How to use QFontDialog to preview non-system fonts

Question

I'd like to use a QFontDialog widget to preview external fonts before installing them. However, by default, QFontDialog apparently only lists installed system fonts.

• Is there a way to specify a custom font folder for QFontDialog?
• If not, is there any other widget that is better suited as a font previewer?

Answer 1

You can't specify custom font folders, but it is possible to add individual fonts using the QFontDatabase class. So all you need to do is iterate over the files in a given folder and add any font files it contains. The documentation notes these limitations:

Currently only TrueType fonts, TrueType font collections, and OpenType fonts are supported.

Note: Adding application fonts on Unix/X11 platforms without fontconfig is currently not supported.

Once all the valid font files have been added, they will show up immediately in the font-dialog. Here is a simple demo (only tested on Linux):

import sys, os, glob
from PyQt5 import QtCore, QtGui, QtWidgets

class Window(QtWidgets.QWidget):
    def __init__(self):
        super(Window, self).__init__()
        self.button1 = QtWidgets.QPushButton('Open Font Folder')
        self.button1.clicked.connect(self.handleButton1)
        self.button2 = QtWidgets.QPushButton('Show Font Dialog')
        self.button2.clicked.connect(self.handleButton2)
        self.fontList = QtWidgets.QListWidget()
        layout = QtWidgets.QVBoxLayout(self)
        layout.addWidget(self.fontList)
        layout.addWidget(self.button1)
        layout.addWidget(self.button2)

    def handleButton1(self):
        path = QtWidgets.QFileDialog.getExistingDirectory(self)
        if path:
            fonts = set()
            self.fontList.clear()
            db = QtGui.QFontDatabase()
            db.removeAllApplicationFonts()
            for filename in glob.glob(os.path.join(path, '*.ttf')):
                fontid = db.addApplicationFont(os.path.join(path, filename))
                if fontid >= 0:
                    fonts.update(db.applicationFontFamilies(fontid))
            self.fontList.addItems(sorted(fonts))
            self.fontList.setCurrentRow(0)

    def handleButton2(self):
        font = QtGui.QFont()
        item = self.fontList.currentItem()
        if item is not None:
            font.setFamily(item.text())
        QtWidgets.QFontDialog.getFont(font, self)

if __name__ == '__main__':

    app = QtWidgets.QApplication(sys.argv)
    window = Window()
    window.setGeometry(600, 100, 200, 200)
    window.show()
    sys.exit(app.exec_())