Improve precondition checks for path points

Add a helper function for checking that a
path point is valid for a path, and use it.

gsk/gskpathbuilder.c

@@ -1401,10 +1401,8 @@ gsk_path_builder_add_segment (GskPathBuilder     *self,
 
   g_return_if_fail (self != NULL);
   g_return_if_fail (path != NULL);
-  g_return_if_fail (start != NULL);
-  g_return_if_fail (end != NULL);
-  g_return_if_fail (start->contour < n_contours);
-  g_return_if_fail (end->contour < n_contours);
+  g_return_if_fail (gsk_path_point_valid (start, path));
+  g_return_if_fail (gsk_path_point_valid (end, path));
 
   current = self->current_point;
 

gsk/gskpathmeasure.c

@@ -22,7 +22,7 @@
 #include "gskpathmeasure.h"
 
 #include "gskpathbuilder.h"
-#include "gskpathpoint.h"
+#include "gskpathpointprivate.h"
 #include "gskcontourprivate.h"
 #include "gskpathprivate.h"
 
@@ -312,9 +312,8 @@ gsk_path_point_get_distance (const GskPathPoint *point,
   const GskContour *contour;
   float contour_offset = 0;
 
-  g_return_val_if_fail (point != NULL, 0);
   g_return_val_if_fail (measure != NULL, 0);
-  g_return_val_if_fail (point->contour < measure->n_contours, 0);
+  g_return_val_if_fail (gsk_path_point_valid (point, measure->path), 0);
 
   contour = gsk_path_get_contour (measure->path, point->contour);
 

gsk/gskpathpoint.c

@@ -21,7 +21,7 @@
 
 #include <math.h>
 
-#include "gskpathpoint.h"
+#include "gskpathpointprivate.h"
 #include "gskcontourprivate.h"
 #include "gdk/gdkprivate.h"
 
@@ -156,10 +156,9 @@ gsk_path_point_get_position (const GskPathPoint *point,
 {
   const GskContour *contour;
 
-  g_return_if_fail (point != NULL);
   g_return_if_fail (path != NULL);
+  g_return_if_fail (gsk_path_point_valid (point, path));
   g_return_if_fail (position != NULL);
-  g_return_if_fail (point->contour < gsk_path_get_n_contours (path));
 
   contour = gsk_path_get_contour (path, point->contour),
   gsk_contour_get_position (contour, point, position);
@@ -195,10 +194,9 @@ gsk_path_point_get_tangent (const GskPathPoint *point,
 {
   const GskContour *contour;
 
-  g_return_if_fail (point != NULL);
   g_return_if_fail (path != NULL);
+  g_return_if_fail (gsk_path_point_valid (point, path));
   g_return_if_fail (tangent != NULL);
-  g_return_if_fail (point->contour < gsk_path_get_n_contours (path));
 
   contour = gsk_path_get_contour (path, point->contour),
   gsk_contour_get_tangent (contour, point, direction, tangent);
@@ -228,9 +226,8 @@ gsk_path_point_get_rotation (const GskPathPoint *point,
 {
   graphene_vec2_t tangent;
 
-  g_return_val_if_fail (point != NULL, 0);
   g_return_val_if_fail (path != NULL, 0);
-  g_return_val_if_fail (point->contour < gsk_path_get_n_contours (path), 0);
+  g_return_val_if_fail (gsk_path_point_valid (point, path), 0);
 
   gsk_path_point_get_tangent (point, path, direction, &tangent);
 
@@ -279,9 +276,8 @@ gsk_path_point_get_curvature (const GskPathPoint *point,
 {
   const GskContour *contour;
 
-  g_return_val_if_fail (point != NULL, 0);
   g_return_val_if_fail (path != NULL, 0);
-  g_return_val_if_fail (point->contour < gsk_path_get_n_contours (path), 0);
+  g_return_val_if_fail (gsk_path_point_valid (point, path), 0);
 
   contour = gsk_path_get_contour (path, point->contour);
   return gsk_contour_get_curvature (contour, point, direction, center);

gsk/gskpathpointprivate.h

@@ -7,5 +7,33 @@ G_BEGIN_DECLS
 
 #define GSK_PATH_POINT_INIT(c,i,tt) ((GskPathPoint){ .contour=(c), .idx=(i), .t=(tt) })
 
+static inline gboolean
+gsk_path_point_valid (const GskPathPoint *point,
+                      GskPath            *path)
+{
+  const GskContour *contour;
+  gsize n_ops;
+
+  if (point == NULL)
+    return FALSE;
+
+  if (path == NULL)
+    return TRUE;
+
+  if (point->contour >= gsk_path_get_n_contours (path))
+    return FALSE;
+
+  contour = gsk_path_get_contour (path, point->contour);
+  n_ops = gsk_contour_get_n_ops (contour);
+  if ((n_ops > 1 && point->idx >= n_ops) ||
+      (n_ops == 1 && point->idx > n_ops))
+    return FALSE;
+
+  if (point->t < 0 || point->t > 1)
+    return FALSE;
+
+  return TRUE;
+}
+
 G_END_DECLS