chordsheet/gui.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Created on Wed May 29 00:02:24 2019

@author: ivan
"""

import sys, fitz, io, subprocess, os
from copy import copy

from PyQt5.QtWidgets import QApplication, QAction, QLabel, QDialogButtonBox, QDialog, QFileDialog, QMessageBox, QPushButton, QLineEdit, QCheckBox, QSpinBox, QDoubleSpinBox, QTableWidgetItem, QTabWidget, QComboBox, QWidget, QScrollArea, QMainWindow, QShortcut
from PyQt5.QtCore import QFile, QObject, Qt, pyqtSlot, QSettings
from PyQt5.QtGui import QPixmap, QImage, QKeySequence
from PyQt5 import uic
from chordsheet.tableView import ChordTableView, BlockTableView , MItemModel, MProxyStyle
 
from reportlab.lib.units import mm, cm, inch, pica
from reportlab.lib.pagesizes import A4, A5, LETTER, LEGAL
from reportlab.pdfbase import pdfmetrics
from reportlab.pdfbase.ttfonts import TTFont

from chordsheet.document import Document, Style, Chord, Block
from chordsheet.render import savePDF
from chordsheet.parsers import parseFingering, parseName

import _version

# set the directory where our files are depending on whether we're running a pyinstaller binary or not
if getattr(sys, 'frozen', False):
    scriptDir = sys._MEIPASS
else:
    scriptDir = os.path.abspath(os.path.dirname(os.path.abspath(__file__)))

QApplication.setAttribute(Qt.AA_EnableHighDpiScaling, True) # enable automatic high DPI scaling on Windows
QApplication.setOrganizationName("Ivan Holmes")
QApplication.setOrganizationDomain("ivanholmes.co.uk")
QApplication.setApplicationName("Chordsheet")
settings = QSettings()

pdfmetrics.registerFont(TTFont('FreeSans', os.path.join(scriptDir, 'fonts', 'FreeSans.ttf')))
if sys.platform == "darwin":
    pdfmetrics.registerFont(TTFont('HelveticaNeue', 'HelveticaNeue.ttc', subfontIndex=0))

# dictionaries for combo boxes
pageSizeDict = {'A4':A4, 'A5':A5, 'Letter':LETTER, 'Legal':LEGAL}
unitDict = {'mm':mm, 'cm':cm, 'inch':inch, 'point':1, 'pica':pica}  # point is 1 because reportlab's native unit is points.

class DocumentWindow(QMainWindow):
    """
    Class for the main window of the application.
    """
    def __init__(self, doc, style, filename=None):
        """
        Initialisation function for the main window of the application.

        Arguments:
        doc -- the Document object for the window to use
        style -- the Style object for the window to use
        """
        super().__init__()
        
        self.doc = doc
        self.style = style
        
        self.lastDoc = copy(self.doc)
        self.currentFilePath = filename

        self.UIFileLoader(str(os.path.join(scriptDir, 'ui','mainwindow.ui')))
        self.UIInitStyle()
        self.updateChordDict()

        self.setCentralWidget(self.window.centralWidget)
        self.setMenuBar(self.window.menuBar)
        self.setWindowTitle("Chordsheet")

        if filename:
            try:
                self.openFile(filename)
            except:
                UnreadableMessageBox().exec()

    def closeEvent(self, event):
        """
        Reimplement the built in closeEvent to allow asking the user to save.
        """
        self.saveWarning()
        
    def UIFileLoader(self, ui_file):
        """
        Loads the .ui file for this window and connects the UI elements to their actions.
        """
        ui_file = QFile(ui_file)
        ui_file.open(QFile.ReadOnly)
 
        self.window = uic.loadUi(ui_file)
        ui_file.close()
        
        # link all the UI elements
        self.window.actionAbout.triggered.connect(self.menuFileAboutAction)

        self.window.actionNew.triggered.connect(self.menuFileNewAction)
        self.window.actionOpen.triggered.connect(self.menuFileOpenAction)
        self.window.actionSave.triggered.connect(self.menuFileSaveAction)
        self.window.actionSave_as.triggered.connect(self.menuFileSaveAsAction)
        self.window.actionSave_PDF.triggered.connect(self.menuFileSavePDFAction)
        self.window.actionPrint.triggered.connect(self.menuFilePrintAction)
        self.window.actionClose.triggered.connect(self.menuFileCloseAction)
        self.window.actionUndo.triggered.connect(self.menuEditUndoAction)
        self.window.actionRedo.triggered.connect(self.menuEditRedoAction)
        self.window.actionCut.triggered.connect(self.menuEditCutAction)
        self.window.actionCopy.triggered.connect(self.menuEditCopyAction)
        self.window.actionPaste.triggered.connect(self.menuEditPasteAction)

        self.window.actionNew.setShortcut(QKeySequence.New)
        self.window.actionOpen.setShortcut(QKeySequence.Open)
        self.window.actionSave.setShortcut(QKeySequence.Save)
        self.window.actionSave_as.setShortcut(QKeySequence.SaveAs)
        self.window.actionSave_PDF.setShortcut(QKeySequence("Ctrl+E"))
        self.window.actionPrint.setShortcut(QKeySequence.Print)
        self.window.actionClose.setShortcut(QKeySequence.Close)
        self.window.actionUndo.setShortcut(QKeySequence.Undo)
        self.window.actionRedo.setShortcut(QKeySequence.Redo)
        self.window.actionCut.setShortcut(QKeySequence.Cut)
        self.window.actionCopy.setShortcut(QKeySequence.Copy)
        self.window.actionPaste.setShortcut(QKeySequence.Paste)

        self.window.pageSizeComboBox.currentIndexChanged.connect(self.pageSizeAction)
        self.window.documentUnitsComboBox.currentIndexChanged.connect(self.unitAction)

        self.window.includedFontCheckBox.stateChanged.connect(self.includedFontAction)
        
        self.window.generateButton.clicked.connect(self.generateAction)

        self.window.guitarVoicingButton.clicked.connect(self.guitarVoicingAction)
        self.window.addChordButton.clicked.connect(self.addChordAction)
        self.window.removeChordButton.clicked.connect(self.removeChordAction)
        self.window.updateChordButton.clicked.connect(self.updateChordAction)
        
        self.window.addBlockButton.clicked.connect(self.addBlockAction)
        self.window.removeBlockButton.clicked.connect(self.removeBlockAction)
        self.window.updateBlockButton.clicked.connect(self.updateBlockAction)

        self.window.chordTableView.clicked.connect(self.chordClickedAction)
        self.window.blockTableView.clicked.connect(self.blockClickedAction)
        
    def UIInitDocument(self):
        """
        Fills the window's fields with the values from its document.
        """
        self.updateTitleBar()

        # set all fields to appropriate values from document
        self.window.titleLineEdit.setText(self.doc.title)
        self.window.composerLineEdit.setText(self.doc.composer)
        self.window.arrangerLineEdit.setText(self.doc.arranger)
        self.window.timeSignatureSpinBox.setValue(self.doc.timeSignature)
        
        self.window.chordTableView.populate(self.doc.chordList)
        self.window.blockTableView.populate(self.doc.blockList)
        self.updateChordDict()
        
    def UIInitStyle(self):
        """
        Fills the window's fields with the values from its style.
        """
        self.window.pageSizeComboBox.addItems(list(pageSizeDict.keys()))
        self.window.pageSizeComboBox.setCurrentText(list(pageSizeDict.keys())[0])
        
        self.window.documentUnitsComboBox.addItems(list(unitDict.keys()))
        self.window.documentUnitsComboBox.setCurrentText(list(unitDict.keys())[0])
        
        self.window.lineSpacingDoubleSpinBox.setValue(self.style.lineSpacing)
        
        self.window.leftMarginLineEdit.setText(str(self.style.leftMargin))
        self.window.topMarginLineEdit.setText(str(self.style.topMargin))
        
        self.window.fontComboBox.setDisabled(True)
        self.window.includedFontCheckBox.setChecked(True)
        
    def pageSizeAction(self, index):
        self.pageSizeSelected = self.window.pageSizeComboBox.itemText(index)
        
    def unitAction(self, index):
        self.unitSelected = self.window.documentUnitsComboBox.itemText(index)
        
    def includedFontAction(self):
        if self.window.includedFontCheckBox.isChecked():
            self.style.useIncludedFont = True
        else:
            self.style.useIncludedFont = False
            
    def chordClickedAction(self, index):
        # set the controls to the values from the selected chord
        self.window.chordNameLineEdit.setText(self.window.chordTableView.model.item(index.row(), 0).text())
        self.window.guitarVoicingLineEdit.setText(self.window.chordTableView.model.item(index.row(), 1).text())

    def blockClickedAction(self, index):
        # set the controls to the values from the selected block
        bChord = self.window.blockTableView.model.item(index.row(), 0).text()
        self.window.blockChordComboBox.setCurrentText(bChord if bChord else "None")
        self.window.blockLengthLineEdit.setText(self.window.blockTableView.model.item(index.row(), 1).text())
        self.window.blockNotesLineEdit.setText(self.window.blockTableView.model.item(index.row(), 2).text())

    def getPath(self, value): 
        """
        Wrapper for Qt settings to return home directory if no setting exists.
        """
        return str((settings.value(value) if settings.value(value) else os.path.expanduser("~")))

    def setPath(self, value, fullpath):
        """
        Wrapper for Qt settings to set path to open/save from next time from current file location.
        """
        return settings.setValue(value, os.path.dirname(fullpath))

    def menuFileNewAction(self):
        self.doc = Document() # new document object
        self.lastDoc = copy(self.doc) # copy this object as reference to check against on quitting
        self.currentFilePath = None # reset file path (this document hasn't been saved yet)
        self.UIInitDocument()
        self.updatePreview()
    
    def menuFileOpenAction(self):
        filePath = QFileDialog.getOpenFileName(self.window.tabWidget, 'Open file', self.getPath("workingPath"), "Chordsheet ML files (*.xml *.cml)")[0]
        if filePath:
            self.openFile(filePath)

    def openFile(self, filePath):
        """
        Opens a file from a file path and sets up the window accordingly.
        """
        self.currentFilePath = filePath
        self.doc.loadXML(self.currentFilePath)
        self.lastDoc = copy(self.doc)
        self.setPath("workingPath", self.currentFilePath)
        self.UIInitDocument()
        self.updatePreview()
    
    def menuFileSaveAction(self):
        self.updateDocument()
        if not self.currentFilePath:
            filePath = QFileDialog.getSaveFileName(self.window.tabWidget, 'Save file', self.getPath("workingPath"), "Chordsheet ML files (*.xml *.cml)")[0]
        else:
            filePath = self.currentFilePath
        self.saveFile(filePath)
    
    def menuFileSaveAsAction(self):
        self.updateDocument()
        filePath = QFileDialog.getSaveFileName(self.window.tabWidget, 'Save file', self.getPath("workingPath"), "Chordsheet ML files (*.xml *.cml)")[0]
        if filePath:
            self.saveFile(filePath)

    def saveFile(self, filePath):
        """
        Saves a file to given file path and sets up environment.
        """
        self.currentFilePath = filePath
        self.doc.saveXML(self.currentFilePath)
        self.lastDoc = copy(self.doc)
        self.setPath("workingPath", self.currentFilePath)
        self.updateTitleBar() # as we may have a new filename
    
    def menuFileSavePDFAction(self):
        self.updateDocument()
        self.updatePreview()
        filePath = QFileDialog.getSaveFileName(self.window.tabWidget, 'Save file', self.getPath("lastExportPath"), "PDF files (*.pdf)")[0]
        if filePath:
            savePDF(d, s, filePath)
            self.setPath("lastExportPath", filePath)
    
    def menuFilePrintAction(self):
        if sys.platform == "darwin":
            pass
        #    subprocess.call()
        else:
            pass

    @pyqtSlot()
    def menuFileCloseAction(self):
        self.saveWarning()

    def menuFileAboutAction(self):
        aDialog = AboutDialog()

    def menuEditUndoAction(self):
        try:
            QApplication.focusWidget().undo() # see if the built in widget supports it
        except:
            pass # if not just fail silently

    def menuEditRedoAction(self):
        try:
            QApplication.focusWidget().redo()
        except:
            pass

    def menuEditCutAction(self):
        try:
            QApplication.focusWidget().cut()
        except:
            pass

    def menuEditCopyAction(self):
        try:
            QApplication.focusWidget().copy()
        except:
            pass

    def menuEditPasteAction(self):
        try:
            QApplication.focusWidget().paste()
        except:
            pass

    def saveWarning(self):
        """
        Function to check if the document has unsaved data in it and offer to save it.
        """
        self.updateDocument() # update the document to catch all changes

        if (self.lastDoc == self.doc):
            self.close()
        else:
            wantToSave = UnsavedMessageBox().exec()
                
            if wantToSave == QMessageBox.Save:
                if not (self.currentFilePath):
                    filePath = QFileDialog.getSaveFileName(self.window.tabWidget, 'Save file', str(os.path.expanduser("~")), "Chordsheet ML files (*.xml *.cml)")
                    self.currentFilePath = filePath[0]
                self.doc.saveXML(self.currentFilePath)
                self.close()
                
            elif wantToSave == QMessageBox.Discard:
                self.close()
            # if cancel or anything else do nothing at all
    
    def guitarVoicingAction(self):
        gdialog = GuitarDialog()
        
        voicing = gdialog.getVoicing()
        if voicing:
            self.window.guitarVoicingLineEdit.setText(voicing)

    def clearChordLineEdits(self):
        self.window.chordNameLineEdit.clear()
        self.window.guitarVoicingLineEdit.clear()
        self.window.chordNameLineEdit.repaint() # necessary on Mojave with PyInstaller (or previous contents will be shown)
        self.window.guitarVoicingLineEdit.repaint()

    def updateChordDict(self):
        """
        Updates the dictionary used to generate the Chord menu (on the block tab)
        """
        self.chordDict = {'None':None}
        self.chordDict.update({c.name:c for c in self.doc.chordList})
        self.window.blockChordComboBox.clear()
        self.window.blockChordComboBox.addItems(list(self.chordDict.keys()))

    def removeChordAction(self):
        if self.window.chordTableView.selectionModel().hasSelection(): # check for selection
            self.updateChords()
        
            row = self.window.chordTableView.selectionModel().currentIndex().row()
            self.doc.chordList.pop(row)

            self.window.chordTableView.populate(self.doc.chordList)
            self.clearChordLineEdits()
            self.updateChordDict()
    
    def addChordAction(self):
        success = False # initialise
        self.updateChords()

        cName = parseName(self.window.chordNameLineEdit.text())
        if cName:
            self.doc.chordList.append(Chord(cName))
            if self.window.guitarVoicingLineEdit.text():
                try:
                    self.doc.chordList[-1].voicings['guitar'] = parseFingering(self.window.guitarVoicingLineEdit.text(), 'guitar')
                    success = True # chord successfully parsed
                except:
                    VoicingWarningMessageBox().exec() # Voicing is malformed,  warn user
            else:
                success = True # chord successfully parsed
        else:
            NameWarningMessageBox().exec() # Chord has no name, warn user

        if success == True: # if chord was parsed properly
            self.window.chordTableView.populate(self.doc.chordList)
            self.clearChordLineEdits()
            self.updateChordDict()

    def updateChordAction(self):
        success = False # see comments above
        if self.window.chordTableView.selectionModel().hasSelection(): # check for selection
            self.updateChords()
            row = self.window.chordTableView.selectionModel().currentIndex().row()
            cName = parseName(self.window.chordNameLineEdit.text())
            if cName:
                self.doc.chordList[row] = Chord(cName)
                if self.window.guitarVoicingLineEdit.text():
                    try:
                        self.doc.chordList[row].voicings['guitar'] = parseFingering(self.window.guitarVoicingLineEdit.text(), 'guitar')
                        success = True
                    except:
                        VoicingWarningMessageBox().exec()
                else:
                    success = True
            else:
                NameWarningMessageBox().exec()
            
            if success == True:
                self.window.chordTableView.populate(self.doc.chordList)
                self.clearChordLineEdits()
                self.updateChordDict()
    
    def clearBlockLineEdits(self):
        self.window.blockLengthLineEdit.clear()
        self.window.blockNotesLineEdit.clear()
        self.window.blockLengthLineEdit.repaint() # necessary on Mojave with PyInstaller (or previous contents will be shown)
        self.window.blockNotesLineEdit.repaint()

    def removeBlockAction(self):
        if self.window.blockTableView.selectionModel().hasSelection(): # check for selection
            self.updateBlocks()

            row = self.window.blockTableView.selectionModel().currentIndex().row()
            self.doc.blockList.pop(row)

            self.window.blockTableView.populate(self.doc.blockList)
    
    def addBlockAction(self):
        self.updateBlocks()

        try:
            bLength = int(self.window.blockLengthLineEdit.text()) # can the value entered for block length be cast as an integer
        except:
            bLength = False

        if bLength: # create the block
            self.doc.blockList.append(Block(bLength,
                                            chord = self.chordDict[self.window.blockChordComboBox.currentText()],
                                            notes = (self.window.blockNotesLineEdit.text() if not "" else None)))
            self.window.blockTableView.populate(self.doc.blockList)
            self.clearBlockLineEdits()
        else:
            LengthWarningMessageBox().exec() # show warning that length was not entered or in wrong format

    def updateBlockAction(self):
        if self.window.blockTableView.selectionModel().hasSelection(): # check for selection
            self.updateBlocks()

            try:
                bLength = int(self.window.blockLengthLineEdit.text())
            except:
                bLength = False

            row = self.window.blockTableView.selectionModel().currentIndex().row()
            if bLength:
                self.doc.blockList[row] = (Block(bLength,
                                                 chord = self.chordDict[self.window.blockChordComboBox.currentText()],
                                                 notes = (self.window.blockNotesLineEdit.text() if not "" else None)))
                self.window.blockTableView.populate(self.doc.blockList)
                self.clearBlockLineEdits()
            else:
                LengthWarningMessageBox().exec()
    
    def generateAction(self):
        self.updateDocument()
        self.updatePreview()

    def updatePreview(self):
        """
        Update the preview shown by rendering a new PDF and drawing it to the scroll area.
        """
        try:
            self.currentPreview = io.BytesIO()
            savePDF(self.doc, self.style, self.currentPreview)

            pdfView = fitz.Document(stream=self.currentPreview, filetype='pdf')
            pix = pdfView[0].getPixmap(matrix = fitz.Matrix(4, 4), alpha = False) # render at 4x resolution and scale

            fmt = QImage.Format_RGB888
            qtimg = QImage(pix.samples, pix.width, pix.height, pix.stride, fmt)

            self.window.imageLabel.setPixmap(QPixmap.fromImage(qtimg).scaled(self.window.scrollArea.width()-30, self.window.scrollArea.height()-30, Qt.KeepAspectRatio, transformMode=Qt.SmoothTransformation))
            # -30 because the scrollarea has a margin of 12 each side (extra for safety)
            self.window.imageLabel.repaint() # necessary on Mojave with PyInstaller (or previous contents will be shown)
        except:
            warning = QMessageBox.warning(self, "Preview failed", "Could not update the preview.", buttons=QMessageBox.Ok, defaultButton=QMessageBox.Ok)
    
    def updateTitleBar(self):
        """
        Update the application's title bar to reflect the current document.
        """
        if self.currentFilePath:
            self.setWindowTitle(_version.appName + " – " + os.path.basename(self.currentFilePath))
        else:
            self.setWindowTitle(_version.appName)

    def updateChords(self):
        """
        Update the chord list by reading the table.
        """
        chordTableList = []
        for i in range(self.window.chordTableView.model.rowCount()):
            chordTableList.append(Chord(parseName(self.window.chordTableView.model.item(i, 0).text()))),
            if self.window.chordTableView.model.item(i, 1).text():
                chordTableList[-1].voicings['guitar'] = parseFingering(self.window.chordTableView.model.item(i, 1).text(), 'guitar')
            
        self.doc.chordList = chordTableList
    
    def updateBlocks(self):
        """
        Update the block list by reading the table.
        """
        blockTableList = []
        for i in range(self.window.blockTableView.model.rowCount()):
            blockLength = int(self.window.blockTableView.model.item(i, 1).text())
            blockChord = self.chordDict[(self.window.blockTableView.model.item(i, 0).text() if self.window.blockTableView.model.item(i, 0).text() else "None")]
            blockNotes = self.window.blockTableView.model.item(i, 2).text() if self.window.blockTableView.model.item(i, 2).text() else None
            blockTableList.append(Block(blockLength, chord=blockChord, notes=blockNotes))
        
        self.doc.blockList = blockTableList

    def updateDocument(self):
        """
        Update the Document object by reading values from the UI.
        """
        self.doc.title = self.window.titleLineEdit.text() # Title can be empty string but not None
        self.doc.composer = (self.window.composerLineEdit.text() if self.window.composerLineEdit.text() else None)
        self.doc.arranger = (self.window.arrangerLineEdit.text() if self.window.arrangerLineEdit.text() else None)
        
        self.doc.timeSignature = int(self.window.timeSignatureSpinBox.value())
        self.style.pageSize = pageSizeDict[self.pageSizeSelected]
        self.style.unit = unitDict[self.unitSelected]
        self.style.leftMargin = int(self.window.leftMarginLineEdit.text())
        self.style.topMargin = int(self.window.topMarginLineEdit.text())
        self.style.lineSpacing = float(self.window.lineSpacingDoubleSpinBox.value())

        self.updateChords()
        self.updateBlocks()
        
        self.style.font = ('FreeSans' if self.style.useIncludedFont else 'HelveticaNeue')
        # something for the font box here
        
class GuitarDialog(QDialog):
    """
    Dialogue to allow the user to enter a guitar chord voicing. Not particularly advanced at present!
    May be extended in future.
    """
    def __init__(self):
        super().__init__()
        self.UIFileLoader(str(os.path.join(scriptDir, 'ui','guitardialog.ui')))
        
    def UIFileLoader(self, ui_file):
        ui_file = QFile(ui_file)
        ui_file.open(QFile.ReadOnly)
 
        self.dialog = uic.loadUi(ui_file)
        ui_file.close()

    def getVoicing(self):
        """
        Show the dialogue and return the voicing that has been entered.
        """
        if self.dialog.exec_() == QDialog.Accepted:
            result = [self.dialog.ELineEdit.text(),
                      self.dialog.ALineEdit.text(),
                      self.dialog.DLineEdit.text(),
                      self.dialog.GLineEdit.text(),
                      self.dialog.BLineEdit.text(),
                      self.dialog.eLineEdit.text()]
            resultJoined = ",".join(result)
            return resultJoined
        else:
            return None

class AboutDialog(QDialog):
    """
    Dialogue showing information about the program.
    """
    def __init__(self):
        super().__init__()
        self.UIFileLoader(str(os.path.join(scriptDir, 'ui','aboutdialog.ui')))
        
        icon = QImage(str(os.path.join(scriptDir, 'ui','icon.png')))
        self.dialog.iconLabel.setPixmap(QPixmap.fromImage(icon).scaled(self.dialog.iconLabel.width(), self.dialog.iconLabel.height(), Qt.KeepAspectRatio, transformMode=Qt.SmoothTransformation))

        self.dialog.versionLabel.setText("Version " + _version.version)

        self.dialog.exec()
        
    def UIFileLoader(self, ui_file):
        ui_file = QFile(ui_file)
        ui_file.open(QFile.ReadOnly)
 
        self.dialog = uic.loadUi(ui_file)
        ui_file.close()

class UnsavedMessageBox(QMessageBox):
    """
    Message box to alert the user of unsaved changes and allow them to choose how to act.
    """
    def __init__(self):
        super().__init__()

        self.setIcon(QMessageBox.Question)
        self.setWindowTitle("Unsaved changes")
        self.setText("The document has been modified.")
        self.setInformativeText("Do you want to save your changes?")
        self.setStandardButtons(QMessageBox.Save | QMessageBox.Discard | QMessageBox.Cancel)
        self.setDefaultButton(QMessageBox.Save)

class UnreadableMessageBox(QMessageBox):
    """
    Message box to warn the user that the chosen file cannot be opened.
    """
    def __init__(self):
        super().__init__()

        self.setIcon(QMessageBox.Warning)
        self.setWindowTitle("File cannot be opened")
        self.setText("The file you have selected cannot be opened.")
        self.setInformativeText("Please make sure it is in the right format.")
        self.setStandardButtons(QMessageBox.Ok)
        self.setDefaultButton(QMessageBox.Ok)

class NameWarningMessageBox(QMessageBox):
    """
    Message box to warn the user that a chord must have a name
    """
    def __init__(self):
        super().__init__()

        self.setIcon(QMessageBox.Warning)
        self.setWindowTitle("Unnamed chord")
        self.setText("Chords must have a name.")
        self.setInformativeText("Please give your chord a name and try again.")
        self.setStandardButtons(QMessageBox.Ok)
        self.setDefaultButton(QMessageBox.Ok)

class VoicingWarningMessageBox(QMessageBox):
    """
    Message box to warn the user that the voicing entered could not be parsed
    """
    def __init__(self):
        super().__init__()

        self.setIcon(QMessageBox.Warning)
        self.setWindowTitle("Malformed voicing")
        self.setText("The voicing you entered was not understood and has not been applied.")
        self.setInformativeText("Please try re-entering it in the correct format.")
        self.setStandardButtons(QMessageBox.Ok)
        self.setDefaultButton(QMessageBox.Ok)

class LengthWarningMessageBox(QMessageBox):
    """
    Message box to warn the user that a block must have a length
    """
    def __init__(self):
        super().__init__()

        self.setIcon(QMessageBox.Warning)
        self.setWindowTitle("Block without valid length")
        self.setText("Blocks must have a whole number length.")
        self.setInformativeText("Please enter a valid length for your block and try again.")
        self.setStandardButtons(QMessageBox.Ok)
        self.setDefaultButton(QMessageBox.Ok)


if __name__ == '__main__':
    app = QApplication(sys.argv)
    
    d = Document()
    s = Style()
    
    w = DocumentWindow(d, s, filename=(sys.argv[1] if len(sys.argv) > 1 else None)) # pass first argument as filename 
    w.show()

    sys.exit(app.exec_())