virtual MIDI keyboard on PyQt4. To run this use commands: jack_control start && timidity -iA -Oj -B2,8

qtkb.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"virtual MIDI keyboard on PyQt4. To run this use commands: jack_control start && timidity -iA -Oj -B2,8"

from PyQt4.QtGui import QGridLayout, QHBoxLayout, QLineEdit, QPushButton, QSizePolicy, QVBoxLayout, QWidget
from PyQt4.QtCore import QSize, SIGNAL, QEvent

# this app will list all MIDI devices and associated numbers
# Pick the correct number associated, and restart the app.
MIDI_DEVICE = 1

class InputState:
    LOWER = 0
    CAPITAL = 1


class KeyButton(QPushButton):
    def __init__(self, key):
        super(KeyButton, self).__init__()

        self._key = key
        self._activeSize = QSize(50,50)
        self.setSizePolicy(QSizePolicy(QSizePolicy.Fixed, QSizePolicy.Fixed))


    def mousePressEvent(self, event):
        self.emit(SIGNAL("sigKeyButtonClicked"), self._key)

    def mouseReleaseEvent(self, event):
        self.emit(SIGNAL("sigKeyButtonClicked"), "")

    def enterEvent(self, event):
        self.setFixedSize(self._activeSize)

    def leaveEvent(self, event):
        self.setFixedSize(self.sizeHint())

    def sizeHint(self):
        return QSize(40, 40)

class NoteEdit(QLineEdit):
    def __init__(self, main, midi):
        self.midi = midi
        self.main = main
        self.pressed = set()
        QLineEdit.__init__(self)
    
    def event(self, event):
        if (event.type() == QEvent.KeyPress):
            if 90 >= event.key() >= 65:
              if event.key() in self.pressed: return False
              self.pressed.add(event.key())
              midi.send_message([0x90, event.key(), 100])
              self.main.getButtonByKey(str(event.text())).enterEvent(event)
              self.main.inputString += (str(event.text()).lower(), str(event.text()).capitalize())[self.main.state]
              
        
        elif (event.type() == QEvent.KeyRelease):
            if 90 >= event.key() >= 65:
              if event.isAutoRepeat(): return False
              self.pressed.remove(event.key())
              midi.send_message([0x80, event.key(), 100])
              self.main.getButtonByKey(str(event.text())).leaveEvent(event)
        
        else: return QLineEdit.event(self, event)
        return True

class VirtualKeyboard(QWidget):
    def __init__(self, midi):
        super(VirtualKeyboard, self).__init__()
        self.midi = midi

        self.globalLayout = QVBoxLayout(self)
        self.keysLayout = QGridLayout()
        self.buttonLayout = QHBoxLayout()

        self.keyListByLines = [
                    ['q', 'w', 'e', 'r', 't', 'y', 'u', 'i', 'o', 'p'],
                    ['a', 's', 'd', 'f', 'g', 'h', 'j', 'k', 'l', ';'],
                    ['z', 'x', 'c', 'v', 'b', 'n', 'm', ',', '.', '/'],
                ]
        self.inputString = ""
        self.state = InputState.LOWER

        self.stateButton = QPushButton()
        self.stateButton.setText('Note')
        self.stateButton.setCheckable(True)
        self.backButton = QPushButton()
        self.backButton.setText('<-')
        self.okButton = QPushButton()
        self.okButton.setText('OK')
        self.cancelButton = QPushButton()
        self.cancelButton.setText("Cancel")

        self.inputLine = NoteEdit(self, midi)


        for lineIndex, line in enumerate(self.keyListByLines):
            for keyIndex, key in enumerate(line):
                buttonName = "keyButton" + key.capitalize()
                self.__setattr__(buttonName, KeyButton(key))
                self.keysLayout.addWidget(self.getButtonByKey(key), self.keyListByLines.index(line), line.index(key))
                self.getButtonByKey(key).setText(key)
                self.connect(self.getButtonByKey(key), SIGNAL("sigKeyButtonClicked"), self.addInputByKey)
                self.keysLayout.setColumnMinimumWidth(keyIndex, 50)
            self.keysLayout.setRowMinimumHeight(lineIndex, 50)

        self.connect(self.stateButton, SIGNAL("clicked()"), self.switchState)
        self.connect(self.backButton, SIGNAL("clicked()"), self.backspace)
        self.connect(self.okButton, SIGNAL("clicked()"), self.emitInputString)
        self.connect(self.cancelButton, SIGNAL("clicked()"), self.emitCancel)


        self.buttonLayout.addWidget(self.cancelButton)
        self.buttonLayout.addWidget(self.backButton)
        self.buttonLayout.addWidget(self.stateButton)
        self.buttonLayout.addWidget(self.okButton)

        self.globalLayout.addWidget(self.inputLine)
        self.globalLayout.addLayout(self.keysLayout)

        self.globalLayout.addLayout(self.buttonLayout)
        self.setSizePolicy(QSizePolicy(QSizePolicy.Fixed, QSizePolicy.Fixed))


    def getButtonByKey(self, key):
        return getattr(self, "keyButton" + key.capitalize())

    def getLineForButtonByKey(self, key):
        return [key in keyList for keyList in self.keyListByLines].index(True)

    def switchState(self):
        self.state = not self.state

    def addInputByKey(self, key):
        if key:
          self.midi.send_message([0x90, ord(key)-32, 100])
          self.key=key
        else:
          self.midi.send_message([0x80, ord(self.key)-32, 100])
          
        self.inputString += (key.lower(), key.capitalize())[self.state]
        self.inputLine.setFocus()

    def backspace(self):
        self.inputLine.setText("")
        self.inputString = ""

    def emitInputString(self):
        self.emit(SIGNAL("sigInputString"), self.inputString)

    def emitCancel(self):
        self.emit(SIGNAL("sigInputString"), "")

    def sizeHint(self):
        return QSize(480, 272)


if __name__ == '__main__':
    import rtmidi
    
    print "Available MIDI devices:"
    midi = rtmidi.MidiOut()
    for i, port in enumerate(midi.get_ports()):
        print str(i) + ": " + port

    print "Connecting to device: " + midi.get_ports()[MIDI_DEVICE]
    midi.open_port(MIDI_DEVICE)

    def printText(text):
        print text
    
    import sys
    from PyQt4.QtGui import QApplication
    
    app = QApplication(sys.argv)
    win = VirtualKeyboard(midi)
    app.connect(win, SIGNAL("sigInputString"), printText)
    win.show()
    app.exec_()