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Part 4 of this project

Data Layer

Model strokes as serializable points

Goal for this part

Model strokes as serializable points.

Treat 04-Data-Layer as the source of truth for this checkpoint. If your local tree drifted, re-clone that folder rather than mixing files from neighbors.

What you should already know

You do not need prior Qt Quick experience for part 1. Later parts assume you finished the earlier snapshots on the same machine.

  • You can open a terminal and run python3
  • You are comfortable editing a .py file and saving it
  • You have a desktop session (not a headless SSH box without display forwarding)

Why Qt Quick fits Brushnook

Qt Quick (QML) is a different path from widgets—declarative UI plus a Canvas for drawing strokes.

Expose brush settings from Python to QML. Keep the stroke list serializable so undo stays understandable.

Checkpoint

After you run the snapshot, you should recognize the behavior described in the goal—before you move on. If the window (or server) never appears, stop and fix the run steps.

Code shape

Snapshots stay small on purpose. Look for this kind of core call as you read the folder:

ctx.beginPath(); ctx.moveTo(x, y);

How to run it

Clone the teaching repo, open 04-Data-Layer, install what the README asks for, then run python app.py.

git clone https://github.com/michaeldunga1/fcc-qml-paint.git
cd fcc-qml-paint/04-Data-Layer
python3 -m venv .venv
source .venv/bin/activate
pip install -r ../requirements.txt
python app.py

Common mistakes

  • Ignoring platform-specific install notes in the snapshot README
  • Creating tables twice with conflicting schemas
  • Forgetting to commit/close the database connection in long sessions
  • Looking for seed data in part 3 before the data layer exists

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