Wire touch input into the model in BoardView.handle_event. A press records
the drag start (new DragInput, heap-allocated so it survives the per-frame
BoardView rebuild between mouse_down and mouse_up); the release resolves the
gesture against the same layout it was drawn with. A swipe — start→end mapped
by swipe_intent to an adjacent-swap intent — is fed straight into
commit_swap: a legal swap applies, cascades (clear→collapse→refill), accrues
score and spends a move; an illegal one reverts, no move. A sub-threshold /
off-board drag carries no intent and falls back to the tap behaviour
(toggle/clear selection). The next frame re-renders board + HUD from the model.
Reuses swipe.sx + board_layout.sx + commit_swap unchanged — this is wiring,
not new legality/cascade logic.
tests/swipe_commit.sx (new golden) drives the full path on the seeded board
(SEED 1337): a rightward swipe (0,0)->(1,0) is illegal (two reds) and reverts
byte-for-byte with no score/move; (5,4)->(6,4) is legal, completes R,R,R on
row 4, awards 30, spends one move.
Sim evidence (iPhone 17, iOS 26.0): goldens/p5_swap_before.png (SCORE 0,
MOVES 30/30) and goldens/p5_swap_after.png (SCORE 30, MOVES 29/30) bracket a
real idb-injected swipe at (276,475)->(327,475) pt = cell (5,4)->(6,4); the
three reds clear and the board matches the model's resolved state.
Tap a gem to select it: BoardView hit-tests the touch to a grid cell and
draws a bright rim + translucent fill over it; tapping the same cell clears
the selection, tapping another moves it, tapping off-board clears it.
Selection only — no swap (that's P5). The HUD renders the live score and
remaining moves (out of the move limit) in the Lato font on a translucent
card above the grid.
The touch→cell geometry is factored into a pure BoardLayout (no GL/stb
imports) that BoardView composes and P5 will reuse for swap endpoints.
tests/hit_test.sx locks point_to_cell as the exact inverse of cell_frame
(every cell center round-trips; off-board taps reject) — headless because
BoardLayout pulls no C imports. goldens/p4_hud.png captures the scene after
a real idb tap at (201,437)pt: the HUD plus a yellow selection rim on the
red gem at cell (col 4, row 3).
Adopt the modules/ui UIPipeline framework (as the chess reference app does)
and replace the P0 placeholder quad with a BoardView (View protocol, modeled
on chess/board_view.sx):
- background.png fills the screen; an 8x8 cell.png grid is centered in the
safe area; each cell's gem is sampled from gems.png by UV column = gem index
(0=red .. 5=purple).
- Drive it from board.sx seeded with 1337 (the board_init golden's seed), so
the on-screen layout matches that snapshot gem-for-gem.
main.sx now hosts the view via UIPipeline (Metal on iOS, GL on desktop) and
heap-allocates the board/asset state behind pointers (UFCS method calls on a
value-typed global mutate a copy, so mutable state must live behind a pointer
as the reference app does).
Vendor the C deps the UI module's image/font path needs (stb_image,
stb_truetype, kb_text_shape, file_utils); their #include "vendors/..." paths
resolve relative to the project root.
Evidence: ios-sim build links clean; tools/run_tests.sh 11/11 pass; running
app captured at goldens/p4_board.png.
