From e2ba2e00a97b9fc496d985572302ad57972a59d2 Mon Sep 17 00:00:00 2001
From: Yongsu Park <pcpenpal@gmail.com>
Date: Wed, 11 Mar 2020 21:13:09 +0900
Subject: [PATCH] win32: Make font dc thread local

---
 src/cairo-mutex-list-private.h |  1 +
 src/win32/cairo-win32-font.c   | 18 +++++++++++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/cairo-mutex-list-private.h b/src/cairo-mutex-list-private.h
index f46afadb0..ca7403006 100644
--- a/src/cairo-mutex-list-private.h
+++ b/src/cairo-mutex-list-private.h
@@ -53,6 +53,7 @@ CAIRO_MUTEX_DECLARE (_cairo_ft_unscaled_font_map_mutex)
 
 #if CAIRO_HAS_WIN32_FONT
 CAIRO_MUTEX_DECLARE (_cairo_win32_font_face_mutex)
+CAIRO_MUTEX_DECLARE (_cairo_win32_font_dc_mutex)
 #endif
 
 #if CAIRO_HAS_XLIB_SURFACE
diff --git a/src/win32/cairo-win32-font.c b/src/win32/cairo-win32-font.c
index 1f217573b..058403513 100644
--- a/src/win32/cairo-win32-font.c
+++ b/src/win32/cairo-win32-font.c
@@ -162,8 +162,19 @@ _cairo_win32_scaled_font_init_glyph_path (cairo_win32_scaled_font_t *scaled_font
 static HDC
 _get_global_font_dc (void)
 {
-    static HDC hdc;
+    static DWORD hdc_tls_index;
+    HDC hdc;
 
+    if (!hdc_tls_index) {
+	CAIRO_MUTEX_LOCK (_cairo_win32_font_dc_mutex);
+	if (!hdc_tls_index) {
+	    hdc_tls_index = TlsAlloc ();
+	    assert (hdc_tls_index != TLS_OUT_OF_INDEXES);
+	}
+	CAIRO_MUTEX_UNLOCK (_cairo_win32_font_dc_mutex);
+    }
+
+    hdc = TlsGetValue (hdc_tls_index);
     if (!hdc) {
 	hdc = CreateCompatibleDC (NULL);
 	if (!hdc) {
@@ -176,6 +187,11 @@ _get_global_font_dc (void)
 	    DeleteDC (hdc);
 	    return NULL;
 	}
+
+	if (!TlsSetValue (hdc_tls_index, hdc)) {
+	    DeleteDC (hdc);
+	    return NULL;
+	}
     }
 
     return hdc;