Shrink to a floating button instead of hiding

With "Shrink to Button" on, the dismiss key shrinks the window to just
itself: a see-through button that can be dragged anywhere. Tapping it
grows the keyboard back around it, kept on screen. KWin moves and
resizes the window through a one-off script, as Wayland clients can't
place themselves.

Also moves the window back on screen whenever it appears (KWin remembers
where the button was), and releases the mouse after a window manager
move or resize, which used to eat the next press on the grab bar.

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

src/CMakeLists.txt

@@ -36,6 +36,7 @@ set(SLOPOSK_QML_FILES
     Key.qml
     AlternatesPopup.qml
     DragHandle.qml
+    FloatingButton.qml
     ResizeHandle.qml
     SectionHeader.qml
     SettingsButton.qml
@@ -91,7 +92,9 @@ qt_add_executable(sloposk
     backend/KWinInputContext.h backend/KWinInputContext.cpp
     backend/KWinFakeInput.h backend/KWinFakeInput.cpp
     backend/WaylandKeymap.h backend/WaylandKeymap.cpp
+    window/CollapseController.h window/CollapseController.cpp
     window/FloatingWindow.h window/FloatingWindow.cpp
+    window/KWinScript.h window/KWinScript.cpp
     window/KWinRule.h window/KWinRule.cpp
 )
 

src/main.cpp

@@ -13,6 +13,7 @@
 #include "layout/LayoutLoader.h"
 #include "layout/LayoutModel.h"
 #include "settings/Settings.h"
+#include "window/CollapseController.h"
 #include "window/FloatingWindow.h"
 #include "window/KWinRule.h"
 #include "window/VisibilityController.h"
@@ -82,12 +83,15 @@ void connectKeySettings(Settings &settings, LayoutModel &model, FloatingWindow &
                      [keepingKeySize, rebuild] { keepingKeySize(rebuild); });
 }
 
-void restoreAndPersistGeometry(FloatingWindow &placement, WindowSettings &settings)
+// The shrunk button's geometry isn't the keyboard's: not saved.
+void restoreAndPersistGeometry(FloatingWindow &placement, WindowSettings &settings, const CollapseController &collapse)
 {
     if (const auto geometry = settings.load(placement.screenName()))
         placement.setGeometry(*geometry);
-    QObject::connect(&placement, &FloatingWindow::geometryChanged, &settings,
-                     [&] { settings.save(placement.screenName(), placement.geometry()); });
+    QObject::connect(&placement, &FloatingWindow::geometryChanged, &settings, [&] {
+        if (!collapse.isCollapsed())
+            settings.save(placement.screenName(), placement.geometry());
+    });
 }
 
 // A focused field shows the keyboard only if KWin's policy wants one now;
@@ -112,7 +116,7 @@ void connectFieldFocus(VisibilityController &visibility, KWinInputMethod &backen
 }
 
 void connectVisibility(VisibilityController &visibility, KWinInputMethod &backend, const Settings &settings,
-                       KeyboardController &controller, FloatingWindow &placement)
+                       FloatingWindow &placement)
 {
     // First, so the initial state below reaches the window too.
     QObject::connect(&visibility, &VisibilityController::visibleChanged, &placement,
@@ -124,10 +128,19 @@ void connectVisibility(VisibilityController &visibility, KWinInputMethod &backen
     // work) there is no focus signal: stay visible so it can be tried out.
     const auto updateStandalone = [&] { visibility.setStandalone(!backend.isAvailable()); };
     QObject::connect(&backend, &KWinInputMethod::availableChanged, &visibility, updateStandalone);
-    QObject::connect(&controller, &KeyboardController::dismissRequested, &visibility, &VisibilityController::hide);
     updateStandalone();
 }
 
+// The dismiss key hides the keyboard, or shrinks it to a floating button.
+void connectDismiss(KeyboardController &controller, const Settings &settings, CollapseController &collapse,
+                    VisibilityController &visibility)
+{
+    QObject::connect(&controller, &KeyboardController::dismissRequested, &visibility, [&] {
+        if (!settings.collapseToButton() || !collapse.collapse())
+            visibility.hide();
+    });
+}
+
 void connectTextContext(KWinInputMethod &backend, KeyboardController &controller)
 {
     QObject::connect(&backend, &TextBackend::activeChanged, &controller,
@@ -191,14 +204,17 @@ int main(int argc, char *argv[])
     installKWinRule(QGuiApplication::desktopFileName());
     FloatingWindow placement(window);
     window->setProperty("placement", QVariant::fromValue(&placement));
+    CollapseController collapse(*window, placement);
+    window->setProperty("collapse", QVariant::fromValue(&collapse));
     WindowSettings windowSettings;
-    restoreAndPersistGeometry(placement, windowSettings);
+    restoreAndPersistGeometry(placement, windowSettings, collapse);
     connectKeySettings(settings, model, placement, *window, rebuildLayout);
 
     VisibilityController visibility;
     KWinVirtualKeyboard virtualKeyboardPolicy;
     connectFieldFocus(visibility, backend, virtualKeyboardPolicy);
-    connectVisibility(visibility, backend, settings, controller, placement);
+    connectVisibility(visibility, backend, settings, placement);
+    connectDismiss(controller, settings, collapse, visibility);
 
     DBusControl dbus(visibility);
     reportDBusControl(diagnostics, dbus.registerOnSessionBus());

src/settings/Settings.cpp

@@ -11,6 +11,7 @@ constexpr auto HoldKeysKey = "typing/holdKeys";
 constexpr auto VisibleSectionsKey = "layout/visibleSections";
 constexpr auto FullKeyboardKey = "layout/fullKeyboard";
 constexpr auto AlwaysVisibleKey = "window/alwaysVisible";
+constexpr auto CollapseToButtonKey = "window/collapseToButton";
 constexpr auto BackgroundOpacityKey = "appearance/backgroundOpacity";
 constexpr auto BlurBackgroundKey = "appearance/blurBackground";
 }
@@ -28,6 +29,7 @@ Settings::Settings(QObject *parent)
         m_visibleSections = {MainSectionId};
     m_fullKeyboard = store.value(FullKeyboardKey, false).toBool();
     m_alwaysVisible = store.value(AlwaysVisibleKey, false).toBool();
+    m_collapseToButton = store.value(CollapseToButtonKey, false).toBool();
     m_backgroundOpacity = qBound(MinBackgroundOpacity, store.value(BackgroundOpacityKey, 1.0).toReal(), 1.0);
     m_blurBackground = store.value(BlurBackgroundKey, true).toBool();
 }
@@ -60,6 +62,15 @@ void Settings::setAlwaysVisible(bool always)
     Q_EMIT alwaysVisibleChanged();
 }
 
+void Settings::setCollapseToButton(bool collapse)
+{
+    if (collapse == m_collapseToButton)
+        return;
+    m_collapseToButton = collapse;
+    QSettings().setValue(CollapseToButtonKey, collapse);
+    Q_EMIT collapseToButtonChanged();
+}
+
 void Settings::setFullKeyboard(bool full)
 {
     if (full == m_fullKeyboard)

src/settings/Settings.h

@@ -23,6 +23,8 @@ class Settings : public QObject
     Q_PROPERTY(bool fullKeyboard READ fullKeyboard WRITE setFullKeyboard NOTIFY fullKeyboardChanged)
     // Shown even without a focused text field, to type into any window.
     Q_PROPERTY(bool alwaysVisible READ alwaysVisible WRITE setAlwaysVisible NOTIFY alwaysVisibleChanged)
+    // The dismiss key shrinks the keyboard to a floating button instead of hiding it.
+    Q_PROPERTY(bool collapseToButton READ collapseToButton WRITE setCollapseToButton NOTIFY collapseToButtonChanged)
     // Opacity of the panel behind the keys (MinBackgroundOpacity–1); keys stay opaque.
     Q_PROPERTY(qreal backgroundOpacity READ backgroundOpacity WRITE setBackgroundOpacity NOTIFY appearanceChanged)
     Q_PROPERTY(qreal minBackgroundOpacity READ minBackgroundOpacity CONSTANT)
@@ -49,6 +51,8 @@ public:
     void setFullKeyboard(bool full);
     bool alwaysVisible() const { return m_alwaysVisible; }
     void setAlwaysVisible(bool always);
+    bool collapseToButton() const { return m_collapseToButton; }
+    void setCollapseToButton(bool collapse);
 
     static constexpr qreal MinBackgroundOpacity = 0.1;
     static qreal minBackgroundOpacity() { return MinBackgroundOpacity; }
@@ -62,6 +66,7 @@ Q_SIGNALS:
     void visibleSectionsChanged();
     void fullKeyboardChanged();
     void alwaysVisibleChanged();
+    void collapseToButtonChanged();
     void appearanceChanged();
 
 private:
@@ -72,6 +77,7 @@ private:
     QStringList m_visibleSections;
     bool m_fullKeyboard = false;
     bool m_alwaysVisible = false;
+    bool m_collapseToButton = false;
     qreal m_backgroundOpacity = 1.0;
     bool m_blurBackground = true;
 };

src/window/CollapseController.cpp

@@ -0,0 +1,74 @@
+#include "CollapseController.h"
+
+#include "FloatingWindow.h"
+
+#include <QQuickWindow>
+
+namespace {
+constexpr int ExpandTimeoutMs = 500;
+
+bool roughlyEqual(QSize a, QSize b)
+{
+    return qAbs(a.width() - b.width()) <= 1 && qAbs(a.height() - b.height()) <= 1;
+}
+} // namespace
+
+CollapseController::CollapseController(QQuickWindow &window, FloatingWindow &placement, QObject *parent)
+    : QObject(parent)
+    , m_window(window)
+    , m_placement(placement)
+{
+    m_expanding.setSingleShot(true);
+    m_expanding.setInterval(ExpandTimeoutMs);
+    connect(&m_expanding, &QTimer::timeout, this, &CollapseController::finishExpanding);
+    connect(&window, &QWindow::widthChanged, this, &CollapseController::windowResized);
+    connect(&window, &QWindow::heightChanged, this, &CollapseController::windowResized);
+}
+
+bool CollapseController::collapse()
+{
+    if (m_collapsed)
+        return true;
+    QVariant rect;
+    QMetaObject::invokeMethod(&m_window, "dismissKeyRect", Q_RETURN_ARG(QVariant, rect));
+    if (rect.toRectF().isEmpty())
+        return false;
+    m_keyRect = rect.toRectF();
+    m_expandedSize = m_window.size();
+    m_collapsed = true;
+    Q_EMIT collapsedChanged();
+    // After the next frame, once the compositor knows the lower minimum size.
+    connect(&m_window, &QQuickWindow::frameSwapped, this, [this] {
+        if (m_collapsed)
+            m_placement.moveResize(m_keyRect, false);
+    }, Qt::SingleShotConnection);
+    return true;
+}
+
+void CollapseController::expand()
+{
+    if (!m_collapsed || m_expanding.isActive())
+        return;
+    if (roughlyEqual(m_window.size(), m_expandedSize)) {
+        finishExpanding(); // never shrank: nothing to move
+        return;
+    }
+    // Stays collapsed until the window has grown, so the keys don't flash squeezed.
+    m_placement.moveResize(QRectF(-m_keyRect.topLeft(), m_expandedSize), true);
+    m_expanding.start();
+}
+
+void CollapseController::windowResized()
+{
+    if (m_expanding.isActive() && roughlyEqual(m_window.size(), m_expandedSize))
+        finishExpanding();
+}
+
+void CollapseController::finishExpanding()
+{
+    m_expanding.stop();
+    if (!roughlyEqual(m_window.size(), m_expandedSize))
+        m_window.resize(m_expandedSize); // no KWin to do it
+    m_collapsed = false;
+    Q_EMIT collapsedChanged();
+}

src/window/CollapseController.h

@@ -0,0 +1,45 @@
+#pragma once
+
+#include <QObject>
+#include <QRectF>
+#include <QSize>
+#include <QTimer>
+
+class FloatingWindow;
+class QQuickWindow;
+
+// Shrinks the keyboard window to just its dismiss key, floating on its own,
+// and grows it back with the key under the button again (kept on screen).
+// The window itself shrinks, so it can be dragged anywhere and covers
+// nothing else. QML draws from `collapsed` and `keyRect`.
+class CollapseController : public QObject
+{
+    Q_OBJECT
+    Q_PROPERTY(bool collapsed READ isCollapsed NOTIFY collapsedChanged)
+    // The key in the full window; the button stays there until the window shrinks.
+    Q_PROPERTY(QRectF keyRect READ keyRect NOTIFY collapsedChanged)
+
+public:
+    CollapseController(QQuickWindow &window, FloatingWindow &placement, QObject *parent = nullptr);
+
+    bool isCollapsed() const { return m_collapsed; }
+    QRectF keyRect() const { return m_keyRect; }
+
+    // False if the keyboard has no dismiss key to shrink to.
+    bool collapse();
+    Q_INVOKABLE void expand();
+
+Q_SIGNALS:
+    void collapsedChanged();
+
+private:
+    void windowResized();
+    void finishExpanding();
+
+    QQuickWindow &m_window;
+    FloatingWindow &m_placement;
+    bool m_collapsed = false;
+    QRectF m_keyRect;
+    QSize m_expandedSize;
+    QTimer m_expanding; // waits for KWin; runs out without it
+};

src/window/FloatingWindow.cpp

@@ -1,6 +1,11 @@
 #include "FloatingWindow.h"
 
+#include "KWinScript.h"
+
 #include <KWindowEffects>
+#include <QCursor>
+#include <QGuiApplication>
+#include <QMouseEvent>
 #include <QPainterPath>
 #include <QScreen>
 #include <QWindow>
@@ -12,6 +17,18 @@ FloatingWindow::FloatingWindow(QWindow *window, QObject *parent)
     window->setFlags(Qt::Tool | Qt::FramelessWindowHint | Qt::WindowStaysOnTopHint | Qt::WindowDoesNotAcceptFocus);
     for (const auto changed : {&QWindow::xChanged, &QWindow::yChanged, &QWindow::widthChanged, &QWindow::heightChanged})
         connect(window, changed, this, &FloatingWindow::geometryChanged);
+    window->installEventFilter(this);
+}
+
+bool FloatingWindow::eventFilter(QObject *watched, QEvent *event)
+{
+    // Exposed means mapped, so KWin knows the window by now.
+    if (watched == m_window && event->type() == QEvent::Expose) {
+        if (m_window->isExposed() && !m_exposed)
+            moveResize(QRectF(QPointF(), m_window->size()), true);
+        m_exposed = m_window->isExposed();
+    }
+    return false;
 }
 
 QRect FloatingWindow::geometry() const
@@ -38,6 +55,30 @@ void FloatingWindow::resizeBy(qreal dw, qreal dh)
     m_window->resize(size);
 }
 
+void FloatingWindow::moveResize(const QRectF &relative, bool keepOnScreen)
+{
+    runKWinScript(QStringLiteral(R"(
+for (const w of workspace.windowList()) {
+    if (w.resourceClass !== "%1")
+        continue;
+    const width = %4, height = %5;
+    let x = w.frameGeometry.x + %2, y = w.frameGeometry.y + %3;
+    if (%6) {
+        const area = workspace.clientArea(KWin.MaximizeArea, w);
+        x = Math.max(area.x, Math.min(x, area.x + area.width - width));
+        y = Math.max(area.y, Math.min(y, area.y + area.height - height));
+    }
+    w.frameGeometry = {x: x, y: y, width: width, height: height};
+}
+)")
+                      .arg(QGuiApplication::desktopFileName())
+                      .arg(relative.x())
+                      .arg(relative.y())
+                      .arg(relative.width())
+                      .arg(relative.height())
+                      .arg(keepOnScreen ? QStringLiteral("true") : QStringLiteral("false")));
+}
+
 void FloatingWindow::setInputRegion(const QRectF &region)
 {
     m_window->setMask(QRegion(region.toAlignedRect()));
@@ -54,6 +95,30 @@ void FloatingWindow::setBlurRegion(const QRectF &region, qreal radius)
     KWindowEffects::enableBlurBehind(m_window, true, QRegion(path.toFillPolygon().toPolygon()));
 }
 
+void FloatingWindow::startMove()
+{
+    if (m_window->startSystemMove())
+        releaseMouse();
+}
+
+void FloatingWindow::startResize(Qt::Edges edges)
+{
+    if (m_window->startSystemResize(edges))
+        releaseMouse();
+}
+
+// The window manager keeps the button's release: without one, the pressed
+// item holds on to the mouse and eats the next press.
+void FloatingWindow::releaseMouse()
+{
+    if (!(QGuiApplication::mouseButtons() & Qt::LeftButton))
+        return; // touch
+    const QPointF global = QCursor::pos(m_window->screen());
+    QMouseEvent release(QEvent::MouseButtonRelease, m_window->mapFromGlobal(global), global, Qt::LeftButton,
+                        Qt::NoButton, QGuiApplication::keyboardModifiers());
+    QCoreApplication::sendEvent(m_window, &release);
+}
+
 void FloatingWindow::show()
 {
     m_window->setVisible(true);

src/window/FloatingWindow.h

@@ -9,7 +9,9 @@ class QWindow;
 // Makes a keyboard window a frameless, always-on-top window that never takes
 // focus. The window manager places it and moves it (Super+drag included);
 // on KWin Wayland that relies on the rule from installKWinRule().
-// Geometry is relative to the window's screen.
+// Each time it appears, it's moved back on screen: KWin remembers where it
+// was, which may be somewhere it was smaller. Geometry is relative to the
+// window's screen.
 class FloatingWindow : public QObject
 {
     Q_OBJECT
@@ -25,18 +27,30 @@ public:
 
     // Grows from the top-left corner; respects the window's minimum size.
     Q_INVOKABLE void resizeBy(qreal dw, qreal dh);
+    // Moves the window by `relative`'s offset and resizes it to its size,
+    // optionally clamped to the screen's free area. Done by KWin (Wayland
+    // clients can't place themselves), so it applies later.
+    void moveResize(const QRectF &relative, bool keepOnScreen);
     // Only this part of the window takes input; the rest passes through.
     Q_INVOKABLE void setInputRegion(const QRectF &region);
     // Asks the compositor to blur behind this rounded rect; an empty rect turns blur off.
     Q_INVOKABLE void setBlurRegion(const QRectF &region, qreal radius);
+    // The window manager's move and resize, for mouse and touch alike.
+    Q_INVOKABLE void startMove();
+    Q_INVOKABLE void startResize(Qt::Edges edges);
     Q_INVOKABLE void show();
     Q_INVOKABLE void hide();
 
 Q_SIGNALS:
     void geometryChanged();
 
+protected:
+    bool eventFilter(QObject *watched, QEvent *event) override;
+
 private:
     QRect screenArea() const;
+    void releaseMouse();
 
     QWindow *m_window;
+    bool m_exposed = false;
 };

src/window/KWinScript.cpp

@@ -0,0 +1,56 @@
+#include "KWinScript.h"
+
+#include <QDBusConnection>
+#include <QDBusMessage>
+#include <QDBusPendingCallWatcher>
+#include <QDBusPendingReply>
+#include <QDir>
+#include <QTemporaryFile>
+#include <QTimer>
+#include <memory>
+
+namespace {
+
+const QString Service = QStringLiteral("org.kde.KWin");
+const QString ScriptingPath = QStringLiteral("/Scripting");
+const QString ScriptingInterface = QStringLiteral("org.kde.kwin.Scripting");
+
+// KWin reads the file on a worker thread some time after `run`.
+constexpr int KeepFileMs = 10'000;
+
+QDBusMessage kwinCall(const QString &path, const QString &interface, const QString &method, const QVariantList &args = {})
+{
+    QDBusMessage call = QDBusMessage::createMethodCall(Service, path, interface, method);
+    call.setArguments(args);
+    return call;
+}
+
+} // namespace
+
+void runKWinScript(const QString &source)
+{
+    static int count = 0;
+    const QString plugin = QStringLiteral("sloposk-%1").arg(++count);
+    // Unloading from within: `stop` right after `run` could beat the script.
+    const QString unload = QStringLiteral("\ncallDBus(\"%1\", \"%2\", \"%3\", \"unloadScript\", \"%4\");\n")
+                               .arg(Service, ScriptingPath, ScriptingInterface, plugin);
+
+    auto file = std::make_shared<QTemporaryFile>(QDir::tempPath() + QStringLiteral("/sloposk-XXXXXX.js"));
+    if (!file->open() || file->write((source + unload).toUtf8()) < 0 || !file->flush()) {
+        qWarning("Can't write a KWin script: %s", qPrintable(file->errorString()));
+        return;
+    }
+    auto *watcher = new QDBusPendingCallWatcher(QDBusConnection::sessionBus().asyncCall(
+        kwinCall(ScriptingPath, ScriptingInterface, QStringLiteral("loadScript"), {file->fileName(), plugin})));
+    QObject::connect(watcher, &QDBusPendingCallWatcher::finished, [file](QDBusPendingCallWatcher *watcher) {
+        watcher->deleteLater();
+        const QDBusPendingReply<int> reply = *watcher;
+        if (reply.isError() || reply.value() < 0) {
+            qWarning("KWin didn't load a script: %s", qPrintable(reply.error().message()));
+            return;
+        }
+        const QString path = ScriptingPath + QStringLiteral("/Script") + QString::number(reply.value());
+        QDBusConnection::sessionBus().asyncCall(kwinCall(path, QStringLiteral("org.kde.kwin.Script"), QStringLiteral("run")));
+        QTimer::singleShot(KeepFileMs, [file] {});
+    });
+}

src/window/KWinScript.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#include <QString>
+
+// Runs a one-off KWin script (JavaScript) over D-Bus; it unloads itself when
+// done. Asynchronous; failures are only logged.
+void runKWinScript(const QString &source);