demo工程暂存 优化菜单界面UI和功能

Demo/lvgl/docs/widgets/core/arc.md

@@ -0,0 +1,94 @@
+```eval_rst
+.. include:: /header.rst 
+:github_url: |github_link_base|/widgets/arc.md
+```
+# Arc (lv_arc)
+
+## Overview
+
+The Arc are consists of a background and a foreground arc. The foregrond (indicator) arc can be adjusted by finger.
+
+## Parts and Styles
+- `LV_PART_MAIN`  It draws a background using the typical background style properties and an arc using the arc style properties. The arc's size and position will respect the *padding* style properties.
+- `LV_PART_INDICATOR` It draws an other arc using the *arc* style properties. It's padding values are interpreted relative to the background arc. 
+- `LV_PART_KNOB`It draws a handle on the end of the indicator. It uses all background properties and padding values. With zero padding the knob size is the same as the indicator's width. 
+Larger padding makes it larger, smaller padding makes it smaller. 
+
+## Usage
+
+### Value and range
+
+A new value can be set by `lv_arc_set_value(arc, new_value)`. 
+The value is interpreted in a range (minimum and maximum values) which can be modified with `lv_arc_set_range(arc, min, max)`.
+The default range is 1..100.
+
+The indicator arc is drawn on the main part's arc. That is if the vale is set to maximum the indicator arc will cover the entire "background" arc.
+To set the start and end angl of the background arc use  the `lv_arc_set_bg_angles(arc, start_angle, end_angle)` function or `lv_arc_set_bg_start/end_angle(arc, start_angle)`. 
+
+Zero degree is at the middle right (3 o'clock) of the object and the degrees are increasing in clockwise direction.
+The angles should be in [0;360] range.
+
+### Rotation
+
+An offset to the 0 degree position can added with `lv_arc_set_rotation(arc, deg)`.
+
+### Mode
+
+The arc can be one of the following modes:
+- `LV_ARC_MODE_NORMAL` The indicator arc is drawn from the minimimum value to the current.
+- `LV_ARC_MODE_REVERSE` The indicator arc is drawn counter clockwise from the maximum value to the current.
+- `LV_ARC_MODE_SYMMETRICAL` The indicator arc is drawn from the middle point to the current value.
+
+The mode can be set by `lv_arc_set_mode(arc, LV_ARC_MODE_...)` and used only if the the angle is set by `lv_arc_set_value()` or the arc is adjusted by finger.
+
+### Change rate
+If the the arc is pressed the current value will set with a limited speed according to the set *change rate*. 
+The change rate is defined in degree/second unit and can be set with `lv_arc_set_change_rage(arc, rate)`
+
+
+### Setting the indicator manually
+It also possible to set the angles o the indicator arc directly with `lv_arc_set_angles(arc, start_angle, end_angle)` function or `lv_arc_set_start/end_angle(arc, start_angle)` sets the angles of the indicator arc. 
+In this case the set "value" and "mode" is ignored.
+
+In other words, settings angles and values are independent. You should use either value and angle settings. Mixing the two might result unintended behavior. 
+
+To make the arc non-adjutabe remove the style of the knob and make the object non-clickable:
+```c
+lv_obj_remove_style(arc, NULL, LV_PART_KNOB);
+lv_obj_clear_flag(arc, LV_OBJ_FLAG_CLICKABLE);
+```
+
+## Events
+- `LV_EVENT_VALUE_CHANGED` sent when the arc is pressed/dragged to set a new value.
+- `LV_EVENT_DRAW_PART_BEGIN` and `LV_EVENT_DRAW_PART_END` are sent for the background rectangle, the background arc, the foreground arc and the knob to allow hooking the drawing. 
+For more detail on the backround rectangle part see the [Base object](/widgets/obj#events)'s documentation. The fields of `lv_obj_draw_dsc_t` is set like the followings:
+  - For both arcs: `clip_area`, `p1` (center of the arc), `radius`, `arc_dsc`, `part`. 
+  - For the knob: `clip_area`, `draw_area`, `rect_dsc`, `part`.
+
+
+Learn more about [Events](/overview/event).
+
+## Keys
+- `LV_KEY_RIGHT/UP` Increases the value by one.
+- `LV_KEY_LEFT/DOWN` Decreases the value by one.
+
+
+Learn more about [Keys](/overview/indev).
+
+
+## Example
+
+```eval_rst
+
+.. include:: ../../../examples/widgets/arc/index.rst
+
+```
+
+## API
+
+```eval_rst
+
+.. doxygenfile:: lv_arc.h
+  :project: lvgl
+
+```