lvgl：对象 obj

1 对象 object

  1.1 对象 lv_obj_t 

    对象object：构建用户界面的基本单位，也称之为控件widgets；对于button,label,image,list等组件都可称之为对象；

//lv_obj.h  对象结构体；
typedef struct _lv_obj_t {
    const lv_obj_class_t *class_p;
    struct _lv_obj_t *parent;
    _lv_obj_spec_attr_t *spec_attr;
    _lv_obj_style_t *styles;
#if LV_USE_USER_DATA
    void *user_data;
#endif
    lv_area_t coords;
    lv_obj_flag_t flags;
    lv_state_t state;
    uint16_t layout_inv : 1;
    uint16_t scr_layout_inv : 1;
    uint16_t skip_trans : 1;
    uint16_t style_cnt  : 6;
    uint16_t h_layout   : 1;
    uint16_t w_layout   : 1;
} lv_obj_t;

    1.2 对象属性

      1.2.1 基本属性 basic attributes

        所有对象共享一些基本属性，如position,size,parent,styles,event handlers等等，可对其进行设置/获取，举例如下；

//obj的pos,class,style,draw,scroll属性等都有自己的xx.c和xx.h，可见obj的重要；
//lv_obj_pos.h
void lv_obj_set_pos(struct _lv_obj_t *obj, lv_coord_t x, lv_coord_t y);
void lv_obj_set_size(struct _lv_obj_t *obj, lv_coord_t w, lv_coord_t h);
lv_coord_t lv_obj_get_width(const struct _lv_obj_t *obj);
 
//lv_obj_styles.h
void lv_obj_add_style(struct _lv_obj_t *obj, lv_style_t *style, lv_style_selector_t selector);
void lv_obj_refresh_style(struct _lv_obj_t *obj, lv_part_t part, lv_style_prop_t prop);

      1.2.2 特定属性 specific attributes

        一些对象拥有一些自己的特殊属性，所以一些对象也会拥有属于自己的特殊函数；

//lv_slider.h  位于widgets/下
static inline void lv_slider_set_range(lv_obj_t *obj, int32_t min, int32_t max);
static inline void lv_slider_set_value(lv_obj_t *obj, int32_t value, lv_anim_enable_t anim);

      1.2.3 父对象

        每个对象只允许有一个父对象，父对象可视为子对象的容器，但是父对象可以允许有多个子对象；

        每个子对象只有在父对象范围内可见，超出部分不可见；子对象会随着父对象的移动而移动；

lv_obj_t * parent = lv_obj_create(lv_scr_act());    /*Create a parent object on the current screen*/
lv_obj_set_size(parent, 100, 80);                   /*Set the size of the parent*/
 
lv_obj_t * obj1 = lv_obj_create(parent);            /*Create an object on the previously created parent object*/
lv_obj_set_pos(obj1, 10, 10);	                    /*Set the position of the new object*/
//lv_obj.c  lv_obj_create()

   1.3 创建/删除对象

/**    //lv_obj.h
 * Create a base object (a rectangle)
 * @param parent    pointer to a parent object. If NULL then a screen will be created.
 * @return          pointer to the new object
 */
lv_obj_t *lv_obj_create(lv_obj_t *parent);
 
/**    //lv_obj_tree.h
 * Delete an object and all of its children.
 * Also remove the objects from their group and remove all animations (if any).
 * Send `LV_EVENT_DELETED` to deleted objects.
 * @param obj       pointer to an object
 */
void lv_obj_del(struct _lv_obj_t *obj);
 
/**    //lv_obj_tree.h
 * Helper function for asynchronously deleting objects.
 * Useful for cases where you can't delete an object directly in an `LV_EVENT_DELETE` handler (i.e. parent).
 * @param obj       object to delete
 * @see lv_async_call  cae在lv_timer周期性回调的时候来删除对象，通常是1ms之后删除，看tick;
 */
void lv_obj_del_async(struct _lv_obj_t *obj);
 
/**    //lv_obj_tree.h
 * Delete all children of an object.
 * Also remove the objects from their group and remove all animations (if any).
 * Send `LV_EVENT_DELETED` to deleted objects.
 * @param obj       pointer to an object
 */
void lv_obj_clean(struct _lv_obj_t *obj);

2 屏幕 screen

  屏幕属于没有parent的obj，屏幕本身也还是obj，可以用创建obj的方式来创建屏幕；

  大约屏幕没啥内容，但是呢又很常见无处不在，屏幕本身也还是obj，所以lvgl把屏幕也概括在了obj章节里；

  2.1 创建屏幕

//对象在创建的时候如果还没有创建好屏幕，那么对象也可以作为屏幕；
lv_obj_t * scr1 = lv_obj_create(NULL);

  2.2 加载屏幕

    lv_scr_act( ), lv_src_load( ), lv_src_load_anim( )都是在default screen上操作的；

    每个screen都是创建在default display上的；default display是最后一个用lv_disp_drv_register( )注册的显示；

// 每个屏幕加载之后会在tick时间后更新，也可能是屏幕会在调用lv_scr_act()之后tick时间更新，先放着；
 
/**   lv_disp.h  获取当前屏幕   
 * Get the active screen of the default display
 * @return pointer to the active screen
 */
static inline lv_obj_t * lv_scr_act(void)
{
    return lv_disp_get_scr_act(lv_disp_get_default());
}
 
//lv_disp.h  加载屏幕
static inline void lv_scr_load(lv_obj_t * scr)
{
    lv_disp_load_scr(scr);
}
/**  lv_disp.c
 * Make a screen active
 * @param scr pointer to a screen
 */
void lv_disp_load_scr(lv_obj_t * scr)
{
    lv_scr_load_anim(scr, LV_SCR_LOAD_ANIM_NONE, 0, 0, false);
}

  2.3 动画加载屏幕

typedef enum {
    LV_SCR_LOAD_ANIM_NONE,          //cae无动画，就是直接加载;
    LV_SCR_LOAD_ANIM_OVER_LEFT,     //cae新屏幕以定向覆盖的方式来加载;
    LV_SCR_LOAD_ANIM_OVER_RIGHT,
    LV_SCR_LOAD_ANIM_OVER_TOP,
    LV_SCR_LOAD_ANIM_OVER_BOTTOM,
    LV_SCR_LOAD_ANIM_MOVE_LEFT,     //cae新旧屏幕一起定向加载;
    LV_SCR_LOAD_ANIM_MOVE_RIGHT,
    LV_SCR_LOAD_ANIM_MOVE_TOP,
    LV_SCR_LOAD_ANIM_MOVE_BOTTOM,
    LV_SCR_LOAD_ANIM_FADE_IN,       //cae在旧屏幕上淡入新屏幕;
    LV_SCR_LOAD_ANIM_FADE_ON = LV_SCR_LOAD_ANIM_FADE_IN, /*For backward compatibility*/
    LV_SCR_LOAD_ANIM_FADE_OUT,
    LV_SCR_LOAD_ANIM_OUT_LEFT,      //cae以旧屏幕定向滑出的方式来加载;
    LV_SCR_LOAD_ANIM_OUT_RIGHT,
    LV_SCR_LOAD_ANIM_OUT_TOP,
    LV_SCR_LOAD_ANIM_OUT_BOTTOM,
} lv_scr_load_anim_t;
/**    //lv_disp.h 以动画方式加载屏幕，本质还是屏幕，而不是动画;
 * Switch screen with animation
 * @param scr pointer to the new screen to load
 * @param anim_type type of the animation from `lv_scr_load_anim_t`, e.g. `LV_SCR_LOAD_ANIM_MOVE_LEFT`
 * @param time time of the animation
 * @param delay delay before the transition
 * @param auto_del true: automatically delete the old screen
 */
void lv_scr_load_anim(lv_obj_t * scr, lv_scr_load_anim_t anim_type, uint32_t time, uint32_t delay, bool auto_del);

  2.4 层 layers

    对于屏幕而言，每个屏幕上都有两层layer，分别是top layer和system layer；

    top layer位于所有obj之上，top layer主要用来放置弹出窗口；

    system layer位于top layer之上；system layer只能放置系统层控件，比如鼠标等；

/**    //lv_disp.h
 * Get the top layer  of the default display
 * @return pointer to the top layer
 */
static inline lv_obj_t *lv_layer_top(void)
{
    return lv_disp_get_layer_top(lv_disp_get_default());
}
//example:
lv_obj_t *bg = lv_layer_top();
lv_obj_set_style_bg_color(bg, lv_color_hex(0x6f8af6), 0);

/**    //lv_disp.h 
 * Get the active screen of the default display
 * @return  pointer to the sys layer
 */
static inline lv_obj_t *lv_layer_sys(void)
{
    return lv_disp_get_layer_sys(lv_disp_get_default());
}
//eg:
perf_label = lv_label_create(lv_layer_sys());
lv_obj_set_style_bg_opa(perf_label, LV_OPA_50, 0);

3 坐标 coordinates

  坐标方向：以父类左上角的坐标为原点，水平方向以x轴正方向为lvgl_obj正方向，垂直方向以y轴负方向为lvgl_obj正方向；

  坐标单位：数值的单位都是像素点 pixels；

  坐标存储：lvgl的坐标信息是存储在styles中的；所以可以单独设置坐标信息，也可以使用style对其进行设置；

  3.1 位置 positions

    3.1.1 位置 position

//lv_obj_pos.h
void lv_obj_set_pos(struct _lv_obj_t * obj, lv_coord_t x, lv_coord_t y);
void lv_obj_set_x(struct _lv_obj_t * obj, lv_coord_t x);
void lv_obj_set_y(struct _lv_obj_t * obj, lv_coord_t y);
void lv_obj_refr_pos(struct _lv_obj_t * obj);    //用法保持怀疑，在tick范围内刷新一遍的话应该不调用也行;

    3.1.2 对齐 align

//lv_area.h 
//child_obj向parent_obj对齐，使用LV_ALIGN_XX，在parent_obj内对齐，以child_obj顶点作为偏移坐标原点；
//                           使用LV_ALIGN_OUT_XX，对齐无效，坐标原点始终是父对象坐标原点;所以不要这么用；
//align_obj向base_obj对齐，  使用LV_ALIGN_OUT_XX，偏移坐标原点为对齐后align_obj原点；
enum _lv_align_t {
    LV_ALIGN_DEFAULT = 0,
    LV_ALIGN_TOP_LEFT,
    LV_ALIGN_TOP_MID,
    LV_ALIGN_TOP_RIGHT,
    LV_ALIGN_BOTTOM_LEFT,
    LV_ALIGN_BOTTOM_MID,
    LV_ALIGN_BOTTOM_RIGHT,
    LV_ALIGN_LEFT_MID,
    LV_ALIGN_RIGHT_MID,
    LV_ALIGN_CENTER,
 
    LV_ALIGN_OUT_TOP_LEFT,
    LV_ALIGN_OUT_TOP_MID,
    LV_ALIGN_OUT_TOP_RIGHT,
    LV_ALIGN_OUT_BOTTOM_LEFT,
    LV_ALIGN_OUT_BOTTOM_MID,
    LV_ALIGN_OUT_BOTTOM_RIGHT,
    LV_ALIGN_OUT_LEFT_TOP,
    LV_ALIGN_OUT_LEFT_MID,
    LV_ALIGN_OUT_LEFT_BOTTOM,
    LV_ALIGN_OUT_RIGHT_TOP,
    LV_ALIGN_OUT_RIGHT_MID,
    LV_ALIGN_OUT_RIGHT_BOTTOM,
};
 
#ifdef DOXYGEN
typedef _lv_align_t lv_align_t;
#else
typedef uint8_t lv_align_t;
#endif /*DOXYGEN*/

//lv_obj_pos.h  
//obj向parent对齐，所以不是设计用来配置LV_ALIGN_OUT_XX的;
void lv_obj_align(lv_obj_t * obj, lv_align_t align, lv_coord_t x_ofs, lv_coord_t y_ofs);
void lv_obj_set_align(lv_obj_t * obj, lv_align_t align);
 
//obj向base对齐，对齐之后以obj顶点作为坐标原点
//LV_ALIGN_OUT_XX：obj在base_obj外对齐;
//LV_ALIGN_XX:     obj在base_obj内对齐;
void lv_obj_align_to(lv_obj_t * obj, const lv_obj_t * base, lv_align_t align, lv_coord_t x_ofs, lv_coord_t y_ofs)

  3.2 尺寸 size

     

//lv_obj_pos.h
void lv_obj_set_size(struct _lv_obj_t * obj, lv_coord_t w, lv_coord_t h);
void lv_obj_set_width(struct _lv_obj_t * obj, lv_coord_t w);    //w: padding left + contain width + padding right
void lv_obj_set_height(struct _lv_obj_t * obj, lv_coord_t h);   //h: padding top + contain height + padding bottom
bool lv_obj_refr_size(struct _lv_obj_t * obj);
 
/**
 * Get the width reduced by the left and right padding and the border width.
 * @param obj       pointer to an object
 * @note            The position of the object is recalculated only on the next redraw. To force coordinate recalculation
 *                  call `lv_obj_update_layout(obj)`.
 * @return          the width which still fits into its parent without causing overflow (making the parent scrollable)
 */
lv_coord_t lv_obj_get_content_width(const struct _lv_obj_t * obj);
 
/**
 * Get the height reduced by the top and bottom padding and the border width.
 * @param obj       pointer to an object
 * @note            The position of the object is recalculated only on the next redraw. To force coordinate recalculation
 *                  call `lv_obj_update_layout(obj)`.
 * @return          the height which still fits into the parent without causing overflow (making the parent scrollable)
 */
lv_coord_t lv_obj_get_content_height(const struct _lv_obj_t * obj);

  3.3 布局 layouts

    用来更新当前对象子类的position和size，和flexbox、grid部件一起使用，对布局进行实时更新么？先放着；

//lv_obj_pos.h   layout函数并不多，先放着;
extern uint16_t LV_LAYOUT_GRID;        //lv_grid.h
extern uint16_t LV_LAYOUT_FLEX;        //lv_flex.h
void lv_obj_set_layout(struct _lv_obj_t * obj, uint32_t layout);

   3.3.1 flags

      用来配置子类对象 如何响应他的父类对象的layout局部；所以这个flag是layout给子类对象使用的；

//lv_obj.h
 
/**
 * On/Off features controlling the object's behavior.
 * OR-ed values are possible
 */
enum {
    LV_OBJ_FLAG_HIDDEN          = (1L << 0),  /**< Make the object hidden. (Like it wasn't there at all)*/
    LV_OBJ_FLAG_CLICKABLE       = (1L << 1),  /**< Make the object clickable by the input devices*/
    LV_OBJ_FLAG_CLICK_FOCUSABLE = (1L << 2),  /**< Add focused state to the object when clicked*/
    LV_OBJ_FLAG_CHECKABLE       = (1L << 3),  /**< Toggle checked state when the object is clicked*/
    LV_OBJ_FLAG_SCROLLABLE      = (1L << 4),  /**< Make the object scrollable*/
    LV_OBJ_FLAG_SCROLL_ELASTIC  = (1L << 5),  /**< Allow scrolling inside but with slower speed*/
    LV_OBJ_FLAG_SCROLL_MOMENTUM = (1L << 6),  /**< Make the object scroll further when "thrown"*/
    LV_OBJ_FLAG_SCROLL_ONE      = (1L << 7),  /**< Allow scrolling only one snappable children*/
    LV_OBJ_FLAG_SCROLL_CHAIN_HOR = (1L << 8), /**< Allow propagating the horizontal scroll to a parent*/
    LV_OBJ_FLAG_SCROLL_CHAIN_VER = (1L << 9), /**< Allow propagating the vertical scroll to a parent*/
    LV_OBJ_FLAG_SCROLL_CHAIN     = (LV_OBJ_FLAG_SCROLL_CHAIN_HOR | LV_OBJ_FLAG_SCROLL_CHAIN_VER),
    LV_OBJ_FLAG_SCROLL_ON_FOCUS = (1L << 10),  /**< Automatically scroll object to make it visible when focused*/
    LV_OBJ_FLAG_SCROLL_WITH_ARROW  = (1L << 11), /**< Allow scrolling the focused object with arrow keys*/
    LV_OBJ_FLAG_SNAPPABLE       = (1L << 12), /**< If scroll snap is enabled on the parent it can snap to this object*/
    LV_OBJ_FLAG_PRESS_LOCK      = (1L << 13), /**< Keep the object pressed even if the press slid from the object*/
    LV_OBJ_FLAG_EVENT_BUBBLE    = (1L << 14), /**< Propagate the events to the parent too*/
    LV_OBJ_FLAG_GESTURE_BUBBLE  = (1L << 15), /**< Propagate the gestures to the parent*/
    LV_OBJ_FLAG_ADV_HITTEST     = (1L << 16), /**< Allow performing more accurate hit (click) test. E.g. consider rounded corners.*/
    LV_OBJ_FLAG_IGNORE_LAYOUT   = (1L << 17), /**< Make the object ignored by layouts,so obj can be set as usual*/
    LV_OBJ_FLAG_FLOATING        = (1L << 18), /**< Do not scroll the object when the parent scrolls and ignore layout,这个等于上一行那个*/
    LV_OBJ_FLAG_OVERFLOW_VISIBLE = (1L << 19), /**< Do not clip the children's content to the parent's boundary*/
 
    LV_OBJ_FLAG_LAYOUT_1        = (1L << 23), /**< Custom flag, free to use by layouts*/
    LV_OBJ_FLAG_LAYOUT_2        = (1L << 24), /**< Custom flag, free to use by layouts*/
 
    LV_OBJ_FLAG_WIDGET_1        = (1L << 25), /**< Custom flag, free to use by widget*/
    LV_OBJ_FLAG_WIDGET_2        = (1L << 26), /**< Custom flag, free to use by widget*/
    LV_OBJ_FLAG_USER_1          = (1L << 27), /**< Custom flag, free to use by user*/
    LV_OBJ_FLAG_USER_2          = (1L << 28), /**< Custom flag, free to use by user*/
    LV_OBJ_FLAG_USER_3          = (1L << 29), /**< Custom flag, free to use by user*/
    LV_OBJ_FLAG_USER_4          = (1L << 30), /**< Custom flag, free to use by user*/
 
};
typedef uint32_t lv_obj_flag_t;
 
/**
 * Set one or more flags
 * @param obj   pointer to an object
 * @param f     R-ed values from `lv_obj_flag_t` to set.
 */
void lv_obj_add_flag(lv_obj_t * obj, lv_obj_flag_t f);
 
/**
 * Clear one or more flags
 * @param obj   pointer to an object
 * @param f     OR-ed values from `lv_obj_flag_t` to set.
 */
void lv_obj_clear_flag(lv_obj_t * obj, lv_obj_flag_t f);

4 小结

  对象obj，对象的基本属性，特殊属性，父对象，增删对象；

  屏幕也是对象，屏幕的创建加载删除；

  然后坐标设置，坐标的定义和使用，其中有layout和flag的作用；