[Feature]: Implement B-spline SVG path component for workflow links #15 by LudoBroche · Pull Request #16 · ewoks-kit/ewoksdraw

LudoBroche · 2026-07-07T14:43:26Z

Description

Closes #15 This PR implements the isolated Bezier SVG component.

Changes Made

New SvgLinkCubicBezier class, to generate an svg element from a CubicBezierPath data structure and the desired style properties (color, stroke_width ...)
CubicBezierPath is a new data class representing the start, end and control points of the bezier path. A helper function (from_points(points, radius)) translate a polyline coordinates into rounded cubic bezier path.

Note to Reviewer(s)

This PR is strictly limited to the SVG path generation. It does not include the ewoks JSON parsing, collision avoidance, routing calculations, or node rendering.

codecov · 2026-07-07T14:45:43Z

Codecov Report

❌ Patch coverage is 95.06173% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/ewoksdraw/svg/svg_element.py	63.63%	4 Missing ⚠️

📢 Thoughts on this report? Let us know!

LudoBroche · 2026-07-07T15:23:16Z

Since, the scope of this PR is not to compute the links coordinates from an ewoks workflows. I created a a small example script to show the API in examples/cubic_bezier_link.py :

Path definition using directly the bezier control points:

letter_w = CubicBezierPath(
    start=(135, 84),
    segments=[
        CubicBezierSegment((142, 124), (145, 154), (158, 156)),
        CubicBezierSegment((169, 158), (176, 102), (187, 102)),
        CubicBezierSegment((198, 102), (196, 157), (210, 157)),
        CubicBezierSegment((224, 157), (236, 105), (244, 84)),
    ],
)

Path definition using polyline coordinates and corner radius :

underline = CubicBezierPath.from_points(
    points=[
        (40, 175),
        (240, 175),
        (240, 205),
        (480, 205),
        (480, 25),
        (320, 25),
        (320, 205),
    ],
    radius=30,
)

Svg Path element create from the CubicBezierPath object :

  svg_w = SvgLinkCubicBezier(
      letter_w,
      color="#00c2a8",
      stroke_width=4,
      stroke_dash="5 10",
  )

svg_underline = SvgLinkCubicBezier(
    underline,
    color="#ff00aa",
    stroke_width=3,
    stroke_dash="12 6",
),

Add elements to the canvas and draw:

canvas = SvgCanvas(width=520, height=220)
canvas.add_element(svg_w)
canvas.add_element(svg_underline)
canvas.draw(output_path)

Of course it's compatible with groups :

links_group = SvgGroup()
links_group.add_elements([svg_w, svg_underline])
links_group.translate(5, 5)
canvas.add_element(links_group)
canvas.draw(output_path)

Voila :

loichuder · 2026-07-13T07:30:40Z

@@ -0,0 +1,3 @@
+from .cubic_bezier_path import CubicBezierPath  # noqa: F401
+from .cubic_bezier_path import CubicBezierSegment  # noqa: F401
+from .cubic_bezier_path import Point  # noqa: F401


I would not export the members of cubic_bezier_path here since this adds maintenance for not much.

Members can be imported by users and consumer modules from their original location.

Removed all init.py imports

loichuder · 2026-07-13T07:36:15Z

-        if tag not in ("rect", "circle", "text", "line"):
+        if tag not in ("rect", "circle", "text", "line", "path"):
            raise ValueError(
                f"Invalid SVG tag: {tag}. Supported tags are 'rect', 'circle', 'text',"


Suggested change

f"Invalid SVG tag: {tag}. Supported tags are 'rect', 'circle', 'text',"

f"Invalid SVG tag: {tag}. Supported tags are 'rect', 'circle', 'text',"path", "

I would suggest to make a constant out of the supported tags to avoid this issue in the future.

loichuder · 2026-07-13T07:37:13Z

        """
+
+        if self._tag == "path":
+            return


Should we print a warning there?

Absolutely

if self._tag == "path": warnings.warn( "set_position() has no effect on 'path' elements; position is " "defined by the path data instead.", stacklevel=2, ) return

loichuder · 2026-07-13T07:40:22Z

+def test_stroke_width_formatted_without_trailing_zero():
+    link = SvgLinkCubicBezier(SIMPLE_PATH, stroke_width=4.0)
+    assert link.get_attr("style") == "stroke-width:4"


What is the point of this test? Is "stroke-width:4.0" not valid SVG?

You right I wanted to reach that line of code.
I can do it in the previous test since it's just a consmetic formating.

loichuder · 2026-07-13T07:43:24Z

+        (None, None, None, None),
+    ],
+)
+def test_style_attribute_combinations(color, stroke_width, stroke_dash, expected_style):


The test is so simple that it could be made more readable by doing the combinations one after the other rather than using parametrize.

Done split the tests in the different style calls.

loichuder · 2026-07-13T13:25:30Z

@@ -0,0 +1,98 @@
+from dataclasses import dataclass
+from typing import Self


Suggested change

from typing import Self

import sys

if sys.version_info < (3, 11):

from typing_extensions import Self

else:

from typing import Self

loichuder · 2026-07-13T13:29:27Z

+    return (1 if end[0] > start[0] else -1, 0)
+
+
+def _distance(start: Point, end: Point) -> float:


This distance is computed with the L1 norm, not the usual L2. Is this normal?

loichuder · 2026-07-13T13:31:03Z

    """

-    def __init__(self, width: int, height: int):
+    def __init__(self, width: int | float, height: int | float):


We can use numbers.Number instead: https://docs.python.org/3.10/library/numbers.html#numbers.Number

loichuder · 2026-07-13T13:36:14Z

 from xml.etree.ElementTree import Element

+SvgTag = Literal["rect", "circle", "text", "line", "path"]
+SUPPORTED_TAGS: Final[tuple[SvgTag, ...]] = get_args(SvgTag)


Didn't know about get_args, pretty sweet.

Final is probably overkill since it does not raise an error at runtime and we don't run type checking.

loichuder · 2026-07-13T13:37:12Z

+        path: CubicBezierPath,
+        color: str | None = None,
+        stroke_width: float | None = None,
+        stroke_dash: str | None = None,


Suggested change

stroke_dash: str | None = None,

stroke_dasharray: str | None = None,

Might as well use the same name as the SVG property 🤷

Issue #15 - First path object implementation with small example

0fd4e25

LudoBroche self-assigned this Jul 7, 2026

LudoBroche linked an issue Jul 7, 2026 that may be closed by this pull request

[Feature]: Implement B-spline SVG path component for workflow links #15

Open

LudoBroche closed this Jul 7, 2026

LudoBroche reopened this Jul 7, 2026

Issue #15 - Oh no ! I forgot the S

7fdf37e

LudoBroche requested a review from loichuder July 7, 2026 15:24

LudoBroche added 2 commits July 7, 2026 17:31

Issue #15 - Ignoring position when svg element is path

9c47ebf

Issue #15 -Typo

e94627f

LudoBroche requested a review from a team July 8, 2026 09:27

LudoBroche changed the title ~~Implement first path object with example~~ [Feature]: Implement B-spline SVG path component for workflow links #15 Jul 8, 2026

Issue #15 - Adding unitest

d2b0c45

LudoBroche marked this pull request as ready for review July 9, 2026 08:04

loichuder reviewed Jul 13, 2026

View reviewed changes

Issue #15 - Review changes

f235daf

LudoBroche requested a review from loichuder July 13, 2026 12:19

loichuder approved these changes Jul 13, 2026

View reviewed changes

	f"Invalid SVG tag: {tag}. Supported tags are 'rect', 'circle', 'text',"
	f"Invalid SVG tag: {tag}. Supported tags are 'rect', 'circle', 'text',"path", "

		@@ -0,0 +1,98 @@
		from dataclasses import dataclass
		from typing import Self

-from typing import Self
+import sys
+if sys.version_info < (3, 11):
+    from typing_extensions import Self
+else:
+    from typing import Self

		return (1 if end[0] > start[0] else -1, 0)


		def _distance(start: Point, end: Point) -> float:

	stroke_dash: str \| None = None,
	stroke_dasharray: str \| None = None,

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