Item constraint handling

[amolenaar]

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Documentation content changes

What is the current behavior?

Item specific constraints are managed in the item. Item needs a reference to a canvas to add/remove constraints to the constraint solver.

Issue Number: N/A

What is the new behavior?

• Pass the Connections object to the item via its constructor. Constraint lifecycle can be managed from there.
• Better interface for Position.
• Items no longer have a canvas reference.
• Protocols for the View.
• Updated tests to use fixtures normally

Does this PR introduce a breaking change?

• Yes
• No

Other information

[sourcery-ai]

Sourcery Code Quality Report

Merging this PR leaves code quality unchanged.

Quality metrics	Before	After	Change
Complexity	0.82 ⭐	0.79 ⭐	-0.03 👍
Method Length	47.01 ⭐	45.58 ⭐	-1.43 👍
Working memory	5.31 ⭐	5.42 ⭐	0.11 👎
Quality	87.75% ⭐	87.75% ⭐	0.00%

Other metrics	Before	After	Change
Lines	4165	4028	-137

Changed files	Quality Before	Quality After	Quality Change
examples/demo.py	88.92% ⭐	88.58% ⭐	-0.34% 👎
examples/exampleitems.py	88.52% ⭐	87.19% ⭐	-1.33% 👎
examples/simple-box.py	86.55% ⭐	86.47% ⭐	-0.08% 👎
gaphas/canvas.py	93.98% ⭐	94.26% ⭐	0.28% 👍
gaphas/connections.py	84.31% ⭐	86.79% ⭐	2.48% 👍
gaphas/connector.py	93.71% ⭐	93.64% ⭐	-0.07% 👎
gaphas/item.py	91.49% ⭐	91.57% ⭐	0.08% 👍
gaphas/position.py	93.24% ⭐	92.81% ⭐	-0.43% 👎
gaphas/segment.py	76.58% ⭐	76.55% ⭐	-0.03% 👎
gaphas/painter/handlepainter.py	77.54% ⭐	77.52% ⭐	-0.02% 👎
gaphas/painter/itempainter.py	92.10% ⭐	92.69% ⭐	0.59% 👍
gaphas/solver/solver.py	90.08% ⭐	90.08% ⭐	0.00%
gaphas/view/gtkview.py	84.42% ⭐	84.41% ⭐	-0.01% 👎
tests/conftest.py	91.34% ⭐	95.02% ⭐	3.68% 👍
tests/test_aspect.py	92.33% ⭐	92.91% ⭐	0.58% 👍
tests/test_canvas.py	81.69% ⭐	80.80% ⭐	-0.89% 👎
tests/test_connections.py	88.96% ⭐	87.67% ⭐	-1.29% 👎
tests/test_element.py	83.81% ⭐	84.31% ⭐	0.50% 👍
tests/test_guide.py	81.97% ⭐	81.24% ⭐	-0.73% 👎
tests/test_item.py	92.00% ⭐	94.56% ⭐	2.56% 👍
tests/test_line.py	87.22% ⭐	86.87% ⭐	-0.35% 👎
tests/test_position.py	85.03% ⭐	85.09% ⭐	0.06% 👍
tests/test_segment.py	79.44% ⭐	78.45% ⭐	-0.99% 👎
tests/test_tool.py	81.75% ⭐	83.89% ⭐	2.14% 👍
tests/test_undo.py	76.67% ⭐	76.36% ⭐	-0.31% 👎
tests/test_view.py	89.24% ⭐	88.24% ⭐	-1.00% 👎

Here are some functions in these files that still need a tune-up:

File	Function	Complexity	Length	Working Memory	Quality	Recommendation
examples/demo.py	create_window	9 🙂	850 ⛔	16 ⛔	31.96% 😞	Try splitting into smaller methods. Extract out complex expressions
gaphas/view/gtkview.py	GtkView.update_back_buffer	22 😞	231 ⛔	11 😞	35.15% 😞	Refactor to reduce nesting. Try splitting into smaller methods. Extract out complex expressions
gaphas/painter/handlepainter.py	HandlePainter._draw_handles	15 🙂	220 ⛔	13 😞	37.74% 😞	Try splitting into smaller methods. Extract out complex expressions
gaphas/view/gtkview.py	GtkView.get_handle_at_point	18 🙂	149 😞	9 🙂	48.65% 😞	Try splitting into smaller methods
gaphas/view/gtkview.py	GtkView.get_port_at_point	11 🙂	125 😞	13 😞	49.95% 😞	Try splitting into smaller methods. Extract out complex expressions

Legend and Explanation

The emojis denote the absolute quality of the code:

• ⭐ excellent
• 🙂 good
• 😞 poor
• ⛔ very poor

The 👍 and 👎 indicate whether the quality has improved or gotten worse with this pull request.

---

Please see our documentation here for details on how these metrics are calculated.

We are actively working on this report - lots more documentation and extra metrics to come!

Let us know what you think of it by mentioning @sourcery-ai in a comment.

[danyeaw]

This is a smart refactoring to better separate the item constraints from the canvas!

Do we need to update the README and constraint.rst, or would you prefer that we create a separate PR to update the docs with all the changes so far?

[amolenaar]

Good point. Let me do that in a separate PR, so I can first see what the impact of the changes in on Gaphor.