Use cairo_scaled_font_t object for text drawing and metrics calculation

* src/ftfont.h (struct font_info): Replace member cr_font_face of type
cairo_font_face_t * with cr_scaled_font of type cairo_scaled_font_t *.
* src/ftcrfont.c: Include math.h for floor, ceiling, and lround.
(ftcrfont_glyph_extents): Use cairo_scaled_font_glyph_extents.
(ftcrfont_open): Create cairo_scaled_font_t object and set it to
cr_scaled_font member of struct font_info.
(ftcrfont_close): Use cairo_scaled_font_destroy.
(ftcrfont_draw): Use cairo_set_scaled_font.

2 files changed, 25 insertions, 8 deletions

diff --git a/src/ftcrfont.c b/src/ftcrfont.c
index 3a98e78d63e..31ff8e87c01 100644
--- a/src/ftcrfont.c
+++ b/src/ftcrfont.c
@@ -19,6 +19,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 
 #include <config.h>
 #include <stdio.h>
+#include <math.h>
 #include <cairo-ft.h>
 
 #include "lisp.h"
@@ -73,7 +74,18 @@ ftcrfont_glyph_extents (struct font *font,
   cache = ftcrfont_info->metrics[row] + col;
 
   if (METRICS_STATUS (cache) == METRICS_INVALID)
-    ftfont_text_extents (font, &glyph, 1, cache);
+    {
+      cairo_glyph_t cr_glyph = {.index = glyph, .x = 0, . y = 0};
+      cairo_text_extents_t extents;
+
+      cairo_scaled_font_glyph_extents (ftcrfont_info->cr_scaled_font,
+                                       &cr_glyph, 1, &extents);
+      cache->lbearing = floor (extents.x_bearing);
+      cache->rbearing = ceil (extents.width + extents.x_bearing);
+      cache->width = lround (extents.x_advance);
+      cache->ascent = ceil (extents.y_bearing);
+      cache->descent = ceil (extents.height - extents.y_bearing);
+    }
 
   if (metrics)
     *metrics = *cache;
@@ -126,8 +138,16 @@ ftcrfont_open (struct frame *f, Lisp_Object entity, int pixel_size)
   FT_New_Size (ft_face, &ftcrfont_info->ft_size_draw);
   FT_Activate_Size (ftcrfont_info->ft_size_draw);
   FT_Set_Pixel_Sizes (ft_face, 0, font->pixel_size);
-  ftcrfont_info->cr_font_face =
+  cairo_font_face_t *font_face =
     cairo_ft_font_face_create_for_ft_face (ft_face, 0);
+  cairo_matrix_t font_matrix, ctm;
+  cairo_matrix_init_scale (&font_matrix, pixel_size, pixel_size);
+  cairo_matrix_init_identity (&ctm);
+  cairo_font_options_t *options = cairo_font_options_create ();
+  ftcrfont_info->cr_scaled_font =
+    cairo_scaled_font_create (font_face, &font_matrix, &ctm, options);
+  cairo_font_face_destroy (font_face);
+  cairo_font_options_destroy (options);
   ftcrfont_info->metrics = NULL;
   ftcrfont_info->metrics_nrows = 0;
   unblock_input ();
@@ -151,7 +171,7 @@ ftcrfont_close (struct font *font)
   if (ftcrfont_info->metrics)
     xfree (ftcrfont_info->metrics);
   FT_Done_Size (ftcrfont_info->ft_size_draw);
-  cairo_font_face_destroy (ftcrfont_info->cr_font_face);
+  cairo_scaled_font_destroy (ftcrfont_info->cr_scaled_font);
   unblock_input ();
 
   ftfont_close (font);
@@ -230,10 +250,7 @@ ftcrfont_draw (struct glyph_string *s,
     }
 
   x_set_cr_source_with_gc_foreground (f, s->gc);
-  cairo_set_font_face (cr, ftcrfont_info->cr_font_face);
-  cairo_set_font_size (cr, s->font->pixel_size);
-  /* cairo_set_font_matrix */
-  /* cairo_set_font_options */
+  cairo_set_scaled_font (cr, ftcrfont_info->cr_scaled_font);
 
   FT_Activate_Size (ftcrfont_info->ft_size_draw);
   cairo_show_glyphs (cr, glyphs, len);
diff --git a/src/ftfont.h b/src/ftfont.h
index b6b0c5ba47b..327cd085acf 100644
--- a/src/ftfont.h
+++ b/src/ftfont.h
@@ -57,7 +57,7 @@ struct font_info
   FT_Matrix matrix;
 
 #ifdef USE_CAIRO
-  cairo_font_face_t *cr_font_face;
+  cairo_scaled_font_t *cr_scaled_font;
   /* To prevent cairo from cluttering the activated FT_Size maintained
      in ftfont.c, we activate this special FT_Size before drawing.  */
   FT_Size ft_size_draw;