feat(drawing-pad): add simple freehand drawing example by chasejoyal · Pull Request #56 · niklabh/oxide

chasejoyal · 2026-09-09T22:30:26Z

What

Simple drawing pad example: freehand strokes, color palette, brush
slider, clear button.

Why

Closes #22 — fills the missing canvas + input example.

How

Single-file on_frame loop. Each frame appends a line segment to a
persisted list, redrawn every frame with a joint circle per point.
Dock has a click-to-select palette, a brush-size ui_slider, and a
ui_button_variant clear button.

Testing

cargo build --target wasm32-unknown-unknown --release -p drawing-pad
cargo fmt --check, cargo clippy -- -D warnings
Manually tested in Oxide browser: draw, switch colors, resize brush, clear.

Summary by CodeRabbit

New Features
- Added a drawing pad example with freehand drawing using mouse input.
- Added smooth line rendering with round brush strokes.
- Added a six-color palette with selectable colors.
- Added an adjustable brush-size slider.
- Added a clear button to remove all drawn content.
- Added visual feedback for the selected color and brush size.
- Added the drawing pad example to the workspace for easier access.

Minimal drawing pad: freehand strokes, color palette, brush-size slider, clear button. Single on_frame loop, no multi-file split. Closes niklabh#22.

coderabbitai · 2026-09-09T22:30:36Z

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Cargo.toml
examples/drawing-pad/Cargo.toml
examples/drawing-pad/src/lib.rs

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📝 Walkthrough

Walkthrough

The pull request adds a drawing-pad workspace crate. It defines persistent drawing state and implements freehand drawing, color selection, canvas clearing, and brush-size adjustment through oxide_sdk.

Changes

Drawing pad example

Layer / File(s)	Summary
Workspace crate setup `Cargo.toml`, `examples/drawing-pad/Cargo.toml`	The workspace includes the new crate. Its manifest defines package metadata, a `cdylib` library, and the `oxide-sdk` path dependency.
Drawing state and data model `examples/drawing-pad/src/lib.rs`	The example defines the palette, layout constants, segment and application state, lazy global initialization, and the `start_app` entry point.
Interactive frame rendering `examples/drawing-pad/src/lib.rs`	`on_frame` reads pointer input, records strokes, redraws segments, handles palette and clear-button input, and updates the brush-size slider.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant User
  participant on_frame
  participant oxide_sdk
  User->>on_frame: Move pointer or press a control
  on_frame->>oxide_sdk: Read canvas and mouse state
  on_frame->>oxide_sdk: Draw segments and controls
  on_frame->>on_frame: Update application state

Merge Risk: ⚪ Minimal · up to 484f4

The drawing example preserves stroke boundaries correctly, with no remaining merge-blocking risk identified.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Linked Issues check	⚠️ Warning	Issue `#22` requires the drawing pad structure, workspace inclusion, freehand mouse drawing, color selection, canvas clearing, brush-size control, `on_frame`, and the listed canvas and input APIs. The c…	Use `canvas_circle` in the drawing implementation, or provide reviewable evidence that the current implementation satisfies Issue `#22`'s required `canvas_circle` API usage.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: adding a simple freehand drawing pad example.
Out of Scope Changes check	✅ Passed	The changes add the requested `examples/drawing-pad` crate, its workspace entry, and the drawing-pad implementation. The input handling, canvas rendering, palette, clear control, and brush-size contro…
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 1 files. (2 skipped: 2 …

Full details: Linked Issues check

Explanation

Issue #22 requires the drawing pad structure, workspace inclusion, freehand mouse drawing, color selection, canvas clearing, brush-size control, on_frame, and the listed canvas and input APIs. The current summary confirms the structure, workspace entry, on_frame, mouse input, canvas_clear, canvas_line, color palette, clear control, brush-size slider, and segment persistence. The implementation summary does not show canvas_circle; it uses line segments with round end caps instead. The reported WASM build, formatting, Clippy, and manual browser checks support the remaining requirements.

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chasejoyal · 2026-09-09T22:59:45Z

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coderabbitai · 2026-09-09T22:59:50Z

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Inline comments:
In `@examples/drawing-pad/src/lib.rs`:
- Line 75: Bound App.segments in the on_frame stroke-append path so repeated
frames cannot grow the stored segment collection without limit; use a bounded
preallocated buffer or rasterize committed strokes while preserving redraw
behavior, and remove any claim that Vec allocation requires an unavailable
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Cap App.segments at MAX_SEGMENTS so a long drawing session can't grow memory/frame cost unbounded. Add doc comments to app/start_app/on_frame to satisfy docstring coverage.

chasejoyal · 2026-09-10T00:05:12Z

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coderabbitai · 2026-09-10T00:05:52Z

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Inline comments:
In `@examples/drawing-pad/src/lib.rs`:
- Line 79: Update the segment-append logic around Segment so it only pushes a
segment when app.last_point exists and differs from point; skip unchanged
pointer positions while preserving normal segment creation for actual movement.
- Line 52: Initialize the bounded app.segments collection with capacity
MAX_SEGMENTS instead of zero capacity, while preserving its Vec type and
existing behavior in on_frame.

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Inline comments:
In `@examples/drawing-pad/src/lib.rs`:
- Around line 79-90: In the segment-recording logic of the drawing handler,
remove the duplicated block and the orphaned Segment fields, leaving one
complete Segment initializer within the existing in_canvas, capacity, and
last_point conditions so the Rust function compiles.

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chasejoyal · 2026-09-14T18:48:02Z

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coderabbitai · 2026-09-14T18:48:07Z

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chasejoyal · 2026-09-14T20:11:19Z

@niklabh All checks pass. Ready for review.

feat(drawing-pad): add simple freehand drawing example

22e3df5

Minimal drawing pad: freehand strokes, color palette, brush-size slider, clear button. Single on_frame loop, no multi-file split. Closes niklabh#22.

coderabbitai Bot reviewed Sep 9, 2026

View reviewed changes

fix(drawing-pad): bound stored segments, add missing docstrings

f0c5419

Cap App.segments at MAX_SEGMENTS so a long drawing session can't grow memory/frame cost unbounded. Add doc comments to app/start_app/on_frame to satisfy docstring coverage.

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Comment thread examples/drawing-pad/src/lib.rs Outdated

Comment thread examples/drawing-pad/src/lib.rs Outdated

chasejoyal and others added 3 commits September 9, 2026 17:15

Update examples/drawing-pad/src/lib.rs

fe63afb

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refactor(drawing-pad): pre-allocate segments with capacity

4fbf0ad

Merge branch 'main' into feat/drawing-pad-example

5fae0e5

coderabbitai Bot reviewed Sep 14, 2026

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Comment thread examples/drawing-pad/src/lib.rs Outdated

Fix duplicated/orphaned segment-recording block in drawing-pad

484f4f8

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Walkthrough

Changes

Sequence Diagram(s)

❌ Failed checks (1 warning)

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