Track changes in FontMaps using a serial

This adds the pango_font_map_get_serial method that lets you see
if a fontmap has changes since the last check. It adds implementations
to all current fontmaps.

https://bugzilla.gnome.org/show_bug.cgi?id=340066

15 files changed, 156 insertions, 7 deletions

diff --git a/docs/pango-sections.txt b/docs/pango-sections.txt
index 5f6ba73c..bce6cf48 100644
--- a/docs/pango-sections.txt
+++ b/docs/pango-sections.txt
@@ -259,6 +259,7 @@ pango_font_map_load_font
 pango_font_map_load_fontset
 pango_font_map_list_families
 pango_font_map_get_shape_engine_type
+pango_font_map_get_serial
 <SUBSECTION>
 PangoFontset
 PANGO_TYPE_FONTSET
diff --git a/docs/tmpl/fonts.sgml b/docs/tmpl/fonts.sgml
index 5e7402d7..ef83dd0f 100644
--- a/docs/tmpl/fonts.sgml
+++ b/docs/tmpl/fonts.sgml
@@ -826,11 +826,13 @@ a particular #PangoFontMap implementation.
             pango_font_map_load_font().
 @list_families: A function to list available font families. See
                 pango_font_map_list_families().
-@load_fontset: a function to load a fontset with a given given description
+@load_fontset: a function to load a fontset with a given description
              suitable for a particular language. See
 	     pango_font_map_load_fontset().
 @shape_engine_type: the type of rendering-system-dependent engines that
              can handle fonts of this fonts loaded with this fontmap.
+@get_serial: a function to get the serial number of the fontmap.
+	     See pango_font_map_get_serial().
 
 <!-- ##### MACRO PANGO_FONT_MAP_CLASS ##### -->
 <para>
@@ -907,6 +909,15 @@ Returns the type of a #PangoFontMap.
 @Returns: 
 
 
+<!-- ##### FUNCTION pango_font_map_get_serial ##### -->
+<para>
+
+</para>
+
+@fontmap: 
+@Returns: 
+
+
 <!-- ##### STRUCT PangoFontset ##### -->
 <para>
 A #PangoFontset represents a set of #PangoFont to use
diff --git a/pango/pango-fontmap.c b/pango/pango-fontmap.c
index 6e90ada1..e1d6bb0f 100644
--- a/pango/pango-fontmap.c
+++ b/pango/pango-fontmap.c
@@ -284,3 +284,33 @@ pango_font_map_get_shape_engine_type (PangoFontMap *fontmap)
   return PANGO_FONT_MAP_GET_CLASS (fontmap)->shape_engine_type;
 }
 
+/**
+ * pango_font_map_get_serial:
+ * @fontmap: a #PangoFontMap
+ *
+ * Returns the current serial number of @fontmap.  The serial number is
+ * initialized to an small number larger than zero when a new fontmap
+ * is created and is increased whenever the fontmap is changed. It may
+ * wrap, but will never have the value 0. Since it can wrap, never compare
+ * it with "less than", always use "not equals".
+ *
+ * The fontmap can only be changed using backend-specific API, like changing
+ * fontmap resolution.
+ *
+ * This can be used to automatically detect changes to a #PangoFontMap, like
+ * in #PangoContext.
+ *
+ * Return value: The current serial number of @fontmap.
+ *
+ * Since: 1.32.4
+ **/
+guint
+pango_font_map_get_serial (PangoFontMap *fontmap)
+{
+  g_return_val_if_fail (PANGO_IS_FONT_MAP (fontmap), 0);
+
+  if (PANGO_FONT_MAP_GET_CLASS (fontmap)->get_serial)
+    return PANGO_FONT_MAP_GET_CLASS (fontmap)->get_serial (fontmap);
+  else
+    return 1;
+}
diff --git a/pango/pango-fontmap.h b/pango/pango-fontmap.h
index 602ec9fe..0f028baa 100644
--- a/pango/pango-fontmap.h
+++ b/pango/pango-fontmap.h
@@ -45,6 +45,7 @@ PangoFontset *pango_font_map_load_fontset  (PangoFontMap                 *fontma
 void          pango_font_map_list_families (PangoFontMap                 *fontmap,
 					    PangoFontFamily            ***families,
 					    int                          *n_families);
+guint         pango_font_map_get_serial    (PangoFontMap                 *fontmap);
 
 #ifdef PANGO_ENABLE_BACKEND
 
@@ -76,7 +77,9 @@ struct _PangoFontMapClass
 				  const PangoFontDescription *desc,
 				  PangoLanguage              *language);
 
-  const char *shape_engine_type;
+  const char     *shape_engine_type;
+
+  guint         (*get_serial)    (PangoFontMap               *fontmap);
 
   /*< private >*/
 
@@ -84,10 +87,9 @@ struct _PangoFontMapClass
   void (*_pango_reserved1) (void);
   void (*_pango_reserved2) (void);
   void (*_pango_reserved3) (void);
-  void (*_pango_reserved4) (void);
 };
 
-const char   *pango_font_map_get_shape_engine_type (PangoFontMap *fontmap);
+G_CONST_RETURN char   *pango_font_map_get_shape_engine_type (PangoFontMap *fontmap);
 
 #endif /* PANGO_ENABLE_BACKEND */
 
diff --git a/pango/pango.def b/pango/pango.def
index ba1289ce..66e70d3b 100644
--- a/pango/pango.def
+++ b/pango/pango.def
@@ -151,6 +151,7 @@ EXPORTS
 	pango_font_get_type
 	pango_font_map_create_context
 	pango_font_map_get_shape_engine_type
+	pango_font_map_get_serial
 	pango_font_map_get_type
 	pango_font_map_list_families
 	pango_font_map_load_font
diff --git a/pango/pangocairo-coretext.h b/pango/pangocairo-coretext.h
index 4310f45f..31faf9be 100644
--- a/pango/pangocairo-coretext.h
+++ b/pango/pangocairo-coretext.h
@@ -39,6 +39,7 @@ struct _PangoCairoCoreTextFontMap
 {
   PangoCoreTextFontMap parent_instance;
 
+  guint serial;
   gdouble dpi;
 };
 
diff --git a/pango/pangocairo-coretextfontmap.c b/pango/pangocairo-coretextfontmap.c
index cd1f3f25..5561358b 100644
--- a/pango/pangocairo-coretextfontmap.c
+++ b/pango/pangocairo-coretextfontmap.c
@@ -34,12 +34,23 @@ struct _PangoCairoCoreTextFontMapClass
   PangoCoreTextFontMapClass parent_class;
 };
 
+static guint
+pango_cairo_core_text_font_map_get_serial (PangoFontMap *fontmap)
+{
+  PangoCairoCoreTextFontMap *cafontmap = PANGO_CAIRO_CORE_TEXT_FONT_MAP (fontmap);
+
+  return cafontmap->serial;
+}
+
 static void
 pango_cairo_core_text_font_map_set_resolution (PangoCairoFontMap *cfontmap,
                                                double             dpi)
 {
   PangoCairoCoreTextFontMap *cafontmap = PANGO_CAIRO_CORE_TEXT_FONT_MAP (cfontmap);
 
+  cafontmap->serial++;
+  if (cafontmap->serial == 0)
+    cafontmap->serial++;
   cafontmap->dpi = dpi;
 }
 
@@ -144,10 +155,13 @@ static void
 pango_cairo_core_text_font_map_class_init (PangoCairoCoreTextFontMapClass *class)
 {
   PangoCoreTextFontMapClass *ctfontmapclass = (PangoCoreTextFontMapClass *)class;
+  PangoFontMapClass *fontmap_class = PANGO_FONT_MAP_CLASS (class);
   GObjectClass *object_class = (GObjectClass *)class;
 
   object_class->finalize = pango_cairo_core_text_font_map_finalize;
 
+  fontmap_class->get_serial = pango_cairo_core_text_font_map_get_serial;
+
   ctfontmapclass->get_resolution = pango_cairo_core_text_font_map_get_resolution_core_text;
   ctfontmapclass->create_font = pango_cairo_core_text_font_map_create_font;
   ctfontmapclass->context_key_get = pango_cairo_core_text_font_map_context_key_get;
@@ -160,5 +174,6 @@ pango_cairo_core_text_font_map_class_init (PangoCairoCoreTextFontMapClass *class
 static void
 pango_cairo_core_text_font_map_init (PangoCairoCoreTextFontMap *cafontmap)
 {
+  cafontmap->serial = 1;
   cafontmap->dpi = 72.;
 }
diff --git a/pango/pangocairo-fc.h b/pango/pangocairo-fc.h
index ea4fccbc..8873d5b3 100644
--- a/pango/pangocairo-fc.h
+++ b/pango/pangocairo-fc.h
@@ -37,6 +37,7 @@ struct _PangoCairoFcFontMap
 {
   PangoFcFontMap parent_instance;
 
+  guint serial;
   double dpi;
 
   FT_Library library;
diff --git a/pango/pangocairo-fcfontmap.c b/pango/pangocairo-fcfontmap.c
index c2b410ee..69fe4929 100644
--- a/pango/pangocairo-fcfontmap.c
+++ b/pango/pangocairo-fcfontmap.c
@@ -33,15 +33,29 @@ struct _PangoCairoFcFontMapClass
   PangoFcFontMapClass parent_class;
 };
 
+static guint
+pango_cairo_fc_font_map_get_serial (PangoFontMap *fontmap)
+{
+  PangoCairoFcFontMap *cffontmap = (PangoCairoFcFontMap *) (fontmap);
+
+  return cffontmap->serial;
+}
+
 static void
 pango_cairo_fc_font_map_set_resolution (PangoCairoFontMap *cfontmap,
 					double             dpi)
 {
   PangoCairoFcFontMap *cffontmap = (PangoCairoFcFontMap *) (cfontmap);
 
-  cffontmap->dpi = dpi;
+  if (dpi != cffontmap->dpi)
+    {
+      cffontmap->serial++;
+      if (cffontmap->serial == 0)
+	cffontmap->serial++;
+      cffontmap->dpi = dpi;
 
-  pango_fc_font_map_cache_clear ((PangoFcFontMap *) (cfontmap));
+      pango_fc_font_map_cache_clear ((PangoFcFontMap *) (cfontmap));
+    }
 }
 
 static double
@@ -162,10 +176,13 @@ static void
 pango_cairo_fc_font_map_class_init (PangoCairoFcFontMapClass *class)
 {
   GObjectClass *gobject_class = G_OBJECT_CLASS (class);
+  PangoFontMapClass *fontmap_class = PANGO_FONT_MAP_CLASS (class);
   PangoFcFontMapClass *fcfontmap_class = PANGO_FC_FONT_MAP_CLASS (class);
 
   gobject_class->finalize  = pango_cairo_fc_font_map_finalize;
 
+  fontmap_class->get_serial = pango_cairo_fc_font_map_get_serial;
+
   fcfontmap_class->fontset_key_substitute = pango_cairo_fc_font_map_fontset_key_substitute;
   fcfontmap_class->get_resolution = pango_cairo_fc_font_map_get_resolution_fc;
 
@@ -188,6 +205,7 @@ pango_cairo_fc_font_map_init (PangoCairoFcFontMap *cffontmap)
   if (error != FT_Err_Ok)
     g_critical ("pango_cairo_font_map_init: Could not initialize freetype");
 
+  cffontmap->serial = 1;
   cffontmap->dpi   = 96.0;
 }
 
diff --git a/pango/pangocairo-win32.h b/pango/pangocairo-win32.h
index 7a71c0a2..33d0ee45 100644
--- a/pango/pangocairo-win32.h
+++ b/pango/pangocairo-win32.h
@@ -38,6 +38,7 @@ struct _PangoCairoWin32FontMap
 {
   PangoWin32FontMap parent_instance;
 
+  guint serial;
   double dpi;
 };
 
diff --git a/pango/pangocairo-win32fontmap.c b/pango/pangocairo-win32fontmap.c
index c5ec6cd2..cd4e12ee 100644
--- a/pango/pangocairo-win32fontmap.c
+++ b/pango/pangocairo-win32fontmap.c
@@ -33,12 +33,23 @@ struct _PangoCairoWin32FontMapClass
   PangoWin32FontMapClass parent_class;
 };
 
+static guint
+pango_cairo_win32_font_map_get_serial (PangoFontMap *fontmap)
+{
+  PangoCairoWin32FontMap *cwfontmap = PANGO_CAIRO_WIN32_FONT_MAP (fontmap);
+
+  return cwfontmap->serial;
+}
+
 static void
 pango_cairo_win32_font_map_set_resolution (PangoCairoFontMap *cfontmap,
 					   double             dpi)
 {
   PangoCairoWin32FontMap *cwfontmap = PANGO_CAIRO_WIN32_FONT_MAP (cfontmap);
 
+  cwfontmap->serial++;
+  if (cwfontmap->serial == 0)
+    cwfontmap->serial++;
   cwfontmap->dpi = dpi;
 }
 
@@ -89,14 +100,17 @@ static void
 pango_cairo_win32_font_map_class_init (PangoCairoWin32FontMapClass *class)
 {
   GObjectClass *gobject_class = G_OBJECT_CLASS (class);
+  PangoFontMapClass *fontmap_class = PANGO_FONT_MAP_CLASS (class);
   PangoWin32FontMapClass *win32fontmap_class = PANGO_WIN32_FONT_MAP_CLASS (class);
 
   gobject_class->finalize  = pango_cairo_win32_font_map_finalize;
+  fontmap_class->get_serial = pango_cairo_win32_font_map_get_serial;
   win32fontmap_class->find_font = pango_cairo_win32_font_map_find_font;
 }
 
 static void
 pango_cairo_win32_font_map_init (PangoCairoWin32FontMap *cwfontmap)
 {
+  cwfontmap->serial = 1;
   cwfontmap->dpi = GetDeviceCaps (pango_win32_get_dc (), LOGPIXELSY);
 }
diff --git a/pango/pangocoretext-fontmap.c b/pango/pangocoretext-fontmap.c
index a8a9b518..7993d59e 100644
--- a/pango/pangocoretext-fontmap.c
+++ b/pango/pangocoretext-fontmap.c
@@ -1191,6 +1191,14 @@ get_first_font (PangoFontset *fontset G_GNUC_UNUSED,
   return TRUE;
 }
 
+static guint
+pango_core_text_font_map_get_serial (PangoFontMap *fontmap)
+{
+  PangoCoreTextFontMap *ctfontmap = PANGO_CORE_TEXT_FONT_MAP (fontmap);
+
+  return ctfontmap->serial;
+}
+
 static PangoFont *
 pango_core_text_font_map_load_font (PangoFontMap               *fontmap,
                                     PangoContext               *context,
@@ -1370,6 +1378,7 @@ pango_core_text_font_map_init (PangoCoreTextFontMap *ctfontmap)
   CFArrayRef ctfaces;
   CFIndex i, count;
 
+  ctfontmap->serial = 1;
   ctfontmap->families = g_hash_table_new_full (g_str_hash, g_str_equal,
                                                g_free, g_object_unref);
 
@@ -1461,6 +1470,7 @@ pango_core_text_font_map_class_init (PangoCoreTextFontMapClass *class)
   fontmap_class->list_families = pango_core_text_font_map_list_families;
   fontmap_class->load_fontset = pango_core_text_font_map_load_fontset;
   fontmap_class->shape_engine_type = PANGO_RENDER_TYPE_CORE_TEXT;
+  fontmap_class->get_serial = pango_core_text_font_map_get_serial;
 }
 
 /*
diff --git a/pango/pangocoretext-private.h b/pango/pangocoretext-private.h
index 3e0dafdc..8076eaea 100644
--- a/pango/pangocoretext-private.h
+++ b/pango/pangocoretext-private.h
@@ -51,6 +51,7 @@ struct _PangoCoreTextFontMap
 {
   PangoFontMap parent_instance;
 
+  guint serial;
   GHashTable *fontset_hash;
   GHashTable *font_hash;
 
diff --git a/pango/pangoft2-fontmap.c b/pango/pangoft2-fontmap.c
index 662b8ad9..996bbb1f 100644
--- a/pango/pangoft2-fontmap.c
+++ b/pango/pangoft2-fontmap.c
@@ -43,6 +43,7 @@ struct _PangoFT2FontMap
 
   FT_Library library;
 
+  guint serial;
   double dpi_x;
   double dpi_y;
 
@@ -66,6 +67,7 @@ static PangoFcFont * pango_ft2_font_map_new_font            (PangoFcFontMap
 							     FcPattern            *pattern);
 static double        pango_ft2_font_map_get_resolution      (PangoFcFontMap       *fcfontmap,
 							     PangoContext         *context);
+static guint         pango_ft2_font_map_get_serial          (PangoFontMap         *fontmap);
 
 static PangoFT2FontMap *pango_ft2_global_fontmap = NULL; /* MT-safe */
 
@@ -75,9 +77,11 @@ static void
 pango_ft2_font_map_class_init (PangoFT2FontMapClass *class)
 {
   GObjectClass *gobject_class = G_OBJECT_CLASS (class);
+  PangoFontMapClass *fontmap_class = PANGO_FONT_MAP_CLASS (class);
   PangoFcFontMapClass *fcfontmap_class = PANGO_FC_FONT_MAP_CLASS (class);
 
   gobject_class->finalize = pango_ft2_font_map_finalize;
+  fontmap_class->get_serial = pango_ft2_font_map_get_serial;
   fcfontmap_class->default_substitute = _pango_ft2_font_map_default_substitute;
   fcfontmap_class->new_font = pango_ft2_font_map_new_font;
   fcfontmap_class->get_resolution = pango_ft2_font_map_get_resolution;
@@ -86,6 +90,7 @@ pango_ft2_font_map_class_init (PangoFT2FontMapClass *class)
 static void
 pango_ft2_font_map_init (PangoFT2FontMap *fontmap)
 {
+  fontmap->serial = 1;
   fontmap->library = NULL;
   fontmap->dpi_x   = 72.0;
   fontmap->dpi_y   = 72.0;
@@ -139,6 +144,14 @@ pango_ft2_font_map_new (void)
   return (PangoFontMap *)ft2fontmap;
 }
 
+static guint
+pango_ft2_font_map_get_serial (PangoFontMap *fontmap)
+{
+  PangoFT2FontMap *ft2fontmap = PANGO_FT2_FONT_MAP (fontmap);
+
+  return ft2fontmap->serial;
+}
+
 /**
  * pango_ft2_font_map_set_default_substitute:
  * @fontmap: a #PangoFT2FontMap
@@ -160,6 +173,10 @@ pango_ft2_font_map_set_default_substitute (PangoFT2FontMap        *fontmap,
 					   gpointer                data,
 					   GDestroyNotify          notify)
 {
+  fontmap->serial++;
+  if (fontmap->serial == 0)
+    fontmap->serial++;
+
   if (fontmap->substitute_destroy)
     fontmap->substitute_destroy (fontmap->substitute_data);
 
@@ -185,6 +202,9 @@ pango_ft2_font_map_set_default_substitute (PangoFT2FontMap        *fontmap,
 void
 pango_ft2_font_map_substitute_changed (PangoFT2FontMap *fontmap)
 {
+  fontmap->serial++;
+  if (fontmap->serial == 0)
+    fontmap->serial++;
   pango_fc_font_map_cache_clear (PANGO_FC_FONT_MAP (fontmap));
 }
 
diff --git a/pango/pangoxft-fontmap.c b/pango/pangoxft-fontmap.c
index 9d210b50..aa891c54 100644
--- a/pango/pangoxft-fontmap.c
+++ b/pango/pangoxft-fontmap.c
@@ -41,6 +41,8 @@ struct _PangoXftFontMap
 {
   PangoFcFontMap parent_instance;
 
+  guint serial;
+
   Display *display;
   int screen;
 
@@ -59,6 +61,7 @@ struct _PangoXftFontMapClass
   PangoFcFontMapClass parent_class;
 };
 
+static guint         pango_xft_font_map_get_serial         (PangoFontMap         *fontmap);
 static void          pango_xft_font_map_default_substitute (PangoFcFontMap       *fcfontmap,
 							    FcPattern            *pattern);
 static PangoFcFont * pango_xft_font_map_new_font           (PangoFcFontMap       *fcfontmap,
@@ -74,16 +77,21 @@ static void
 pango_xft_font_map_class_init (PangoXftFontMapClass *class)
 {
   GObjectClass *gobject_class = G_OBJECT_CLASS (class);
+  PangoFontMapClass *fontmap_class = PANGO_FONT_MAP_CLASS (class);
   PangoFcFontMapClass *fcfontmap_class = PANGO_FC_FONT_MAP_CLASS (class);
 
   gobject_class->finalize  = pango_xft_font_map_finalize;
+
+  fontmap_class->get_serial = pango_xft_font_map_get_serial;
+
   fcfontmap_class->default_substitute = pango_xft_font_map_default_substitute;
   fcfontmap_class->new_font = pango_xft_font_map_new_font;
 }
 
 static void
-pango_xft_font_map_init (PangoXftFontMap *xftfontmap G_GNUC_UNUSED)
+pango_xft_font_map_init (PangoXftFontMap *xftfontmap)
 {
+  xftfontmap->serial = 1;
 }
 
 static void
@@ -105,6 +113,14 @@ pango_xft_font_map_finalize (GObject *object)
 }
 
 
+static guint
+pango_xft_font_map_get_serial (PangoFontMap *fontmap)
+{
+  PangoXftFontMap *xftfontmap = PANGO_XFT_FONT_MAP (fontmap);
+
+  return xftfontmap->serial;
+}
+
 static PangoFontMap *
 pango_xft_find_font_map (Display *display,
 			 int      screen)
@@ -283,6 +299,10 @@ pango_xft_set_default_substitute (Display                *display,
 {
   PangoXftFontMap *xftfontmap = (PangoXftFontMap *)pango_xft_get_font_map (display, screen);
 
+  xftfontmap->serial++;
+  if (xftfontmap->serial == 0)
+    xftfontmap->serial++;
+
   if (xftfontmap->substitute_destroy)
     xftfontmap->substitute_destroy (xftfontmap->substitute_data);
 
@@ -312,6 +332,9 @@ pango_xft_substitute_changed (Display *display,
 {
   PangoXftFontMap *xftfontmap = (PangoXftFontMap *)pango_xft_get_font_map (display, screen);
 
+  xftfontmap->serial++;
+  if (xftfontmap->serial == 0)
+    xftfontmap->serial++;
   pango_fc_font_map_cache_clear (PANGO_FC_FONT_MAP (xftfontmap));
 }