Update user and developer documentation to match current features

src/sas/qtgui/MainWindow/media/preferences_help.rst

@@ -45,6 +45,9 @@ use the `Classic` theme as a fall back for any styles not defined in the stylesh
 is a stylesheet. For more information on writing Qt stylesheets, please see the
 `Qt style sheet reference <https://doc.qt.io/qt-6/stylesheet-reference.html>`_ *persistent*
 
+**Font Size** Select the font size that will be used throughout the SasView application. Font sizes defined in User themes
+will override this setting.
+
 **QT Screen Scale Factor**: A percent scaling factor that is applied all element sizes within the GUI. A restart of
 SasView is required to take effect. *persistent*
 

src/sas/qtgui/Utilities/Preferences/DisplayPreferencesWidget.py

@@ -18,11 +18,13 @@ def __init__(self):
                                'QT_AUTO_SCREEN_SCALE_FACTOR': "Enable Automatic Scaling"}
 
     def _addAllWidgets(self):
+        self.addHorizontalLine()
         self.theme = self.addComboBox(title="Theme", params=style.get_theme_names(), default=style.theme)
         self.theme.currentIndexChanged.connect(self._previewTheme)
         self.font_size = self.addComboBox(title="Font Size", params=['10.0', '12.0', '14.0'],
                                           default=str(style.font_size))
         self.font_size.currentIndexChanged.connect(self._previewFont)
+        self.addHorizontalLine()
         self.qtScaleFactor = self.addFloatInput(
             title="QT Screen Scale Factor",
             default_number=config.QT_SCALE_FACTOR)

src/sas/system/style.py

@@ -9,6 +9,14 @@ class StyleSheet:
     Class used to manage all available themes.
 
     Built-in themes are available in sas.system.themes. User themes should live in ~/.sasview/themes.
+
+    *CSS Order of operations:*
+    Each operation overrides any previous operation to allow user themes to take precedence over any built-in thematic
+    elements.
+        1. The default font size and fonts are set.
+        2. The base style sheet is set -> typically either classic.css for user themes or themes.STYLE_BASE for built-in
+        3. Color palettes are applied (Dark or Light), if applicable.
+        4. User theme elements are applied.
     """
 
     def __init__(self):
@@ -54,7 +62,7 @@ def get_theme_names(self) -> List[str]:
         return list(self._available_themes.keys())
 
     def _create_full_theme(self):
-        """Private method that combines settings so users can separately set fonts and color palettes."""
+        """Private method that combines settings to allow fonts and color palettes to be set separately."""
         css = load_theme(self.theme)
         font_str = format_font_size(self.font_size)
         self._css = f"{font_str}{css}"

src/sas/system/themes/__init__.py

@@ -14,6 +14,7 @@
     'Dark': Path(os.path.join(os.path.dirname(__file__), 'dark.css')),
     'Classic': Path(os.path.join(os.path.dirname(__file__), 'classic.css')),
 }
+# A list of style sheets that use the base style given in the STYLE_BASE
 USES_STYLE_BASE = ['Light', 'Dark']
 
 # A template string for setting the font size
@@ -63,6 +64,8 @@ def format_font_size(font_size: float) -> str:
     return FONT.format(font_size)
 
 
+# STYLE_BASE defines the base sizes and behaviors of all widgets and interactive elements for the Light and Dark themes.
+# The styles are here, so they are not considered as a separate style sheet when looking at built-in themes.
 STYLE_BASE = """
 /* QWidget Properties */
 QWidget:focus {outline: none;}