Refactor `DisplayDriver` to be a true parent class; add Factory

diff --git a/src/seedsigner/gui/renderer.py b/src/seedsigner/gui/renderer.py
index d0e2381..e572964 100644
--- a/src/seedsigner/gui/renderer.py
+++ b/src/seedsigner/gui/renderer.py
@@ -1,9 +1,7 @@
 from PIL import Image, ImageDraw
 from threading import Lock
 
-# from seedsigner.hardware.st7789_mpy import ST7789
-from seedsigner.hardware.displays.display_driver import ALL_DISPLAY_TYPES, DISPLAY_TYPE__ILI9341, DISPLAY_TYPE__ILI9486, DISPLAY_TYPE__ST7789, DisplayDriver
-from seedsigner.hardware.displays.ili9341 import ILI9341, ILI9341_TFTWIDTH, ILI9341_TFTHEIGHT
+from seedsigner.hardware.displays.display_driver import ALL_DISPLAY_TYPES, DISPLAY_TYPE__ILI9341, DISPLAY_TYPE__ILI9486, DISPLAY_TYPE__ST7789, DisplayDriverFactory
 from seedsigner.models.settings import Settings
 from seedsigner.models.settings_definition import SettingsConstants
 from seedsigner.models.singleton import ConfigurableSingleton
@@ -45,7 +43,12 @@ class Renderer(ConfigurableSingleton):
             raise Exception(f"Invalid display type: {self.display_type}")
 
         width, height = display_config.split("_")[1].split("x")
-        self.disp = DisplayDriver(self.display_type, width=int(width), height=int(height))
+
+        if self.disp:
+            # Existing instances might need to close resources like pwm
+            self.disp.cleanup()
+
+        self.disp = DisplayDriverFactory.instantiate_display_driver(self.display_type, width=int(width), height=int(height))
 
         if Settings.get_instance().get_value(SettingsConstants.SETTING__DISPLAY_COLOR_INVERTED, default_if_none=True) == SettingsConstants.OPTION__ENABLED:
             self.disp.invert()
diff --git a/src/seedsigner/hardware/displays/ST7789.py b/src/seedsigner/hardware/displays/ST7789.py
index 67d9175..b399aa6 100644
--- a/src/seedsigner/hardware/displays/ST7789.py
+++ b/src/seedsigner/hardware/displays/ST7789.py
@@ -2,16 +2,23 @@ import spidev
 import RPi.GPIO as GPIO
 import time
 import array
+from dataclasses import dataclass
 
+from seedsigner.hardware.displays.display_driver import DisplayDriver
 
 
-class ST7789(object):
-    """class for ST7789  240*240 1.3inch OLED displays."""
 
-    def __init__(self):
-        self.width = 240
-        self.height = 240
+@dataclass
+class ST7789(DisplayDriver):
+    """
+    The original SeedSigner display driver.
 
+    Note that self._width and self._height are provided by the parent DisplayDriver class
+    and are set during instantiation via the DisplayDriverFactory.
+
+    class for ST7789  240*240 1.3inch OLED displays.
+    """
+    def __post_init__(self):
         #Initialize DC RST pin
         self._dc = 22
         self._rst = 13
diff --git a/src/seedsigner/hardware/displays/display_driver.py b/src/seedsigner/hardware/displays/display_driver.py
index a41bb32..9903476 100644
--- a/src/seedsigner/hardware/displays/display_driver.py
+++ b/src/seedsigner/hardware/displays/display_driver.py
@@ -1,41 +1,19 @@
+from dataclasses import dataclass
+
+
 DISPLAY_TYPE__ST7789 = "st7789"
 DISPLAY_TYPE__ILI9341 = "ili9341"
 DISPLAY_TYPE__ILI9486 = "ili9486"
 
 ALL_DISPLAY_TYPES = [DISPLAY_TYPE__ST7789, DISPLAY_TYPE__ILI9341, DISPLAY_TYPE__ILI9486]
 
+    
 
+@dataclass
 class DisplayDriver:
-    def __init__(self, display_type: str = DISPLAY_TYPE__ST7789, width: int = None, height: int = None):
-        if display_type not in ALL_DISPLAY_TYPES:
-            raise ValueError(f"Invalid display type: {display_type}")
-        self.display_type = display_type
-
-        if self.display_type == DISPLAY_TYPE__ST7789:
-            if width not in [240, 320] or height != 240:
-                raise ValueError("ST7789 display only supports 240x240 or 320x240 resolutions")
+    _width: int
+    _height: int
 
-            if width == 240:
-                # TODO: For now the original ST7789 driver has to be used for 240x240.
-                # The mpy version below renders incorrectly (almost like each row of pixels
-                # is one pixel short, so the entire screen exhibits a diagonal skew).
-                from seedsigner.hardware.displays.ST7789 import ST7789
-                self.display = ST7789()
-
-            elif width == 320:
-                from seedsigner.hardware.displays.st7789_mpy import ST7789
-                # Have to swap width and height; screen is natively 240x320
-                self.display = ST7789(width=height, height=width)
-        
-        elif self.display_type == DISPLAY_TYPE__ILI9341:
-            from seedsigner.hardware.displays.ili9341 import ILI9341
-            self.display = ILI9341()
-            self.display.begin()
-        
-        elif self.display_type == DISPLAY_TYPE__ILI9486:
-            # TODO: improve performance of ili9486 driver
-            raise Exception("ILI9486 display not implemented yet")
-    
 
     def __str__(self):
         return f"DisplayDriver(display_type={self.display_type}, width={self.width}, height={self.height})"
@@ -43,18 +21,63 @@ class DisplayDriver:
 
     @property
     def width(self):
-        return self.display.width
+        return self._width
 
 
     @property
     def height(self):
-        return self.display.height
+        return self._height
 
 
     def invert(self, enabled: bool = True):
         """Invert how the display interprets colors"""
-        self.display.invert(enabled)
+        raise Exception("Must be implemented in child class")
 
 
     def show_image(self, image, x_start: int = 0, y_start: int = 0):
-        self.display.show_image(image, x_start, y_start)
\ No newline at end of file
+        raise Exception("Must be implemented in child class")
+    
+
+    def cleanup(self):
+        """Cleanup resources related to the display driver."""
+        pass
+
+
+
+class DisplayDriverFactory:
+    """
+    Manages all logic related to instantiating display drivers based on type and resolution.
+
+    Imports for specific display drivers are done within this class to avoid circular imports.
+    """
+
+    @classmethod
+    def instantiate_display_driver(cls, display_type: str = DISPLAY_TYPE__ST7789, width: int = None, height: int = None) -> DisplayDriver:
+        if display_type not in ALL_DISPLAY_TYPES:
+            raise ValueError(f"Invalid display type: {display_type}")
+
+        if display_type == DISPLAY_TYPE__ST7789:
+            if width not in [240, 320] or height != 240:
+                raise ValueError("ST7789 display only supports 240x240 or 320x240 resolutions")
+
+            if width == 240:
+                # TODO: For now the original ST7789 driver has to be used for 240x240.
+                # The mpy version below renders incorrectly (almost like each row of pixels
+                # is one pixel short, so the entire screen exhibits a diagonal skew).
+                from seedsigner.hardware.displays.ST7789 import ST7789 as original_ST7789
+                return original_ST7789(_width=width, _height=height)
+
+            elif width == 320:
+                from seedsigner.hardware.displays.st7789_mpy import ST7789 as mpy_ST7789
+                # Have to swap width and height; screen is natively 240x320
+                return mpy_ST7789(_width=height, _height=width)
+
+        elif display_type == DISPLAY_TYPE__ILI9341:
+            from seedsigner.hardware.displays.ili9341 import ILI9341
+            display = ILI9341(_width=width, _height=height)
+            display.begin()
+            return display
+        
+        elif display_type == DISPLAY_TYPE__ILI9486:
+            # TODO: improve performance of ili9486 driver
+            raise Exception("ILI9486 display not implemented yet")
diff --git a/src/seedsigner/hardware/displays/st7789_mpy.py b/src/seedsigner/hardware/displays/st7789_mpy.py
index 5a7bd5f..2aad703 100644
--- a/src/seedsigner/hardware/displays/st7789_mpy.py
+++ b/src/seedsigner/hardware/displays/st7789_mpy.py
@@ -54,8 +54,11 @@ import array
 import spidev
 import RPi.GPIO as GPIO
 
+from dataclasses import dataclass
 from math import sin, cos
 
+from seedsigner.hardware.displays.display_driver import DisplayDriver
+
 #
 # This allows sphinx to build the docs
 #
@@ -228,7 +231,9 @@ def color565(red, green=0, blue=0):
     return (red & 0xF8) << 8 | (green & 0xFC) << 3 | blue >> 3
 
 
-class ST7789:
+
+@dataclass
+class ST7789(DisplayDriver):
     """
     ST7789 driver class
 
@@ -262,20 +267,15 @@ class ST7789:
 
     """
 
-    def __init__(
-        self,
-        # spi,
-        width,
-        height,
-        reset=13,
-        dc=22,
-        cs=None,
-        backlight=18,
-        rotation=1,
-        color_order=BGR,
-        custom_init=None,
-        custom_rotations=None,
-    ):
+    def __post_init__(self):
+        reset=13
+        dc=22
+        cs=None
+        backlight=18
+        rotation=1
+        color_order=BGR
+        custom_init=None
+        custom_rotations=None
 
         GPIO.setmode(GPIO.BOARD)
         GPIO.setwarnings(False)
@@ -290,20 +290,20 @@ class ST7789:
         """
         Initialize display.
         """
-        self.rotations = custom_rotations or self._find_rotations(width, height)
+        self.rotations = custom_rotations or self._find_rotations(self.width, self.height)
         if not self.rotations:
             supported_displays = ", ".join(
                 [f"{display[0]}x{display[1]}" for display in _SUPPORTED_DISPLAYS]
             )
             raise ValueError(
-                f"Unsupported {width}x{height} display. Supported displays: {supported_displays}"
+                f"Unsupported {self.width}x{self.height} display. Supported displays: {supported_displays}"
             )
 
         if dc is None:
             raise ValueError("dc pin is required.")
 
-        self.physical_width = self.width = width
-        self.physical_height = self.height = height
+        self.physical_width = self.width
+        self.physical_height = self.height
         self.xstart = 0
         self.ystart = 0
         self.spi = spi
@@ -445,8 +445,8 @@ class ST7789:
         self._rotation = rotation
         (
             madctl,
-            self.width,
-            self.height,
+            self._width,   # have to use the settable internal vars
+            self._height,  # have to use the settable internal vars
             self.xstart,
             self.ystart,
             self.needs_swap,