Ubisam-MobileGit/tasks/054-cpp-pairs-and-fold-layouts.md

TASK-054: C++ header/source pairs and unfolded-window layouts

Status: implemented; required checks pass; not yet confirmed on a device Owner: Claude Reviewer: human product owner

Outcome

C++ keeps a declaration in a header and its definition in a source file, and many of the team use a Z Fold7 or Fold8. A header or source file now knows its counterpart: on a phone it is one tap away, and a method can be followed to the same method in the other file; on a window 600dp or wider the two are shown side by side. The wide layouts also put the directory's files and the outline beside the code, and show a diff as before and after, side by side.

Scope

• Included: counterpartOf, CodeBrowserViewModel.openSibling / loadCounterpart, the pair switch and jump button, the two-pane pair with the panes following each other, the side pane of files and outline, the side-by-side diff, and Home's two-pane layout.
• Excluded: a pair whose halves are in different directories (include/ and src/); more than one source file for one header.

Writable paths

• app/src/main/java/com/ubisam/ubgitea/feature/codebrowser/
• app/src/main/java/com/ubisam/ubgitea/feature/history/FileDiffScreen.kt
• app/src/main/java/com/ubisam/ubgitea/feature/home/HomeScreen.kt
• app/src/main/java/com/ubisam/ubgitea/ui/shell/

Acceptance criteria

• A .h .hpp .hh .hxx file pairs with a .cpp .cc .cxx .c file of the same name in the same directory.
• On a phone the counterpart opens from a switch under the title, and from a button that goes to the same method.
• At 600dp and wider the pair is side by side, header on the left, and can be turned off.
• The counterpart is fetched only when it is going to be shown.
• A counterpart that fails to load, or is not text, says so in its own pane and leaves the other usable.
• At 600dp and wider a diff is before and after, side by side, with rows kept level.
• Below 700dp the side pane is narrower, for the Z Fold8's narrower inner display.
• Build, unit tests and lint pass.
• Confirmed on the human product owner's device (phone and unfolded Z Fold).

Security and privacy

No additional concerns.

Required checks

./gradlew compileDebugKotlin compileDebugUnitTestKotlin testDebugUnitTest assembleDebug lintDebug

Evidence

Recorded on 2026-09-28 in the worktree awesome-pascal-3f2ada, with Android Studio's bundled JDK (D:\AndroidStudio\jbr, OpenJDK 21). TASK-050 to TASK-054 were built together and checked together:

• ./gradlew compileDebugKotlin compileDebugUnitTestKotlin testDebugUnitTest assembleDebug lintDebug -- passed.
• Unit tests: 409 in 45 suites, 0 failures, 0 errors (289 before this work).
• Lint: 0 errors, 55 warnings (dependency updates, unused resources, KTX suggestions).
• Emulator (API 36, sdk_gphone64_x86_64): the debug APK installs and launches without a crash and shows the sign-in screen with the logo and the new palette. Nothing past sign-in could be reached: that needs a company account.
• Not done: any check on a physical device. None was visible to adb during this work.
• Covered by CodeSearchTest (counterpart lookup) and SymbolOutlineTest (matching a method across a header and its source). The layouts themselves have no automated test.
• Unit tests were written by a delegated worker from handoff/2026-09-28_unit-tests-redesign.md; the full run above was repeated here afterwards.

Known limitations

• Inner-display sizes used for design (Fold7 / Fold8 Ultra about 750x832dp, Fold8 about 650x870dp) are estimated from panel resolution; the real value depends on the screen-zoom setting. Layouts switch on width, not on device.
• The panes follow each other only while one is being dragged, not during the fling after it.

Review findings

None yet.