updated for version 7.4.393

Problem:    Text drawing on newer MS-Windows systems is suboptimal.  Some
            multi-byte characters are not displayed, even though the same font
            in Notepad can display them. (Srinath Avadhanula)
Solution:   Add the 'renderoptions' option to enable Direct-X drawing. (Taro
            Muraoka)

src/gui_w48.c

@@ -2785,6 +2785,10 @@ _OnPaint(
 
 	out_flush();	    /* make sure all output has been processed */
 	(void)BeginPaint(hwnd, &ps);
+#if defined(FEAT_DIRECTX)
+	if (IS_ENABLE_DIRECTX())
+	    DWriteContext_BeginDraw(s_dwc);
+#endif
 
 #ifdef FEAT_MBYTE
 	/* prevent multi-byte characters from misprinting on an invalid
@@ -2800,9 +2804,20 @@ _OnPaint(
 #endif
 
 	if (!IsRectEmpty(&ps.rcPaint))
+	{
+#if defined(FEAT_DIRECTX)
+	    if (IS_ENABLE_DIRECTX())
+		DWriteContext_BindDC(s_dwc, s_hdc, &ps.rcPaint);
+#endif
 	    gui_redraw(ps.rcPaint.left, ps.rcPaint.top,
 		    ps.rcPaint.right - ps.rcPaint.left + 1,
 		    ps.rcPaint.bottom - ps.rcPaint.top + 1);
+	}
+
+#if defined(FEAT_DIRECTX)
+	if (IS_ENABLE_DIRECTX())
+	    DWriteContext_EndDraw(s_dwc);
+#endif
 	EndPaint(hwnd, &ps);
     }
 }
@@ -3043,6 +3058,12 @@ gui_mch_insert_lines(
     void
 gui_mch_exit(int rc)
 {
+#if defined(FEAT_DIRECTX)
+    DWriteContext_Close(s_dwc);
+    DWrite_Final();
+    s_dwc = NULL;
+#endif
+
     ReleaseDC(s_textArea, s_hdc);
     DeleteObject(s_brush);