[pango: 1/2] pangowin32: Read the font fallback list from the registry instead of hardcoding it for some fonts.

[Emmanuele Bassi <ebassi src gnome org>]

commit f523c25c12cd19c59fbc3db4a4fe08bae5307802
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Mon Dec 3 23:12:27 2018 +0100

    pangowin32: Read the font fallback list from the registry instead of hardcoding it for some fonts.
    
    We only had a fallback list for "Segoe UI" which is the default Windows font, but not on
    Chinese or Korean Windows version which use "JhengHei UI" etc. and fall back to "Segoe UI".
    
    Instead of hardcoding the fallbacks in the alias list read them from the registry
    (HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\FontLink\SystemLink)
    
    This should allow us to use the default Windows font by default in gtk+ on Win8+,
    see https://gitlab.gnome.org/GNOME/gtk/merge_requests/436 for details.
    
    This also bumps the required Windows version to Vista for RegGetValueW().

 pango/pangowin32-fontmap.c | 105 ++++++++++++++++++++++++++++++++++++++++++++-
 pango/pangowin32.h         |   2 +-
 2 files changed, 104 insertions(+), 3 deletions(-)
---
diff --git a/pango/pangowin32-fontmap.c b/pango/pangowin32-fontmap.c
index 12fa4f26..0cf8f5a0 100644
--- a/pango/pangowin32-fontmap.c
+++ b/pango/pangowin32-fontmap.c
@@ -449,8 +449,6 @@ handle_alias_line (GString    *line_buffer,
 
 static const char * const builtin_aliases[] = {
   "courier = \"courier new\"",
-  "\"segoe ui\" = \"segoe ui,meiryo,malgun gothic,microsoft jhenghei,microsoft yahei,gisha,leelawadee,arial 
unicode ms,browallia new,mingliu,simhei,gulimche,ms gothic,sylfaen,kartika,latha,mangal,raavi\"",
-  "tahoma = \"tahoma,arial unicode ms,lucida sans unicode,browallia new,mingliu,simhei,gulimche,ms 
gothic,sylfaen,kartika,latha,mangal,raavi\"",
   /* It sucks to use the same GulimChe, MS Gothic, Sylfaen, Kartika,
    * Latha, Mangal and Raavi fonts for all three of sans, serif and
    * mono, but it isn't like there would be much choice. For most
@@ -490,6 +488,108 @@ read_builtin_aliases (GHashTable *ht_aliases)
 
   g_string_free (line_buffer, TRUE);
 }
+
+#define MAX_VALUE_NAME 16383
+
+static void
+read_windows_fallbacks (GHashTable *ht_aliases)
+{
+  DWORD value_index;
+  HKEY hkey;
+  LSTATUS status;
+  GString *line_buffer;
+
+  /* https://docs.microsoft.com/en-us/globalization/input/font-technology */
+  status = RegOpenKeyExW (HKEY_LOCAL_MACHINE,
+                          L"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\FontLink\\SystemLink",
+                          0,
+                          KEY_READ,
+                          &hkey);
+  if (status != ERROR_SUCCESS)
+    return;
+
+  line_buffer = g_string_new (NULL);
+  status = ERROR_SUCCESS;
+  for (value_index = 0; status != ERROR_NO_MORE_ITEMS; value_index++)
+    {
+      wchar_t name[MAX_VALUE_NAME];
+      DWORD name_length = MAX_VALUE_NAME, value_length = 0;
+      char *errstring = NULL;
+      gchar *utf8_name;
+      wchar_t *value_data, *entry;
+      size_t entry_len;
+
+      status = RegEnumValueW (hkey, value_index, name, &name_length,
+                              NULL, NULL, NULL, NULL);
+
+      if (status != ERROR_SUCCESS)
+        continue;
+
+      utf8_name = g_utf16_to_utf8 (name, -1, NULL, NULL, NULL);
+      if (utf8_name == NULL)
+        continue;
+      g_string_truncate (line_buffer, 0);
+      g_string_append_printf (line_buffer,
+                              "\"%s\" = \"%s",
+                              utf8_name,
+                              utf8_name);
+      g_free (utf8_name);
+
+      status = RegGetValueW (hkey, NULL, name, RRF_RT_REG_MULTI_SZ,
+                             NULL, NULL, &value_length);
+      if (status != ERROR_SUCCESS)
+        continue;
+
+      value_data = g_malloc (value_length);
+      status = RegGetValueW (hkey, NULL, name, RRF_RT_REG_MULTI_SZ, NULL,
+                             value_data, &value_length);
+      if (status != ERROR_SUCCESS)
+        {
+          g_free (value_data);
+          continue;
+        }
+
+      entry = value_data;
+      entry_len = wcslen (entry);
+      while (entry_len > 0)
+        {
+          wchar_t *comma;
+          gchar *entry_utf8;
+
+          comma = wcsstr (entry, L",");
+          /* The value after the first comma, as long as it isn't followed
+           * by another comma with a font scale */
+          if (comma && wcsstr (comma + 1, L",") == NULL)
+            {
+              g_string_append (line_buffer, ",");
+              entry_utf8 = g_utf16_to_utf8 (comma + 1, -1, NULL, NULL, NULL);
+              if (entry_utf8 != NULL)
+                {
+                  g_string_append (line_buffer, entry_utf8);
+                  g_free (entry_utf8);
+                }
+            }
+
+          entry += entry_len + 1;
+          entry_len = wcslen (entry);
+        }
+      g_free (value_data);
+      g_string_append (line_buffer, "\"");
+
+      handle_alias_line (line_buffer, &errstring, ht_aliases);
+      if (errstring != NULL)
+        {
+          g_warning ("error in windows fallback: %s (%s)\n",
+                     errstring, line_buffer->str);
+          g_free (errstring);
+          errstring = NULL;
+        }
+    }
+
+  RegCloseKey (hkey);
+  g_string_free (line_buffer, TRUE);
+}
+
 #endif
 
 
@@ -502,6 +602,7 @@ load_aliases (void)
                                                   NULL);
 
 #ifdef HAVE_CAIRO_WIN32
+  read_windows_fallbacks (ht_aliases);
   read_builtin_aliases (ht_aliases);
 #endif
 
diff --git a/pango/pangowin32.h b/pango/pangowin32.h
index c9b440cb..99a738c9 100644
--- a/pango/pangowin32.h
+++ b/pango/pangowin32.h
@@ -32,7 +32,7 @@ G_BEGIN_DECLS
 
 #define STRICT
 #ifndef _WIN32_WINNT
-#define _WIN32_WINNT 0x0501    /* To get ClearType-related macros */
+#define _WIN32_WINNT 0x0600    /* To get ClearType-related macros */
 #endif
 #include <windows.h>
 #undef STRICT