[region] Fix status propagation for regions

When an operation fails, store the status code in the destination
region rather than leaving it unchanged.

1 files changed, 52 insertions, 14 deletions

diff --git a/src/cairo-region.c b/src/cairo-region.c
index 55898d9c9..aec1bdf15 100644
--- a/src/cairo-region.c
+++ b/src/cairo-region.c
@@ -42,6 +42,40 @@ const cairo_region_t _cairo_region_nil = {
     CAIRO_STATUS_NO_MEMORY,		/* status */
 };
 
+/**
+ * cairo_region_set_error:
+ * @region: a region
+ * @status: a status value indicating an error
+ *
+ * Atomically sets region->status to @status and calls _cairo_error;
+ * Does nothing if status is %CAIRO_STATUS_SUCCESS or any of the internal
+ * status values.
+ *
+ * All assignments of an error status to region->status should happen
+ * through cairo_region_set_error(). Note that due to the nature of
+ * the atomic operation, it is not safe to call this function on the
+ * nil objects.
+ *
+ * The purpose of this function is to allow the user to set a
+ * breakpoint in _cairo_error() to generate a stack trace for when the
+ * user causes cairo to detect an error.
+ *
+ * Return value: the error status.
+ **/
+static cairo_status_t
+cairo_region_set_error (cairo_region_t *region,
+			cairo_status_t status)
+{
+    if (status == CAIRO_STATUS_SUCCESS || status >= CAIRO_INT_STATUS_UNSUPPORTED)
+	return status;
+
+    /* Don't overwrite an existing error. This preserves the first
+     * error, which is the most significant. */
+    _cairo_status_set_error (&region->status, status);
+
+    return _cairo_error (status);
+}
+
 cairo_region_t *
 cairo_region_create (void)
 {
@@ -172,7 +206,7 @@ cairo_region_subtract (cairo_region_t *dst, cairo_region_t *other)
 	return other->status;
     
     if (!pixman_region32_subtract (&dst->rgn, &dst->rgn, &other->rgn))
-	return _cairo_error (CAIRO_STATUS_NO_MEMORY);
+	return cairo_region_set_error (dst, CAIRO_STATUS_NO_MEMORY);
 
     return CAIRO_STATUS_SUCCESS;
 }
@@ -207,9 +241,9 @@ cairo_region_intersect (cairo_region_t *dst, cairo_region_t *other)
 
     if (other->status)
 	return other->status;
-    
+
     if (!pixman_region32_intersect (&dst->rgn, &dst->rgn, &other->rgn))
-	return _cairo_error (CAIRO_STATUS_NO_MEMORY);
+	return cairo_region_set_error (dst, CAIRO_STATUS_NO_MEMORY);
 
     return CAIRO_STATUS_SUCCESS;
 }
@@ -218,7 +252,7 @@ cairo_status_t
 cairo_region_intersect_rectangle (cairo_region_t *dst,
 				  const cairo_rectangle_int_t *rect)
 {
-    cairo_status_t result = CAIRO_STATUS_SUCCESS;
+    cairo_status_t status = CAIRO_STATUS_SUCCESS;
     pixman_region32_t region;
 
     if (dst->status)
@@ -228,11 +262,11 @@ cairo_region_intersect_rectangle (cairo_region_t *dst,
 			       rect->x, rect->y, rect->width, rect->height);
 
     if (!pixman_region32_intersect (&dst->rgn, &dst->rgn, &region))
-	result = _cairo_error (CAIRO_STATUS_NO_MEMORY);
+	status = cairo_region_set_error (dst, CAIRO_STATUS_NO_MEMORY);
 
     pixman_region32_fini (&region);
     
-    return result;
+    return status;
 }
 
 cairo_status_t
@@ -246,7 +280,7 @@ cairo_region_union (cairo_region_t *dst,
 	return other->status;
 
     if (!pixman_region32_union (&dst->rgn, &dst->rgn, &other->rgn))
-	return _cairo_error (CAIRO_STATUS_NO_MEMORY);
+	return cairo_region_set_error (dst, CAIRO_STATUS_NO_MEMORY);
 
     return CAIRO_STATUS_SUCCESS;
 }
@@ -255,14 +289,18 @@ cairo_status_t
 cairo_region_union_rectangle (cairo_region_t *dst,
 			      const cairo_rectangle_int_t *rect)
 {
-    if (!pixman_region32_union_rect (&dst->rgn, &dst->rgn,
-				     rect->x, rect->y,
-				     rect->width, rect->height))
-    {
-	return _cairo_error (CAIRO_STATUS_NO_MEMORY);
-    }
+    cairo_status_t status = CAIRO_STATUS_SUCCESS;
+    pixman_region32_t region;
 
-    return CAIRO_STATUS_SUCCESS;
+    pixman_region32_init_rect (&region,
+			       rect->x, rect->y, rect->width, rect->height);
+    
+    if (!pixman_region32_union (&dst->rgn, &dst->rgn, &region))
+	status = cairo_region_set_error (dst, CAIRO_STATUS_NO_MEMORY);
+
+    pixman_region32_fini (&region);
+    
+    return status;
 }
 
 cairo_bool_t