From 65ee2e4d7f2be8036457e3cdca0e26e09eb56e0b Mon Sep 17 00:00:00 2001
From: Paul Buetow <paul@buetow.org>
Date: Fri, 1 May 2026 15:57:13 +0300
Subject: add readme and so on

---
 web/js/selection.js | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)

(limited to 'web/js/selection.js')

diff --git a/web/js/selection.js b/web/js/selection.js
index 00b91b8..c83fd81 100644
--- a/web/js/selection.js
+++ b/web/js/selection.js
@@ -14,6 +14,21 @@ function refreshCards() {
   return Array.from(document.querySelectorAll('.media-card, .media-row'));
 }
 
+// Compute grid geometry from the rendered cards.
+function gridGeometry(cards) {
+  if (!cards.length) return { cols: 0, rowMap: [] };
+  const first = cards[0].getBoundingClientRect();
+  let colCount = 0;
+  for (let i = 0; i < cards.length; i++) {
+    const r = cards[i].getBoundingClientRect();
+    if (Math.round(r.top) !== Math.round(first.top)) break;
+    colCount++;
+  }
+  // rowMap[i] = row index of cards[i]
+  const rowMap = cards.map((_, i) => Math.floor(i / colCount));
+  return { cols: colCount || 1, rowMap };
+}
+
 export function select(index) {
   const cards = refreshCards();
   if (!cards.length) { selectedIndex = -1; return; }
@@ -39,5 +54,60 @@ export function next(step = 1) {
 }
 
 export function prev(step = 1) { next(-step); }
+
+// Grid-aware keyboard navigation
+export function navLeft() {
+  const cards = refreshCards();
+  if (!cards.length) return;
+  const { cols } = gridGeometry(cards);
+  if (cols === 0) return;
+  const row = Math.floor(selectedIndex / cols);
+  const col = selectedIndex % cols;
+  if (col > 0) {
+    select(selectedIndex - 1);
+  } else if (row > 0) {
+    // wrap to end of previous row
+    select(row * cols - 1);
+  }
+}
+
+export function navRight() {
+  const cards = refreshCards();
+  if (!cards.length) return;
+  const { cols } = gridGeometry(cards);
+  if (cols === 0) return;
+  const row = Math.floor(selectedIndex / cols);
+  const col = selectedIndex % cols;
+  const lastInRow = Math.min((row + 1) * cols, cards.length) - 1;
+  if (col < (lastInRow - row * cols)) {
+    select(selectedIndex + 1);
+  } else if (selectedIndex < cards.length - 1) {
+    // wrap to start of next row
+    select(Math.min((row + 1) * cols, cards.length - 1));
+  }
+}
+
+export function navUp() {
+  const cards = refreshCards();
+  if (!cards.length) return;
+  const { cols } = gridGeometry(cards);
+  if (cols === 0) return;
+  const idxAbove = selectedIndex - cols;
+  if (idxAbove >= 0) {
+    select(idxAbove);
+  }
+}
+
+export function navDown() {
+  const cards = refreshCards();
+  if (!cards.length) return;
+  const { cols } = gridGeometry(cards);
+  if (cols === 0) return;
+  const idxBelow = selectedIndex + cols;
+  if (idxBelow < cards.length) {
+    select(idxBelow);
+  }
+}
+
 export function currentIndex() { return selectedIndex; }
 export function currentElement() { return refreshCards()[selectedIndex] ?? null; }
-- 
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