Use gsettings font rendering entries for pgtk builds

If present, apply the gsettings font hinting and antialiasing
entries when creating a font in cairo.  Do this at
initialization and when the entries change, re-rendering the
frames.

* src/ftcrfont.c (ftcrfont_open): Use the font_options derived
from gsettings when opening a font.
(ftcrfont_cached_font_ok): Report a cached font as invalid if
its font options differ from the current options inside
gsettings.
* src/xsettings.c (apply_gsettings_font_hinting)
(apply_gsettings_font_alias, apply_gsettings_font_rgba_order):
Convert the settings from GSettings to the cairo_font_options_t
object.
(init_gsettings, something_changed_gsettingsCB): Invoke the
apply functions if the relevant settings changed.
(store_font_options_changed): Store an event to re-render the
fonts.
(xsetting_get_font_options)
* src/xsettings.h (xsettings_get_font_options): New function.

3 files changed, 185 insertions, 0 deletions

diff --git a/src/ftcrfont.c b/src/ftcrfont.c
index 98a28af5f22..6bb41110d5c 100644
--- a/src/ftcrfont.c
+++ b/src/ftcrfont.c
@@ -37,6 +37,9 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #include "font.h"
 #include "ftfont.h"
 #include "pdumper.h"
+#ifdef HAVE_PGTK
+#include "xsettings.h"
+#endif
 
 #ifdef USE_BE_CAIRO
 #define RED_FROM_ULONG(color)   (((color) >> 16) & 0xff)
@@ -168,7 +171,12 @@ ftcrfont_open (struct frame *f, Lisp_Object entity, int pixel_size)
   cairo_matrix_t font_matrix, ctm;
   cairo_matrix_init_scale (&font_matrix, pixel_size, pixel_size);
   cairo_matrix_init_identity (&ctm);
+
+#ifdef HAVE_PGTK
+  cairo_font_options_t *options = xsettings_get_font_options ();
+#else
   cairo_font_options_t *options = cairo_font_options_create ();
+#endif
 #ifdef USE_BE_CAIRO
   if (be_use_subpixel_antialiasing ())
     cairo_font_options_set_antialias (options, CAIRO_ANTIALIAS_SUBPIXEL);
@@ -624,6 +632,28 @@ ftcrfont_draw (struct glyph_string *s,
   return len;
 }
 
+#ifdef HAVE_PGTK
+/* Determine if FONT_OBJECT is a valid cached font for ENTITY by
+   comparing the options used to open it with the user's current
+   preferences specified via GSettings.  */
+static bool
+ftcrfont_cached_font_ok (struct frame *f, Lisp_Object font_object,
+                         Lisp_Object entity)
+{
+  struct font_info *info = (struct font_info *) XFONT_OBJECT (font_object);
+
+  cairo_font_options_t *options = cairo_font_options_create ();
+  cairo_scaled_font_get_font_options (info->cr_scaled_font, options);
+  cairo_font_options_t *gsettings_options = xsettings_get_font_options ();
+
+  bool equal = cairo_font_options_equal (options, gsettings_options);
+  cairo_font_options_destroy (options);
+  cairo_font_options_destroy (gsettings_options);
+
+  return equal;
+}
+#endif
+
 #ifdef HAVE_HARFBUZZ
 
 static Lisp_Object
@@ -694,6 +724,9 @@ struct font_driver const ftcrfont_driver =
 #endif
   .filter_properties = ftfont_filter_properties,
   .combining_capability = ftfont_combining_capability,
+#ifdef HAVE_PGTK
+  .cached_font_ok = ftcrfont_cached_font_ok
+#endif
   };
 #ifdef HAVE_HARFBUZZ
 struct font_driver ftcrhbfont_driver;
diff --git a/src/xsettings.c b/src/xsettings.c
index 71d02e61525..e71887e03d9 100644
--- a/src/xsettings.c
+++ b/src/xsettings.c
@@ -215,11 +215,116 @@ struct xsettings
 #define GSETTINGS_FONT_NAME  "font-name"
 #endif
 
+#ifdef HAVE_PGTK
+#define GSETTINGS_FONT_ANTIALIASING  "font-antialiasing"
+#define GSETTINGS_FONT_RGBA_ORDER    "font-rgba-order"
+#define GSETTINGS_FONT_HINTING       "font-hinting"
+#endif
 
 /* The single GSettings instance, or NULL if not connected to GSettings.  */
 
 static GSettings *gsettings_client;
 
+#ifdef HAVE_PGTK
+
+/* The cairo font_options as obtained using gsettings.  */
+static cairo_font_options_t *font_options;
+
+/* Store an event for re-rendering of the fonts.  */
+static void
+store_font_options_changed (void)
+{
+  if (dpyinfo_valid (first_dpyinfo))
+    store_config_changed_event (Qfont_render,
+                                XCAR (first_dpyinfo->name_list_element));
+}
+
+/* Apply changes in the hinting system setting.  */
+static void
+apply_gsettings_font_hinting (GSettings *settings)
+{
+  GVariant *val = g_settings_get_value (settings, GSETTINGS_FONT_HINTING);
+  if (val)
+    {
+      g_variant_ref_sink (val);
+      if (g_variant_is_of_type (val, G_VARIANT_TYPE_STRING))
+        {
+          const char *hinting = g_variant_get_string (val, NULL);
+
+          if (!strcmp (hinting, "full"))
+            cairo_font_options_set_hint_style (font_options,
+                                               CAIRO_HINT_STYLE_FULL);
+          else if (!strcmp (hinting, "medium"))
+            cairo_font_options_set_hint_style (font_options,
+                                               CAIRO_HINT_STYLE_MEDIUM);
+          else if (!strcmp (hinting, "slight"))
+            cairo_font_options_set_hint_style (font_options,
+                                               CAIRO_HINT_STYLE_SLIGHT);
+          else if (!strcmp (hinting, "none"))
+            cairo_font_options_set_hint_style (font_options,
+                                               CAIRO_HINT_STYLE_NONE);
+        }
+      g_variant_unref (val);
+    }
+}
+
+/* Apply changes in the antialiasing system setting.  */
+static void
+apply_gsettings_font_antialias (GSettings *settings)
+{
+  GVariant *val = g_settings_get_value (settings, GSETTINGS_FONT_ANTIALIASING);
+  if (val)
+    {
+      g_variant_ref_sink (val);
+      if (g_variant_is_of_type (val, G_VARIANT_TYPE_STRING))
+        {
+          const char *antialias = g_variant_get_string (val, NULL);
+
+          if (!strcmp (antialias, "none"))
+            cairo_font_options_set_antialias (font_options,
+                                              CAIRO_ANTIALIAS_NONE);
+          else if (!strcmp (antialias, "grayscale"))
+            cairo_font_options_set_antialias (font_options,
+                                              CAIRO_ANTIALIAS_GRAY);
+          else if (!strcmp (antialias, "rgba"))
+            cairo_font_options_set_antialias (font_options,
+                                              CAIRO_ANTIALIAS_SUBPIXEL);
+        }
+      g_variant_unref (val);
+    }
+}
+
+/* Apply the settings for the rgb element ordering.  */
+static void
+apply_gsettings_font_rgba_order (GSettings *settings)
+{
+  GVariant *val = g_settings_get_value (settings,
+                                        GSETTINGS_FONT_RGBA_ORDER);
+  if (val)
+    {
+      g_variant_ref_sink (val);
+      if (g_variant_is_of_type (val, G_VARIANT_TYPE_STRING))
+        {
+          const char *rgba_order = g_variant_get_string (val, NULL);
+
+          if (!strcmp (rgba_order, "rgb"))
+            cairo_font_options_set_subpixel_order (font_options,
+                                                   CAIRO_SUBPIXEL_ORDER_RGB);
+          else if (!strcmp (rgba_order, "bgr"))
+            cairo_font_options_set_subpixel_order (font_options,
+                                                   CAIRO_SUBPIXEL_ORDER_BGR);
+          else if (!strcmp (rgba_order, "vrgb"))
+            cairo_font_options_set_subpixel_order (font_options,
+                                                   CAIRO_SUBPIXEL_ORDER_VRGB);
+          else if (!strcmp (rgba_order, "vbgr"))
+            cairo_font_options_set_subpixel_order (font_options,
+                                                   CAIRO_SUBPIXEL_ORDER_VBGR);
+        }
+      g_variant_unref (val);
+    }
+}
+#endif /* HAVE_PGTK */
+
 /* Callback called when something changed in GSettings.  */
 
 static void
@@ -273,6 +378,23 @@ something_changed_gsettingsCB (GSettings *settings,
         }
     }
 #endif /* USE_CAIRO || HAVE_XFT */
+#ifdef HAVE_PGTK
+  else if (!strcmp (key, GSETTINGS_FONT_ANTIALIASING))
+    {
+      apply_gsettings_font_antialias (settings);
+      store_font_options_changed ();
+    }
+  else if (!strcmp (key, GSETTINGS_FONT_HINTING))
+    {
+      apply_gsettings_font_hinting (settings);
+      store_font_options_changed ();
+    }
+  else if (!strcmp (key, GSETTINGS_FONT_RGBA_ORDER))
+    {
+      apply_gsettings_font_rgba_order (settings);
+      store_font_options_changed ();
+    }
+#endif /* HAVE_PGTK */
 }
 
 #endif /* HAVE_GSETTINGS */
@@ -900,6 +1022,16 @@ init_gsettings (void)
         dupstring (&current_font, g_variant_get_string (val, NULL));
       g_variant_unref (val);
     }
+
+  /* Only use the gsettings font entries for the Cairo backend
+     running on PGTK.  */
+#ifdef HAVE_PGTK
+  font_options = cairo_font_options_create ();
+  apply_gsettings_font_antialias (gsettings_client);
+  apply_gsettings_font_hinting (gsettings_client);
+  apply_gsettings_font_rgba_order (gsettings_client);
+#endif /* HAVE_PGTK */
+
 #endif /* USE_CAIRO || HAVE_XFT */
 
 #endif /* HAVE_GSETTINGS */
@@ -1021,6 +1153,17 @@ xsettings_get_system_normal_font (void)
 }
 #endif
 
+#ifdef HAVE_PGTK
+/* Return the cairo font options, updated from the gsettings font
+   config entries.  The caller should call cairo_font_options_destroy
+   on the result.  */
+cairo_font_options_t *
+xsettings_get_font_options (void)
+{
+  return cairo_font_options_copy (font_options);
+}
+#endif
+
 DEFUN ("font-get-system-normal-font", Ffont_get_system_normal_font,
        Sfont_get_system_normal_font,
        0, 0, 0,
@@ -1073,6 +1216,10 @@ syms_of_xsettings (void)
   gconf_client = NULL;
   PDUMPER_IGNORE (gconf_client);
 #endif
+#ifdef HAVE_PGTK
+  font_options = NULL;
+  PDUMPER_IGNORE (font_options);
+#endif
 
   DEFSYM (Qmonospace_font_name, "monospace-font-name");
   DEFSYM (Qfont_name, "font-name");
diff --git a/src/xsettings.h b/src/xsettings.h
index ccaa36489d0..5e5df37062b 100644
--- a/src/xsettings.h
+++ b/src/xsettings.h
@@ -23,6 +23,8 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #ifndef HAVE_PGTK
 #include "dispextern.h"
 #include <X11/Xlib.h>
+#else
+#include <cairo.h>
 #endif
 
 struct x_display_info;
@@ -41,5 +43,8 @@ extern const char *xsettings_get_system_font (void);
 extern const char *xsettings_get_system_normal_font (void);
 #endif
 
+#ifdef HAVE_PGTK
+extern cairo_font_options_t *xsettings_get_font_options (void);
+#endif
 
 #endif /* XSETTINGS_H */