API: add defaults handling to SharedPreferences and only save non-defaults

ThomasFarstrike · ThomasFarstrike · commit 27d1af993138 · 2025-12-02T12:08:47.000+01:00
diff --git a/CLAUDE.md b/CLAUDE.md
@@ -410,7 +410,7 @@ Current stable version: 0.3.3 (as of latest CHANGELOG entry)
 ```python
 from mpos.config import SharedPreferences
 
-# Load preferences
+# Basic usage
 prefs = SharedPreferences("com.example.myapp")
 value = prefs.get_string("key", "default_value")
 number = prefs.get_int("count", 0)
@@ -422,6 +422,28 @@ editor.put_string("key", "value")
 editor.put_int("count", 42)
 editor.put_dict("data", {"key": "value"})
 editor.commit()
+
+# Using constructor defaults (reduces config file size)
+# Values matching defaults are not saved to disk
+prefs = SharedPreferences("com.example.myapp", defaults={
+    "brightness": -1,
+    "volume": 50,
+    "theme": "dark"
+})
+
+# Returns constructor default (-1) if not stored
+brightness = prefs.get_int("brightness")  # Returns -1
+
+# Method defaults override constructor defaults
+brightness = prefs.get_int("brightness", 100)  # Returns 100
+
+# Stored values override all defaults
+prefs.edit().put_int("brightness", 75).commit()
+brightness = prefs.get_int("brightness")  # Returns 75
+
+# Setting to default value removes it from storage (auto-cleanup)
+prefs.edit().put_int("brightness", -1).commit()
+# brightness is no longer stored in config.json, saves space
 ```
 
 **Intent system**: Launch activities and pass data
diff --git a/internal_filesystem/apps/com.micropythonos.camera/assets/camera_app.py b/internal_filesystem/apps/com.micropythonos.camera/assets/camera_app.py
@@ -467,7 +467,7 @@ def apply_camera_settings(self, prefs, cam, use_webcam):
     
         try:
             # Basic image adjustments
-            brightness = prefs.get_int("brightness", 0)
+            brightness = prefs.get_int("brightness", CameraSettingsActivity.DEFAULTS.get("brightness"))
             cam.set_brightness(brightness)
     
             contrast = prefs.get_int("contrast", 0)
diff --git a/internal_filesystem/apps/com.micropythonos.camera/assets/camera_settings.py b/internal_filesystem/apps/com.micropythonos.camera/assets/camera_settings.py
@@ -9,7 +9,7 @@
 class CameraSettingsActivity(Activity):
     """Settings activity for comprehensive camera configuration."""
 
-    DEFAULT_WIDTH = 320 # 240 would be better but webcam doesn't support this (yet)
+    DEFAULT_WIDTH = 240 # 240 would be better but webcam doesn't support this (yet)
     DEFAULT_HEIGHT = 240
     DEFAULT_COLORMODE = True
     DEFAULT_SCANQR_WIDTH = 960
@@ -31,6 +31,10 @@ class CameraSettingsActivity(Activity):
     scale_default=False
     binning_default=False
 
+    DEFAULTS = {
+        "brightness": 1,
+    }
+
     # Resolution options for desktop/webcam
     WEBCAM_RESOLUTIONS = [
         ("160x120", "160x120"),
@@ -291,7 +295,7 @@ def create_basic_tab(self, tab, prefs):
         self.ui_controls["resolution"] = dropdown
 
         # Brightness
-        brightness = prefs.get_int("brightness", 0)
+        brightness = prefs.get_int("brightness", self.DEFAULTS.get("brightness"))
         slider, label, cont = self.create_slider(tab, "Brightness", -2, 2, brightness, "brightness")
         self.ui_controls["brightness"] = slider
 
diff --git a/internal_filesystem/lib/mpos/config.py b/internal_filesystem/lib/mpos/config.py
@@ -2,10 +2,11 @@
 import os
 
 class SharedPreferences:
-    def __init__(self, appname, filename="config.json"):
-        """Initialize with appname and filename for preferences."""
+    def __init__(self, appname, filename="config.json", defaults=None):
+        """Initialize with appname, filename, and optional defaults for preferences."""
         self.appname = appname
         self.filename = filename
+        self.defaults = defaults if defaults is not None else {}
         self.filepath = f"data/{self.appname}/{self.filename}"
         self.data = {}
         self.load()
@@ -36,31 +37,80 @@ def load(self):
     def get_string(self, key, default=None):
         """Retrieve a string value for the given key, with a default if not found."""
         to_return = self.data.get(key)
-        if to_return is None and default is not None:
-            to_return = default
+        if to_return is None:
+            # Method default takes precedence
+            if default is not None:
+                to_return = default
+            # Fall back to constructor default
+            elif key in self.defaults:
+                to_return = self.defaults[key]
         return to_return
 
     def get_int(self, key, default=0):
         """Retrieve an integer value for the given key, with a default if not found."""
-        try:
-            return int(self.data.get(key, default))
-        except (TypeError, ValueError):
+        if key in self.data:
+            try:
+                return int(self.data[key])
+            except (TypeError, ValueError):
+                return default
+        # Key not in stored data, check defaults
+        # Method default takes precedence if explicitly provided (not the hardcoded 0)
+        # Otherwise use constructor default if exists
+        if default != 0:
             return default
+        if key in self.defaults:
+            try:
+                return int(self.defaults[key])
+            except (TypeError, ValueError):
+                return 0
+        return 0
 
     def get_bool(self, key, default=False):
         """Retrieve a boolean value for the given key, with a default if not found."""
-        try:
-            return bool(self.data.get(key, default))
-        except (TypeError, ValueError):
+        if key in self.data:
+            try:
+                return bool(self.data[key])
+            except (TypeError, ValueError):
+                return default
+        # Key not in stored data, check defaults
+        # Method default takes precedence if explicitly provided (not the hardcoded False)
+        # Otherwise use constructor default if exists
+        if default != False:
             return default
+        if key in self.defaults:
+            try:
+                return bool(self.defaults[key])
+            except (TypeError, ValueError):
+                return False
+        return False
 
     def get_list(self, key, default=None):
         """Retrieve a list for the given key, with a default if not found."""
-        return self.data.get(key, default if default is not None else [])
+        if key in self.data:
+            return self.data[key]
+        # Key not in stored data, check defaults
+        # Method default takes precedence if provided
+        if default is not None:
+            return default
+        # Fall back to constructor default
+        if key in self.defaults:
+            return self.defaults[key]
+        # Return empty list as hardcoded fallback
+        return []
 
     def get_dict(self, key, default=None):
         """Retrieve a dictionary for the given key, with a default if not found."""
-        return self.data.get(key, default if default is not None else {})
+        if key in self.data:
+            return self.data[key]
+        # Key not in stored data, check defaults
+        # Method default takes precedence if provided
+        if default is not None:
+            return default
+        # Fall back to constructor default
+        if key in self.defaults:
+            return self.defaults[key]
+        # Return empty dict as hardcoded fallback
+        return {}
 
     def edit(self):
         """Return an Editor object to modify preferences."""
@@ -197,14 +247,31 @@ def remove_all(self):
         self.temp_data = {}
         return self
 
+    def _filter_defaults(self, data):
+        """Remove keys from data that match constructor defaults."""
+        if not self.preferences.defaults:
+            return data
+
+        filtered = {}
+        for key, value in data.items():
+            if key in self.preferences.defaults:
+                if value != self.preferences.defaults[key]:
+                    filtered[key] = value
+                # else: skip saving, matches default
+            else:
+                filtered[key] = value  # No default, always save
+        return filtered
+
     def apply(self):
         """Save changes to the file asynchronously (emulated)."""
-        self.preferences.data = self.temp_data.copy()
+        filtered_data = self._filter_defaults(self.temp_data)
+        self.preferences.data = filtered_data
         self.preferences.save_config()
 
     def commit(self):
         """Save changes to the file synchronously."""
-        self.preferences.data = self.temp_data.copy()
+        filtered_data = self._filter_defaults(self.temp_data)
+        self.preferences.data = filtered_data
         self.preferences.save_config()
         return True
 
diff --git a/tests/test_shared_preferences.py b/tests/test_shared_preferences.py
