plugin: extend double-click selection to '' "" `` quote pairs

docs/PLAN.md

@@ -185,11 +185,16 @@ Therefore the palette is replaced, not extended, and the replacement is built on
 - Double-clicking next to a bracket (`()[]{}`) selects the text strictly between
   the matching pair, **multi-line aware** and nesting-aware. Adjacency is checked
   on both sides of the click; openers select forward, closers select backward.
+- Double-clicking next to a quote (`''`, `""`, `` `` ``) selects the text strictly
+  between the enclosing pair. Quotes are symmetric and non-nesting, so matching is
+  **line-local**: direction is decided by the parity of same-kind quotes preceding
+  the clicked one (even → opener, scan forward; odd → closer, scan backward), via
+  `isQuote` / `quoteIsOpener` / `findQuoteForward` / `findQuoteBackward`.
 - Implemented in the event filter via `selectBracketPairAt`: maps the click to a
   document cursor (`coordinatesToCursor`), reads neighbouring characters
   (`characterAt`), scans with depth counting across line ends, and sets the
-  selection. When no bracket is adjacent it falls through to Kate's default
+  selection. When no bracket or quote is adjacent it falls through to Kate's
-  double-click (word select).
+  default double-click (word select).
 - A left double-click leaves the button held, so it also arms the chord anchor:
   the user can go straight from a double-click (bracket- or word-select) into a
   left+middle / left+right chord without releasing.

src/plugin/ollieplugin.cpp

@@ -89,6 +89,16 @@ QChar matchingBracket(QChar c, bool &isOpener)
     }
 }
 
+// Quote delimiters understood by the double-click selection feature. Unlike
+// brackets these are symmetric (same opening and closing char) and do not nest,
+// so matching is handled separately: scan the click's line for the enclosing
+// pair of identical quote chars.
+bool isQuote(QChar c)
+{
+    const ushort u = c.unicode();
+    return u == '\'' || u == '"' || u == '`';
+}
+
 // Advance a cursor by one character, wrapping across line ends. Returns false
 // at end of document.
 bool stepForward(KTextEditor::Document *doc, KTextEditor::Cursor &c)
@@ -164,6 +174,45 @@ KTextEditor::Cursor findOpener(KTextEditor::Document *doc, KTextEditor::Cursor p
     return KTextEditor::Cursor::invalid();
 }
 
+// Count occurrences of \a q on \a line in columns [0, col). An even count means
+// the quote at \a col opens a pair; odd means it closes one. Quotes do not nest,
+// so parity of preceding quotes decides direction.
+bool quoteIsOpener(KTextEditor::Document *doc, int line, int col, QChar q)
+{
+    int count = 0;
+    for (int c = 0; c < col; ++c) {
+        if (doc->characterAt(KTextEditor::Cursor(line, c)) == q) {
+            ++count;
+        }
+    }
+    return (count % 2) == 0;
+}
+
+// Find the matching quote char of the same kind on \a line, searching columns
+// (col, lineLength) forward. Returns the closer's cursor, or invalid if none.
+KTextEditor::Cursor findQuoteForward(KTextEditor::Document *doc, int line, int col, QChar q)
+{
+    const int len = doc->lineLength(line);
+    for (int c = col + 1; c < len; ++c) {
+        if (doc->characterAt(KTextEditor::Cursor(line, c)) == q) {
+            return KTextEditor::Cursor(line, c);
+        }
+    }
+    return KTextEditor::Cursor::invalid();
+}
+
+// Find the matching quote char of the same kind on \a line, searching columns
+// [0, col) backward. Returns the opener's cursor, or invalid if none.
+KTextEditor::Cursor findQuoteBackward(KTextEditor::Document *doc, int line, int col, QChar q)
+{
+    for (int c = col - 1; c >= 0; --c) {
+        if (doc->characterAt(KTextEditor::Cursor(line, c)) == q) {
+            return KTextEditor::Cursor(line, c);
+        }
+    }
+    return KTextEditor::Cursor::invalid();
+}
+
 // Prefix marking a palette id that is a ":" command string to execute rather
 // than a QAction to trigger.
 const QLatin1String kCmdPrefix("ollie:cmd:");
@@ -1167,6 +1216,40 @@ bool OllieView::selectBracketPairAt(KTextEditor::View *view, const QPoint &globa
     const bool haveLeft = stepBackward(doc, leftCur);
     const QChar leftCh = haveLeft ? doc->characterAt(leftCur) : QChar();
 
+    // Quote pairs ('' "" ``) are symmetric and non-nesting: resolve them on the
+    // click's line and select the content between the enclosing pair. Handled
+    // before brackets since the two delimiter sets are disjoint.
+    {
+        QChar q;
+        int qCol = -1;
+        if (isQuote(rightCh)) {
+            q = rightCh;
+            qCol = at.column();
+        } else if (haveLeft && isQuote(leftCh)) {
+            q = leftCh;
+            qCol = leftCur.column();
+        }
+        if (!q.isNull()) {
+            const int line = at.line();
+            KTextEditor::Cursor qOpen = KTextEditor::Cursor::invalid();
+            KTextEditor::Cursor qClose = KTextEditor::Cursor::invalid();
+            if (quoteIsOpener(doc, line, qCol, q)) {
+                qOpen = KTextEditor::Cursor(line, qCol);
+                qClose = findQuoteForward(doc, line, qCol, q);
+            } else {
+                qClose = KTextEditor::Cursor(line, qCol);
+                qOpen = findQuoteBackward(doc, line, qCol, q);
+            }
+            if (!qOpen.isValid() || !qClose.isValid()) {
+                return false; // unbalanced quote on this line
+            }
+            const KTextEditor::Cursor innerStart(line, qOpen.column() + 1);
+            view->setSelection(KTextEditor::Range(innerStart, qClose));
+            view->setCursorPosition(qClose);
+            return true;
+        }
+    }
+
     bool rOpener = false;
     const QChar rMatch = matchingBracket(rightCh, rOpener);
     bool lOpener = false;