[pango: 1/2] win32: Use GPrivate-managed display device context

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

commit f59acff3b08d60f1d3d3469efd6d603f707bc07f
Author: Yongsu Park <pcpenpal gmail com>
Date:   Tue May 19 09:35:43 2020 +0000

    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 destroyed, the HDC is no longer valid.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

 pango/pangocairo-win32fontmap.c |  2 +-
 pango/pangowin32-fontmap.c      | 59 +++++++++++++++++++++++++++--------------
 pango/pangowin32-private.h      |  4 ++-
 pango/pangowin32.c              | 52 +++++++++++++++++++++++-------------
 4 files changed, 76 insertions(+), 41 deletions(-)
---
diff --git a/pango/pangocairo-win32fontmap.c b/pango/pangocairo-win32fontmap.c
index b58d16f6..94500fd6 100644
--- a/pango/pangocairo-win32fontmap.c
+++ b/pango/pangocairo-win32fontmap.c
@@ -121,5 +121,5 @@ static void
 pango_cairo_win32_font_map_init (PangoCairoWin32FontMap *cwfontmap)
 {
   cwfontmap->serial = 1;
-  cwfontmap->dpi = GetDeviceCaps (pango_win32_get_dc (), LOGPIXELSY);
+  cwfontmap->dpi = GetDeviceCaps (_pango_win32_get_display_dc (), LOGPIXELSY);
 }
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);
diff --git a/pango/pangowin32-private.h b/pango/pangowin32-private.h
index 082470e7..f5620b87 100644
--- a/pango/pangowin32-private.h
+++ b/pango/pangowin32-private.h
@@ -272,7 +272,9 @@ void            _pango_win32_fontmap_cache_remove   (PangoFontMap   *fontmap,
 _PANGO_EXTERN
 HFONT          _pango_win32_font_get_hfont         (PangoFont          *font);
 
-extern HDC _pango_win32_hdc;
+_PANGO_EXTERN
+HDC             _pango_win32_get_display_dc                 (void);
+
 extern gboolean _pango_win32_debug;
 
 #endif /* __PANGOWIN32_PRIVATE_H__ */
diff --git a/pango/pangowin32.c b/pango/pangowin32.c
index 737cfa14..8849d4af 100644
--- a/pango/pangowin32.c
+++ b/pango/pangowin32.c
@@ -43,7 +43,6 @@
 
 #define MAX_FREED_FONTS 256
 
-HDC _pango_win32_hdc;
 gboolean _pango_win32_debug = FALSE;
 
 static void pango_win32_font_dispose    (GObject             *object);
@@ -134,19 +133,21 @@ _pango_win32_font_init (PangoWin32Font *win32font)
   win32font->glyph_info = g_hash_table_new_full (NULL, NULL, NULL, g_free);
 }
 
-/**
- * pango_win32_get_dc:
- *
- * Obtains a handle to the Windows device context that is used by Pango.
- *
- * Return value: A handle to the Windows device context that is used by Pango.
- **/
+static GPrivate display_dc_key = G_PRIVATE_INIT ((GDestroyNotify) DeleteDC);
+
 HDC
-pango_win32_get_dc (void)
+_pango_win32_get_display_dc (void)
 {
-  if (g_once_init_enter (&_pango_win32_hdc))
+  HDC hdc = g_private_get (&display_dc_key);
+
+  if (hdc == NULL)
     {
-      HDC hdc = CreateDC ("DISPLAY", NULL, NULL, NULL);
+      hdc = CreateDC ("DISPLAY", NULL, NULL, NULL);
+
+      if (G_UNLIKELY (hdc == NULL))
+       g_warning ("CreateDC() failed");
+
+      g_private_set (&display_dc_key, hdc);
 
       /* Also do some generic pangowin32 initialisations... this function
        * is a suitable place for those as it is called from a couple
@@ -156,10 +157,22 @@ pango_win32_get_dc (void)
       if (getenv ("PANGO_WIN32_DEBUG") != NULL)
        _pango_win32_debug = TRUE;
 #endif
-      g_once_init_leave (&_pango_win32_hdc, hdc);
     }
 
-  return _pango_win32_hdc;
+  return hdc;
+}
+
+/**
+ * pango_win32_get_dc:
+ *
+ * Obtains a handle to the Windows device context that is used by Pango.
+ *
+ * Return value: A handle to the Windows device context that is used by Pango.
+ **/
+HDC
+pango_win32_get_dc (void)
+{
+  return _pango_win32_get_display_dc ();
 }
 
 /**
@@ -198,7 +211,7 @@ _pango_win32_font_class_init (PangoWin32FontClass *class)
   class->done_font = pango_win32_font_real_done_font;
   class->get_metrics_factor = pango_win32_font_real_get_metrics_factor;
 
-  pango_win32_get_dc ();
+  _pango_win32_get_display_dc ();
 }
 
 /**
@@ -448,7 +461,7 @@ pango_win32_font_get_glyph_extents (PangoFont      *font,
 
   if (!info)
     {
-      HDC hdc = pango_win32_get_dc ();
+      HDC hdc = _pango_win32_get_display_dc ();
 
       info = g_new0 (PangoWin32GlyphInfo, 1);
 
@@ -478,7 +491,7 @@ pango_win32_font_get_glyph_extents (PangoFont      *font,
       info->ink_rect.y = - PANGO_SCALE * gm.gmptGlyphOrigin.y;
       info->ink_rect.height = PANGO_SCALE * gm.gmBlackBoxY;
 
-      GetTextMetrics (_pango_win32_hdc, &tm);
+      GetTextMetrics (hdc, &tm);
       info->logical_rect.x = 0;
       info->logical_rect.width = PANGO_SCALE * gm.gmCellIncX;
       info->logical_rect.y = - PANGO_SCALE * tm.tmAscent;
@@ -555,9 +568,10 @@ pango_win32_font_get_metrics (PangoFont     *font,
        {
          PangoCoverage *coverage;
          TEXTMETRIC tm;
+         HDC hdc = _pango_win32_get_display_dc ();
 
-         SelectObject (_pango_win32_hdc, hfont);
-         GetTextMetrics (_pango_win32_hdc, &tm);
+         SelectObject (hdc, hfont);
+         GetTextMetrics (hdc, &tm);
 
          metrics->ascent = tm.tmAscent * PANGO_SCALE;
          metrics->descent = tm.tmDescent * PANGO_SCALE;
@@ -1215,7 +1229,7 @@ hfont_reference_table (hb_face_t *face, hb_tag_t tag, void *user_data)
   DWORD size;
 
   /* We have a common DC for our PangoWin32Font, so let's just use it */
-  hdc = pango_win32_get_dc ();
+  hdc = _pango_win32_get_display_dc ();
   hfont = (HFONT) user_data;
 
   /* we want to restore things, just to be safe */