GUI: status bar rendering. Power: battery indicator. (#207)

* Menu: animation. Irukagotchi: idle image.
* Power: battery, usb activity widget
* Power: tune battery max voltage and clamp overshoot
* get initial charge state

Co-authored-by: Aleksandr Kutuzov <aku@plooks.com>
Co-authored-by: aanper <mail@s3f.ru>

applications/gui/widget.h

@@ -8,14 +8,51 @@ typedef struct Widget Widget;
 typedef void (*WidgetDrawCallback)(CanvasApi* api, void* context);
 typedef void (*WidgetInputCallback)(InputEvent* event, void* context);
 
+/*
+ * Widget allocator
+ * always returns widget or stops system if not enough memory.
+ */
 Widget* widget_alloc();
+
+/*
+ * Widget deallocator
+ * Ensure that widget was unregistered in GUI system before use.
+ */
 void widget_free(Widget* widget);
 
+/*
+ * Set widget width.
+ * Will be used to limit canvas drawing area and autolayout feature.
+ * @param width - wanted width, 0 - auto.
+ */
+void widget_set_width(Widget* widget, uint8_t width);
+uint8_t widget_get_width(Widget* widget);
+
+/*
+ * Set widget height.
+ * Will be used to limit canvas drawing area and autolayout feature.
+ * @param height - wanted height, 0 - auto.
+ */
+void widget_set_height(Widget* widget, uint8_t height);
+uint8_t widget_get_height(Widget* widget);
+
+/*
+ * Enable or disable widget rendering.
+ * @param enabled.
+ */
 void widget_enabled_set(Widget* widget, bool enabled);
 bool widget_is_enabled(Widget* widget);
 
+/*
+ * Widget event callbacks
+ * @param callback - appropriate callback function
+ * @param context - context to pass to callback
+ */
 void widget_draw_callback_set(Widget* widget, WidgetDrawCallback callback, void* context);
 void widget_input_callback_set(Widget* widget, WidgetInputCallback callback, void* context);
 
-// emit update signal
+/*
+ * Emit update signal to GUI system.
+ * Rendering will happen later after GUI system process signal.
+ */
 void widget_update(Widget* widget);