fix: screenshot permission (#28), back handling (#30), cleanup (#35)

[compot-dev]

Fixes #28, fixes #30, fixes #35.

⚠️ Do not merge before testing on a device (label awaiting device test).

Issue	Problem	Fix
#28	On Android 6–9 screenshots were not saved: WRITE_EXTERNAL_STORAGE was never requested at runtime	The permission is requested on the first long press, and the screenshot is taken once it is granted. A refusal shows a message
#30	Android 16 (targetSdk 36): back gestures no longer arrive as KEYCODE_BACK; lint reported GestureBackNavigation	The activity no longer intercepts Back. The menu (a focusable PopupWindow) and the dialogs handle it themselves, including predictive back gestures via their own OnBackInvokedDispatcher. enableOnBackInvokedCallback="true" gives Android 13–15 the same behaviour
#35	Small items	See below

#35 checklist

• Removed the ProGuard rule for the no longer existing Decoder$Frame.
• The 5-thread pool in RtspClient: already gone with RtspSession (refactor: shared RtspSession for single view and Quad (#33, #9, #18, #19, #27) #45).
• FramePool: separate size classes. Small frames (≤ 64 KiB) are rounded up to a power of two; large ones to 256 KiB steps, and the large class is bounded. Small requests no longer take key-frame buffers, and key frames reuse them.
• The screenshot PNG is encoded on a background thread.
• SuspiciousIndentation: already gone with refactor: shared RtspSession for single view and Quad (#33, #9, #18, #19, #27) #45.
• KEY_MAX_INPUT_SIZE and the single-view NAL buffer are both 2 MiB, so 4K key frames fit; MediaCodec treats the 1280×720 size only as a hint.

Lint

The baseline is refreshed and contains no errors, only warnings: GestureBackNavigation and SuspiciousIndentation are gone.

Tests

FramePoolTest is new: capacity rounding, reuse, size-class separation, bounded large class. All JVM tests pass; assembleDebug and lintDebug pass.

Device checklist

• Android 6–9: long press asks for the permission, then the screenshot is saved to Pictures (Screenshots fail on Android 6–9: storage permission is never requested #28)
• Android 10+: the screenshot is saved without a prompt; the UI does not stutter on the long press
• Back: with the menu open it closes the menu; without the menu it leaves the app. Check on Android 13+ and, if possible, on Android 16 with the gesture (Android 16 (targetSdk 36): migrate Back handling to OnBackInvokedCallback #30)
• The URL editor and the WebUI dialog close with Back

[qodo-free-for-open-source-projects]

PR Summary by Qodo

Fix screenshot permissions and Back handling; improve frame reuse

🐞 Bug fix ✨ Enhancement 🧪 Tests ⚙️ Configuration changes 🕐 20-40 Minutes

AI Description

• Request screenshot storage permission on Android 6–9 and save PNGs off the UI thread.
• Let popups and dialogs handle Back, including predictive back gestures.
• Improve key-frame buffer reuse and 4K NAL capacity; refresh tests and lint baseline.

Diagram

graph TD
  P["Storage Permission"] --> D["Decoder Activity"] --> M["MediaStore"]
  D --> U["Popup and Dialogs"]
  D --> N["NAL Assembler"] --> F["Frame Pool"]
  N --> C["MediaCodec Manager"]

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High-Level Assessment

The following are alternative approaches to this PR:

1. Pool by exact rounded capacity

• ➕ Avoids polling and discarding an undersized frame within a broad size class.
• ➖ Requires more queues and bookkeeping for capacities that may see little reuse.

Recommendation: Keep the two-class pool as a proportionate fix for small packets competing with key-frame buffers. The rounded-capacity alternative is worth revisiting only if profiling shows substantial allocation or discard within either class; complete the requested device tests before merging.

Files changed (7) +140 / -44

Enhancement (1) +32 / -10

FramePool.javaSeparate and bound frame-buffer size classes +32/-10

Separate and bound frame-buffer size classes

• Splits recycled frames into small and bounded large queues. Rounds new capacities for reuse so small requests do not consume key-frame buffers.

android/app/src/main/java/com/openipc/decoder/FramePool.java

Bug fix (3) +46 / -8

AndroidManifest.xmlEnable platform Back callbacks +5/-2

Enable platform Back callbacks

• Enables OnBackInvokedCallback behavior for the application and adds a tools API annotation for the manifest attribute.

android/app/src/main/AndroidManifest.xml

Decoder.javaGate screenshots on permission and stop intercepting Back +36/-5

Gate screenshots on permission and stop intercepting Back

• Requests storage permission before screenshots on Android 6–9, resumes after a grant, and encodes and saves PNGs on a worker thread. Removes KEYCODE_BACK interception while retaining Escape handling, and uses the shared 2 MiB NAL limit.

android/app/src/main/java/com/openipc/decoder/Decoder.java

MediaCodecManager.javaMatch codec input capacity to 2 MiB NAL limit +5/-1

Match codec input capacity to 2 MiB NAL limit

• Defines a shared maximum NAL size and raises the MediaCodec input-size hint to accommodate larger key frames.

android/app/src/main/java/com/openipc/decoder/MediaCodecManager.java

Tests (1) +59 / -0

FramePoolTest.javaTest frame capacity, reuse, and pool bounds +59/-0

Test frame capacity, reuse, and pool bounds

• Adds JVM tests for capacity rounding, small-frame reuse, separation from large frames, and bounded large-frame retention.

android/app/src/test/java/com/openipc/decoder/FramePoolTest.java

Other (2) +3 / -26

lint-baseline.xmlRefresh resolved lint findings +2/-24

Refresh resolved lint findings

• Removes the Back-navigation and unused-attribute baseline entries and adjusts manifest line references. The remaining entries are warnings.

android/app/lint-baseline.xml

proguard-rules.proRemove obsolete Frame keep rule +1/-2

Remove obsolete Frame keep rule

• Deletes the keep rule for the no-longer-existing Decoder$Frame class.

android/app/proguard-rules.pro

[qodo-free-for-open-source-projects]

Code Review by Qodo

🐞 Bugs (0) 📘 Rule violations (0) 📎 Requirement gaps (0) 🎨 UX issues (0) 🔗 Cross-repo conflicts (0) 📜 Skill insights (0)

1. Pooled buffers disappear on misses ✓ Resolved

Description

FramePool.obtain() drops the polled frame whenever its capacity is below size and immediately
allocates a replacement. When requests of different rounded capacities share a queue, a smaller
entry can be removed before a suitable later entry, causing avoidable allocations and reducing
reuse.

Code

android/app/src/main/java/com/openipc/decoder/FramePool.java[R34-36]

+        Frame frame = (isSmall ? small : large).poll();
     if (frame != null && frame.data().length >= size) {
         frame.setLength(0);

Evidence

The selected queue is polled once, and an undersized frame is neither returned nor searched around
before a new allocation is made. capacityFor() creates multiple capacities within both size
classes, so mismatched entries can coexist and be discarded by this path, violating the requirement
to reuse suitable buffers without discarding mismatched ones.

Separate and bound FramePool buffer reuse
android/app/src/main/java/com/openipc/decoder/FramePool.java[33-40]
android/app/src/main/java/com/openipc/decoder/FramePool.java[54-60]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

## Issue description
`FramePool.obtain()` removes one frame from the selected queue and permanently discards it when its capacity is too small for the request. Different rounded capacities coexist in each queue, so this loses reusable buffers and causes unnecessary allocations.
## Fix Focus Areas
- android/app/src/main/java/com/openipc/decoder/FramePool.java[33-40]
## Recommended Fix
When the polled frame is undersized, return it to the appropriate queue or search the queue for a suitable frame without discarding mismatched entries. Preserve the existing small/large separation and capacity bounds, and add a regression test covering a smaller buffer encountered before a suitable larger buffer.

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

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[compot-dev]

Device-tested (#53): the screenshot permission is requested and screenshots are saved; Back exits correctly. FramePool keeps undersized frames (unit tests). Rebased onto the current v2, CI is green.