Bug 563356 – The input area of firefox and the blank width after text in

2008-12-05  Behdad Esfahbod  <behdad@gnome.org>

        Bug 563356 – The input area of firefox and the blank width after text
        in gnome-menu was stretched too wide, under pango-1.22.3

        * docs/tmpl/fonts.sgml:
        * pango/pango-impl-utils.h:
        * pango/pangocairo-atsuifont.c
        (pango_cairo_atsui_font_create_metrics_for_context):
        * pango/pangocairo-win32font.c
        (pango_cairo_win32_font_create_metrics_for_context):
        * pango/pangofc-font.c (pango_fc_font_create_metrics_for_context):
        For approximate_char_width calculation take each char's width into
        account.  That is, do a weighted average instead of uniform average.
        g_unichar_iszerowidth() chars count as 0, g_unichar_iswide() chars
        count 2, and the rest count as 1.  Pretty much wcwidth() behavior.
        See bug report for rationale.

svn path=/trunk/; revision=2747

6 files changed, 57 insertions, 4 deletions

diff --git a/ChangeLog b/ChangeLog
index 2b9932bf..03fe4467 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,21 @@
+2008-12-05  Behdad Esfahbod  <behdad@gnome.org>
+
+	Bug 563356 – The input area of firefox and the blank width after text
+	in gnome-menu was stretched too wide, under pango-1.22.3
+
+	* docs/tmpl/fonts.sgml:
+	* pango/pango-impl-utils.h:
+	* pango/pangocairo-atsuifont.c
+	(pango_cairo_atsui_font_create_metrics_for_context):
+	* pango/pangocairo-win32font.c
+	(pango_cairo_win32_font_create_metrics_for_context):
+	* pango/pangofc-font.c (pango_fc_font_create_metrics_for_context):
+	For approximate_char_width calculation take each char's width into
+	account.  That is, do a weighted average instead of uniform average.
+	g_unichar_iszerowidth() chars count as 0, g_unichar_iswide() chars
+	count 2, and the rest count as 1.  Pretty much wcwidth() behavior.
+	See bug report for rationale.
+
 2008-11-28  Behdad Esfahbod  <behdad@gnome.org>
 
 	Bug 562574 – Pangocariowin32 is leaking every cairo font it ever
diff --git a/docs/tmpl/fonts.sgml b/docs/tmpl/fonts.sgml
index 460e60b8..4b91624b 100644
--- a/docs/tmpl/fonts.sgml
+++ b/docs/tmpl/fonts.sgml
@@ -441,7 +441,10 @@ of their meaning.
 @descent: the distance from the baseline to the lowest point of the glyphs of
 	 the font. This is positive in practically all fonts.
 @approximate_char_width: approximate average width of the regular glyphs of
-         the font.
+         the font.  Note that for this calculation, East Asian characters
+	 (those passing g_unichar_iswide()) are counted as double-width.
+	 This produces a more uniform value for this measure across languages
+	 and results in more uniform and more expected UI sizes.
 @approximate_digit_width: approximate average width of the glyphs for digits
          of the font.
 @underline_position: position of the underline. This is normally negative.
diff --git a/pango/pango-impl-utils.h b/pango/pango-impl-utils.h
index e21988f1..a04d4241 100644
--- a/pango/pango-impl-utils.h
+++ b/pango/pango-impl-utils.h
@@ -23,6 +23,7 @@
 #ifndef __PANGO_IMPL_UTILS_H__
 #define __PANGO_IMPL_UTILS_H__
 
+#include <glib.h>
 #include <glib-object.h>
 #include <pango/pango.h>
 
@@ -92,6 +93,36 @@ void _pango_shape_get_extents (gint              n_chars,
 			       PangoRectangle   *ink_rect,
 			       PangoRectangle   *logical_rect);
 
+
+/* We define these functions static here because we don't want to add public API
+ * for them (if anything, it belongs to glib, but glib found it trivial enough
+ * not to add API for).  At some point metrics calculations will be
+ * centralized and this mess can be minimized.  Or so I hope.
+ */
+
+static inline G_GNUC_UNUSED int
+pango_unichar_width (gunichar c)
+{
+  return G_UNLIKELY (g_unichar_iszerowidth (c)) ? 0 :
+	   G_UNLIKELY (g_unichar_iswide (c)) ? 2 : 1;
+}
+
+static G_GNUC_UNUSED glong
+pango_utf8_strwidth (const gchar *p)
+{
+  glong len = 0;
+  g_return_val_if_fail (p != NULL, 0);
+
+  while (*p)
+    {
+      len += pango_unichar_width (g_utf8_get_char (p));
+      p = g_utf8_next_char (p);
+    }
+
+  return len;
+}
+
+
 G_END_DECLS
 
 #endif /* __PANGO_IMPL_UTILS_H__ */
diff --git a/pango/pangocairo-atsuifont.c b/pango/pangocairo-atsuifont.c
index 7706fbf8..ac060ccd 100644
--- a/pango/pangocairo-atsuifont.c
+++ b/pango/pangocairo-atsuifont.c
@@ -24,6 +24,7 @@
 
 #import <Cocoa/Cocoa.h>
 
+#include "pango-impl-utils.h"
 #include "pangoatsui-private.h"
 #include "pangocairo.h"
 #include "pangocairo-private.h"
@@ -148,7 +149,7 @@ pango_cairo_atsui_font_create_metrics_for_context (PangoCairoFont *font,
   pango_layout_set_text (layout, sample_str, -1);
   pango_layout_get_extents (layout, NULL, &extents);
 
-  metrics->approximate_char_width = extents.width / g_utf8_strlen (sample_str, -1);
+  metrics->approximate_char_width = extents.width / pango_utf8_strwidth (sample_str);
 
   pango_layout_set_text (layout, "0123456789", -1);
   metrics->approximate_digit_width = max_glyph_width (layout);
diff --git a/pango/pangocairo-win32font.c b/pango/pangocairo-win32font.c
index 875f9526..4dda4ece 100644
--- a/pango/pangocairo-win32font.c
+++ b/pango/pangocairo-win32font.c
@@ -150,7 +150,7 @@ pango_cairo_win32_font_create_metrics_for_context (PangoCairoFont *font,
   pango_layout_set_text (layout, sample_str, -1);
   pango_layout_get_extents (layout, NULL, &extents);
 
-  metrics->approximate_char_width = extents.width / g_utf8_strlen (sample_str, -1);
+  metrics->approximate_char_width = extents.width / pango_utf8_strwidth (sample_str);
 
   pango_layout_set_text (layout, "0123456789", -1);
   metrics->approximate_digit_width = max_glyph_width (layout);
diff --git a/pango/pangofc-font.c b/pango/pangofc-font.c
index b5d65ca6..8a5b9ac8 100644
--- a/pango/pangofc-font.c
+++ b/pango/pangofc-font.c
@@ -496,7 +496,7 @@ pango_fc_font_create_metrics_for_context (PangoFcFont   *fcfont,
   pango_layout_get_extents (layout, NULL, &extents);
 
   metrics->approximate_char_width =
-    extents.width / g_utf8_strlen (sample_str, -1);
+    extents.width / pango_utf8_strwidth (sample_str);
 
   pango_layout_set_text (layout, "0123456789", -1);
   metrics->approximate_digit_width = max_glyph_width (layout);