[gtk/wip/fanc999/gtk-3-24-meson-msvc: 29/297] GDK W32: Always set gtk-font-name to the active UI font. Fixes #1484

[Chun-wei Fan <fanchunwei src gnome org>]

commit 48a4362782b07201b96081f62848266f59f42cb0
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Thu Nov 29 23:19:38 2018 +0100

    GDK W32: Always set gtk-font-name to the active UI font. Fixes #1484
    
    This makes apps use "Segoe UI 9" by default instead of whatever matches "Sans 10".
    It also cleans up the code and uses some new pango API while at it.
    
    This was previously disabled in 9e686d1fb5cb20 because it led to a poor glyph coverage
    on certain versions of Windows which don't default to "Segoe UI 9" (Chinese, Korean, ..)
    because the font fallback list was missing in pango.
    
    This is about to get fixed in https://gitlab.gnome.org/GNOME/pango/merge_requests/34
    so enable it again when we detect a new enough pango version.

 gdk/win32/gdkproperty-win32.c | 94 +++++++++++++++++++++----------------------
 1 file changed, 45 insertions(+), 49 deletions(-)
---
diff --git a/gdk/win32/gdkproperty-win32.c b/gdk/win32/gdkproperty-win32.c
index 7c780428c0..5891debeea 100644
--- a/gdk/win32/gdkproperty-win32.c
+++ b/gdk/win32/gdkproperty-win32.c
@@ -27,6 +27,7 @@
 #include <string.h>
 #include <stdlib.h>
 #include <glib/gprintf.h>
+#include <pango/pangowin32.h>
 
 #include "gdkscreen.h"
 #include "gdkproperty.h"
@@ -239,6 +240,32 @@ _gdk_win32_window_delete_property (GdkWindow *window,
     }
 }
 
+static gchar*
+_get_system_font_name (HDC hdc)
+{
+  NONCLIENTMETRICSW ncm;
+  PangoFontDescription *font_desc;
+  gchar *result, *font_desc_string;
+  int logpixelsy;
+  gint font_size;
+
+  ncm.cbSize = sizeof(NONCLIENTMETRICSW);
+  if (!SystemParametersInfoW (SPI_GETNONCLIENTMETRICS, ncm.cbSize, &ncm, 0))
+    return NULL;
+
+  logpixelsy = GetDeviceCaps (hdc, LOGPIXELSY);
+  font_desc = pango_win32_font_description_from_logfontw (&ncm.lfMessageFont);
+  font_desc_string = pango_font_description_to_string (font_desc);
+  pango_font_description_free (font_desc);
+
+  /* https://docs.microsoft.com/en-us/windows/desktop/api/wingdi/ns-wingdi-taglogfonta */
+  font_size = -MulDiv (ncm.lfMessageFont.lfHeight, 72, logpixelsy);
+  result = g_strdup_printf ("%s %d", font_desc_string, font_size);
+  g_free (font_desc_string);
+
+  return result;
+}
+
 /*
   For reference, from gdk/x11/gdksettings.c:
 
@@ -371,58 +398,27 @@ _gdk_win32_screen_get_setting (GdkScreen   *screen,
     }
   else if (strcmp ("gtk-font-name", name) == 0)
     {
-      NONCLIENTMETRICS ncm;
-      CPINFOEX cpinfoex_default, cpinfoex_curr_thread;
-      OSVERSIONINFO info;
-      BOOL result_default, result_curr_thread;
-
-      info.dwOSVersionInfoSize = sizeof (OSVERSIONINFO);
-
-      /* TODO: Fallback to using Pango on Windows 8 and later,
-       * as this method of handling gtk-font-name does not work
-       * well there, where garbled text will be displayed for texts
-       * that are not supported by the default menu font.  Look for
-       * whether there is a better solution for this on Windows 8 and
-       * later
-       */
-      if (!GetVersionEx (&info) ||
-          info.dwMajorVersion > 6 ||
-          (info.dwMajorVersion == 6 && info.dwMinorVersion >= 2))
-        return FALSE;
-
-      /* check whether the system default ANSI codepage matches the
-       * ANSI code page of the running thread.  If so, continue, otherwise
-       * fall back to using Pango to handle gtk-font-name
-       */
-      result_default = GetCPInfoEx (CP_ACP, 0, &cpinfoex_default);
-      result_curr_thread = GetCPInfoEx (CP_THREAD_ACP, 0, &cpinfoex_curr_thread);
-
-      if (!result_default ||
-          !result_curr_thread ||
-          cpinfoex_default.CodePage != cpinfoex_curr_thread.CodePage)
-        return FALSE;
-
-      ncm.cbSize = sizeof(NONCLIENTMETRICS);
-      if (SystemParametersInfo (SPI_GETNONCLIENTMETRICS, ncm.cbSize, &ncm, FALSE))
+      gchar *font_name = _get_system_font_name (_gdk_display_hdc);
+
+      if (font_name)
         {
-          /* Pango finally uses GetDeviceCaps to scale, we use simple
-          * approximation here.
-          */
-          int nHeight = (0 > ncm.lfMenuFont.lfHeight ? - 3 * ncm.lfMenuFont.lfHeight / 4 : 10);
-          if (OUT_STRING_PRECIS == ncm.lfMenuFont.lfOutPrecision)
-            GDK_NOTE(MISC, g_print("gdk_screen_get_setting(%s) : ignoring bitmap font '%s'\n",
-                                   name, ncm.lfMenuFont.lfFaceName));
-          else if (ncm.lfMenuFont.lfFaceName && strlen(ncm.lfMenuFont.lfFaceName) > 0 &&
-                   /* Avoid issues like those described in bug #135098 */
-                   g_utf8_validate (ncm.lfMenuFont.lfFaceName, -1, NULL))
+          /* The pango font fallback list got fixed during 1.43, before that
+           * using anything but "Segoe UI" would lead to a poor glyph coverage */
+          if (pango_version_check (1, 43, 0) != NULL &&
+              g_ascii_strncasecmp (font_name, "Segoe UI", strlen ("Segoe UI")) != 0)
             {
-              char *s = g_strdup_printf ("%s %d", ncm.lfMenuFont.lfFaceName, nHeight);
-              GDK_NOTE(MISC, g_print("gdk_screen_get_setting(%s) : %s\n", name, s));
-              g_value_set_string (value, s);
-
-              g_free(s);
-              return TRUE;
+              g_free (font_name);
+              return FALSE;
             }
+
+          GDK_NOTE(MISC, g_print("gdk_screen_get_setting(\"%s\") : %s\n", name, font_name));
+          g_value_take_string (value, font_name);
+          return TRUE;
+        }
+      else
+        {
+          g_warning ("gdk_screen_get_setting: Detecting the system font failed");
+          return FALSE;
         }
     }
   else if (strcmp ("gtk-im-module", name) == 0)