[cairo-font-options] Check for the nil-object.

The design is for the user to create a cairo_font_options_t object with
cairo_font_options_create() and then is free to use it with any Cairo
operation. This requires us to check when we may be about to overwrite
the read-only nil object.

src/cairo-font-face.c

@@ -455,6 +455,11 @@ _cairo_toy_font_face_scaled_font_create (void                *abstract_font_face
 {
     cairo_toy_font_face_t *font_face = abstract_font_face;
     const cairo_scaled_font_backend_t * backend = CAIRO_SCALED_FONT_BACKEND_DEFAULT;
+    cairo_status_t status;
+
+    status = cairo_font_options_status ((cairo_font_options_t *) options);
+    if (status)
+	return status;
 
     return backend->create_toy (font_face,
 				font_matrix, ctm, options, scaled_font);

src/cairo-font-options.c

@@ -113,8 +113,12 @@ slim_hidden_def (cairo_font_options_create);
 cairo_font_options_t *
 cairo_font_options_copy (const cairo_font_options_t *original)
 {
-    cairo_font_options_t *options = malloc (sizeof (cairo_font_options_t));
+    cairo_font_options_t *options;
 
+    if (original == &_cairo_font_options_nil)
+	return (cairo_font_options_t *)&_cairo_font_options_nil;
+
+    options = malloc (sizeof (cairo_font_options_t));
     if (!options)
 	return (cairo_font_options_t *)&_cairo_font_options_nil;
 
@@ -157,6 +161,7 @@ cairo_font_options_status (cairo_font_options_t *options)
     else
 	return CAIRO_STATUS_SUCCESS;
 }
+slim_hidden_def (cairo_font_options_status);
 
 /**
  * cairo_font_options_merge:

src/cairo-gstate.c

@@ -1286,15 +1286,13 @@ _cairo_gstate_get_font_matrix (cairo_gstate_t *gstate,
     *matrix = gstate->font_matrix;
 }
 
-cairo_status_t
+void
 _cairo_gstate_set_font_options (cairo_gstate_t             *gstate,
 				const cairo_font_options_t *options)
 {
     _cairo_gstate_unset_scaled_font (gstate);
 
     gstate->font_options = *options;
-
-    return CAIRO_STATUS_SUCCESS;
 }
 
 void

src/cairo-scaled-font.c

@@ -348,6 +348,10 @@ _cairo_scaled_font_init (cairo_scaled_font_t               *scaled_font,
     cairo_matrix_t inverse;
     cairo_status_t status;
 
+    status = cairo_font_options_status ((cairo_font_options_t *) options);
+    if (status)
+	return status;
+
     /* Initialize scaled_font->scale early for easier bail out on an
      * invalid matrix. */
     _cairo_scaled_font_init_key (scaled_font, font_face,
@@ -480,6 +484,9 @@ cairo_scaled_font_create (cairo_font_face_t          *font_face,
     if (font_face->status)
 	return (cairo_scaled_font_t *)&_cairo_scaled_font_nil;
 
+    if (cairo_font_options_status ((cairo_font_options_t *) options))
+	return (cairo_scaled_font_t *)&_cairo_scaled_font_nil;
+
     font_map = _cairo_scaled_font_map_lock ();
     if (font_map == NULL)
 	return (cairo_scaled_font_t *)&_cairo_scaled_font_nil;
@@ -1644,6 +1651,9 @@ void
 cairo_scaled_font_get_font_options (cairo_scaled_font_t		*scaled_font,
 				    cairo_font_options_t	*options)
 {
+    if (cairo_font_options_status (options))
+	return;
+
     if (scaled_font->status) {
 	_cairo_font_options_init_default (options);
 	return;

src/cairo-surface.c

@@ -603,6 +603,9 @@ void
 cairo_surface_get_font_options (cairo_surface_t       *surface,
 				cairo_font_options_t  *options)
 {
+    if (cairo_font_options_status (options))
+	return;
+
     if (!surface->has_font_options) {
 	surface->has_font_options = TRUE;
 

src/cairo.c

@@ -2641,9 +2641,11 @@ cairo_set_font_options (cairo_t                    *cr,
     if (cr->status)
 	return;
 
-    status = _cairo_gstate_set_font_options (cr->gstate, options);
+    status = cairo_font_options_status ((cairo_font_options_t *) options);
     if (status)
 	_cairo_set_error (cr, status);
+
+    _cairo_gstate_set_font_options (cr->gstate, options);
 }
 
 /**
@@ -2661,6 +2663,10 @@ void
 cairo_get_font_options (cairo_t              *cr,
 			cairo_font_options_t *options)
 {
+    /* check that we aren't trying to overwrite the nil object */
+    if (cairo_font_options_status (options))
+	return;
+
     _cairo_gstate_get_font_options (cr->gstate, options);
 }
 
@@ -2698,9 +2704,7 @@ cairo_set_scaled_font (cairo_t                   *cr,
     if (status)
         goto BAIL;
 
-    status = _cairo_gstate_set_font_options (cr->gstate, &scaled_font->options);
-    if (status)
-        goto BAIL;
+    _cairo_gstate_set_font_options (cr->gstate, &scaled_font->options);
 
     return;
 

src/cairoint.h

@@ -1346,7 +1346,7 @@ cairo_private void
 _cairo_gstate_get_font_options (cairo_gstate_t       *gstate,
 				cairo_font_options_t *options);
 
-cairo_private cairo_status_t
+cairo_private void
 _cairo_gstate_set_font_options (cairo_gstate_t	           *gstate,
 				const cairo_font_options_t *options);
 
@@ -2378,6 +2378,7 @@ slim_hidden_proto (cairo_font_options_set_antialias);
 slim_hidden_proto (cairo_font_options_set_hint_metrics);
 slim_hidden_proto (cairo_font_options_set_hint_style);
 slim_hidden_proto (cairo_font_options_set_subpixel_order);
+slim_hidden_proto (cairo_font_options_status);
 slim_hidden_proto (cairo_get_current_point);
 slim_hidden_proto (cairo_get_matrix);
 slim_hidden_proto (cairo_get_tolerance);