Add draw.aarect() to draw anti-aliased and rounded rectangles

[Fantastair]

Implemented the enhancement mentioned in #3700.

• Added the following to src_c/draw.c:

  • draw_round_rect_xiaolinwu() function, used to draw anti-aliased rounded rectangles (corresponding to the functionality of draw_round_rect(), but internally uses draw_circle_xiaolinwu() to draw the rounded corners).
  • The aarect() function serves as the Python API interface. Its parameters and functionality are identical to the draw.rect() function, except it draws anti-aliased rounded rectangles. Internally, it calls draw_round_rect_xiaolinwu().

• Added example code related to aarect() in docs/reST/ref/code_examples/draw_module_example.py.

• Added function annotations for aarect() in buildconfig/stubs/pygame/draw.pyi.

• Added aarect()-related unit tests to test/draw_test.py. (Incidentally, I noticed the test_color_validation subtest in the DrawModuleTest class lacked coverage for draw.rect(), so I added it as well.)

[coderabbitai]

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📝 Walkthrough

Walkthrough

Adds a new public drawing function, pygame.draw.aarect, implemented in C (Xiaolin Wu anti-aliasing), with pyi stub, documentation examples, and tests; binds the C implementation to the draw module and exposes it in the test suite.

Changes

Cohort / File(s)	Summary
Type Definitions buildconfig/stubs/pygame/draw.pyi	Added aarect signature with parameters for surface, color, rect, width, and per-corner border radii.
Documentation docs/reST/ref/code_examples/draw_module_example.py	Added three example calls demonstrating pygame.draw.aarect with various widths and rounded-corner configurations.
Core Implementation src_c/draw.c	Added aarect Python-exposed function, argument parsing/validation, surface lock/unlock, and draw_round_rect_xiaolinwu helper implementing anti-aliased rounded-rectangle rendering; registered aarect in module method table.
Tests test/draw_test.py	Added DrawAARectMixin and DrawAARectTest, exposed draw_aarect alias on DrawTestCase, and extended tests to validate argument forms, clipping, widths, colors, and bounding rectangles for aarect.

Sequence Diagram(s)

sequenceDiagram
    participant Py as Python caller
    participant DrawMod as draw module binding
    participant CImpl as C implementation (aarect)
    participant SDL as SDL_Surface

    Py->>DrawMod: pygame.draw.aarect(surface, color, rect, ...)
    DrawMod->>CImpl: call aarect(...) (args parsed)
    CImpl->>CImpl: validate args & compute radii/area
    CImpl->>SDL: lock surface
    CImpl->>CImpl: if rounded -> draw_round_rect_xiaolinwu(...)
    CImpl->>SDL: blit/modify pixels within drawn area
    CImpl->>SDL: unlock surface
    CImpl-->>DrawMod: return drawn Rect
    DrawMod-->>Py: return Rect

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related issues

• Issue #3700: Implements the requested pygame.draw.aarect API (C implementation, binding, stub, docs, tests).

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 68.75% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: adding the draw.aarect() function for anti-aliased and rounded rectangles, which is the primary focus of all modifications across the codebase.
Description check	✅ Passed	The description is directly related to the changeset, detailing the specific files modified, functions added (draw_round_rect_xiaolinwu and aarect), and additional documentation and test coverage provided.

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[coderabbitai]

Actionable comments posted: 2

🤖 Fix all issues with AI agents

In `@src_c/draw.c`:
- Around line 4259-4268: Run the formatter to fix clang-format issues affecting
draw_round_rect_xiaolinwu and surrounding declarations: execute "python3 dev.py
format" (or "python3 dev.py all" to catch all files), review the changes to the
draw_round_rect_xiaolinwu function signature and local variable declarations
(pts, q_top, q_left, q_bottom, q_right, f) to ensure only style changes were
applied, then stage and commit the formatted changes.

In `@test/draw_test.py`:
- Around line 5173-5180: The tests assign to an unused variable bounds_rect
inside assertRaises blocks causing F841 lint errors; remove the assignments so
the calls to self.draw_aarect(...) are executed only for their exception check
(e.g., change "bounds_rect = self.draw_aarect(...)" to "self.draw_aarect(...)"
in the assertRaises blocks). Apply the same change for all occurrences mentioned
(other blocks around lines referencing draw_aarect and bounds_rect).

[coderabbitai]

⚠️ Potential issue | 🟠 Major

Fix F841 lint errors from unused bounds_rect assignments.

Ruff/Flake8 flag these as unused locals; this can fail CI. Drop the assignments inside the assertRaises blocks.

✅ Suggested fix (apply similarly to the other blocks)

-            with self.assertRaises(TypeError):
-                bounds_rect = self.draw_aarect(surface, pygame.Color("white"))
+            with self.assertRaises(TypeError):
+                self.draw_aarect(surface, pygame.Color("white"))

Also applies to: 5196-5201, 5241-5249, 5358-5360, 5383-5385, 5473-5477, 5518-5522

🧰 Tools

🪛 Flake8 (7.3.0)

[error] 5180-5180: local variable 'bounds_rect' is assigned to but never used

(F841)

🪛 Ruff (0.14.14)

[error] 5180-5180: Local variable bounds_rect is assigned to but never used

Remove assignment to unused variable bounds_rect

(F841)

🤖 Prompt for AI Agents

In `@test/draw_test.py` around lines 5173 - 5180, The tests assign to an unused
variable bounds_rect inside assertRaises blocks causing F841 lint errors; remove
the assignments so the calls to self.draw_aarect(...) are executed only for
their exception check (e.g., change "bounds_rect = self.draw_aarect(...)" to
"self.draw_aarect(...)" in the assertRaises blocks). Apply the same change for
all occurrences mentioned (other blocks around lines referencing draw_aarect and
bounds_rect).