win32: Use GPrivate-managed display device context

The document of [CreateDCA][1] says:

> If lpszDriver or lpszDevice is DISPLAY, the thread that calls
> CreateDC owns the HDC that is created. When this thread is
> destroyed, the HDC is no longer valid. Thus, if you create the HDC
> and pass it to another thread, then exit the first thread,
> the second thread will not be able to use the HDC.

So this change introduces GPrivate to fix potential problem.

This also fixes the problem caused by accessing the global
variable DC directly, which makes some early call to Pango functions
fail.

(e.g., failure of calling pango_win32_font_description_from_logfontw
from _get_system_font_name in GTK.)

[1]: https://docs.microsoft.com/windows/win32/api/wingdi/nf-wingdi-createdca

1 files changed, 39 insertions, 20 deletions

diff --git a/pango/pangowin32-fontmap.c b/pango/pangowin32-fontmap.c
index 905fdee2..ff7a6e94 100644
--- a/pango/pangowin32-fontmap.c
+++ b/pango/pangowin32-fontmap.c
@@ -199,6 +199,12 @@ pango_win32_inner_enum_proc (LOGFONTW    *lfp,
   return 1;
 }
 
+struct EnumProcData
+{
+  HDC hdc;
+  PangoWin32FontMap *font_map;
+};
+
 static int CALLBACK
 pango_win32_enum_proc (LOGFONTW       *lfp,
                        NEWTEXTMETRICW *metrics,
@@ -206,6 +212,7 @@ pango_win32_enum_proc (LOGFONTW       *lfp,
                        LPARAM          lParam)
 {
   LOGFONTW lf;
+  struct EnumProcData *data = (struct EnumProcData *) lParam;
 
   PING (("%S: %lu %lx", lfp->lfFaceName, fontType, metrics->ntmFlags));
 
@@ -213,9 +220,9 @@ pango_win32_enum_proc (LOGFONTW       *lfp,
     {
       lf = *lfp;
 
-      EnumFontFamiliesExW (_pango_win32_hdc, &lf,
+      EnumFontFamiliesExW (data->hdc, &lf,
                            (FONTENUMPROCW) pango_win32_inner_enum_proc,
-                           lParam, 0);
+                           (LPARAM) data->font_map, 0);
     }
 
   return 1;
@@ -709,6 +716,8 @@ static void
 _pango_win32_font_map_init (PangoWin32FontMap *win32fontmap)
 {
   LOGFONTW logfont;
+  HDC hdc = _pango_win32_get_display_dc ();
+  struct EnumProcData enum_proc_data;
 
   win32fontmap->families =
     g_hash_table_new_full ((GHashFunc) case_insensitive_str_hash,
@@ -730,9 +739,13 @@ _pango_win32_font_map_init (PangoWin32FontMap *win32fontmap)
 
   memset (&logfont, 0, sizeof (logfont));
   logfont.lfCharSet = DEFAULT_CHARSET;
-  EnumFontFamiliesExW (_pango_win32_hdc, &logfont,
+
+  enum_proc_data.hdc = hdc;
+  enum_proc_data.font_map = win32fontmap;
+
+  EnumFontFamiliesExW (hdc, &logfont,
                        (FONTENUMPROCW) pango_win32_enum_proc,
-                       (LPARAM) win32fontmap, 0);
+                       (LPARAM) &enum_proc_data, 0);
 
   g_hash_table_foreach (win32fontmap->families, synthesize_foreach, win32fontmap);
 
@@ -744,7 +757,7 @@ _pango_win32_font_map_init (PangoWin32FontMap *win32fontmap)
   create_standard_family (win32fontmap, "Fantasy");
   create_standard_family (win32fontmap, "System-ui");
 
-  win32fontmap->resolution = (PANGO_SCALE / (double) GetDeviceCaps (_pango_win32_hdc, LOGPIXELSY)) * 72.0;
+  win32fontmap->resolution = (PANGO_SCALE / (double) GetDeviceCaps (hdc, LOGPIXELSY)) * 72.0;
 }
 
 static void
@@ -807,7 +820,7 @@ _pango_win32_font_map_class_init (PangoWin32FontMapClass *class)
   fontmap_class->shape_engine_type = PANGO_RENDER_TYPE_WIN32;
   fontmap_class->get_face = pango_win32_font_map_get_face;
 
-  pango_win32_get_dc ();
+  _pango_win32_get_display_dc ();
 }
 
 /**
@@ -1159,6 +1172,7 @@ get_family_nameA (const LOGFONTA *lfp)
 {
   HFONT hfont;
   HFONT oldhfont;
+  HDC hdc;
 
   struct name_header header;
   struct name_record record;
@@ -1189,17 +1203,19 @@ get_family_nameA (const LOGFONTA *lfp)
   if ((hfont = CreateFontIndirect (lfp)) == NULL)
     goto fail0;
 
-  if ((oldhfont = SelectObject (_pango_win32_hdc, hfont)) == NULL)
+  hdc = _pango_win32_get_display_dc ();
+
+  if ((oldhfont = SelectObject (hdc, hfont)) == NULL)
     goto fail1;
 
-  if (!_pango_win32_get_name_header (_pango_win32_hdc, &header))
+  if (!_pango_win32_get_name_header (hdc, &header))
     goto fail2;
 
   PING (("%d name records", header.num_records));
 
   for (i = 0; i < header.num_records; i++)
     {
-      if (!_pango_win32_get_name_record (_pango_win32_hdc, i, &record))
+      if (!_pango_win32_get_name_record (hdc, i, &record))
         goto fail2;
 
       if ((record.name_id != 1 && record.name_id != 16) || record.string_length <= 0)
@@ -1234,11 +1250,11 @@ get_family_nameA (const LOGFONTA *lfp)
   else
     goto fail2;
 
-  if (!_pango_win32_get_name_record (_pango_win32_hdc, name_ix, &record))
+  if (!_pango_win32_get_name_record (hdc, name_ix, &record))
     goto fail2;
 
   string = g_malloc (record.string_length + 1);
-  if (GetFontData (_pango_win32_hdc, NAME,
+  if (GetFontData (hdc, NAME,
                    header.string_storage_offset + record.string_offset,
                    string, record.string_length) != record.string_length)
     goto fail2;
@@ -1264,14 +1280,14 @@ get_family_nameA (const LOGFONTA *lfp)
 
   PING (("%s", name));
 
-  SelectObject (_pango_win32_hdc, oldhfont);
+  SelectObject (hdc, oldhfont);
   DeleteObject (hfont);
 
   return name;
 
  fail2:
   g_free (string);
-  SelectObject (_pango_win32_hdc, oldhfont);
+  SelectObject (hdc, oldhfont);
 
  fail1:
   DeleteObject (hfont);
@@ -1343,6 +1359,7 @@ get_family_nameW (const LOGFONTW *lfp)
 {
   HFONT hfont;
   HFONT oldhfont;
+  HDC hdc;
 
   struct name_header header;
   struct name_record record;
@@ -1373,17 +1390,19 @@ get_family_nameW (const LOGFONTW *lfp)
   if ((hfont = CreateFontIndirectW (lfp)) == NULL)
     goto fail0;
 
-  if ((oldhfont = SelectObject (_pango_win32_hdc, hfont)) == NULL)
+  hdc = _pango_win32_get_display_dc ();
+
+  if ((oldhfont = SelectObject (hdc, hfont)) == NULL)
     goto fail1;
 
-  if (!_pango_win32_get_name_header (_pango_win32_hdc, &header))
+  if (!_pango_win32_get_name_header (hdc, &header))
     goto fail2;
 
   PING (("%d name records", header.num_records));
 
   for (i = 0; i < header.num_records; i++)
     {
-      if (!_pango_win32_get_name_record (_pango_win32_hdc, i, &record))
+      if (!_pango_win32_get_name_record (hdc, i, &record))
         goto fail2;
 
       if ((record.name_id != 1 && record.name_id != 16) || record.string_length <= 0)
@@ -1416,11 +1435,11 @@ get_family_nameW (const LOGFONTW *lfp)
   else
     goto fail2;
 
-  if (!_pango_win32_get_name_record (_pango_win32_hdc, name_ix, &record))
+  if (!_pango_win32_get_name_record (hdc, name_ix, &record))
     goto fail2;
 
   string = g_malloc (record.string_length + 1);
-  if (GetFontData (_pango_win32_hdc, NAME,
+  if (GetFontData (hdc, NAME,
                    header.string_storage_offset + record.string_offset,
                    string, record.string_length) != record.string_length)
     goto fail2;
@@ -1446,14 +1465,14 @@ get_family_nameW (const LOGFONTW *lfp)
 
   PING (("%s", name));
 
-  SelectObject (_pango_win32_hdc, oldhfont);
+  SelectObject (hdc, oldhfont);
   DeleteObject (hfont);
 
   return name;
 
  fail2:
   g_free (string);
-  SelectObject (_pango_win32_hdc, oldhfont);
+  SelectObject (hdc, oldhfont);
 
  fail1:
   DeleteObject (hfont);