Add a check for proper contour calls

p5/core/vertex.py

@@ -35,6 +35,7 @@
 is_curve = False
 is_quadratic = False
 is_contour = False
+has_contour = False
 is_first_contour = True
 
 __all__ = ['begin_shape', 'end_shape', 'begin_contour', 'end_contour',
@@ -47,11 +48,11 @@ def begin_shape(kind=TESS):
     :param kind: TESS, POINTS, LINES, TRIANGLES, TRIANGLE_FAN, TRIANGLE_STRIP, QUADS, or QUAD_STRIP; defaults to TESS
     :type kind: SType
     """
-    global shape_kind, vertices, contour_vertices, vertices_types, contour_vertices_types, is_contour
+    global shape_kind, vertices, contour_vertices, vertices_types, contour_vertices_types, has_contour
     global curr_contour_vertices, curr_contour_vertices_types
 
     shape_kind = kind
-    is_contour = False
+    has_contour = False
     vertices = []
     vertices_types = []
     contour_vertices = []
@@ -88,7 +89,7 @@ def curve_vertex(x, y, z=0):
     if p5.mode == "3D":
         return
     if builtins.current_renderer == 'vispy':
-        if is_contour:
+        if has_contour:
             curr_contour_vertices.append((x, y, z))
             curr_contour_vertices_types.append(2)
         else:
@@ -126,15 +127,15 @@ def bezier_vertex(x2, y2, x3, y3, x4, y4):
     if p5.mode == "3D":
         return
     if builtins.current_renderer == 'vispy':
-        if is_contour:
+        if has_contour:
             curr_contour_vertices.append((x2, y2, x3, y3, x4, y4))
             curr_contour_vertices_types.append(3)
         else:
             vertices.append((x2, y2, x3, y3, x4, y4))
             vertices_types.append(3)
     elif builtins.current_renderer == 'skia':
         vert_data = [x2, y2, x3, y3, x4, y4, {"is_vert": False}]
-        if is_contour:
+        if has_contour:
             contour_vertices.append(vert_data)
         else:
             vertices.append(vert_data)
@@ -164,15 +165,15 @@ def quadratic_vertex(cx, cy, x3, y3):
     is_quadratic = True
 
     if builtins.current_renderer == 'vispy':
-        if is_contour:
+        if has_contour:
             curr_contour_vertices.append((cx, cy, x3, y3))
             curr_contour_vertices_types.append(4)
         else:
             vertices.append((cx, cy, x3, y3))
             vertices_types.append(3)
     elif builtins.current_renderer == 'skia':
         vert_data = [cx, cy, x3, y3, {"is_vert": False}]
-        if is_contour:
+        if has_contour:
             contour_vertices.append(vert_data)
         else:
             vertices.append(vert_data)
@@ -198,7 +199,7 @@ def vertex(x, y, z=0):
     if p5.mode == "3D":
         return
     if builtins.current_renderer == 'vispy':
-        if is_contour:
+        if has_contour:
             curr_contour_vertices.append((x, y, z))
             curr_contour_vertices_types.append(1)
         else:
@@ -209,7 +210,7 @@ def vertex(x, y, z=0):
                      tuple(255 * c for c in p5.renderer.style.stroke_color), {}]
         vert_data[-1]["is_vert"] = True
 
-        if is_contour:
+        if has_contour:
             if len(contour_vertices) == 0:
                 vert_data[-1]["move_to"] = True
             contour_vertices.append(vert_data)
@@ -229,7 +230,8 @@ def begin_contour():
     for internal shapes, draw vertices shape in counter-clockwise.
 
     """
-    global is_contour, contour_vertices, contour_vertices_types
+    global has_contour, contour_vertices, contour_vertices_types, has_contour, is_contour
+    has_contour = True
     is_contour = True
     contour_vertices = []
     contour_vertices_types = []
@@ -240,7 +242,8 @@ def end_contour():
 
     For more info, see :any:`begin_contour`.
     """
-    global is_contour, curr_contour_vertices, curr_contour_vertices_types, is_first_contour
+    global has_contour, curr_contour_vertices, curr_contour_vertices_types, is_first_contour, has_contour, is_contour
+    is_contour = False
 
     if builtins.current_renderer == 'vispy':
         # Close contour
@@ -355,10 +358,10 @@ def end_shape(mode=""):
     :type mode: str
 
     """
-    global is_bezier, is_curve, is_quadratic, is_contour, is_first_contour
+    global is_bezier, is_curve, is_quadratic, has_contour, is_first_contour, has_contour, is_contour
     if is_curve or is_bezier or is_quadratic:
         assert shape_kind == TESS, "Should not specify primitive type for a curve"
-
+    assert not is_contour, "begin_contour called without calling end_contour"
     if len(vertices) == 0:
         return
 
@@ -396,15 +399,15 @@ def end_shape(mode=""):
 
     elif builtins.current_renderer == 'skia':
         close_shape = mode == 'CLOSE'
-        if close_shape and not is_contour:
+        if close_shape and not has_contour:
             vertices.append(vertices[0])
-        p5.renderer.end_shape(mode, vertices, is_curve, is_bezier, is_quadratic, is_contour,
+        p5.renderer.end_shape(mode, vertices, is_curve, is_bezier, is_quadratic, has_contour,
                               None if shape_kind == TESS else shape_kind)
         if close_shape:
             vertices.pop()
 
     is_bezier = False
     is_curve = False
     is_quadratic = False
-    is_contour = False
+    has_contour = False
     is_first_contour = True