Bug 485536 – underline_position can be zero

2007-11-29  Behdad Esfahbod  <behdad@gnome.org>

        Bug 485536 – underline_position can be zero

        * pango/pango-utils.c (pango_cairo_quantize_line_geometry):
        Document that returned position may be zero.

        * pango/pangocairo-win32font.c
        (pango_cairo_win32_font_create_metrics_for_context):
        * pango/pangofc-font.c (get_face_metrics):
        Handle case of underline_position==0 after rounding.


svn path=/trunk/; revision=2506

4 files changed, 35 insertions, 15 deletions

diff --git a/pango/opentype/harfbuzz-impl.c b/pango/opentype/harfbuzz-impl.c
index 79b837de..4ba70ed4 100644
--- a/pango/opentype/harfbuzz-impl.c
+++ b/pango/opentype/harfbuzz-impl.c
@@ -65,5 +65,7 @@ _hb_free( HB_Pointer  block )
 HB_INTERNAL HB_Error
 _hb_err (HB_Error code)
 {
+  static int numerr = 0;
+  numerr++;
   return code;
 }
diff --git a/pango/pango-utils.c b/pango/pango-utils.c
index 51d8fd01..1776ab9f 100644
--- a/pango/pango-utils.c
+++ b/pango/pango-utils.c
@@ -1593,6 +1593,9 @@ pango_is_zero_width (gunichar ch)
  * multiples of %PANGO_SCALE. The purpose of this function is to avoid
  * such lines looking blurry.
  *
+ * Care is taken to make sure @thickness is at least 1 when this function
+ * returns, but returned @position may become zero as a result of rounding.
+ *
  * Since: 1.12
  */
 void
diff --git a/pango/pangocairo-win32font.c b/pango/pangocairo-win32font.c
index af4e1d07..d01e6f0b 100644
--- a/pango/pangocairo-win32font.c
+++ b/pango/pangocairo-win32font.c
@@ -140,6 +140,9 @@ pango_cairo_win32_font_create_metrics_for_context (PangoCairoFont *font,
 				&metrics->underline_position);
   pango_quantize_line_geometry (&metrics->strikethrough_thickness,
 				&metrics->strikethrough_position);
+  /* Quantizing may have pushed underline_position to 0.  Not good */
+  if (metrics->underline_position == 0)
+    metrics->underline_position = - metrics->underline_thickness;
 
   layout = pango_layout_new (context);
   font_desc = pango_font_describe_with_absolute_size ((PangoFont *) font);
diff --git a/pango/pangofc-font.c b/pango/pangofc-font.c
index d2c395ff..bd185bd8 100644
--- a/pango/pangofc-font.c
+++ b/pango/pangofc-font.c
@@ -304,7 +304,7 @@ get_face_metrics (PangoFcFont      *fcfont,
   TT_OS2 *os2;
   gboolean have_transform = FALSE;
 
-  if (!face)
+  if (G_UNLIKELY (!face))
     {
       metrics->descent = 0;
       metrics->ascent = PANGO_SCALE * PANGO_UNKNOWN_GLYPH_HEIGHT;
@@ -358,27 +358,32 @@ get_face_metrics (PangoFcFont      *fcfont,
       metrics->ascent = PANGO_UNITS_26_6 (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 = 0;
+  metrics->underline_position = 0;
+
+  {
+    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);
+  }
+
+  if (metrics->underline_thickness == 0 || metrics->underline_position == 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);
-    }
+  metrics->strikethrough_thickness = 0;
+  metrics->strikethrough_position = 0;
 
   os2 = FT_Get_Sfnt_Table (face, ft_sfnt_os2);
-  if (os2 && os2->version != 0xFFFF && os2->yStrikeoutSize != 0)
+  if (os2 && os2->version != 0xFFFF)
     {
       FT_Fixed ft_thickness, ft_position;
 
@@ -388,12 +393,14 @@ get_face_metrics (PangoFcFont      *fcfont,
       ft_position = FT_MulFix (os2->yStrikeoutPosition, face->size->metrics.y_scale);
       metrics->strikethrough_position = PANGO_UNITS_26_6 (ft_position);
     }
-  else
+
+  if (metrics->strikethrough_thickness == 0 || metrics->strikethrough_position == 0)
     {
       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.
    */
@@ -403,8 +410,13 @@ get_face_metrics (PangoFcFont      *fcfont,
 				    &metrics->underline_position);
       pango_quantize_line_geometry (&metrics->strikethrough_thickness,
 				    &metrics->strikethrough_position);
+
+      /* Quantizing may have pushed underline_position to 0.  Not good */
+      if (metrics->underline_position == 0)
+	metrics->underline_position = - metrics->underline_thickness;
     }
 
+
   PANGO_FC_FONT_UNLOCK_FACE (fcfont);
 }