MI uses OS default font settings

mantidimaging/gui/windows/main/presenter.py

@@ -41,13 +41,14 @@
     'density_scale': '-5',
 
     # font
-    'font_size': '10px',
+    'font_size': settings.value('default_font_size', defaultValue='12') + 'px',
 }
 
-if settings.contains("extra_style") and settings.value('extra_style'):
+if settings.contains("extra_style") and settings.value('extra_style') is not None:
     extra_style = settings.value('extra_style')
 else:
     settings.setValue('extra_style', extra_style_default)
+    extra_style = extra_style_default
 settings.setValue('os_theme', darkdetect.theme())
 
 
@@ -856,7 +857,7 @@ def do_update_UI(self) -> None:
         os_theme = settings.value('os_theme')
         use_dark_mode = settings.value('use_dark_mode')
         override_os_theme = settings.value('override_os_theme')
-        font = QFont("Arial", int(extra_style['font_size'].replace('px', '')))
+        font = QFont(settings.value('default_font_family'), int(extra_style['font_size'].replace('px', '')))
         for window in [
                 self.view, self.view.recon, self.view.live_viewer, self.view.spectrum_viewer, self.view.filters,
                 self.view.settings_window

mantidimaging/gui/windows/settings/presenter.py

@@ -26,7 +26,10 @@ def __init__(self, view: SettingsWindowView, main_window: MainWindowView):
         self.view = view
         self.main_window = main_window
         self.current_theme = settings.value('theme_selection')
-        self.current_menu_font_size = settings.value('extra_style')['font_size']
+        if settings.value('selected_font_size') is None:
+            self.current_menu_font_size = settings.value('default_font_size')
+        else:
+            self.current_menu_font_size = settings.value('selected_font_size')
 
     def set_theme(self):
         self.current_theme = self.view.current_theme
@@ -39,6 +42,7 @@ def set_theme(self):
 
     def set_extra_style(self):
         extra_style = settings.value('extra_style')
+        settings.setValue('selected_font_size', self.view.current_menu_font_size)
         extra_style.update({'font_size': self.view.current_menu_font_size + 'px'})
         settings.setValue('extra_style', extra_style)
         self.main_window.presenter.do_update_UI()

mantidimaging/main.py

@@ -10,7 +10,7 @@
 
 from PyQt5.QtWidgets import QApplication
 from PyQt5 import QtCore
-from PyQt5.QtGui import QGuiApplication
+from PyQt5.QtGui import QGuiApplication, QFont, QFontInfo
 
 import mantidimaging.core.parallel.manager as pm
 
@@ -69,6 +69,10 @@ def setup_application() -> QApplication:
     if theme_selection:
         q_application.setStyle(settings.value('theme_selection'))
 
+    default_font = QFont('-1')
+    default_font_info = QFontInfo(default_font)
+    settings.setValue('default_font_size', str(default_font.pointSize()))
+    settings.setValue('default_font_family', str(default_font_info.family()))
     q_application.setApplicationName("Mantid Imaging")
     q_application.setOrganizationName("mantidproject")
     q_application.setOrganizationDomain("mantidproject.org")