Slide sideways on space to move the cursor

As on phone keyboards: a sideways move on space moves the cursor right
away, along the line only, without blanking the keys. Long-press space
still opens the full trackpad.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -8,7 +8,7 @@ iPad-style floating on-screen keyboard for Plasma Wayland. Qt 6, C++ core, QML U
 - "Hold Keys" (⚙): keys stay down while touched, like a hardware keyboard (games, Shift+click, system key repeat); modifiers are plain keys, dead keys compose in the app; touch conveniences off
 - Letters follow the system keyboard layout; the globe key switches it
 - Auto-capitalization, double-space → ". " (both optional, ⚙ on the bottom bar), backspace repeat → word delete
-- Long-press space = trackpad; slide from `.?123` onto a symbol and release
+- Slide sideways on space to move the cursor; long-press space = trackpad (lines too); slide from `.?123` onto a symbol and release
 - Compact (iPad) or full (iPad Pro) keyboard: number row, punctuation, tab, caps lock, ctrl/alt/super, dead keys
 - Ctrl/Alt/Super stick like shift (tap, double-tap, hold) and turn keys into shortcuts; a tapped or held shift joins them (Shift+F5, Shift+Tab, Shift+arrows), auto-shift and caps lock don't
 - Optional PC key blocks: function row, navigation (ins/home/pg up, del/end/pg dn, arrows), numeric keypad; any mix, typing keys included (⚙)

src/input/PointerTracker.cpp

@@ -26,8 +26,14 @@ void PointerTracker::moveTo(QPointF pos)
         return;
     m_moved = true;
 
-    if (m_key.type == KeyType::LayerSwitch)
+    if (m_key.type == KeyType::LayerSwitch) {
         m_gesture = Gesture::Slide;
+    } else if (m_config.gestures && m_key.type == KeyType::Space && qAbs(delta.x()) > qAbs(delta.y())) {
+        // From the press point: the slop counts towards the first step.
+        m_gesture = Gesture::Trackpad;
+        m_trackpadOrigin = m_start;
+        m_trackpadLines = false;
+    }
     else if (m_config.gestures && !m_key.flick.isEmpty() && delta.y() > qAbs(delta.x()))
         m_gesture = Gesture::Flick;
 }
@@ -63,7 +69,8 @@ QPoint PointerTracker::takeTrackpadSteps()
 
     const QPointF travel = m_position - m_trackpadOrigin;
     // Truncate towards zero so jitter around the origin doesn't step.
-    const QPoint total(int(travel.x() / m_config.trackpadStep), int(travel.y() / m_config.trackpadRowStep));
+    const int rows = m_trackpadLines ? int(travel.y() / m_config.trackpadRowStep) : 0;
+    const QPoint total(int(travel.x() / m_config.trackpadStep), rows);
     const QPoint steps = total - m_trackpadStepsTaken;
     m_trackpadStepsTaken = total;
     return steps;

src/input/PointerTracker.h

@@ -11,7 +11,8 @@
 //   Tap        pressed, not (yet) anything else
 //   Flick      moved down on a key with a flick symbol
 //   LongPress  held still on a key with alternates
-//   Trackpad   held still on space; movement moves the text cursor
+//   Trackpad   held still on space; movement moves the text cursor. Sliding
+//              sideways on space moves it too, along the line only.
 //   Slide      moved off a layer key (type a symbol, then switch back)
 class PointerTracker
 {
@@ -56,5 +57,6 @@ private:
     Gesture m_gesture = Gesture::Tap;
     bool m_moved = false;
     QPointF m_trackpadOrigin;
+    bool m_trackpadLines = true; // vertical travel moves between lines
     QPoint m_trackpadStepsTaken;
 };

tests/tst_keyboardsurface.cpp

@@ -208,6 +208,17 @@ private Q_SLOTS:
         QCOMPARE(engine.output, QString());
         QCOMPARE(engine.keysyms, (QList<quint32>{XKB_KEY_Right, XKB_KEY_Right, XKB_KEY_Right}));
     }
+
+    void spaceSlideMovesCursorAtOnce()
+    {
+        const QPoint space = keyCenter({}, u"space"_s);
+        QTest::touchEvent(&window, touchscreen).press(0, space);
+        QTest::touchEvent(&window, touchscreen).move(0, space - QPoint(30, 0));
+        QVERIFY(!qobject_cast<KeyboardSurface *>(keyboard)->isTrackpadActive()); // keys keep their labels
+        QTest::touchEvent(&window, touchscreen).release(0, space - QPoint(30, 0));
+        QCOMPARE(engine.output, QString());
+        QCOMPARE(engine.keysyms, (QList<quint32>{XKB_KEY_Left, XKB_KEY_Left}));
+    }
 };
 
 QTEST_MAIN(TestKeyboardSurface)

tests/tst_pointertracker.cpp

@@ -111,6 +111,33 @@ private Q_SLOTS:
         QCOMPARE(t.takeTrackpadSteps(), QPoint(-3, -1));
     }
 
+    void spaceSlideSidewaysMovesAlongTheLine()
+    {
+        PointerTracker t(ofType(KeyType::Space), {100, 0}, config());
+        t.moveTo({112, 5});
+        QCOMPARE(t.gesture(), Gesture::Trackpad);
+        QCOMPARE(t.takeTrackpadSteps(), QPoint(1, 0)); // the slop counts
+        t.moveTo({75, -50});
+        QCOMPARE(t.takeTrackpadSteps(), QPoint(-3, 0)); // no line changes
+        QVERIFY(!t.longPressElapsed());
+    }
+
+    void spaceSlideVerticallyStaysTap()
+    {
+        PointerTracker t(ofType(KeyType::Space), {100, 0}, config());
+        t.moveTo({105, -20});
+        QCOMPARE(t.gesture(), Gesture::Tap);
+    }
+
+    void spaceSlideNeedsGestures()
+    {
+        PointerTracker::Config c = config();
+        c.gestures = false;
+        PointerTracker t(ofType(KeyType::Space), {100, 0}, c);
+        t.moveTo({140, 0});
+        QCOMPARE(t.gesture(), Gesture::Tap);
+    }
+
     void layerKeySlides()
     {
         PointerTracker t(ofType(KeyType::LayerSwitch), {0, 0}, config());