  fcfont->font_pattern);
 }
 
+static void
+quantize_position (int *thickness,
+		   int *position)
+{
+  int thickness_pixels = (*thickness + PANGO_SCALE / 2) / PANGO_SCALE;
+  if (thickness_pixels == 0)
+    thickness_pixels = 1;
+  
+  if (thickness_pixels & 1)
+    {
+      int new_center = ((*position - *thickness / 2) & ~(PANGO_SCALE - 1)) + PANGO_SCALE / 2;
+      *position = new_center + (PANGO_SCALE * thickness_pixels) / 2;
+    }
+  else
+    {
+      int new_center = ((*position - *thickness / 2 + PANGO_SCALE / 2) & ~(PANGO_SCALE - 1));
+      *position = new_center + (PANGO_SCALE * thickness_pixels) / 2;
+    }
+
+  *thickness = thickness_pixels * PANGO_SCALE;
+}
+
 /* For Xft, it would be slightly more efficient to simply to
  * call Xft, and also more robust against changes in Xft.
  * But for now, we simply use the same code for all backends.
@@ -220,10 +244,16 @@ static void
 get_face_metrics (PangoFcFont      *fcfont,
 		  PangoFontMetrics *metrics)
 {
+  FcBool hinting;
   FT_Face face = pango_fc_font_lock_face (fcfont);
   FcMatrix *fc_matrix;
   FT_Matrix ft_matrix;
+  TT_OS2 *os2;
   gboolean have_transform = FALSE;
+
+  if (FcPatternGetBool (fcfont->font_pattern,
+			FC_HINTING, 0, &hinting) != FcResultMatch)
+    hinting = FcTrue;
   
   if  (FcPatternGetMatrix (fcfont->font_pattern,
 			   FC_MATRIX, 0, &fc_matrix) == FcResultMatch)
@@ -256,6 +286,51 @@ get_face_metrics (PangoFcFont      *fcfont,
       metrics->descent = - PANGO_UNITS_26_6 (face->size->metrics.descender);
       metrics->ascent = PANGO_UNITS_26_6 (face->size->metrics.ascender);
     }
+
+  /* Versions of FreeType < 2.1.8 get underline thickness wrong
+   * for Postscript fonts (always zero), so we need a fallback
+   */
+  if (face->underline_thickness == 0)
+    {
+      metrics->underline_thickness = (PANGO_SCALE * face->size->metrics.y_ppem) / 14;
+      metrics->underline_position = - metrics->underline_thickness;
+    }
+  else
+    {
+      FT_Fixed ft_thickness, ft_position;
+      
+      ft_thickness = FT_MulFix (face->underline_thickness, face->size->metrics.y_scale);
+      metrics->underline_thickness = PANGO_UNITS_26_6 (ft_thickness);
+
+      ft_position = FT_MulFix (face->underline_position, face->size->metrics.y_scale);
+      metrics->underline_position = PANGO_UNITS_26_6 (ft_position);
+    }
+
+  os2 = FT_Get_Sfnt_Table (face, ft_sfnt_os2);
+  if (os2 && os2->version != 0xFFFF && os2->yStrikeoutSize != 0)
+    {
+      FT_Fixed ft_thickness, ft_position;
+      
+      ft_thickness = FT_MulFix (os2->yStrikeoutSize, face->size->metrics.y_scale);
+      metrics->strikethrough_thickness = PANGO_UNITS_26_6 (ft_thickness);
+
+      ft_position = FT_MulFix (os2->yStrikeoutPosition, face->size->metrics.y_scale);
+      metrics->strikethrough_position = PANGO_UNITS_26_6 (ft_position);
+    }
+  else
+    {
+      metrics->strikethrough_thickness = metrics->underline_thickness;
+      metrics->strikethrough_position = (PANGO_SCALE * face->size->metrics.y_ppem) / 4;
+    }
+
+  /* If hinting is on for this font, quantize the underline and strikethrough position
+   * to integer values.
+   */
+  if (hinting)
+    {
+      quantize_position (&metrics->underline_thickness, &metrics->underline_position);
+      quantize_position (&metrics->strikethrough_thickness, &metrics->strikethrough_position);
+    }
   
   pango_fc_font_unlock_face (fcfont);
 }