macOS: Clarify that QCocoaKeyMapper only computes 8 modifier states

Change-Id: Ie4a53bbc16cde7b4aa68172015bbfeaa9e316bcc
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

2 files changed, 8 insertions, 24 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoakeymapper.h b/src/plugins/platforms/cocoa/qcocoakeymapper.h
index c0540bfe1d..dbf164c18e 100644
--- a/src/plugins/platforms/cocoa/qcocoakeymapper.h
+++ b/src/plugins/platforms/cocoa/qcocoakeymapper.h
@@ -49,27 +49,6 @@
 
 QT_BEGIN_NAMESPACE
 
-/*
-    \internal
-    A Mac KeyboardLayoutItem has 8 possible states:
-        1. Unmodified
-        2. Shift
-        3. Control
-        4. Control + Shift
-        5. Alt
-        6. Alt + Shift
-        7. Alt + Control
-        8. Alt + Control + Shift
-        9. Meta
-        10. Meta + Shift
-        11. Meta + Control
-        12. Meta + Control + Shift
-        13. Meta + Alt
-        14. Meta + Alt + Shift
-        15. Meta + Alt + Control
-        16. Meta + Alt + Control + Shift
-*/
-
 class QCocoaKeyMapper
 {
 public:
@@ -83,8 +62,8 @@ public:
     static Qt::Key fromCocoaKey(QChar keyCode);
 
 private:
-    using VirtualKeyCode = unsigned short;
-    struct KeyMap : std::array<char32_t, 16>
+    static constexpr int kNumModifierCombinations = 16;
+    struct KeyMap : std::array<char32_t, kNumModifierCombinations>
     {
         // Initialize first element to a sentinel that allows us
         // to distinguish an uninitialized map from an initialized.
@@ -94,6 +73,8 @@ private:
     };
 
     bool updateKeyboard();
+
+    using VirtualKeyCode = unsigned short;
     const KeyMap &keyMapForKey(VirtualKeyCode virtualKey, QChar unicodeKey) const;
 
     QCFType<TISInputSourceRef> m_currentInputSource = nullptr;
diff --git a/src/plugins/platforms/cocoa/qcocoakeymapper.mm b/src/plugins/platforms/cocoa/qcocoakeymapper.mm
index bcc5a9ef0c..d1654e84bb 100644
--- a/src/plugins/platforms/cocoa/qcocoakeymapper.mm
+++ b/src/plugins/platforms/cocoa/qcocoakeymapper.mm
@@ -444,6 +444,8 @@ static constexpr Qt::KeyboardModifiers modifierCombinations[] = {
 */
 const QCocoaKeyMapper::KeyMap &QCocoaKeyMapper::keyMapForKey(VirtualKeyCode virtualKey, QChar unicodeKey) const
 {
+    static_assert(sizeof(modifierCombinations) / sizeof(Qt::KeyboardModifiers) == kNumModifierCombinations);
+
     const_cast<QCocoaKeyMapper *>(this)->updateKeyboard();
 
     auto &keyMap = m_keyMap[virtualKey];
@@ -452,7 +454,7 @@ const QCocoaKeyMapper::KeyMap &QCocoaKeyMapper::keyMapForKey(VirtualKeyCode virt
 
     qCDebug(lcQpaKeyMapper, "Updating key map for virtual key = 0x%02x!", (uint)virtualKey);
 
-    for (int i = 0; i < 16; ++i) {
+    for (int i = 0; i < kNumModifierCombinations; ++i) {
         Q_ASSERT(!i || keyMap[i] == 0);
 
         auto qtModifiers = modifierCombinations[i];
@@ -514,6 +516,7 @@ QList<int> QCocoaKeyMapper::possibleKeys(const QKeyEvent *event) const
     // is always valid, and the first priority.
     ret << int(unmodifiedKey + eventModifiers);
 
+    // FIXME: We only compute the first 8 combinations. Why?
     for (int i = 1; i < 8; ++i) {
         auto keyAfterApplyingModifiers = keyMap[i];
         if (keyAfterApplyingModifiers == unmodifiedKey)