revealer plugin: move font initialisation to earlier

Co-authored-by: SomberNight <somber.night@protonmail.com>

electrum/plugins/revealer/qt.py

@@ -19,6 +19,7 @@ import traceback
 from decimal import Decimal
 from functools import partial
 import sys
+from typing import TYPE_CHECKING
 
 import qrcode
 from PyQt5.QtPrintSupport import QPrinter
@@ -39,6 +40,10 @@ from electrum.gui.qt.main_window import StatusBarButton
 from .revealer import RevealerPlugin
 
 
+if TYPE_CHECKING:
+    from electrum.gui.qt import ElectrumGui
+
+
 class Plugin(RevealerPlugin):
 
     MAX_PLAINTEXT_LEN = 189  # chars
@@ -63,6 +68,16 @@ class Plugin(RevealerPlugin):
         make_dir(self.base_dir)
 
         self.extension = False
+        self._init_qt_received = False
+
+    @hook
+    def init_qt(self, gui: 'ElectrumGui'):
+        if self._init_qt_received:  # only need/want the first signal
+            return
+        self._init_qt_received = True
+        # load custom fonts (note: here, and not in __init__, as it needs the QApplication to be created)
+        QFontDatabase.addApplicationFont(os.path.join(os.path.dirname(__file__), 'SourceSans3-Bold.otf'))
+        QFontDatabase.addApplicationFont(os.path.join(os.path.dirname(__file__), 'DejaVuSansMono-Bold.ttf'))
 
     @hook
     def create_status_bar(self, sb):
@@ -402,7 +417,6 @@ class Plugin(RevealerPlugin):
         bitmap.fill(Qt.white)
         painter = QPainter()
         painter.begin(bitmap)
-        QFontDatabase.addApplicationFont(os.path.join(os.path.dirname(__file__), 'SourceSans3-Bold.otf'))
         if len(txt) < 102 :
             fontsize = 15
             linespace = 15
@@ -548,13 +562,13 @@ class Plugin(RevealerPlugin):
         painter = QPainter()
         painter.begin(printer)
         painter.drawImage(553,533, image)
-        font = QFont('Source Sans Pro', 10, QFont.Bold)
+        font = QFont('Source Sans 3', 10, QFont.Bold)
         painter.setFont(font)
         painter.drawText(254,277, _("Calibration sheet"))
-        font = QFont('Source Sans Pro', 7, QFont.Bold)
+        font = QFont('Source Sans 3', 7, QFont.Bold)
         painter.setFont(font)
         painter.drawText(600,2077, _("Instructions:"))
-        font = QFont('Source Sans Pro', 7, QFont.Normal)
+        font = QFont("", 7, QFont.Normal)
         painter.setFont(font)
         painter.drawText(700, 2177, _("1. Place this paper on a flat and well illuminated surface."))
         painter.drawText(700, 2277, _("2. Align your Revealer borderlines to the dashed lines on the top and left."))
@@ -644,7 +658,6 @@ class Plugin(RevealerPlugin):
 
         #print code
         f_size = 37
-        QFontDatabase.addApplicationFont(os.path.join(os.path.dirname(__file__), 'DejaVuSansMono-Bold.ttf'))
         font = QFont("DejaVu Sans Mono", f_size-11, QFont.Bold)
         font.setPixelSize(35)
         painter.setFont(font)