Fix aaline width and blend conflict

Author: ankith26

buildconfig/stubs/pygame/draw.pyi

@@ -508,7 +508,7 @@ def aaline(
     :param int width: (optional) used for line thickness
 
             | if width >= 1, used for line thickness (default is 1)
-            | if width < 1, nothing will be drawn
+            | if width < 1, a line of width == 1 will be drawn
 
     :returns: a rect bounding the changed pixels, if nothing is drawn the
         bounding rect's position will be the ``start_pos`` parameter value (float
@@ -521,8 +521,9 @@ def aaline(
     .. versionchangedold:: 2.0.0 Added support for keyword arguments.
     .. versionchanged:: 2.4.0 Removed deprecated 'blend' argument
     .. versionchanged:: 2.5.0 ``blend`` argument re-added for backcompat, but will
-        always raise a deprecation exception when used
-    .. versionchanged:: 2.5.3 Added line width
+        do nothing different and always raise a deprecation exception when used.
+    .. versionchanged:: 2.5.6 Added ``width`` in place of the deprecated
+        ``blend`` argument in a way that doesn't break backcompat too much.
     """
 
 def aalines(

src_c/draw.c

@@ -135,7 +135,9 @@ aaline(PyObject *self, PyObject *arg, PyObject *kwargs)
     static char *keywords[] = {"surface", "color", "start_pos", "end_pos",
                                "width",   "blend", NULL};
 
-    if (!PyArg_ParseTupleAndKeywords(arg, kwargs, "O!OOO|iO", keywords,
+    // blend argument is keyword only for backcompat.
+    // if it is passed as a positional argument, it will be handled in width
+    if (!PyArg_ParseTupleAndKeywords(arg, kwargs, "O!OOO|i$O", keywords,
                                      &pgSurface_Type, &surfobj, &colorobj,
                                      &start, &end, &width, &blend)) {
         return NULL; /* Exception already set. */
@@ -180,10 +182,6 @@ aaline(PyObject *self, PyObject *arg, PyObject *kwargs)
         return RAISE(PyExc_TypeError, "invalid end_pos argument");
     }
 
-    if (width < 1) {
-        return pgRect_New4((int)startx, (int)starty, 0, 0);
-    }
-
     if (!pgSurface_Lock(surfobj)) {
         return RAISE(PyExc_RuntimeError, "error locking surface");
     }
@@ -193,6 +191,8 @@ aaline(PyObject *self, PyObject *arg, PyObject *kwargs)
                           starty, endx, endy, width, drawn_area);
     }
     else {
+        // For all width <= 1 treat it as width == 1, this helps compat
+        // with the old blend argument
         draw_aaline(surf, surf_clip_rect, surf_format, color, startx, starty,
                     endx, endy, drawn_area, 0, 0, 0);
     }

test/draw_test.py

@@ -2453,13 +2453,21 @@ def test_aaline__blend_warning(self):
                 # Cause all warnings to always be triggered.
                 warnings.simplefilter("always")
                 # Trigger DeprecationWarning.
-                self.draw_aaline(
-                    pygame.Surface((2, 2)), (0, 0, 0, 50), (0, 0), (2, 2), 1, blend
+                bounding1 = self.draw_aaline(
+                    pygame.Surface((2, 2)), (0, 0, 0, 50), (0, 0), (2, 2), blend=blend
+                )
+                # Doesn't trigger DeprecationWarning, interepreted as width
+                bounding1 = self.draw_aaline(
+                    pygame.Surface((2, 2)), (0, 0, 0, 50), (0, 0), (2, 2), blend
                 )
                 # Check if there is only one warning and is a DeprecationWarning.
                 self.assertEqual(len(w), count + 1)
                 self.assertTrue(issubclass(w[-1].category, DeprecationWarning))
 
+                # check that the line gets drawn
+                self.assertEqual(bounding1, bounding2)
+                self.assertEqual(bounding1, (0, 0, 2, 2))
+
     def test_aaline__kwargs(self):
         """Ensures draw aaline accepts the correct kwargs"""
         surface = pygame.Surface((4, 4))
@@ -2681,11 +2689,10 @@ def test_aaline__valid_width_values(self):
         for width in (-100, -10, -1, 0, 1, 10, 100):
             surface.fill(surface_color)  # Clear for each test.
             kwargs["width"] = width
-            expected_color = line_color if width > 0 else surface_color
 
             bounds_rect = self.draw_aaline(**kwargs)
 
-            self.assertEqual(surface.get_at(pos), expected_color)
+            self.assertEqual(surface.get_at(pos), line_color)
             self.assertIsInstance(bounds_rect, pygame.Rect)
 
     def test_aaline__valid_start_pos_formats(self):
@@ -2928,15 +2935,9 @@ def test_aaline__bounding_rect(self):
                             surface, line_color, start, end, thickness
                         )
 
-                        if 0 < thickness:
-                            # Calculating the expected_rect after the line is
-                            # drawn (it uses what is actually drawn).
-                            expected_rect = create_bounding_rect(
-                                surface, surf_color, start
-                            )
-                        else:
-                            # Nothing drawn.
-                            expected_rect = pygame.Rect(start, (0, 0))
+                        # Calculating the expected_rect after the line is
+                        # drawn (it uses what is actually drawn).
+                        expected_rect = create_bounding_rect(surface, surf_color, start)
 
                         self.assertEqual(
                             bounding_rect,