[pango] CoreText: Remove absolute size and scaling to screen resolution.

[John Ralls <jralls src gnome org>]

commit 8ab2cc198469b4a46b1536c4f5c5d3396a6444b4
Author: John Ralls <jralls ceridwen us>
Date:   Tue Aug 15 09:21:26 2017 +0200

    CoreText: Remove absolute size and scaling to screen resolution.
    
    Cairo's CGFont backend already handles scaling fonts to the display
    resolution, so scaling to the screen screen resolution in Pango's
    CoreText backend generates double-sized text on a Retina display.
    
    The layout test depended on providing a (bogus) resolution of 96DPI and
    scaling the font to it in order to obtain the "expected" layout
    results. This is replaced by adjusting the font size in test-layout.c
    if Pango is compiled for CoreText.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=782393

 pango/pangocairo-coretextfont.c    |   22 +----------
 pango/pangocairo-coretextfontmap.c |    2 +-
 pango/pangocoretext-fontmap.c      |   69 +++++++++++++----------------------
 pango/pangocoretext-private.h      |    2 +-
 pango/pangocoretext.c              |    4 ++
 tests/test-layout.c                |   11 +++++-
 6 files changed, 44 insertions(+), 66 deletions(-)
---
diff --git a/pango/pangocairo-coretextfont.c b/pango/pangocairo-coretextfont.c
index 0f2a9ef..c07f1c7 100644
--- a/pango/pangocairo-coretextfont.c
+++ b/pango/pangocairo-coretextfont.c
@@ -36,8 +36,6 @@ struct _PangoCairoCoreTextFont
 {
   PangoCoreTextFont font;
   PangoCairoFontPrivate cf_priv;
-
-  int abs_size;
 };
 
 struct _PangoCairoCoreTextFontClass
@@ -164,18 +162,6 @@ pango_cairo_core_text_font_create_base_metrics_for_context (PangoCairoFont *font
   return metrics;
 }
 
-static PangoFontDescription *
-pango_cairo_core_text_font_describe_absolute (PangoFont *font)
-{
-  PangoFontDescription *desc;
-  PangoCairoCoreTextFont *cafont = (PangoCairoCoreTextFont *) font;
-
-  desc = pango_font_describe (font);
-  pango_font_description_set_absolute_size (desc, cafont->abs_size);
-
-  return desc;
-}
-
 static void
 pango_cairo_core_text_font_finalize (GObject *object)
 {
@@ -196,7 +182,6 @@ pango_cairo_core_text_font_class_init (PangoCairoCoreTextFontClass *class)
 
   font_class->get_glyph_extents = pango_cairo_core_text_font_get_glyph_extents;
   font_class->get_metrics = _pango_cairo_font_get_metrics;
-  font_class->describe_absolute = pango_cairo_core_text_font_describe_absolute;
 }
 
 static void
@@ -214,11 +199,10 @@ _pango_cairo_core_text_font_new (PangoCairoCoreTextFontMap  *cafontmap,
   CTFontRef font_ref;
   CTFontDescriptorRef ctdescriptor;
   CGFontRef font_id;
-  double size, abs_size;
+  double size;
   cairo_matrix_t font_matrix;
 
-  abs_size = pango_core_text_font_key_get_absolute_size (key);
-  size = pango_units_to_double (abs_size);
+  size = pango_units_to_double (pango_core_text_font_key_get_size (key));
 
   size /= pango_matrix_get_font_scale_factor (pango_core_text_font_key_get_matrix (key));
 
@@ -235,8 +219,6 @@ _pango_cairo_core_text_font_new (PangoCairoCoreTextFontMap  *cafontmap,
   cafont = g_object_new (PANGO_TYPE_CAIRO_CORE_TEXT_FONT, NULL);
   cfont = PANGO_CORE_TEXT_FONT (cafont);
 
-  cafont->abs_size = abs_size;
-
   _pango_core_text_font_set_ctfont (cfont, font_ref);
 
   if (synthesize_italic)
diff --git a/pango/pangocairo-coretextfontmap.c b/pango/pangocairo-coretextfontmap.c
index 5054b7a..ba5dcec 100644
--- a/pango/pangocairo-coretextfontmap.c
+++ b/pango/pangocairo-coretextfontmap.c
@@ -186,5 +186,5 @@ static void
 pango_cairo_core_text_font_map_init (PangoCairoCoreTextFontMap *cafontmap)
 {
   cafontmap->serial = 1;
-  cafontmap->dpi = 96.;
+  cafontmap->dpi = 72.;
 }
diff --git a/pango/pangocoretext-fontmap.c b/pango/pangocoretext-fontmap.c
index 6cd9fe9..4d10184 100644
--- a/pango/pangocoretext-fontmap.c
+++ b/pango/pangocoretext-fontmap.c
@@ -827,12 +827,6 @@ get_scaled_size (PangoCoreTextFontMap       *fontmap,
 {
   double size = pango_font_description_get_size (desc);
 
-  if (!pango_font_description_get_size_is_absolute (desc))
-    {
-      double dpi = pango_core_text_font_map_get_resolution (fontmap, context);
-      size = size * dpi / 72.;
-    }
-
   return .5 + pango_matrix_get_font_scale_factor (pango_context_get_matrix (context)) * size;
 }
 
@@ -846,7 +840,7 @@ struct _PangoCoreTextFontsetKey
   PangoLanguage *language;
   PangoFontDescription *desc;
   PangoMatrix matrix;
-  int pixelsize;
+  int pointsize;
   double resolution;
   PangoGravity gravity;
   gpointer context_key;
@@ -865,7 +859,7 @@ pango_core_text_fontset_key_init (PangoCoreTextFontsetKey    *key,
   key->fontmap = fontmap;
   get_context_matrix (context, &key->matrix);
   key->language = language;
-  key->pixelsize = get_scaled_size (fontmap, context, desc);
+  key->pointsize = get_scaled_size (fontmap, context, desc);
   key->resolution = pango_core_text_font_map_get_resolution (fontmap, context);
   key->gravity = pango_context_get_gravity (context);
   key->desc = pango_font_description_copy_static (desc);
@@ -885,7 +879,7 @@ pango_core_text_fontset_key_copy (const PangoCoreTextFontsetKey *old)
   key->fontmap = old->fontmap;
   key->matrix = old->matrix;
   key->language = old->language;
-  key->pixelsize = old->pixelsize;
+  key->pointsize = old->pointsize;
   key->resolution = old->resolution;
   key->gravity = old->gravity;
   key->desc = pango_font_description_copy (old->desc);
@@ -929,7 +923,7 @@ pango_core_text_fontset_key_equal (const PangoCoreTextFontsetKey *key_a,
                                    const PangoCoreTextFontsetKey *key_b)
 {
   if (key_a->language == key_b->language &&
-      key_a->pixelsize == key_b->pixelsize &&
+      key_a->pointsize == key_b->pointsize &&
       key_a->resolution == key_b->resolution &&
       key_a->gravity == key_b->gravity &&
       pango_font_description_equal (key_a->desc, key_b->desc) &&
@@ -979,7 +973,7 @@ struct _PangoCoreTextFontKey
   CTFontDescriptorRef ctfontdescriptor;
   PangoMatrix matrix;
   PangoGravity gravity;
-  int pixelsize;
+  int pointsize;
   double resolution;
   gboolean synthetic_italic;
   gpointer context_key;
@@ -995,7 +989,7 @@ pango_core_text_font_key_init (PangoCoreTextFontKey    *key,
   key->fontmap = ctfontmap;
   key->ctfontdescriptor = ctdescriptor;
   key->matrix = *pango_core_text_fontset_key_get_matrix (fontset_key);
-  key->pixelsize = fontset_key->pixelsize;
+  key->pointsize = fontset_key->pointsize;
   key->resolution = fontset_key->resolution;
   key->synthetic_italic = synthetic_italic;
   key->gravity = pango_core_text_fontset_key_get_gravity (fontset_key);
@@ -1011,7 +1005,7 @@ pango_core_text_font_key_copy (const PangoCoreTextFontKey *old)
   key->ctfontdescriptor = old->ctfontdescriptor;
   CFRetain (key->ctfontdescriptor);
   key->matrix = old->matrix;
-  key->pixelsize = old->pixelsize;
+  key->pointsize = old->pointsize;
   key->resolution = old->resolution;
   key->synthetic_italic = old->synthetic_italic;
   key->gravity = old->gravity;
@@ -1057,7 +1051,7 @@ pango_core_text_font_key_equal (const PangoCoreTextFontKey *key_a,
   if (CFEqual (key_a->ctfontdescriptor, key_b->ctfontdescriptor) &&
       memcmp (&key_a->matrix, &key_b->matrix, 4 * sizeof (double)) == 0 &&
       key_a->gravity == key_b->gravity &&
-      key_a->pixelsize == key_b->pixelsize &&
+      key_a->pointsize == key_b->pointsize &&
       key_a->resolution == key_b->resolution &&
       key_a->synthetic_italic == key_b->synthetic_italic)
     {
@@ -1073,9 +1067,9 @@ pango_core_text_font_key_equal (const PangoCoreTextFontKey *key_a,
 }
 
 int
-pango_core_text_font_key_get_absolute_size (const PangoCoreTextFontKey *key)
+pango_core_text_font_key_get_size (const PangoCoreTextFontKey *key)
 {
-  return key->pixelsize;
+  return key->pointsize;
 }
 
 double
@@ -1162,32 +1156,34 @@ pango_core_text_font_map_new_font (PangoCoreTextFontMap    *fontmap,
 static gboolean
 find_best_match (PangoCoreTextFamily         *font_family,
                  const PangoFontDescription  *description,
-                 PangoFontDescription       **best_description,
                  PangoCoreTextFace          **best_face)
 {
   PangoFontDescription *new_desc;
+  PangoFontDescription *best_description = NULL;
   int i;
 
-  *best_description = NULL;
   *best_face = NULL;
 
   for (i = 0; i < font_family->n_faces; i++)
     {
       new_desc = pango_font_face_describe (font_family->faces[i]);
 
-      if (pango_font_description_better_match (description, *best_description, new_desc))
+      if (pango_font_description_better_match (description, best_description,
+                                               new_desc))
        {
-         pango_font_description_free (*best_description);
-         *best_description = new_desc;
+         pango_font_description_free (best_description);
+         best_description = new_desc;
          *best_face = (PangoCoreTextFace *)font_family->faces[i];
        }
       else
        pango_font_description_free (new_desc);
     }
 
-  if (*best_description)
-    return TRUE;
-
+  if (best_description)
+    {
+      pango_font_description_free (best_description);
+      return TRUE;
+    }
   return FALSE;
 }
 
@@ -1557,33 +1553,20 @@ pango_core_text_fontset_new (PangoCoreTextFontsetKey    *key,
 
   if (font_family)
     {
-      PangoFontDescription *best_description;
       PangoCoreTextFace *best_face;
-      gint size;
-      gboolean is_absolute;
 
       /* Force a listing of the available faces */
       pango_font_family_list_faces ((PangoFontFamily *)font_family, NULL, NULL);
 
-      if (!find_best_match (font_family, description, &best_description, &best_face))
+      if (!find_best_match (font_family, description, &best_face))
        return NULL;
 
-      size = pango_font_description_get_size (description);
-      if (size < 0)
-        return NULL;
-
-      is_absolute = pango_font_description_get_size_is_absolute (description);
-      if (is_absolute)
-        pango_font_description_set_absolute_size (best_description, size);
-      else
-        pango_font_description_set_size (best_description, size);
+      best_font =
+           pango_core_text_font_map_new_font (key->fontmap,
+                                              key,
+                                              best_face->ctfontdescriptor,
+                                              best_face->synthetic_italic);
 
-      best_font = pango_core_text_font_map_new_font (key->fontmap,
-                                                     key,
-                                                     best_face->ctfontdescriptor,
-                                                     best_face->synthetic_italic);
-
-      pango_font_description_free (best_description);
     }
   else
     return NULL;
diff --git a/pango/pangocoretext-private.h b/pango/pangocoretext-private.h
index 8bf4c75..c6c642c 100644
--- a/pango/pangocoretext-private.h
+++ b/pango/pangocoretext-private.h
@@ -99,7 +99,7 @@ void                  _pango_core_text_font_set_ctfont           (PangoCoreTextF
 PangoFontDescription *_pango_core_text_font_description_from_ct_font_descriptor (CTFontDescriptorRef desc);
 
 _PANGO_EXTERN
-int                   pango_core_text_font_key_get_absolute_size    (const PangoCoreTextFontKey *key);
+int                   pango_core_text_font_key_get_size    (const PangoCoreTextFontKey *key);
 _PANGO_EXTERN
 double                pango_core_text_font_key_get_resolution       (const PangoCoreTextFontKey *key);
 _PANGO_EXTERN
diff --git a/pango/pangocoretext.c b/pango/pangocoretext.c
index a8c0b5d..8cba1aa 100644
--- a/pango/pangocoretext.c
+++ b/pango/pangocoretext.c
@@ -225,6 +225,10 @@ pango_core_text_font_class_init (PangoCoreTextFontClass *class)
   object_class->finalize = pango_core_text_font_finalize;
 
   font_class->describe = pango_core_text_font_describe;
+  /* In CoreText the device unit is points so describe_absoulute and
+   * describe are the same.
+   */
+  font_class->describe_absolute = pango_core_text_font_describe;
   font_class->get_coverage = pango_core_text_font_get_coverage;
   font_class->find_shaper = pango_core_text_font_find_shaper;
   font_class->get_font_map = pango_core_text_font_get_font_map;
diff --git a/tests/test-layout.c b/tests/test-layout.c
index 0a6a2c1..07ca690 100644
--- a/tests/test-layout.c
+++ b/tests/test-layout.c
@@ -27,6 +27,7 @@
 #include <unistd.h>
 #endif
 
+#include "config.h"
 #include <pango/pangocairo.h>
 #include "test-common.h"
 
@@ -264,8 +265,16 @@ test_file (const gchar *filename, GString *string)
   parse_params (contents, &width, &ellipsize_at, &ellipsize, &wrap);
 
   layout = pango_layout_new (context);
-
+/* The layout tests are predicated on scaling fonts to 90 DPI, but
+ * Apple's font APIs (CoreText and CoreGraphics) don't work that way
+ * so we have to use a bigger font to get the results to agree with
+ * the expected values.
+ */
+#if defined (HAVE_CORE_TEXT) && defined (HAVE_CAIRO_QUARTZ)
+  desc = pango_font_description_from_string ("Cantarell 14.5");
+#else
   desc = pango_font_description_from_string ("Cantarell 11");
+#endif
   pango_layout_set_font_description (layout, desc);
   pango_font_description_free (desc);