Migrate pix_n_flix module to Conductor

[Akshay-2007-1]

Summary

• Replaces the array-of-arrays Pixel/Pixels/Filter API with opaque image handles, accessed one channel at a time via get_pixel_value(source, x, y, p)/set_pixel_value(dest, x, y, p, v) - matching the design Martin laid out for this module rather than letting students index dest[x][y] directly.
• Splits the bundle/tab boundary into two channels: a control channel (makeRpc - dimensions, fps, volume, input source) and a dedicated frame channel that transfers raw ArrayBuffers instead of structured-cloning them. A plain RPC call always clones its arguments, which would copy a full video frame twice per frame.
• get_pixel_value/set_pixel_value carry an unconditional sync twin backed by the module's own buffer registry (keyed by the same identifier Conductor's opaque_make assigns), so per-pixel access from a student filter can skip the async-generator round trip - up to widthheight8 calls/frame otherwise.
• All camera/video/canvas/requestAnimationFrame ownership moves to the tab, since the module now runs in a Worker with no DOM access.

Dependencies

This depends on two still-open engine PRs for the sync fast path to actually activate at runtime:

• Preserve a moduleMethod's .sync twin through BaseModulePlugin.initialise() conductor#54
• py2js: closure_call_sync fast path for module closures called from Python py-slang#353

Until both land (and the conductor catalog pin here is bumped), get_pixel_value/set_pixel_value still work correctly, just through the existing async path.

Not in this PR

red_of/green_of/blue_of/alpha_of/set_rgba and the old Pixel type are intentionally left out of this migration's exports rather than guessing at their replacement - a follow-up decision once the opaque-handle pipeline is confirmed working end to end.

Test plan

• tsc --noEmit and eslint clean on both the bundle and the tab
• New unit tests for the buffer-shape helpers (functions.test.ts) pass
• Manual browser verification (camera feed + a real filter) - not done yet, needed before merging out of draft

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[gemini-code-assist]

Caution

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[Akshay-2007-1]

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Walkthrough

PixNFlix was reworked from standalone functions and a React tab into Conductor module and tab plugins. The implementation now transfers RGBA frames through dedicated channels, applies filters using opaque image buffers, supports synchronous pixel operations, and provides updated media controls and UI state handling.

Changes

PixNFlix migration

Layer / File(s)	Summary
Image buffer contracts and utilities src/bundles/pix_n_flix/src/types.ts, src/bundles/pix_n_flix/src/functions.ts, src/bundles/pix_n_flix/src/__tests__/functions.test.ts	Introduces ImageBuffer, RGBA buffer creation, coordinate and channel validation, pixel access, dimension-checked copying, and utility tests.
Conductor module and frame protocol src/bundles/pix_n_flix/src/protocol.ts, src/bundles/pix_n_flix/src/index.ts	Defines control and frame channels, implements the module plugin, manages frame buffers and filters, exposes media controls, and adds synchronous pixel methods.
Tab capture and rendering plugin src/tabs/Pixnflix/src/index.tsx	Adds the Conductor tab plugin with camera/media input handling, frame capture and rendering, playback controls, RPC handlers, and React UI.
Bundle and tab project configuration src/bundles/pix_n_flix/package.json, src/bundles/pix_n_flix/tsconfig.json, src/tabs/Pixnflix/package.json, src/tabs/Pixnflix/tsconfig.json	Updates dependencies and TypeScript configuration for the new bundle and tab source layout.

Estimated code review effort: 4 (Complex) | ~60 minutes

Sequence Diagram(s)

sequenceDiagram
  participant PixNFlixTabPlugin
  participant FrameChannel
  participant PixNFlixModulePlugin
  participant FilterClosure
  PixNFlixTabPlugin->>FrameChannel: send captured-frame
  FrameChannel->>PixNFlixModulePlugin: deliver captured frame
  PixNFlixModulePlugin->>FilterClosure: apply filter
  FilterClosure-->>PixNFlixModulePlugin: return filtered buffer
  PixNFlixModulePlugin->>FrameChannel: send filtered-frame
  FrameChannel->>PixNFlixTabPlugin: render filtered frame

Loading

Suggested reviewers: martin-henz, leeyi45

Poem

A rabbit hops through frames of light,
Buffers glow in black and white.
Filters dance, then channels sing,
Cameras loop on every spring.
Conductor guides the pixel flow—
“Hop approved!” the bunnies know.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly and concisely identifies the primary change: migrating the pix_n_flix module to Conductor.
Description check	✅ Passed	The description explains the migration, motivation, dependencies, intentional omissions, and test status, but it omits the template’s type and checklist sections.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/migrate-pix-n-flix

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Actionable comments posted: 6

🧹 Nitpick comments (5)

src/bundles/pix_n_flix/src/index.ts (2)

344-347: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Stray blank line inside the guard.

Line 345 is an empty line between the if and its throw; also worth noting __ensureTabLoaded() runs before the argument check, so an invalid pause_at still spawns the tab.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/bundles/pix_n_flix/src/index.ts` around lines 344 - 347, Remove the stray
blank line between the pause_time guard and its throw in the pause_at validation
logic. Do not alter the surrounding validation or __ensureTabLoaded() behavior.

---

352-374: 🎯 Functional Correctness | 🔵 Trivial | ⚡ Quick win

Inconsistent validation feedback across the control methods.

pause_at throws on bad input, while set_dimensions (Lines 358-360) and set_fps (Lines 370-372) silently no-op out-of-range values, and set_loop_count (Line 422) accepts any negative number as "infinite". For students, a silent no-op is hard to debug; consider throwing EvaluatorNumberRangeError consistently (or documenting the clamping) across all four.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/bundles/pix_n_flix/src/index.ts` around lines 352 - 374, The control
methods use inconsistent out-of-range handling. Update set_dimensions, set_fps,
and set_loop_count to validate inputs consistently with pause_at by throwing
EvaluatorNumberRangeError for invalid values, while preserving valid-value
behavior and the intentional infinite-loop representation if applicable.

src/tabs/Pixnflix/src/index.tsx (3)

313-327: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Element sizes are set imperatively but hard-coded in JSX.

updateDimensions mutates video/image/canvas .width/.height directly while the JSX (Lines 474-476) renders them with the constant DEFAULT_WIDTH/DEFAULT_HEIGHT. The state already carries the current dimensions — driving the JSX attributes from state.width/state.height keeps the DOM authoritative under React and avoids silently reverting to defaults on any remount.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/tabs/Pixnflix/src/index.tsx` around lines 313 - 327, Update the JSX
rendering of the video, image, and canvas elements to use the current
state.width and state.height values instead of DEFAULT_WIDTH and DEFAULT_HEIGHT.
Keep updateDimensions responsible for updating state so React remains the
authoritative source after remounts.

---

474-487: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Small a11y gaps in the view.

The hidden <img> (Line 474) has no alt attribute, and the volume range input (Line 486) is only visually labelled by the adjacent "Volume:" text. Add alt="" for the decorative image and associate the slider with a <label htmlFor>/aria-label.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/tabs/Pixnflix/src/index.tsx` around lines 474 - 487, Update the JSX view
around the hidden img and volume slider: add alt="" to the decorative img, and
give the range input an accessible name by associating it with a label via
htmlFor/id or adding an aria-label. Preserve the existing volume behavior and
visibility conditions.

---

404-417: 🩺 Stability & Availability | 🔵 Trivial | 💤 Low value

Object URLs are never revoked.

Each dropped/selected file creates a blob URL that is retained for the lifetime of the page. Revoke the previous one when replacing src (e.g. in onload/onloadeddata).

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/tabs/Pixnflix/src/index.tsx` around lines 404 - 417, Update
__handleFileDrop to track and revoke the previous object URL whenever a new
video or image file replaces the media source, and revoke each newly created URL
after the corresponding media element has loaded. Preserve the existing playback
and state transitions while ensuring dropped-file blob URLs are not retained for
the page lifetime.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@src/bundles/pix_n_flix/src/index.ts`:
- Around line 426-437: Update the stop() method and its documentation so
stopping the module also stops the tab-side requestAnimationFrame capture loop,
camera stream, and further frame handling via the existing
__tabRpc/frame-channel mechanism; add the corresponding tab-side stop handling
and ensure __endStreaming() still lets the Run terminate naturally.
- Around line 155-157: Update __handleCapturedFrame and its __frameChannel
subscription so every asynchronous failure, including opaque_make and send, is
caught rather than becoming an unhandled rejection. On failure, emit a
filtered-frame using the unmodified captured source so the tab’s pending-frame
promise resolves and capture processing continues. Preserve normal
filtered-frame behavior when processing succeeds.
- Around line 196-205: Update __unregisterBuffer to release the evaluator opaque
handle using the active evaluator/interface’s supported free or delete operation
before removing it from __buffers. Ensure every per-frame opaque created by
__registerBuffer is released when its destination/result handle reaches the end
of its lifetime.

In `@src/tabs/Pixnflix/src/index.tsx`:
- Around line 234-239: Update __stopCapture to clear the in-flight
__pendingFrame state when stopping capture, and settle its associated
__captureAndSendFrame promise by rejecting or otherwise explicitly abandoning
it. Ensure a subsequent __startCapture allows __tick to schedule frames
normally, while preserving the existing cancellation and timestamp reset
behavior.
- Around line 203-219: Update __releaseCamera to clear the video element’s
srcObject after stopping all MediaStream tracks, so __requestCamera can
reacquire the camera during detach/re-attach and tab-hide cycles. Preserve the
existing track cleanup behavior.
- Around line 272-275: Update the keep-aspect-ratio branch in the canvas
rendering method around ctx.rect and ctx.fill to call ctx.beginPath() before
defining the letterbox rectangle, ensuring each frame fills only the current
rect instead of accumulating prior paths.

---

Nitpick comments:
In `@src/bundles/pix_n_flix/src/index.ts`:
- Around line 344-347: Remove the stray blank line between the pause_time guard
and its throw in the pause_at validation logic. Do not alter the surrounding
validation or __ensureTabLoaded() behavior.
- Around line 352-374: The control methods use inconsistent out-of-range
handling. Update set_dimensions, set_fps, and set_loop_count to validate inputs
consistently with pause_at by throwing EvaluatorNumberRangeError for invalid
values, while preserving valid-value behavior and the intentional infinite-loop
representation if applicable.

In `@src/tabs/Pixnflix/src/index.tsx`:
- Around line 313-327: Update the JSX rendering of the video, image, and canvas
elements to use the current state.width and state.height values instead of
DEFAULT_WIDTH and DEFAULT_HEIGHT. Keep updateDimensions responsible for updating
state so React remains the authoritative source after remounts.
- Around line 474-487: Update the JSX view around the hidden img and volume
slider: add alt="" to the decorative img, and give the range input an accessible
name by associating it with a label via htmlFor/id or adding an aria-label.
Preserve the existing volume behavior and visibility conditions.
- Around line 404-417: Update __handleFileDrop to track and revoke the previous
object URL whenever a new video or image file replaces the media source, and
revoke each newly created URL after the corresponding media element has loaded.
Preserve the existing playback and state transitions while ensuring dropped-file
blob URLs are not retained for the page lifetime.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 24e90763-d4fb-4a7f-8ed7-0d4926f4db4e

📥 Commits

Reviewing files that changed from the base of the PR and between 6ad0dce and 12b0bcc.

⛔ Files ignored due to path filters (1)

• yarn.lock is excluded by !**/yarn.lock, !**/*.lock

📒 Files selected for processing (14)

• src/bundles/pix_n_flix/package.json
• src/bundles/pix_n_flix/src/__tests__/functions.test.ts
• src/bundles/pix_n_flix/src/__tests__/index.test.tsx
• src/bundles/pix_n_flix/src/functions.ts
• src/bundles/pix_n_flix/src/index.ts
• src/bundles/pix_n_flix/src/protocol.ts
• src/bundles/pix_n_flix/src/start.ts
• src/bundles/pix_n_flix/src/types.ts
• src/bundles/pix_n_flix/tsconfig.json
• src/bundles/pix_n_flix/vitest.config.ts
• src/tabs/Pixnflix/index.tsx
• src/tabs/Pixnflix/package.json
• src/tabs/Pixnflix/src/index.tsx
• src/tabs/Pixnflix/tsconfig.json

💤 Files with no reviewable changes (4)

• src/bundles/pix_n_flix/vitest.config.ts
• src/bundles/pix_n_flix/src/start.ts
• src/tabs/Pixnflix/index.tsx
• src/bundles/pix_n_flix/src/tests/index.test.tsx

[martin-henz]

Review by Claude (Sonnet):

Review: PR #824 — Migrate pix_n_flix module to Conductor

Scope: 15 files, +1250/−1550. Replaces pix_n_flix's array-of-arrays Pixel API with opaque image handles (get_pixel_value/set_pixel_value), splits the module/tab boundary into a control RPC channel + a dedicated zero-copy frame channel, and moves all DOM/camera/canvas ownership into the tab since the module now runs in a Worker.

Overview

This is a substantial, well-reasoned architectural migration mirroring the already-migrated sound module's patterns (RPC via makeRpc, tab-owned DOM, sync/async closure dual path). The code is heavily commented explaining why (dual-mode compilation, sync fast-path constraints, transfer vs. structured-clone), which is genuinely valuable here given how much engine-internals knowledge this PR encodes — appropriate given the complexity, even though it's far more comment-dense than typical.

Correctness issues

1. Lost parameter validation on set_dimensions, set_fps, set_loop_count (src/index.ts). Pre-migration, these threw a student-facing error via assertNumberWithinRange for out-of-range/non-integer input:

• set_dimensions/set_fps now silently no-op on out-of-range values instead of throwing — a student calling set_dimensions(9999, 9999) gets no feedback at all instead of a clear error.
• set_loop_count has no validation at all now (old code rejected non-integers like 0.5 or "a" with a thrown error). A fractional loop count now silently flows into the tab's __loopCount, where __handleVideoEnded's this.__loopsPlayed > this.__loopCount comparison will behave subtly wrong (e.g. stopping after 1 loop instead of the old "less than 1 → treated as 1" semantics) rather than failing loudly.

@moduleMethod's DataType list only enforces type (is-a-number), not range/integer constraints — those need the same manual assertInRange-style guard already used for pixel coordinates. Worth adding before merge, since silent behavior changes are worse for students than the previous explicit errors.
2. Camera un-mirroring is new, undocumented behavior (src/tabs/Pixnflix/src/index.tsx, __captureAndSendFrame). The capture step now applies ctx.translate(width, 0); ctx.scale(-1, 1) for the camera feed to counter the OS "selfie" mirror convention. The pre-migration tab never did this — it's a genuine visual/pixel-data change for every student using the live camera, not called out in the PR description, and it's exactly the kind of thing the PR's own checklist flags as unverified ("Manual browser verification … not done yet"). Worth confirming this is intentional and testing it explicitly, since it changes what red_of-successor filters see at each (x,y).
3. Unused export: PIX_N_FLIX_TAB_NAME (protocol.ts) doesn't appear to be referenced anywhere — the module uses tabLoader.tabs[0] and the tab uses its own local PIX_N_FLIX_TAB_ID. Minor, but worth removing or wiring up if it was meant to be used for the tab-loader lookup instead of the positional tabs[0].

Risks / things to confirm before merging out of draft

• Backward compatibility break, called out by the author but worth restating: red_of/green_of/blue_of/alpha_of/set_rgba and the old array-based Pixel type are dropped entirely with no replacement yet. Any existing assessments/missions using the old API will break. This needs coordination with content owners, not just an engineering follow-up.
• Test coverage gap: the new unit tests (functions.test.ts) only cover the pure buffer helpers. The much larger and more novel surface — PixNFlixModulePlugin (RPC wiring, callFilterClosure's sync/async fast-path selection, frame handling, buffer registry lifecycle) and the entire tab-side plugin (camera lifecycle, capture loop, backpressure) — has zero automated coverage. Given this is where most of the real complexity and risk lives, and manual browser verification is explicitly still pending, this is the biggest outstanding risk on the PR.
• External dependency: the sync fast path (the main performance win described in the PR) is inert until conductor#54 and py-slang#353 land and the catalog pin is bumped. Fine as a staged rollout, but worth a tracking note/issue so it doesn't get forgotten once this merges.

Nits

• pause_at throws a plain EvaluatorRuntimeError while functions.ts/copyImageBuffer use EvaluatorNumberRangeError/EvaluatorParameterTypeError with an eslint-disable for the throw-runtime-error rule — worth double-checking this is deliberate (i.e. EvaluatorRuntimeError is the rule-compliant type) rather than an oversight, since it's the one throw site without that comment.
• __ensureTabLoaded hardcodes tabLoader.tabs[0]; fine for a single-tab module but slightly fragile if that ever changes.

Verdict

Solid architecture and clearly reasons through the hard parts (RPC vs. transferable frames, sync/async closure duality, buffer lifecycle). Before taking it out of draft, I'd prioritize: (1) restoring range/integer validation on set_dimensions/set_fps/set_loop_count, (2) confirming the camera-mirroring change is intentional via manual testing, and (3) at least some integration-level tests or manual verification of the module↔tab frame round-trip before relying on it in production.

[martin-henz]

I think this is ready to be merged. Best have a version in "production" for Avengers to play with.

[Akshay-2007-1]

Test Snippets to run (Examples)

1. Local File usage with filter

from pix_n_flix import use_local_file, get_pixel, red_of, green_of, blue_of, alpha_of, set_rgba, image_width, image_height, install_filter

def invert(src, dest):
    w = round(image_width())
    h = round(image_height())
    for x in range(w):
        for y in range(h):
            p = get_pixel(src, x, y)
            q = get_pixel(dest, x, y)
            set_rgba(q, 255 - red_of(p), 255 - green_of(p), 255 - blue_of(p), alpha_of(p))

use_local_file()
install_filter(invert)

2. set_dimensions / set_fps / set_volume / keep_aspect_ratio

from pix_n_flix import set_dimensions, set_fps, set_volume, keep_aspect_ratio, install_filter, copy_image

install_filter(copy_image)
set_dimensions(320, 240)
set_fps(20)
set_volume(75)
keep_aspect_ratio(True)

3. pause_at / get_video_time

from pix_n_flix import install_filter, copy_image, pause_at, get_video_time

install_filter(copy_image)
pause_at(5000)
elapsed = get_video_time()
print(elapsed)

4. get_pixel/red_of/green_of/blue_of/alpha_of/set_rgba, ALONG with invert

from pix_n_flix import get_pixel, red_of, green_of, blue_of, alpha_of, set_rgba, image_width, image_height, install_filter

def invert(src, dest):
    w = round(image_width())
    h = round(image_height())
    for x in range(w):
        for y in range(h):
            p = get_pixel(src, x, y)
            q = get_pixel(dest, x, y)
            set_rgba(q, 255 - red_of(p), 255 - green_of(p), 255 - blue_of(p), alpha_of(p))

install_filter(invert)

5. Compose Filter

from pix_n_flix import get_pixel_value, set_pixel_value, image_width, image_height, install_filter, compose_filter

def grayscale(src, dest):
    w = round(image_width())
    h = round(image_height())
    for x in range(w):
        for y in range(h):
            r = get_pixel_value(src, x, y, 0)
            g = get_pixel_value(src, x, y, 1)
            b = get_pixel_value(src, x, y, 2)
            avg = (r + g + b) / 3
            set_pixel_value(dest, x, y, 0, math_floor(avg))
            set_pixel_value(dest, x, y, 1, math_floor(avg))
            set_pixel_value(dest, x, y, 2, math_floor(avg))
            set_pixel_value(dest, x, y, 3, math_floor(get_pixel_value(src, x, y, 3)))

def invert(src, dest):
    w = round(image_width())
    h = round(image_height())
    for x in range(w):
        for y in range(h):
            for p in range(3):
                set_pixel_value(dest, x, y, p, 255 - get_pixel
            set_pixel_value(dest, x, y, 3, math_floor(get_pixel_value(src, x, y, 3)))

install_filter(compose_filter(grayscale, invert))

6. Reset filter

from pix_n_flix import install_filter, reset_filter, copy_image

def my_filter(src, dest):
    copy_image(src, dest)

install_filter(my_filter)
reset_filter()

7. pause_at/get_video_time (since stateful REPL isnt a thing, we use timeout for sync times)

from pix_n_flix import install_filter, copy_image, pause_at, get_video_time

install_filter(copy_image)
pause_at(5000)

def report_time():
    elapsed = get_video_time()
    print(elapsed)

set_timeout(report_time, 5000)

8. stop

from pix_n_flix import install_filter, copy_image, stop

install_filter(copy_image)
stop()

Expect no video buffer for the same!

9. Image URLs

from pix_n_flix import get_pixel_value, set_pixel_value, image_width, image_height, install_filter, compose_filter, use_image_url

def grayscale(src, dest):
    w = round(image_width())
    h = round(image_height())
    for x in range(w):
        for y in range(h):
            r = get_pixel_value(src, x, y, 0)
            g = get_pixel_value(src, x, y, 1)
            b = get_pixel_value(src, x, y, 2)
            avg = (r + g + b) / 3
            set_pixel_value(dest, x, y, 0, math_floor(avg))
            set_pixel_value(dest, x, y, 1, math_floor(avg))
            set_pixel_value(dest, x, y, 2, math_floor(avg))
            set_pixel_value(dest, x, y, 3, math_floor(get_pixel_value(src, x, y, 3)))

use_image_url("https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcT24VCmiHF__F7Uku7XftFlctyMmOUJJXkosTVhKfWEIZwkd_0iQcRZgxk&s=10")
install_filter(grayscale)

10. Video URLs

from pix_n_flix import use_local_file, use_image_url, use_video_url, install_filter, copy_image, image_width, image_height, set_pixel_value, get_pixel_value

def invert(src, dest):
    w = round(image_width())
    h = round(image_height())
    for x in range(w):
        for y in range(h):
            for p in range(3):
                set_pixel_value(dest, x, y, p, 255 - get_pixel_value(src, x, y, p))
            set_pixel_value(dest, x, y, 3, math_floor(get_pixel_value(src, x, y, 3)))

use_video_url("https://samplelib.com/mp4/sample-20s-360p.mp4")
install_filter(invert)