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

8 files changed, 87 insertions, 20 deletions

diff --git a/ChangeLog b/ChangeLog
index fd490e6e..f2c4635e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,17 @@
 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.
+
+2007-11-29  Behdad Esfahbod  <behdad@gnome.org>
+
 	Bug 500549 – pangocairo.h should include pango.h and cairo.h
 
 	* pango/pangocairo.h: #include <pango/pango.h>
diff --git a/examples/cairoshape.c b/examples/cairoshape.c
index addde87e..0845c587 100644
--- a/examples/cairoshape.c
+++ b/examples/cairoshape.c
@@ -1,4 +1,25 @@
-/* example to use pangocairo to render arbitrary shapes inside a text layout */
+/* Example code to show how to use pangocairo to render arbitrary shapes
+ * inside a text layout, positioned by Pango.  This has become possibly
+ * using the following API added in Pango 1.18:
+ * 
+ * 	pango_cairo_context_set_shape_renderer ()
+ *
+ * This examples uses a small parser to convert shapes in the format of
+ * SVG paths to cairo instructions.  You can typically extract these from
+ * the SVG file's <path> elements directly.
+ *
+ * The code then searches for the Unicode bullet character in the layout
+ * text and automatically adds PangoAttribtues to the layout to replace
+ * each of the with a rendering of the GNOME Foot logo.
+ *
+ *
+ * Written by Behdad Esfahbod, 2007
+ *
+ * Permission to use, copy, modify, distribute, and sell this example
+ * for any purpose is hereby granted without fee.
+ * It is provided "as is" without express or implied warranty.
+ */
+
 
 #include <stdio.h>
 #include <string.h>
@@ -120,7 +141,7 @@ get_layout (cairo_t *cr)
 
   attrs = pango_attr_list_new ();
 
-  /* set gnome shape attributes for bullets */
+  /* Set gnome shape attributes for all bullets */
   for (p = text; (p = strstr (p, BULLET)); p += strlen (BULLET))
     {
       PangoAttribute *attr;
@@ -148,6 +169,8 @@ draw_text (cairo_t *cr, int *width, int *height)
 
   PangoLayout *layout = get_layout (cr);
 
+  /* Adds a fixed 10-pixel margin on the sides. */
+
   if (width || height)
     {
       pango_layout_get_pixel_size (layout, width, height);
@@ -179,6 +202,8 @@ int main (int argc, char **argv)
 
   filename = argv[1];
 
+  /* First create and use a 0x0 surface, to measure how large
+   * the final surface needs to be */
   surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32,
 					0, 0);
   cr = cairo_create (surface);
@@ -186,6 +211,7 @@ int main (int argc, char **argv)
   cairo_destroy (cr);
   cairo_surface_destroy (surface);
 
+  /* Now create the final surface and draw to it. */
   surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32,
 					width, height);
   cr = cairo_create (surface);
@@ -196,6 +222,7 @@ int main (int argc, char **argv)
   draw_text (cr, NULL, NULL);
   cairo_destroy (cr);
 
+  /* Write out the surface as PNG */
   status = cairo_surface_write_to_png (surface, filename);
   cairo_surface_destroy (surface);
 
diff --git a/examples/cairosimple.c b/examples/cairosimple.c
index d07f004c..faef3267 100644
--- a/examples/cairosimple.c
+++ b/examples/cairosimple.c
@@ -1,4 +1,4 @@
-/* simple example to use pangocairo to render rotated text */
+/* Simple example to use pangocairo to render rotated text */
 
 #include <math.h>
 #include <pango/pangocairo.h>
diff --git a/examples/cairotwisted.c b/examples/cairotwisted.c
index 180cd447..47d1e3d9 100644
--- a/examples/cairotwisted.c
+++ b/examples/cairotwisted.c
@@ -1,5 +1,13 @@
-/* example to use pangocairo to render text projected on a path */
-/* Written by Behdad Esfahbod, 2006.  Not copyrighted, in public domain. */
+/* Example code to show how to use pangocairo to render text
+ * projected on a path.
+ *
+ *
+ * Written by Behdad Esfahbod, 2006..2007
+ *
+ * Permission to use, copy, modify, distribute, and sell this example
+ * for any purpose is hereby granted without fee.
+ * It is provided "as is" without express or implied warranty.
+ */
 
 #include <math.h>
 #include <stdlib.h>
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);
 }