如何根据当前的键盘布局从 QKeyEvent 捕获 QKeySequence？

Question

我需要这样做来配置我的应用程序。 我有重新实现 keyPressEvent 方法的 QLineEdit 字段。

QKeyEvent *ke = ...
QString txt;

if(ke->modifiers() & Qt::ControlModifier)
    txt += "Ctrl+";
if(ke->modifiers() & Qt::AltModifier)
    txt += "Alt+";
if(ke->modifiers() & Qt::ShiftModifier)
    txt += "Shift+";

if(ke->key() >= Qt::Key_0 && ke->key() <= Qt::Key_9)
    txt += ('0' + ke->key() - Qt::Key_0);
else if(ke->key() >= Qt::Key_A && ke->key() <= Qt::Key_Z)
    txt += ('A' + ke->key() - Qt::Key_A);
ui->hotkeyEdit->setText(txt);

但此解决方案只能使用英文字符创建快捷方式。例如，当我使用俄语键盘布局时，此代码将显示相同的序列，但使用英文字符，放置在同一个键盘键上。

Answer 1

您可能会发现函数QKeySequence().toString() 非常有用。

以下是我用来捕获用户定义的快捷方式的部分代码。通过一些修改，它可以做你项目中需要的任何事情。希望它有所帮助（对不起，蹩脚的身份）：

if (event->type() == QEvent::KeyPress){ 
    QKeyEvent *keyEvent = static_cast<QKeyEvent*>(event); 

    int keyInt = keyEvent->key(); 
    Qt::Key key = static_cast<Qt::Key>(keyInt); 
    if(key == Qt::Key_unknown){ 
        qDebug() << "Unknown key from a macro probably"; 
        return; 
    } 
    // the user have clicked just and only the special keys Ctrl, Shift, Alt, Meta. 
    if(key == Qt::Key_Control || 
        key == Qt::Key_Shift || 
        key == Qt::Key_Alt || 
        key == Qt::Key_Meta)
    { 
        qDebug() << "Single click of special key: Ctrl, Shift, Alt or Meta"; 
        qDebug() << "New KeySequence:" << QKeySequence(keyInt).toString(QKeySequence::NativeText); 
        return; 
    } 

    // check for a combination of user clicks 
    Qt::KeyboardModifiers modifiers = keyEvent->modifiers(); 
    QString keyText = keyEvent->text(); 
    // if the keyText is empty than it's a special key like F1, F5, ... 
    qDebug() << "Pressed Key:" << keyText; 

    QList<Qt::Key> modifiersList; 
    if(modifiers & Qt::ShiftModifier) 
        keyInt += Qt::SHIFT; 
    if(modifiers & Qt::ControlModifier) 
        keyInt += Qt::CTRL; 
    if(modifiers & Qt::AltModifier) 
        keyInt += Qt::ALT; 
    if(modifiers & Qt::MetaModifier) 
        keyInt += Qt::META; 

    qDebug() << "New KeySequence:" << QKeySequence(keyInt).toString(QKeySequence::NativeText); 
}

Answer 2

如果有人关心上述 Tihomir Dolapchiev 解决方案的 python 版本。我刚刚翻译了它，效果很好。只是张贴以供将来参考。

class KeySequenceEdit(QtGui.QLineEdit):
    """
    This class is mainly inspired by
    http://stackoverflow.com/a/6665017

    """

    def __init__(self, keySequence, *args):
        super(KeySequenceEdit, self).__init__(*args)

        self.keySequence = keySequence
        self.setKeySequence(keySequence)

    def setKeySequence(self, keySequence):
        self.keySequence = keySequence
        self.setText(self.keySequence.toString(QtGui.QKeySequence.NativeText))


    def keyPressEvent(self, e):
        if e.type() == QtCore.QEvent.KeyPress:
            key = e.key()

            if key == QtCore.Qt.Key_unknown:
                warnings.warn("Unknown key from a macro probably")
                return

            # the user have clicked just and only the special keys Ctrl, Shift, Alt, Meta.
            if(key == QtCore.Qt.Key_Control or
            key == QtCore.Qt.Key_Shift or
            key == QtCore.Qt.Key_Alt or
            key == QtCore.Qt.Key_Meta):
                print("Single click of special key: Ctrl, Shift, Alt or Meta")
                print("New KeySequence:", QtGui.QKeySequence(key).toString(QtGui.QKeySequence.NativeText))
                return

            # check for a combination of user clicks
            modifiers = e.modifiers()
            keyText = e.text()
            # if the keyText is empty than it's a special key like F1, F5, ...
            print("Pressed Key:", keyText)

            if modifiers & QtCore.Qt.ShiftModifier:
                key += QtCore.Qt.SHIFT
            if modifiers & QtCore.Qt.ControlModifier:
                key += QtCore.Qt.CTRL
            if modifiers & QtCore.Qt.AltModifier:
                key += QtCore.Qt.ALT
            if modifiers & QtCore.Qt.MetaModifier:
                key += QtCore.Qt.META

            print("New KeySequence:", QtGui.QKeySequence(key).toString(QtGui.QKeySequence.NativeText))

            self.setKeySequence(QtGui.QKeySequence(key))

Answer 3

您可以为操作分配键盘快捷键。

这里有一些方法可以做到这一点。

actionName->setShortcut(QKeySequence::New); //for predefined shortcuts like new, close, open..

或者你可以用这个定义你自己的快捷方式

actionName->setShortcut(QKeySequence("Ctrl+N")); // sets Ctrl + N for w.e the action does

在第一种情况下，qt 会自动检测并为该特定操作分配适当的快捷方式。在第二种情况下，您可以选择自己想要的快捷方式并将其键入为字符串。它会自动解析并理解。

这避免了将密钥捕获用于不必要的目的。

Answer 4

首选standard seqence。

来自Keyboard Layout Issues：

因此，在指定可用于各种不同键盘布局的键序列时，使用人类可读的字符串和硬编码的键代码都可能存在问题。只有使用标准快捷键才能保证用户能够使用开发人员想要的快捷键。

Answer 5

最简单的方法是：

if(event->type() == QEvent::KeyPress)
{
    QKeyEvent *keyEvent = static_cast<QKeyEvent*>(event);
    qDebug() << "delete" << keyEvent->matches(QKeySequence::Delete);
    qDebug() << "copy" << keyEvent->matches(QKeySequence::Copy);
    qDebug() << "paste" << keyEvent->matches(QKeySequence::Paste);
}

Answer 6

如果 Qt 用户想要它用于 Qml，我就是这样做的。

但是，您可能不想要一些额外的功能。我将代码留在这里，让用户适应。

TextField {
    Layout.fillWidth: true
    placeholderText: qsTr("Shortcut")
    text: shortcut
    onTextChanged: myModel.setPropertyAndUpdate(index, "shortcut", text, this)

    property var modifiers: ({ 0x02000000: "Shift", 0x04000000: "Ctrl", 0x08000000: "Alt", 0x10000000: "Meta", 0x20000000: "Keypad", 0x40000000: "GroupSwitch" })
    property var keys: ({
        0x01000000: "Escape", 0x01000001: "Tab", 0x01000002: "Backtab", 0x01000003: "Backspace", 0x01000004: "Return", 0x01000005: "Enter", 0x01000006: "Insert", 0x01000007: "Delete", 0x01000008: "Pause", 0x01000009: "Print", 0x0100000a: "SysReq", 0x0100000b: "Clear", 0x01000010: "Home", 0x01000011: "End", 0x01000012: "Left", 0x01000013: "Up", 0x01000014: "Right", 0x01000015: "Down", 0x01000016: "PageUp", 0x01000017: "PageDown", 0x01000020: "Shift", 0x01000021: "Control", 0x01000022: "Meta", 0x01000023: "Alt", 0x01001103: "AltGr", 0x01000024: "CapsLock", 0x01000025: "NumLock", 0x01000026: "ScrollLock", 0x01000030: "F1", 0x01000031: "F2", 0x01000032: "F3", 0x01000033: "F4", 0x01000034: "F5", 0x01000035: "F6", 0x01000036: "F7", 0x01000037: "F8", 0x01000038: "F9", 0x01000039: "F10", 0x0100003a: "F11", 0x0100003b: "F12", 0x0100003c: "F13", 0x0100003d: "F14", 0x0100003e: "F15", 0x0100003f: "F16", 0x01000040: "F17", 0x01000041: "F18", 0x01000042: "F19", 0x01000043: "F20", 0x01000044: "F21", 0x01000045: "F22", 0x01000046: "F23", 0x01000047: "F24", 0x01000048: "F25", 0x01000049: "F26", 0x0100004a: "F27", 0x0100004b: "F28", 0x0100004c: "F29", 0x0100004d: "F30", 0x0100004e: "F31", 0x0100004f: "F32", 0x01000050: "F33", 0x01000051: "F34", 0x01000052: "F35", 0x01000053: "Super_L", 0x01000054: "Super_R", 0x01000055: "Menu", 0x01000056: "Hyper_L", 0x01000057: "Hyper_R", 0x01000058: "Help", 0x01000059: "Direction_L", 0x01000060: "Direction_R", 0x20: "Space", 0x21: "Exclam", 0x22: "QuoteDbl", 0x23: "NumberSign", 0x24: "Dollar", 0x25: "Percent", 0x26: "Ampersand", 0x27: "Apostrophe", 0x28: "ParenLeft", 0x29: "ParenRight", 0x2a: "Asterisk", 0x2b: "Plus", 0x2c: "Comma", 0x2d: "Minus", 0x2e: "Period", 0x2f: "Slash", 0x30: "0", 0x31: "1", 0x32: "2", 0x33: "3", 0x34: "4", 0x35: "5", 0x36: "6", 0x37: "7", 0x38: "8", 0x39: "9", 0x3a: "Colon", 0x3b: "Semicolon", 0x3c: "Less", 0x3d: "Equal", 0x3e: "Greater", 0x3f: "Question", 0x40: "At", 0x41: "A", 0x42: "B", 0x43: "C", 0x44: "D", 0x45: "E", 0x46: "F", 0x47: "G", 0x48: "H", 0x49: "I", 0x4a: "J", 0x4b: "K", 0x4c: "L", 0x4d: "M", 0x4e: "N", 0x4f: "O", 0x50: "P", 0x51: "Q", 0x52: "R", 0x53: "S", 0x54: "T", 0x55: "U", 0x56: "V", 0x57: "W", 0x58: "X", 0x59: "Y", 0x5a: "Z", 0x5b: "BracketLeft", 0x5c: "Backslash", 0x5d: "BracketRight", 0x5e: "AsciiCircum", 0x5f: "Underscore", 0x60: "QuoteLeft", 0x7b: "BraceLeft", 0x7c: "Bar", 0x7d: "BraceRight", 0x7e: "AsciiTilde", 0x0a0: "nobreakspace", 0x0a1: "exclamdown", 0x0a2: "cent", 0x0a3: "sterling", 0x0a4: "currency", 0x0a5: "yen", 0x0a6: "brokenbar", 0x0a7: "section", 0x0a8: "diaeresis", 0x0a9: "copyright", 0x0aa: "ordfeminine", 0x0ab: "guillemotleft", 0x0ac: "notsign", 0x0ad: "hyphen", 0x0ae: "registered", 0x0af: "macron", 0x0b0: "degree", 0x0b1: "plusminus", 0x0b2: "twosuperior", 0x0b3: "threesuperior", 0x0b4: "acute", 0x0b5: "mu", 0x0b6: "paragraph", 0x0b7: "periodcentered", 0x0b8: "cedilla", 0x0b9: "onesuperior", 0x0ba: "masculine", 0x0bb: "guillemotright", 0x0bc: "onequarter", 0x0bd: "onehalf", 0x0be: "threequarters", 0x0bf: "questiondown", 0x0c0: "Agrave", 0x0c1: "Aacute", 0x0c2: "Acircumflex", 0x0c3: "Atilde", 0x0c4: "Adiaeresis", 0x0c5: "Aring", 0x0c6: "AE", 0x0c7: "Ccedilla", 0x0c8: "Egrave", 0x0c9: "Eacute", 0x0ca: "Ecircumflex", 0x0cb: "Ediaeresis", 0x0cc: "Igrave", 0x0cd: "Iacute", 0x0ce: "Icircumflex", 0x0cf: "Idiaeresis", 0x0d0: "ETH", 0x0d1: "Ntilde", 0x0d2: "Ograve", 0x0d3: "Oacute", 0x0d4: "Ocircumflex", 0x0d5: "Otilde", 0x0d6: "Odiaeresis", 0x0d7: "multiply", 0x0d8: "Ooblique", 0x0d9: "Ugrave", 0x0da: "Uacute", 0x0db: "Ucircumflex", 0x0dc: "Udiaeresis", 0x0dd: "Yacute", 0x0de: "THORN", 0x0df: "ssharp", 0x0f7: "division", 0x0ff: "ydiaeresis", 0x01001120: "Multi_key", 0x01001137: "Codeinput", 0x0100113c: "SingleCandidate", 0x0100113d: "MultipleCandidate", 0x0100113e: "PreviousCandidate", 0x0100117e: "Mode_switch", 0x01001121: "Kanji", 0x01001122: "Muhenkan", 0x01001123: "Henkan", 0x01001124: "Romaji", 0x01001125: "Hiragana", 0x01001126: "Katakana", 0x01001127: "Hiragana_Katakana", 0x01001128: "Zenkaku", 0x01001129: "Hankaku", 0x0100112a: "Zenkaku_Hankaku", 0x0100112b: "Touroku", 0x0100112c: "Massyo", 0x0100112d: "Kana_Lock", 0x0100112e: "Kana_Shift", 0x0100112f: "Eisu_Shift", 0x01001130: "Eisu_toggle", 0x01001131: "Hangul", 0x01001132: "Hangul_Start", 0x01001133: "Hangul_End", 0x01001134: "Hangul_Hanja", 0x01001135: "Hangul_Jamo", 0x01001136: "Hangul_Romaja", 0x01001138: "Hangul_Jeonja", 0x01001139: "Hangul_Banja", 0x0100113a: "Hangul_PreHanja", 0x0100113b: "Hangul_PostHanja", 0x0100113f: "Hangul_Special", 0x01001250: "Dead_Grave", 0x01001251: "Dead_Acute", 0x01001252: "Dead_Circumflex", 0x01001253: "Dead_Tilde", 0x01001254: "Dead_Macron", 0x01001255: "Dead_Breve", 0x01001256: "Dead_Abovedot", 0x01001257: "Dead_Diaeresis", 0x01001258: "Dead_Abovering", 0x01001259: "Dead_Doubleacute", 0x0100125a: "Dead_Caron", 0x0100125b: "Dead_Cedilla", 0x0100125c: "Dead_Ogonek", 0x0100125d: "Dead_Iota", 0x0100125e: "Dead_Voiced_Sound", 0x0100125f: "Dead_Semivoiced_Sound", 0x01001260: "Dead_Belowdot", 0x01001261: "Dead_Hook", 0x01001262: "Dead_Horn", 0x01001263: "Dead_Stroke", 0x01001264: "Dead_Abovecomma", 0x01001265: "Dead_Abovereversedcomma", 0x01001266: "Dead_Doublegrave", 0x01001267: "Dead_Belowring", 0x01001268: "Dead_Belowmacron", 0x01001269: "Dead_Belowcircumflex", 0x0100126a: "Dead_Belowtilde", 0x0100126b: "Dead_Belowbreve", 0x0100126c: "Dead_Belowdiaeresis", 0x0100126d: "Dead_Invertedbreve", 0x0100126e: "Dead_Belowcomma", 0x0100126f: "Dead_Currency", 0x01001280: "Dead_a", 0x01001281: "Dead_A", 0x01001282: "Dead_e", 0x01001283: "Dead_E", 0x01001284: "Dead_i", 0x01001285: "Dead_I", 0x01001286: "Dead_o", 0x01001287: "Dead_O", 0x01001288: "Dead_u", 0x01001289: "Dead_U", 0x0100128a: "Dead_Small_Schwa", 0x0100128b: "Dead_Capital_Schwa", 0x0100128c: "Dead_Greek", 0x01001290: "Dead_Lowline", 0x01001291: "Dead_Aboveverticalline", 0x01001292: "Dead_Belowverticalline", 0x01001293: "Dead_Longsolidusoverlay", 0x01000061: "Back", 0x01000062: "Forward", 0x01000063: "Stop", 0x01000064: "Refresh", 0x01000070: "VolumeDown", 0x01000071: "VolumeMute", 0x01000072: "VolumeUp", 0x01000073: "BassBoost", 0x01000074: "BassUp", 0x01000075: "BassDown", 0x01000076: "TrebleUp", 0x01000077: "TrebleDown", 0x01000080: "MediaPlay", 0x01000081: "MediaStop", 0x01000082: "MediaPrevious", 0x01000083: "MediaNext", 0x01000084: "MediaRecord", 0x1000085: "MediaPause", 0x1000086: "MediaTogglePlayPause", 0x01000090: "HomePage", 0x01000091: "Favorites", 0x01000092: "Search", 0x01000093: "Standby", 0x01000094: "OpenUrl", 0x010000a0: "LaunchMail", 0x010000a1: "LaunchMedia", 0x010000a2: "Launch0", 0x010000a3: "Launch1", 0x010000a4: "Launch2", 0x010000a5: "Launch3", 0x010000a6: "Launch4", 0x010000a7: "Launch5", 0x010000a8: "Launch6", 0x010000a9: "Launch7", 0x010000aa: "Launch8", 0x010000ab: "Launch9", 0x010000ac: "LaunchA", 0x010000ad: "LaunchB", 0x010000ae: "LaunchC", 0x010000af: "LaunchD", 0x010000b0: "LaunchE", 0x010000b1: "LaunchF", 0x0100010e: "LaunchG", 0x0100010f: "LaunchH", 0x010000b2: "MonBrightnessUp", 0x010000b3: "MonBrightnessDown", 0x010000b4: "KeyboardLightOnOff", 0x010000b5: "KeyboardBrightnessUp", 0x010000b6: "KeyboardBrightnessDown", 0x010000b7: "PowerOff", 0x010000b8: "WakeUp", 0x010000b9: "Eject", 0x010000ba: "ScreenSaver", 0x010000bb: "WWW", 0x010000bc: "Memo", 0x010000bd: "LightBulb", 0x010000be: "Shop", 0x010000bf: "History", 0x010000c0: "AddFavorite", 0x010000c1: "HotLinks", 0x010000c2: "BrightnessAdjust", 0x010000c3: "Finance", 0x010000c4: "Community", 0x010000c5: "AudioRewind", 0x010000c6: "BackForward", 0x010000c7: "ApplicationLeft", 0x010000c8: "ApplicationRight", 0x010000c9: "Book", 0x010000ca: "CD", 0x010000cb: "Calculator", 0x010000cc: "ToDoList", 0x010000cd: "ClearGrab", 0x010000ce: "Close", 0x010000cf: "Copy", 0x010000d0: "Cut", 0x010000d1: "Display", 0x010000d2: "DOS", 0x010000d3: "Documents", 0x010000d4: "Excel", 0x010000d5: "Explorer", 0x010000d6: "Game", 0x010000d7: "Go", 0x010000d8: "iTouch", 0x010000d9: "LogOff", 0x010000da: "Market", 0x010000db: "Meeting", 0x010000dc: "MenuKB", 0x010000dd: "MenuPB", 0x010000de: "MySites", 0x010000df: "News", 0x010000e0: "OfficeHome", 0x010000e1: "Option", 0x010000e2: "Paste", 0x010000e3: "Phone", 0x010000e4: "Calendar", 0x010000e5: "Reply", 0x010000e6: "Reload", 0x010000e7: "RotateWindows", 0x010000e8: "RotationPB", 0x010000e9: "RotationKB", 0x010000ea: "Save", 0x010000eb: "Send", 0x010000ec: "Spell", 0x010000ed: "SplitScreen", 0x010000ee: "Support", 0x010000ef: "TaskPane", 0x010000f0: "Terminal", 0x010000f1: "Tools", 0x010000f2: "Travel", 0x010000f3: "Video", 0x010000f4: "Word", 0x010000f5: "Xfer", 0x010000f6: "ZoomIn", 0x010000f7: "ZoomOut", 0x010000f8: "Away", 0x010000f9: "Messenger", 0x010000fa: "WebCam", 0x010000fb: "MailForward", 0x010000fc: "Pictures", 0x010000fd: "Music", 0x010000fe: "Battery", 0x010000ff: "Bluetooth", 0x01000100: "WLAN", 0x01000101: "UWB", 0x01000102: "AudioForward", 0x01000103: "AudioRepeat", 0x01000104: "AudioRandomPlay", 0x01000105: "Subtitle", 0x01000106: "AudioCycleTrack", 0x01000107: "Time", 0x01000108: "Hibernate", 0x01000109: "View", 0x0100010a: "TopMenu", 0x0100010b: "PowerDown", 0x0100010c: "Suspend", 0x0100010d: "ContrastAdjust", 0x01000110: "TouchpadToggle", 0x01000111: "TouchpadOn", 0x01000112: "TouchpadOff", 0x01000113: "MicMute", 0x01000114: "Red", 0x01000115: "Green", 0x01000116: "Yellow", 0x01000117: "Blue", 0x01000118: "ChannelUp", 0x01000119: "ChannelDown", 0x0100011a: "Guide", 0x0100011b: "Info", 0x0100011c: "Settings", 0x0100011d: "MicVolumeUp", 0x0100011e: "MicVolumeDown", 0x01000120: "New", 0x01000121: "Open", 0x01000122: "Find", 0x01000123: "Undo", 0x01000124: "Redo", 0x0100ffff: "MediaLast", 0x01ffffff: "unknown", 0x01100004: "Call", 0x01100020: "Camera", 0x01100021: "CameraFocus", 0x01100000: "Context1", 0x01100001: "Context2", 0x01100002: "Context3", 0x01100003: "Context4", 0x01100006: "Flip", 0x01100005: "Hangup", 0x01010002: "No", 0x01010000: "Select", 0x01010001: "Yes", 0x01100007: "ToggleCallHangup", 0x01100008: "VoiceDial", 0x01100009: "LastNumberRedial", 0x01020003: "Execute", 0x01020002: "Printer", 0x01020005: "Play", 0x01020004: "Sleep", 0x01020006: "Zoom", 0x0102000a: "Exit", 0x01020001: "Cancel"
    })
    property var modifierKeys: [Qt.Key_Alt, Qt.Key_Meta, Qt.Key_Control, Qt.Key_Shift, Qt.Key_NumLock, Qt.Key_Mode_switch]

    property bool lastWasNotModifier: false
    function parseKeyEvent(event, released) {
        if (!autoShortcut.checked)
            return

        if (!released && (event.key == Qt.Key_Backspace || event.key == Qt.Key_Delete) && event.modifiers == Qt.NoModifier) {
            text = ""
            event.accepted = true
            return
        }

        var isModifier = false
        modifierKeys.forEach(function(modifKey) {
            if (modifKey == event.key)
                isModifier = true
        })
        if (released && lastWasNotModifier) {
            event.accepted = true
            return
        }

        lastWasNotModifier = !isModifier

        if (event.key == Qt.Key_unknown) {
            console.log("Unknown key from a macro probably")
            //text = ""
            event.accepted = true
            return
        }

        var result = ""
        // var result = lastWasNotModifier ? text + "," : ""
        if (!(event.modifiers & Qt.NoModifier)) {
            for(var modifier in modifiers) {
                if (modifier & event.modifiers)
                    result += modifiers[modifier] + "+"
            }
        }

        if (!released && !isModifier) {
            result += keys[event.key]
        }
        if (text.endsWith('+')) {
            var t = text.split(',')
            text = t.slice(0, t.length - 1).join(',')
        }
        if (text) {
            if (text.endsWith(','))
                text = text + result
            else
                text = text + ',' + result
        }
        else {
            text = result
        }
        event.accepted = true
    }
    Keys.onPressed: parseKeyEvent(event, false)
    Keys.onReleased: parseKeyEvent(event, true)

    ToolButton {
        id: autoShortcut
        anchors {
            top: parent.top
            bottom: parent.bottom
            right: parent.right
            bottomMargin: 2
            topMargin: 2
            rightMargin: 2
        }
        text: qsTr("auto")
        checkable: true
        checked: true
        tooltip: qsTr("Wheter this line tries to create shortcut with you keypresses.\nIf disabled, you will be able to enter any key sequence as plain text")
    }
}

Answer 7

尝试在 keyPressEvent 中捕获 QKeySequence 可能无法按预期工作。我找到了解决方案：

//  || event->type()== QEvent::ShortcutOverride is the key point
if (event->type() == QEvent::KeyPress || event->type()== QEvent::ShortcutOverride)
{
    QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
    if (keyEvent->matches(QKeySequence::Save))
    {
        // Do save
    }
}

我希望对某人有所帮助。 :)

参考：QWidget::eventFilter() not catching key combinations