chordsheet/csgui/pdfViewer.py

from PyQt5.QtWidgets import QScrollArea, QLabel, QVBoxLayout, QWidget, QSizePolicy
from PyQt5.QtCore import Qt, QPoint, QSize
from PyQt5.QtGui import QPixmap, QImage, QResizeEvent, QPainter

import fitz

class PDFLabel(QLabel):
    def __init__(self, parent):
        super().__init__(parent)
        self.parent = parent
        self.setSizePolicy(QSizePolicy.MinimumExpanding, QSizePolicy.Preferred)
    
    def paintEvent(self, event):
        self.adjustSize()
        if self.pixmap() is not None:
            painter = QPainter(self)
            # painter.setRenderHint(QPainter.Antialiasing)
            
            parentLayoutMargins = self.parent.scrollAreaLayout.getContentsMargins()
            parentMargins = self.parent.getContentsMargins()
            
            if self.parent.verticalScrollBar().isVisible():
                scrollBarWidth = self.parent.verticalScrollBar().sizeHint().width()
            else:
                scrollBarWidth = 0
            
            totalMargin = parentLayoutMargins[0] + parentLayoutMargins[2] + \
                            parentMargins[0]*2 + scrollBarWidth
                
            idealWidth = self.parent.width() - totalMargin
            # print(idealWidth)
            pixSize = self.pixmap().size()
            # print(pixSize)
            # print((self.parent.scrollAreaContents.size()))
            
            pixSize.scale(idealWidth, 1000000, Qt.KeepAspectRatio)
            
            scaledPix = self.pixmap().scaled(pixSize, Qt.KeepAspectRatio, Qt.SmoothTransformation)
            painter.drawPixmap(QPoint(), scaledPix)
            self.setMaximumSize(pixSize)

class PDFViewer(QScrollArea):
    def __init__(self, parent):
        super().__init__(parent)
        self.scrollAreaContents = QWidget()
        self.scrollAreaLayout = QVBoxLayout()

        self.setWidget(self.scrollAreaContents)
        self.setWidgetResizable(True)
        self.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        # set a fixed background colour
        # on some OSes (Mac, Haiku) it is grey automatically but not on KDE
        self.setStyleSheet('PDFViewer {background-color: #D8D8D8}')

        self.scrollAreaContents.setLayout(self.scrollAreaLayout)
        self.pixmapList = []      
        self.lastVScrollPosition = None
    
    def update_pdf(self, pdf):
        self.render(pdf)
        self.clear()
        self.show()

    def render(self, pdf):
        """
        Update the preview shown by rendering a new PDF and drawing it to the scroll area.
        """

        self.pixmapList = []
        pdfView = fitz.Document(stream=pdf, filetype='pdf')
        for page in pdfView:
            # needs to be high enough for big monitors. 300 should do it...
            self.pixmapList.append(page.get_pixmap(dpi=300, alpha=False))
                    
    def clear(self):
        self.lastVScrollPosition = self.verticalScrollBar().value()
        while self.scrollAreaLayout.count():
            item = self.scrollAreaLayout.takeAt(0)
            w = item.widget()
            if w:
                w.deleteLater()
    
    def show(self):
        for p in self.pixmapList:
            label = PDFLabel(parent=self)
            label.setAlignment(Qt.AlignHCenter)
            qtimg = QImage(p.samples, p.width, p.height, p.stride, QImage.Format_RGB888)
            label.setPixmap(QPixmap.fromImage(qtimg))
            self.scrollAreaLayout.addWidget(label)
        
        self.scrollAreaLayout.addStretch(1)
        
        # Somewhat of a hack. Should really replace pixmaps in place
        # rather than removing labels elsewhere in code.
        if self.lastVScrollPosition:
            self.verticalScrollBar().setValue(self.lastVScrollPosition)