Text rules: auto-capitalization, double-space period, backspace repeat

- TextContext: field purpose/hints and text before the cursor, reported by
  the backend (KWin content_type + surrounding_text)
- TextRules: sentence-start and double-space heuristics, deletion helpers
- KeyRepeater: held backspace repeats, then deletes whole words (Ctrl+BS)
- Controller keeps a best-guess of the text before the cursor so rules work
  instantly and in fields that don't report surrounding text
- No auto-capitalization or smart punctuation in password/URL/email fields

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

src/CMakeLists.txt

@@ -2,11 +2,14 @@
 
 qt_add_library(sloposk_core STATIC
     backend/TextBackend.h
+    backend/TextContext.h
     engine/InputEngine.h
     engine/DirectEngine.h engine/DirectEngine.cpp
     input/ShiftState.h input/ShiftState.cpp
     input/PointerTracker.h input/PointerTracker.cpp
     input/AlternatesPicker.h input/AlternatesPicker.cpp
+    input/KeyRepeater.h input/KeyRepeater.cpp
+    input/TextRules.h input/TextRules.cpp
     input/KeyboardController.h input/KeyboardController.cpp
     input/KeyboardSurface.h input/KeyboardSurface.cpp
     layout/Layout.h

src/backend/KWinInputContext.cpp

@@ -67,9 +67,18 @@ void KWinInputContext::sendKeysym(quint32 sym, Qt::KeyboardModifiers modifiers)
 
 void KWinInputContext::zwp_input_method_context_v1_surrounding_text(const QString &text, uint32_t cursor, uint32_t)
 {
-    m_surroundingText = text;
-    m_cursorPosition = utf8OffsetToIndex(text, cursor);
-    Q_EMIT surroundingChanged();
+    m_context.hasSurroundingText = true;
+    m_context.textBeforeCursor = text.left(utf8OffsetToIndex(text, cursor));
+    Q_EMIT contextChanged();
+}
+
+void KWinInputContext::zwp_input_method_context_v1_content_type(uint32_t hint, uint32_t purpose)
+{
+    // input-method-v1 uses zwp_text_input_v1's values, which TextContext mirrors.
+    m_context.hints = hint;
+    m_context.purpose = purpose <= uint32_t(TextContext::Purpose::Terminal) ? TextContext::Purpose(purpose)
+                                                                          : TextContext::Purpose::Normal;
+    Q_EMIT contextChanged();
 }
 
 void KWinInputContext::zwp_input_method_context_v1_commit_state(uint32_t serial)
@@ -79,9 +88,9 @@ void KWinInputContext::zwp_input_method_context_v1_commit_state(uint32_t serial)
 
 void KWinInputContext::zwp_input_method_context_v1_reset()
 {
-    m_surroundingText.clear();
-    m_cursorPosition = -1;
-    Q_EMIT surroundingChanged();
+    m_context.hasSurroundingText = false;
+    m_context.textBeforeCursor.clear();
+    Q_EMIT contextChanged();
 }
 
 void KWinInputContext::announceModifiers()

src/backend/KWinInputContext.h

@@ -1,11 +1,13 @@
 #pragma once
 
 #include "InputMethodProtocol.h"
+#include "TextContext.h"
 
 #include <QObject>
 
 // One input-method context: exists while a text field is focused.
-// Owns the serial bookkeeping and the UTF-8 <-> QString offset conversion.
+// Owns the serial bookkeeping and translates what the field reports
+// (UTF-8 byte offsets, protocol enums) into a TextContext.
 class KWinInputContext : public QObject, public QtWayland::zwp_input_method_context_v1
 {
     Q_OBJECT
@@ -14,18 +16,18 @@ public:
     explicit KWinInputContext(::zwp_input_method_context_v1 *object, QObject *parent = nullptr);
     ~KWinInputContext() override;
 
-    QString surroundingText() const { return m_surroundingText; }
-    int cursorPosition() const { return m_cursorPosition; }
+    TextContext context() const { return m_context; }
 
     void commit(const QString &text);
     void preedit(const QString &text);
     void sendKeysym(quint32 keysym, Qt::KeyboardModifiers modifiers);
 
 Q_SIGNALS:
-    void surroundingChanged();
+    void contextChanged();
 
 protected:
     void zwp_input_method_context_v1_surrounding_text(const QString &text, uint32_t cursor, uint32_t anchor) override;
+    void zwp_input_method_context_v1_content_type(uint32_t hint, uint32_t purpose) override;
     void zwp_input_method_context_v1_commit_state(uint32_t serial) override;
     void zwp_input_method_context_v1_reset() override;
 
@@ -33,6 +35,5 @@ private:
     void announceModifiers();
 
     uint32_t m_serial = 0;
-    QString m_surroundingText;
-    int m_cursorPosition = -1;
+    TextContext m_context;
 };

src/backend/KWinInputMethod.cpp

@@ -37,14 +37,9 @@ bool KWinInputMethod::isActive() const
     return m_context != nullptr;
 }
 
-QString KWinInputMethod::surroundingText() const
+TextContext KWinInputMethod::context() const
 {
-    return m_context ? m_context->surroundingText() : QString();
-}
-
-int KWinInputMethod::cursorPosition() const
-{
-    return m_context ? m_context->cursorPosition() : -1;
+    return m_context ? m_context->context() : TextContext();
 }
 
 void KWinInputMethod::commitText(const QString &text)
@@ -68,7 +63,7 @@ void KWinInputMethod::sendKeysym(quint32 keysym, Qt::KeyboardModifiers modifiers
 void KWinInputMethod::activate(::zwp_input_method_context_v1 *context)
 {
     m_context = std::make_unique<KWinInputContext>(context);
-    connect(m_context.get(), &KWinInputContext::surroundingChanged, this, &TextBackend::surroundingChanged);
+    connect(m_context.get(), &KWinInputContext::contextChanged, this, &TextBackend::contextChanged);
     Q_EMIT activeChanged();
 }
 
@@ -76,5 +71,5 @@ void KWinInputMethod::deactivate()
 {
     m_context.reset();
     Q_EMIT activeChanged();
-    Q_EMIT surroundingChanged();
+    Q_EMIT contextChanged();
 }

src/backend/KWinInputMethod.h

@@ -40,8 +40,7 @@ public:
     bool isAvailable() const;
 
     bool isActive() const override;
-    QString surroundingText() const override;
-    int cursorPosition() const override;
+    TextContext context() const override;
 
     void commitText(const QString &text) override;
     void setPreedit(const QString &text) override;

src/backend/TextBackend.h

@@ -1,5 +1,7 @@
 #pragma once
 
+#include "TextContext.h"
+
 #include <QObject>
 #include <QString>
 
@@ -10,8 +12,6 @@ class TextBackend : public QObject
 {
     Q_OBJECT
     Q_PROPERTY(bool active READ isActive NOTIFY activeChanged)
-    Q_PROPERTY(QString surroundingText READ surroundingText NOTIFY surroundingChanged)
-    Q_PROPERTY(int cursorPosition READ cursorPosition NOTIFY surroundingChanged)
 
 public:
     using QObject::QObject;
@@ -19,9 +19,8 @@ public:
     // True while a text field is focused and accepts input.
     virtual bool isActive() const = 0;
 
-    // Text around the cursor, if the backend knows it (empty otherwise).
-    virtual QString surroundingText() const { return {}; }
-    virtual int cursorPosition() const { return -1; }
+    // What the focused field reported about itself (defaults if nothing).
+    virtual TextContext context() const { return {}; }
 
     Q_INVOKABLE virtual void commitText(const QString &text) = 0;
     Q_INVOKABLE virtual void setPreedit(const QString &text) = 0;
@@ -29,5 +28,5 @@ public:
 
 Q_SIGNALS:
     void activeChanged();
-    void surroundingChanged();
+    void contextChanged();
 };

src/backend/TextContext.h

@@ -0,0 +1,40 @@
+#pragma once
+
+#include <QString>
+
+// What the focused text field tells us about itself. Values mirror
+// zwp_text_input_v1's content purpose and hints; backends map onto these.
+struct TextContext {
+    enum class Purpose {
+        Normal, Alpha, Digits, Number, Phone, Url, Email, Name,
+        Password, Date, Time, DateTime, Terminal,
+    };
+
+    enum Hint : quint32 {
+        AutoCompletion = 0x1,
+        AutoCorrection = 0x2,
+        AutoCapitalization = 0x4,
+        Lowercase = 0x8,
+        Uppercase = 0x10,
+        Titlecase = 0x20,
+        HiddenText = 0x40,
+        SensitiveData = 0x80,
+        Latin = 0x100,
+        Multiline = 0x200,
+    };
+
+    bool hasSurroundingText = false;
+    QString textBeforeCursor;
+    Purpose purpose = Purpose::Normal;
+    quint32 hints = 0;
+
+    // Prose fields get iOS conveniences; codes, addresses and secrets don't.
+    bool isProse() const
+    {
+        const bool prosePurpose = purpose == Purpose::Normal || purpose == Purpose::Alpha
+                                  || purpose == Purpose::Name;
+        return prosePurpose && !(hints & (HiddenText | SensitiveData));
+    }
+
+    bool allowsAutoCapitalization() const { return isProse() && !(hints & Lowercase); }
+};

src/engine/DirectEngine.cpp

@@ -12,7 +12,7 @@ void DirectEngine::commitText(const QString &text)
     m_backend.commitText(text);
 }
 
-void DirectEngine::sendKeysym(quint32 keysym)
+void DirectEngine::sendKeysym(quint32 keysym, Qt::KeyboardModifiers modifiers)
 {
-    m_backend.sendKeysym(keysym);
+    m_backend.sendKeysym(keysym, modifiers);
 }

src/engine/DirectEngine.h

@@ -10,7 +10,7 @@ public:
     explicit DirectEngine(TextBackend &backend);
 
     void commitText(const QString &text) override;
-    void sendKeysym(quint32 keysym) override;
+    void sendKeysym(quint32 keysym, Qt::KeyboardModifiers modifiers) override;
 
 private:
     TextBackend &m_backend;

src/engine/InputEngine.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <QString>
+#include <qnamespace.h>
 
 // Turns what the keyboard produces into text operations.
 // DirectEngine passes them straight through; prediction and swipe engines
@@ -11,5 +12,5 @@ public:
     virtual ~InputEngine() = default;
 
     virtual void commitText(const QString &text) = 0;
-    virtual void sendKeysym(quint32 keysym) = 0;
+    virtual void sendKeysym(quint32 keysym, Qt::KeyboardModifiers modifiers = Qt::NoModifier) = 0;
 };

src/input/KeyRepeater.cpp

@@ -0,0 +1,31 @@
+#include "KeyRepeater.h"
+
+KeyRepeater::KeyRepeater(QObject *parent)
+    : KeyRepeater(Timing{}, parent)
+{
+}
+
+KeyRepeater::KeyRepeater(Timing timing, QObject *parent)
+    : QObject(parent)
+    , m_timing(timing)
+{
+    connect(&m_timer, &QTimer::timeout, this, &KeyRepeater::fire);
+}
+
+void KeyRepeater::start()
+{
+    m_held.start();
+    m_timer.start(m_timing.initialDelayMs);
+}
+
+void KeyRepeater::stop()
+{
+    m_timer.stop();
+}
+
+void KeyRepeater::fire()
+{
+    const bool wordMode = m_held.elapsed() >= m_timing.wordModeAfterMs;
+    m_timer.setInterval(wordMode ? m_timing.wordIntervalMs : m_timing.intervalMs);
+    Q_EMIT repeat(wordMode);
+}

src/input/KeyRepeater.h

@@ -0,0 +1,37 @@
+#pragma once
+
+#include <QElapsedTimer>
+#include <QObject>
+#include <QTimer>
+
+// Auto-repeat for a held key (backspace). After holding long enough it
+// switches to word mode, like iOS deleting whole words.
+class KeyRepeater : public QObject
+{
+    Q_OBJECT
+
+public:
+    struct Timing {
+        int initialDelayMs = 500;
+        int intervalMs = 90;
+        int wordModeAfterMs = 2000; // counted from start()
+        int wordIntervalMs = 250;
+    };
+
+    explicit KeyRepeater(QObject *parent = nullptr);
+    KeyRepeater(Timing timing, QObject *parent = nullptr);
+
+    void start();
+    void stop();
+    bool isRunning() const { return m_timer.isActive(); }
+
+Q_SIGNALS:
+    void repeat(bool wordMode);
+
+private:
+    void fire();
+
+    Timing m_timing;
+    QTimer m_timer;
+    QElapsedTimer m_held;
+};

src/input/KeyboardController.cpp

@@ -1,4 +1,5 @@
 #include "KeyboardController.h"
+#include "TextRules.h"
 
 #include "engine/InputEngine.h"
 #include "layout/LayoutModel.h"
@@ -11,6 +12,11 @@ static_assert(int(KeyboardController::ShiftMode::Off) == int(ShiftState::Mode::O
 static_assert(int(KeyboardController::ShiftMode::Once) == int(ShiftState::Mode::Once));
 static_assert(int(KeyboardController::ShiftMode::Locked) == int(ShiftState::Mode::Locked));
 
+namespace {
+// Enough history for the text rules; fields may report megabytes.
+constexpr qsizetype MaxTextBefore = 256;
+}
+
 KeyboardController::KeyboardController(InputEngine &engine, LayoutModel &model,
                                        const LayoutRepository &layouts, QObject *parent)
     : QObject(parent)
@@ -20,6 +26,7 @@ KeyboardController::KeyboardController(InputEngine &engine, LayoutModel &model,
 {
     if (!m_layouts.layouts().isEmpty())
         m_model.setLayout(m_layouts.layouts().first());
+    connect(&m_backspaceRepeater, &KeyRepeater::repeat, this, &KeyboardController::deleteBackward);
 }
 
 KeyboardController::ShiftMode KeyboardController::shiftMode() const
@@ -34,7 +41,8 @@ void KeyboardController::keyDown(const KeyDef &key, qint64 timeMs)
         changeShift([&] { m_shift.press(timeMs); });
         break;
     case KeyType::Backspace:
-        m_engine.sendKeysym(XKB_KEY_BackSpace);
+        deleteBackward(false);
+        m_backspaceRepeater.start();
         break;
     case KeyType::LayerSwitch:
         m_layerBeforeSwitch = m_model.layerName();
@@ -51,6 +59,9 @@ void KeyboardController::keyUp(const KeyDef &key, KeyOutput output, const QStrin
     case KeyType::Shift:
         changeShift([&] { m_shift.release(); });
         break;
+    case KeyType::Backspace:
+        m_backspaceRepeater.stop();
+        break;
     case KeyType::Character:
         if (output == KeyOutput::Alternate && !alternate.isEmpty())
             typeText(alternate);
@@ -64,6 +75,8 @@ void KeyboardController::keyUp(const KeyDef &key, KeyOutput output, const QStrin
         break;
     case KeyType::Enter:
         m_engine.sendKeysym(XKB_KEY_Return);
+        m_textBefore += u'\n';
+        autoCapitalize();
         break;
     case KeyType::Globe:
         nextLayout();
@@ -80,6 +93,8 @@ void KeyboardController::keyCancelled(const KeyDef &key)
 {
     if (key.type == KeyType::Shift)
         changeShift([&] { m_shift.release(); });
+    else if (key.type == KeyType::Backspace)
+        m_backspaceRepeater.stop();
 }
 
 void KeyboardController::slideReleased(const KeyDef &target, qint64 timeMs)
@@ -100,6 +115,21 @@ void KeyboardController::moveCursor(QPoint steps)
     repeat(qMax(0, -steps.y()), XKB_KEY_Up);
 }
 
+void KeyboardController::resetContext()
+{
+    m_context = {};
+    m_textBefore.clear();
+    autoCapitalize();
+}
+
+void KeyboardController::setContext(const TextContext &context)
+{
+    m_context = context;
+    if (context.hasSurroundingText)
+        m_textBefore = context.textBeforeCursor.right(MaxTextBefore);
+    autoCapitalize();
+}
+
 void KeyboardController::nextLayout()
 {
     const auto &layouts = m_layouts.layouts();
@@ -111,8 +141,31 @@ void KeyboardController::nextLayout()
 
 void KeyboardController::typeText(const QString &text)
 {
+    if (text == u" " && m_context.isProse() && TextRules::wantsDoubleSpacePeriod(m_textBefore)) {
+        m_engine.sendKeysym(XKB_KEY_BackSpace);
+        m_textBefore.chop(1);
+        typeText(QStringLiteral(". "));
+        return;
+    }
+
     m_engine.commitText(text);
+    m_textBefore = (m_textBefore + text).right(MaxTextBefore);
     changeShift([&] { m_shift.characterTyped(); });
+    autoCapitalize();
+}
+
+void KeyboardController::deleteBackward(bool wholeWord)
+{
+    m_engine.sendKeysym(XKB_KEY_BackSpace, wholeWord ? Qt::ControlModifier : Qt::NoModifier);
+    m_textBefore = wholeWord ? TextRules::withoutLastWord(m_textBefore)
+                             : TextRules::withoutLastCharacter(m_textBefore);
+    autoCapitalize();
+}
+
+void KeyboardController::autoCapitalize()
+{
+    const bool capitalize = m_context.allowsAutoCapitalization() && TextRules::startsSentence(m_textBefore);
+    changeShift([&] { m_shift.setAutomatic(capitalize); });
 }
 
 template<typename Change>

src/input/KeyboardController.h

@@ -1,6 +1,8 @@
 #pragma once
 
+#include "KeyRepeater.h"
 #include "ShiftState.h"
+#include "backend/TextContext.h"
 #include "layout/Layout.h"
 
 #include <QObject>
@@ -14,9 +16,10 @@ class LayoutRepository;
 // Which of a key's outputs the gesture selected.
 enum class KeyOutput { Primary, Flick, Alternate };
 
-// Keyboard rules: what each key does, shift, layers and layout switching.
-// Knows nothing about touch or Wayland: it receives key presses and talks to
-// an InputEngine.
+// Keyboard rules: what each key does, shift, layers, layout switching and the
+// iOS conveniences (auto-capitalization, double-space period, backspace
+// repeat). Knows nothing about touch or Wayland: it receives key presses and
+// text-field context, and talks to an InputEngine.
 class KeyboardController : public QObject
 {
     Q_OBJECT
@@ -41,6 +44,11 @@ public:
     // Space-bar trackpad: move the text cursor by whole steps.
     void moveCursor(QPoint steps);
 
+    // A field was focused or unfocused: forget what we knew about the text.
+    void resetContext();
+    // The focused field reported new text/content type.
+    void setContext(const TextContext &context);
+
     Q_INVOKABLE void nextLayout();
 
 Q_SIGNALS:
@@ -49,6 +57,8 @@ Q_SIGNALS:
 
 private:
     void typeText(const QString &text);
+    void deleteBackward(bool wholeWord);
+    void autoCapitalize();
     template<typename Change>
     void changeShift(Change change);
 
@@ -56,6 +66,12 @@ private:
     LayoutModel &m_model;
     const LayoutRepository &m_layouts;
     ShiftState m_shift;
+    KeyRepeater m_backspaceRepeater;
     int m_layoutIndex = 0;
     QString m_layerBeforeSwitch;
+
+    TextContext m_context;
+    // Best guess of the text before the cursor: the field's last report plus
+    // what we typed since. Fields that don't report text rely on the latter.
+    QString m_textBefore;
 };

src/input/TextRules.cpp

@@ -0,0 +1,57 @@
+#include "TextRules.h"
+
+namespace TextRules {
+
+namespace {
+
+bool endsSentence(QChar c)
+{
+    return c == u'.' || c == u'!' || c == u'?' || c == u'…';
+}
+
+qsizetype trailingSpaceStart(const QString &text)
+{
+    qsizetype i = text.size();
+    while (i > 0 && text[i - 1].isSpace() && text[i - 1] != u'\n')
+        --i;
+    return i;
+}
+
+} // namespace
+
+bool startsSentence(const QString &textBeforeCursor)
+{
+    if (textBeforeCursor.isEmpty() || textBeforeCursor.endsWith(u'\n'))
+        return true;
+    if (!textBeforeCursor.back().isSpace())
+        return false;
+
+    const qsizetype end = trailingSpaceStart(textBeforeCursor);
+    return end == 0 || textBeforeCursor[end - 1] == u'\n' || endsSentence(textBeforeCursor[end - 1]);
+}
+
+bool wantsDoubleSpacePeriod(const QString &textBeforeCursor)
+{
+    const qsizetype n = textBeforeCursor.size();
+    return n >= 2 && textBeforeCursor[n - 1] == u' ' && textBeforeCursor[n - 2].isLetterOrNumber();
+}
+
+QString withoutLastCharacter(const QString &text)
+{
+    if (text.isEmpty())
+        return text;
+    const bool pair = text.size() >= 2 && text.back().isLowSurrogate() && text[text.size() - 2].isHighSurrogate();
+    return text.chopped(pair ? 2 : 1);
+}
+
+QString withoutLastWord(const QString &text)
+{
+    qsizetype i = text.size();
+    while (i > 0 && text[i - 1].isSpace())
+        --i;
+    while (i > 0 && !text[i - 1].isSpace())
+        --i;
+    return text.left(i);
+}
+
+} // namespace TextRules

src/input/TextRules.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include <QString>
+
+// Pure text heuristics behind the iOS conveniences.
+namespace TextRules {
+
+// True at the start of a sentence: empty text, after a newline, or after
+// sentence-ending punctuation followed by whitespace.
+bool startsSentence(const QString &textBeforeCursor);
+
+// True if typing another space should turn "word " into "word. ".
+bool wantsDoubleSpacePeriod(const QString &textBeforeCursor);
+
+// `text` without its last character (surrogate pairs count as one).
+QString withoutLastCharacter(const QString &text);
+
+// `text` without its trailing word and the whitespace after it,
+// matching what Ctrl+Backspace does in most editors.
+QString withoutLastWord(const QString &text);
+
+} // namespace TextRules

src/main.cpp

@@ -72,6 +72,9 @@ int main(int argc, char *argv[])
     QObject::connect(&backend, &TextBackend::activeChanged, &app, updateVisibility);
     QObject::connect(&backend, &KWinInputMethod::availableChanged, &app, updateVisibility);
     QObject::connect(&controller, &KeyboardController::dismissRequested, &placement, &FloatingWindow::hide);
+    QObject::connect(&backend, &TextBackend::activeChanged, &controller, &KeyboardController::resetContext);
+    QObject::connect(&backend, &TextBackend::contextChanged, &controller,
+                     [&] { controller.setContext(backend.context()); });
     updateVisibility();
 
     installDevHooks(backend, *window);