Bug 329547 – pango_layout_get_pixel_extents and

2006-04-29  Behdad Esfahbod  <behdad@gnome.org>

        Bug 329547 – pango_layout_get_pixel_extents and
        pango_layout_get_pixel_size cause off-by-one metrics

        * docs/pango-sections.txt:
        * docs/tmpl/glyphs.sgml:
        * pango/pango-types.h: Define PANGO_PIXELS_FLOOR and
        * PANGO_PIXELS_CEIL.

        * pango/pango-layout.c (pango_layout_get_pixel_extents),
        (pango_layout_get_pixel_size): Make sure logical rects are
        consistent and ink rects are inclusive.

7 files changed, 65 insertions, 25 deletions

diff --git a/ChangeLog b/ChangeLog
index cd7b247e..8c020efc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,18 @@
 2006-04-29  Behdad Esfahbod  <behdad@gnome.org>
 
+	Bug 329547 – pango_layout_get_pixel_extents and
+	pango_layout_get_pixel_size cause off-by-one metrics
+
+	* docs/pango-sections.txt:
+	* docs/tmpl/glyphs.sgml:
+	* pango/pango-types.h: Define PANGO_PIXELS_FLOOR and PANGO_PIXELS_CEIL.
+
+	* pango/pango-layout.c (pango_layout_get_pixel_extents),
+	(pango_layout_get_pixel_size): Make sure logical rects are
+	consistent and ink rects are inclusive.
+
+2006-04-29  Behdad Esfahbod  <behdad@gnome.org>
+
 	* docs/tmpl/atsui-fonts.sgml:
 	* docs/tmpl/coverage-maps.sgml:
 	* docs/tmpl/engines.sgml:
diff --git a/docs/pango-sections.txt b/docs/pango-sections.txt
index 060253e4..e7f86471 100644
--- a/docs/pango-sections.txt
+++ b/docs/pango-sections.txt
@@ -64,6 +64,8 @@ pango_item_get_type
 <FILE>glyphs</FILE>
 PANGO_SCALE
 PANGO_PIXELS
+PANGO_PIXELS_FLOOR
+PANGO_PIXELS_CEIL
 PangoRectangle
 PANGO_ASCENT
 PANGO_DESCENT
diff --git a/docs/tmpl/glyphs.sgml b/docs/tmpl/glyphs.sgml
index 873a9f78..b43cbb6a 100644
--- a/docs/tmpl/glyphs.sgml
+++ b/docs/tmpl/glyphs.sgml
@@ -37,7 +37,23 @@ points (as in "12 point font"), rather than pixels.
 
 <!-- ##### MACRO PANGO_PIXELS ##### -->
 <para>
-Converts a dimension to device units.
+Converts a dimension to device units by rounding.
+</para>
+
+@d: a dimension in Pango units.
+
+
+<!-- ##### MACRO PANGO_PIXELS_FLOOR ##### -->
+<para>
+Converts a dimension to device units by flooring.
+</para>
+
+@d: a dimension in Pango units.
+
+
+<!-- ##### MACRO PANGO_PIXELS_CEIL ##### -->
+<para>
+Converts a dimension to device units by ceiling.
 </para>
 
 @d: a dimension in Pango units.
diff --git a/pango/fonts.c b/pango/fonts.c
index 69c3fef1..59da712a 100644
--- a/pango/fonts.c
+++ b/pango/fonts.c
@@ -378,7 +378,7 @@ pango_font_description_get_size (const PangoFontDescription *desc)
 /**
  * pango_font_description_set_absolute_size:
  * @desc: a #PangoFontDescription
- * @size: the new size, in Pango units. There are #PANGO_SCALE Pango units in one
+ * @size: the new size, in Pango units. There are %PANGO_SCALE Pango units in one
  *   device unit. For an output backend where a device unit is a pixel, a @size
  *   value of 10 * PANGO_SCALE gives a 10 pixel font.
  * 
@@ -1341,7 +1341,7 @@ pango_font_metrics_unref (PangoFontMetrics *metrics)
  * actual drawn ink. It is necessary to lay out the text to figure
  * where the ink will be.)
  * 
- * Return value: the ascent, in Pango units. (1 point == #PANGO_SCALE Pango units.)
+ * Return value: the ascent, in Pango units. (1 point == %PANGO_SCALE Pango units.)
  **/
 int
 pango_font_metrics_get_ascent (PangoFontMetrics *metrics)
@@ -1361,7 +1361,7 @@ pango_font_metrics_get_ascent (PangoFontMetrics *metrics)
  * actual drawn ink. It is necessary to lay out the text to figure
  * where the ink will be.)
  * 
- * Return value: the descent, in Pango units. (1 point == #PANGO_SCALE Pango units.)
+ * Return value: the descent, in Pango units. (1 point == %PANGO_SCALE Pango units.)
  **/
 int
 pango_font_metrics_get_descent (PangoFontMetrics *metrics)
@@ -1380,7 +1380,7 @@ pango_font_metrics_get_descent (PangoFontMetrics *metrics)
  * determining the initial size for a window. Actual characters in
  * text will be wider and narrower than this.
  * 
- * Return value: the character width, in Pango units. (1 point == #PANGO_SCALE Pango units.)
+ * Return value: the character width, in Pango units. (1 point == %PANGO_SCALE Pango units.)
  **/
 int
 pango_font_metrics_get_approximate_char_width (PangoFontMetrics *metrics)
@@ -1401,7 +1401,7 @@ pango_font_metrics_get_approximate_char_width (PangoFontMetrics *metrics)
  * is generally somewhat more accurate than the result of
  * pango_font_metrics_get_approximate_char_width() for digits.
  * 
- * Return value: the digit width, in Pango units. (1 point == #PANGO_SCALE Pango units.)
+ * Return value: the digit width, in Pango units. (1 point == %PANGO_SCALE Pango units.)
  **/
 int
 pango_font_metrics_get_approximate_digit_width (PangoFontMetrics *metrics)
diff --git a/pango/pango-attributes.c b/pango/pango-attributes.c
index 08353219..ea7c268b 100644
--- a/pango/pango-attributes.c
+++ b/pango/pango-attributes.c
@@ -472,7 +472,7 @@ pango_attr_size_new_internal (int size,
 
 /**
  * pango_attr_size_new:
- * @size: the font size, in #PANGO_SCALE<!-- -->ths of a point.
+ * @size: the font size, in %PANGO_SCALE<!-- -->ths of a point.
  * 
  * Create a new font-size attribute in fractional points.
  * 
@@ -487,7 +487,7 @@ pango_attr_size_new (int size)
 
 /**
  * pango_attr_size_new_absolute:
- * @size: the font size, in #PANGO_SCALE<!-- -->ths of a device unit.
+ * @size: the font size, in %PANGO_SCALE<!-- -->ths of a device unit.
  * 
  * Create a new font-size attribute in device units.
  * 
diff --git a/pango/pango-layout.c b/pango/pango-layout.c
index d321177a..7b4b5c4e 100644
--- a/pango/pango-layout.c
+++ b/pango/pango-layout.c
@@ -1275,7 +1275,7 @@ pango_layout_index_to_line_and_extents (PangoLayout     *layout,
  * @line:      location to store resulting line index. (which will
  *             between 0 and pango_layout_get_line_count(layout) - 1)
  * @x_pos:     location to store resulting position within line
- *             (in thousandths of a device unit)
+ *             (%PANGO_SCALE units per device unit)
  *
  * Converts from byte @index_ within the @layout to line and X position.
  * (X position is measured from the left edge of the line)
@@ -2261,20 +2261,26 @@ pango_layout_get_pixel_extents (PangoLayout *layout,
 
   if (ink_rect)
     {
-      ink_rect->width = (ink_rect->width + PANGO_SCALE / 2) / PANGO_SCALE;
-      ink_rect->height = (ink_rect->height + PANGO_SCALE / 2) / PANGO_SCALE;
+      int orig_x = ink_rect->x;
+      int orig_y = ink_rect->y;
 
-      ink_rect->x = PANGO_PIXELS (ink_rect->x);
-      ink_rect->y = PANGO_PIXELS (ink_rect->y);
+      ink_rect->x = PANGO_PIXELS_FLOOR (ink_rect->x);
+      ink_rect->y = PANGO_PIXELS_FLOOR (ink_rect->y);
+
+      ink_rect->width  = PANGO_PIXELS_CEIL (orig_x + ink_rect->width ) - ink_rect->x;
+      ink_rect->height = PANGO_PIXELS_CEIL (orig_y + ink_rect->height) - ink_rect->y;
     }
 
   if (logical_rect)
     {
-      logical_rect->width = (logical_rect->width + PANGO_SCALE / 2) / PANGO_SCALE;
-      logical_rect->height = (logical_rect->height + PANGO_SCALE / 2) / PANGO_SCALE;
+      int orig_x = logical_rect->x;
+      int orig_y = logical_rect->y;
 
       logical_rect->x = PANGO_PIXELS (logical_rect->x);
       logical_rect->y = PANGO_PIXELS (logical_rect->y);
+
+      logical_rect->width  = PANGO_PIXELS (orig_x + logical_rect->width ) - logical_rect->x;
+      logical_rect->height = PANGO_PIXELS (orig_y + logical_rect->height) - logical_rect->y;
     }
 }
 
@@ -2285,7 +2291,7 @@ pango_layout_get_pixel_extents (PangoLayout *layout,
  * @height: location to store the logical height, or %NULL
  * 
  * Determines the logical width and height of a #PangoLayout
- * in Pango units. (device units divided by %PANGO_SCALE). This
+ * in Pango units. (device units scaled by %PANGO_SCALE). This
  * is simply a convenience function around pango_layout_get_extents().
  **/
 void
@@ -2311,8 +2317,9 @@ pango_layout_get_size (PangoLayout *layout,
  * 
  * Determines the logical width and height of a #PangoLayout
  * in device units. (pango_layout_get_size() returns the width
- * and height in thousandths of a device unit.) This
- * is simply a convenience function around pango_layout_get_extents().
+ * and height scaled by %PANGO_SCALE.) This
+ * is simply a convenience function around
+ * pango_layout_get_pixel_extents().
  **/
 void
 pango_layout_get_pixel_size (PangoLayout *layout,
@@ -2321,12 +2328,12 @@ pango_layout_get_pixel_size (PangoLayout *layout,
 {
   PangoRectangle logical_rect;
 
-  pango_layout_get_extents (layout, NULL, &logical_rect);
+  pango_layout_get_pixel_extents (layout, NULL, &logical_rect);
 
   if (width)
-    *width = (logical_rect.width + PANGO_SCALE / 2) / PANGO_SCALE;
+    *width = logical_rect.width;
   if (height)
-    *height = (logical_rect.height + PANGO_SCALE / 2) / PANGO_SCALE;
+    *height = logical_rect.height;
 }
 
 static void
diff --git a/pango/pango-types.h b/pango/pango-types.h
index 6a198a60..980658a3 100644
--- a/pango/pango-types.h
+++ b/pango/pango-types.h
@@ -127,10 +127,12 @@ double pango_matrix_get_font_scale_factor (const PangoMatrix *matrix);
 
 #define PANGO_SCALE 1024
 #define PANGO_PIXELS(d) (((int)(d) + 512) >> 10)
-/* The above expression is just slightly wrong for floating point d;
- * We'd expect -512.5 => -1 but instead we get 0. That's unlikely
- * to matter for practical use and the expression is much more
- * compact and faster than alternatives that work exactly for both
+#define PANGO_PIXELS_FLOOR(d) (((int)(d)) >> 10)
+#define PANGO_PIXELS_CEIL(d) (((int)(d) + 1023) >> 10)
+/* The above expressions are just slightly wrong for floating point d;
+ * For example we'd expect PANGO_PIXELS(-512.5) => -1 but instead we get 0.
+ * That's unlikely to matter for practical use and the expression is much
+ * more compact and faster than alternatives that work exactly for both
  * integers and floating point.
  */