add multiple windows support with shared session, add shortcuts

src/hints.cpp

@@ -2,7 +2,7 @@
 
 namespace {
 
-constexpr auto kChars = "asdfghjkl";
+constexpr auto kChars = "1qaz2wsx3edc4rfv5tgb6yhn7ujm8ik9ol0p";
 
 // Installs window.__attHints and shows the labels. "@CHARS@" is substituted
 // with kChars before running.
@@ -178,6 +178,75 @@ constexpr auto kShowScript = R"JS(
 })();
 )JS";
 
+constexpr auto kFocusInputScript = R"JS(
+(function () {
+    'use strict';
+    const TEXT_INPUTS = new Set(['', 'text', 'search', 'email', 'url', 'tel',
+                                 'password', 'number']);
+
+    function isTextField(el) {
+        if (el.disabled || el.readOnly)
+            return false;
+        if (el.tagName === 'TEXTAREA')
+            return true;
+        // Only the root of an editable region, not every element inside it.
+        if (el.isContentEditable)
+            return !el.parentElement?.isContentEditable;
+        return el.tagName === 'INPUT' && TEXT_INPUTS.has((el.getAttribute('type') || '').toLowerCase());
+    }
+
+    function isVisible(el) {
+        const style = getComputedStyle(el);
+        if (style.visibility !== 'visible' || style.display === 'none')
+            return false;
+        const r = el.getBoundingClientRect();
+        return r.width >= 1 && r.height >= 1;
+    }
+
+    function inViewport(el) {
+        const r = el.getBoundingClientRect();
+        return r.bottom > 0 && r.right > 0 && r.top < innerHeight && r.left < innerWidth;
+    }
+
+    // Document order, descending into each open shadow root right after its host.
+    function* elements(root) {
+        for (const el of root.querySelectorAll('*')) {
+            yield el;
+            if (el.shadowRoot)
+                yield* elements(el.shadowRoot);
+        }
+    }
+
+    let fallback = null;
+    let target = null;
+    for (const el of elements(document)) {
+        if (!isTextField(el) || !isVisible(el))
+            continue;
+        if (inViewport(el)) {
+            target = el;
+            break;
+        }
+        fallback = fallback || el;
+    }
+    target = target || fallback;
+    if (!target)
+        return false;
+
+    target.scrollIntoView({ block: 'nearest', inline: 'nearest' });
+    target.focus();
+    // Put the cursor after any existing text, ready to type or edit.
+    if (typeof target.setSelectionRange === 'function') {
+        try {
+            target.setSelectionRange(target.value.length, target.value.length);
+        } catch (e) {
+            // type=email/number don't support selection ranges.
+        }
+    }
+    // From outside a shadow root, document.activeElement is only its host.
+    return target.getRootNode().activeElement === target;
+})();
+)JS";
+
 QString callScript(const QString &call)
 {
     return QStringLiteral("window.__attHints ? window.__attHints.%1 : { state: 'none' };")
@@ -214,4 +283,9 @@ QString clearScript()
     return callScript(QStringLiteral("clear()"));
 }
 
+QString focusInputScript()
+{
+    return QString::fromUtf8(kFocusInputScript);
+}
+
 } // namespace hints