Validate frames and coordinate spaces

Stage 1 of 4. Read the project prerequisites before starting; this stage builds on the preceding contracts.

What changes

A screenshot has physical pixel dimensions while native desktop clicks may use logical coordinates. Validate positive bounded dimensions and a finite display scale, then reject points outside the frame before converting by floor division. The frame generation identifies which observation justified an action.

Work through one concrete case

A screenshot is640x400 physical pixels at scale 2. Pixel(200,100) maps to logical(100,50). Pixel(640,100) is already outside the image and must not become a plausible logical coordinate through division.

Change the lab inputs and calculate the result before reading its metrics. The figure computes from those inputs; the implementation tests below remain the source of completion evidence.

Implement the contract

Implement Frame.validate, Frame.logical_point in your workspace main.rs. Keep earlier stages working. Read the function signatures and tests first, then implement one boundary at a time. The fixture is a deterministic test backend, and its results do not establish native operating-system behavior.

Use the public API contract and the typed starter signatures. Return values from core functions and let the supplied driver own file input, argument parsing and presentation.

Validate bounds in physical space first; then floor each coordinate divided by scale. Check finiteness before converting floats to unsigned integers.

Verify and inspect

From the repository root, initialize once with python3 scripts/project_test.py desktop-control --init learning-artifacts/desktop-control. Then grade cumulatively:

python3 scripts/project_test.py desktop-control --stage 1 --path learning-artifacts/desktop-control --strict

A fresh workspace should fail until you implement the contract. After every stage is complete, run your actual artifact from the supplied sample:

cd learning-artifacts/desktop-control
rustc --edition 2021 cli.rs -o desktop-cli
./desktop-cli samples/actions.tsv desktop-frames

Investigate the failure boundary

Try NaN, negative coordinates and scale 0. Each error must occur before Backend.click is called.

References

Rust process commands AppleScript language guide PNG specification