Chart（图表） (lv_chart)

Overview（概述）

显示原文

Charts are a basic object to visualize data points. Currently Line charts (connect points with lines and/or draw points on them) and Bar charts are supported.

Charts can have: - division lines - 2 y axis - axis ticks and texts on ticks - cursors - scrolling and zooming

图表是可视化数据点的基本对象。目前支持折线图（用折线连接点和/或在其上绘制点）和条形图。

图表可以有： - 分割线 - 2 y 轴 - 轴刻度和文本刻度 - 光标 - 滚动和缩放

Parts and Styles（零件和样式）

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LV_PART_MAIN The background of the chart. Uses all the typical background and line (for the division lines) related style properties. Padding makes the series area smaller. For column charts pad_column sets the space between the columns of the adjacent indices.
LV_PART_SCROLLBAR The scrollbar used if the chart is zoomed. See the Base object's documentation for details.
LV_PART_ITEMS Refers to the line or bar series.
- Line chart: The line properties are used by the lines. width, height, bg_color and radius is used to set the appearance of points.
- Bar chart: The typical background properties are used to style the bars. pad_column sets the space between the columns on the same index.
LV_PART_INDICATOR Refers to the points on line and scatter chart (small circles or squares).
LV_PART_CURSOR Line properties are used to style the cursors. width, height, bg_color and radius are used to set the appearance of points.

LV_PART_MAIN 图表的背景。使用所有典型的背景和线条（用于分割线）相关样式性能。填充使系列区域更小。对于列图表设置 pad_column 相邻索引。
LV_PART_SCROLLBAR 缩放图表时使用的滚动条。看有关详细信息，请参阅基本对象的文档。
LV_PART_ITEMS 指线或条形系列。
- 折线图：折线属性由折线使用。 width, height, bg_color 和 radius 用于设置点的外观。
- 条形图：典型的背景属性用于设置进度条。 pad_column 设置相同的索引。
LV_PART_INDICATOR 指折线图和散点图上的点（小圆圈或正方形）。
LV_PART_CURSOR 线条属性用于设置游标的样式。 width, height, bg_color and radius 用于设置点的外观。

Usage（用法）

Chart type（图表类型）

显示原文

The following data display types exist:

LV_CHART_TYPE_NONE: Do not display any data. Can be used to hide the series.
LV_CHART_TYPE_LINE: Draw lines between the data points and/or points (rectangles or circles) on the data points.
LV_CHART_TYPE_BAR: Draw bars.
LV_CHART_TYPE_SCATTER: X/Y chart drawing point's and lines between the points. .

You can specify the display type with lv_chart_set_type(chart, LV_CHART_TYPE_...).

存在以下数据显示类型：

LV_CHART_TYPE_NONE: 不显示任何数据。可用于隐藏系列。
LV_CHART_TYPE_LINE: 在数据点和/或数据点上的点（矩形或圆圈）之间绘制线条。
LV_CHART_TYPE_BAR: 绘制条。
LV_CHART_TYPE_SCATTER:X/Y 图表绘制点和点之间的线。.

您可以使用 lv_chart_set_type(chart, LV_CHART_TYPE_...) 指定显示类型。

Data series（数据系列）

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You can add any number of series to the charts by lv_chart_add_series(chart, color, axis). This allocates an lv_chart_series_t structure which contains the chosen color and an array for the data points. can have the following values:

axis tells which axis's range should be used to scale the values.

lv_chart_set_ext_y_array(chart, ser, value_array) makes the chart use an external array for the given series. value_array should look like this: int32_t * value_array[num_points]. The array size needs to be large enough to hold all the points of that series. The array's pointer will be saved in the chart so it needs to be global, static or dynamically allocated. Note: you should call lv_chart_refresh(chart) after the external data source has been updated to update the chart.

The value array of a series can be obtained with lv_chart_get_y_array(chart, ser), which can be used with ext_array or normal arrays.

For LV_CHART_TYPE_SCATTER type lv_chart_set_ext_x_array(chart, ser, value_array) and lv_chart_get_x_array(chart, ser) can be used as well.

您可以按 lv_chart_add_series(chart, color, axis) 向图表添加任意数量的序列。这将分配一个 lv_chart_series_t 结构，其中包含所选的数据点的数组。 axis 可以具有以下值：

axis 指示应使用哪个轴的范围来缩放值。

lv_chart_set_ext_y_array(chart, ser, value_array) 制作图表对给定序列使用外部数组。 value_array 应该看起来像 int32_t * value_array[num_points]。数组大小需要足够大以容纳该系列的所有点。这 array 的指针将保存在图表中，因此它需要是全局的，静态或动态分配。注意：您应该 lv_chart_refresh(chart) 在外部数据源已更新被以更新图表。

一个级数的值数组可以用 lv_chart_get_y_array(chart, ser) 获得，可以一起使用 ext_array 或 普通数组s。

对于 LV_CHART_TYPE_SCATTER 类型 lv_chart_set_ext_x_array(chart, ser, value_array) 和 lv_chart_get_x_array(chart, ser) 也可以使用。

Modify the data（修改数据）

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You have several options to set the data of series:

Set the values manually in the array like ser1->points[3] = 7 and refresh the chart with lv_chart_refresh(chart).
Use lv_chart_set_value_by_id(chart, ser, id, value) where id is the index of the point you wish to update.
Use the lv_chart_set_next_value(chart, ser, value).
Initialize all points to a given value with lv_chart_set_all_value(chart, ser, value).

Use LV_CHART_POINT_NONE as value to make the library skip drawing that point, column, or line segment.

For LV_CHART_TYPE_SCATTER type lv_chart_set_value_by_id2(chart, ser, id, value) and lv_chart_set_next_value2(chart, ser, x_value, y_value) can be used as well.

有几个选项可以设置序列数据：

在数组中手动设置值，例如 ser1->points[3] = 7 ，并使用 lv_chart_refresh(chart) 刷新图表。
使用 lv_chart_set_value_by_id(chart, ser, id, value) 其中id是要更新的点的索引。id
使用 lv_chart_set_next_value(chart, ser, value)。
使用 lv_chart_set_all_value(chart, ser, value) 将所有点初始化为给定值。

使用 LV_CHART_POINT_NONE 作为值可使库跳过该点，列或线段的绘制。

对于 LV_CHART_TYPE_SCATTER 类型 lv_chart_set_value_by_id2(chart, ser, id, value) 和 lv_chart_set_next_value2(chart, ser, x_value, y_value) 也可以使用。

Update modes（更新模式）

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lv_chart_set_next_value() can behave in two ways depending on update mode:

LV_CHART_UPDATE_MODE_SHIFT: Shift old data to the left and add the new one to the right.
LV_CHART_UPDATE_MODE_CIRCULAR: Add the new data in circular fashion, like an ECG diagram.

The update mode can be changed with lv_chart_set_update_mode(chart, LV_CHART_UPDATE_MODE_...).

lv_chart_set_next_value() 可以以两种方式运行，具体取决于 更新模式 ：

LV_CHART_UPDATE_MODE_SHIFT: 将旧数据向左移动，将新数据添加到右侧。
LV_CHART_UPDATE_MODE_CIRCULAR: 以循环方式添加新数据，如心电图。

更新模式可以通过 lv_chart_set_update_mode(chart, LV_CHART_UPDATE_MODE_...)。

Number of points（点数）

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The number of points in the series can be modified by lv_chart_set_point_count(chart, point_num). The default value is 10. Note: this also affects the number of points processed when an external buffer is assigned to a series, so you need to be sure the external array is large enough.

序列中的点数可以通过 lv_chart_set_point_count(chart, point_num) 进行修改。默认值为 10。注意：这也会影响外部处理的点数缓冲区被分配给一个系列，所以你需要确保外部数组足够大。

Handling large number of points

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On line charts, if the number of points is greater than the pixels horizontally, the Chart will draw only vertical lines to make the drawing of large amount of data effective. If there are, let's say, 10 points to a pixel, LVGL searches the smallest and the largest value and draws a vertical lines between them to ensure no peaks are missed.

在折线图上，如果点数大于像素数在水平方向上，图表将只绘制垂直线以使大量数据的绘制效果。如果有，比方说，10指向像素，LVGL搜索最小值和最大值在它们之间画一条垂直线，以确保没有遗漏峰值。以确保不会遗漏任何峰值。

Vertical range（垂直范围）

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You can specify the minimum and maximum values in y-direction with lv_chart_set_range(chart, axis, min, max). axis can be LV_CHART_AXIS_PRIMARY (left axis) or LV_CHART_AXIS_SECONDARY (right axis).

The value of the points will be scaled proportionally. The default range is: 0..100.

您可以使用 lv_chart_set_range(chart, axis, min, max) 指定 y 方向的最小值和最大值。 axis 可以是（左轴）或（右轴）。LV_CHART_AXIS_PRIMARY (左轴) 或 LV_CHART_AXIS_SECONDARY (右轴).

点的值将按比例缩放。默认范围是：0..100。

Division lines（分割线）

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The number of horizontal and vertical division lines can be modified by lv_chart_set_div_line_count(chart, hdiv_num, vdiv_num). The default settings are 3 horizontal and 5 vertical division lines. If there is a visible border on a side and no padding on that side, the division line would be drawn on top of the border and therefore it won't be drawn.

水平和垂直分割线的数量可以通过 lv_chart_set_div_line_count(chart, hdiv_num, vdiv_num) 进行修改。默认设置为 3 条水平分割线和 5 条垂直分割线。如果有一个一侧可见边框，该侧没有填充，即分界线将绘制在边框的顶部，因此不会绘制。

Override default start point for series（覆盖序列的默认起点）

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If you want a plot to start from a point other than the default which is point[0] of the series, you can set an alternative index with the function lv_chart_set_x_start_point(chart, ser, id) where id is the new index position to start plotting from.

Note that LV_CHART_UPDATE_MODE_SHIFT also changes the start_point.

如果希望绘图从序列的默认点以外的点 point[0] 开始，则可以使用函数 lv_chart_set_x_start_point(chart, ser, id) 其中 id 要从中开始绘图的新索引位置。

请注意， start_point 这也会更改。

Tick marks and labels（刻度线和标签）

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With the help of Scale, vertical and horizontal scales can be added in a very flexible way. See the example below to learn more.

借助 Scale，可以非常灵活地添加垂直和水平刻度。请参阅下面的示例以了解更多信息。

Zoom（缩放）

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To zoom the chart all you need to is wrapping it into a parent container and set the chart's width or height to larger value. This way the chart will be scrollable on its parent.

要缩放图表，您只需将其包装到父容器中并设置图表的宽度或高度即可到更大的价值。这样，图表就可以在其父级上滚动。

Cursor（光标）

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A cursor can be added with lv_chart_cursor_t * c1 = lv_chart_add_cursor(chart, color, dir);. The possible values of dir LV_DIR_NONE/RIGHT/UP/LEFT/DOWN/HOR/VER/ALL or their OR-ed values to tell in which direction(s) should the cursor be drawn.

lv_chart_set_cursor_pos(chart, cursor, &point) sets the position of the cursor. pos is a pointer to an lv_point_t variable. E.g. lv_point_t point = {10, 20}. If the chart is scrolled the cursor will remain in the same place.

lv_chart_get_point_pos_by_id(chart, series, id, &point_out) gets the coordinate of a given point. It's useful to place the cursor at a given point.

lv_chart_set_cursor_point(chart, cursor, series, point_id) sticks the cursor at a point. If the point's position changes (new value or scrolling) the cursor will move with the point.

可以使用 lv_chart_cursor_t * c1 = lv_chart_add_cursor(chart, color, dir); 添加光标。 dir LV_DIR_NONE/RIGHT/UP/LEFT/DOWN/HOR/VER/ALL 的可能值或或它们的OR-ed 值用于指示应在哪个方向上绘制光标。

lv_chart_set_cursor_pos(chart, cursor, &point) 设置光标。 pos 是指向 lv_point_t 变量的指针。例如 lv_point_t point = {10, 20} 。如果图表滚动光标将保留在同一个地方。

lv_chart_get_point_pos_by_id(chart, series, id, &point_out) 获取给定点的坐标。将光标放在给定的位置很有用。

lv_chart_set_cursor_point(chart, cursor, series, point_id) 摇杆光标位于某个点。如果点的位置发生变化（新值或滚动）光标将随点移动。

Events（事件）

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LV_EVENT_VALUE_CHANGED Sent when a new point is clicked pressed. lv_chart_get_pressed_point(chart) returns the zero-based index of the pressed point.

See the events of the Base object too.

Learn more about Events（事件）.

LV_EVENT_VALUE_CHANGED 单击按下新点时发送。lv_chart_get_pressed_point(chart) 返回从零开始的索引按下的点。

另请参阅基本对象的事件。

详细了解更多 Events（事件）。

Keys（按键）

显示原文

No Keys are processed by the object type.

Learn more about Keys（按键）.

对象类型不处理任何按键。

了解有关 Keys（按键）的更多信息。

Example

[English]

Line Chart

#include "../../lv_examples.h"
#if LV_USE_CHART && LV_BUILD_EXAMPLES

/**
 * A very basic line chart
 */
void lv_example_chart_1(void)
{
    /*Create a chart*/
    lv_obj_t * chart;
    chart = lv_chart_create(lv_screen_active());
    lv_obj_set_size(chart, 200, 150);
    lv_obj_center(chart);
    lv_chart_set_type(chart, LV_CHART_TYPE_LINE);   /*Show lines and points too*/

    /*Add two data series*/
    lv_chart_series_t * ser1 = lv_chart_add_series(chart, lv_palette_main(LV_PALETTE_GREEN), LV_CHART_AXIS_PRIMARY_Y);
    lv_chart_series_t * ser2 = lv_chart_add_series(chart, lv_palette_main(LV_PALETTE_RED), LV_CHART_AXIS_SECONDARY_Y);

    uint32_t i;
    for(i = 0; i < 10; i++) {
        /*Set the next points on 'ser1'*/
        lv_chart_set_next_value(chart, ser1, lv_rand(10, 50));

        /*Directly set points on 'ser2'*/
        ser2->y_points[i] = lv_rand(50, 90);
    }

    lv_chart_refresh(chart); /*Required after direct set*/
}

#endif

Axis ticks and labels with scrolling

#include "../../lv_examples.h"
#if LV_USE_CHART && LV_BUILD_EXAMPLES

/**
 * Use lv_scale to add ticks to a scrollable chart
 */
void lv_example_chart_2(void)
{
    /*Create a container*/
    lv_obj_t * main_cont = lv_obj_create(lv_screen_active());
    lv_obj_set_size(main_cont, 200, 150);
    lv_obj_center(main_cont);

    /*Create a transparent wrapper for the chart and the scale.
     *Set a large width, to make it scrollable on the main container*/
    lv_obj_t * wrapper = lv_obj_create(main_cont);
    lv_obj_remove_style_all(wrapper);
    lv_obj_set_size(wrapper, lv_pct(300), lv_pct(100));
    lv_obj_set_flex_flow(wrapper, LV_FLEX_FLOW_COLUMN);

    /*Create a chart on the wrapper
     *Set it's width to 100% to fill the large wrapper*/
    lv_obj_t * chart = lv_chart_create(wrapper);
    lv_obj_set_width(chart, lv_pct(100));
    lv_obj_set_flex_grow(chart, 1);
    lv_chart_set_type(chart, LV_CHART_TYPE_BAR);
    lv_chart_set_range(chart, LV_CHART_AXIS_PRIMARY_Y, 0, 100);
    lv_chart_set_range(chart, LV_CHART_AXIS_SECONDARY_Y, 0, 400);
    lv_chart_set_point_count(chart, 12);
    lv_obj_set_style_radius(chart, 0, 0);

    /*Create a scale also with 100% width*/
    lv_obj_t * scale_bottom = lv_scale_create(wrapper);
    lv_scale_set_mode(scale_bottom, LV_SCALE_MODE_HORIZONTAL_BOTTOM);
    lv_obj_set_size(scale_bottom, lv_pct(100), 25);
    lv_scale_set_total_tick_count(scale_bottom, 12);
    lv_scale_set_major_tick_every(scale_bottom, 1);
    lv_obj_set_style_pad_hor(scale_bottom, lv_chart_get_first_point_center_offset(chart), 0);

    static const char * month[] = {"Jan", "Febr", "March", "Apr", "May", "Jun", "July", "Aug", "Sept", "Oct", "Nov", "Dec", NULL};
    lv_scale_set_text_src(scale_bottom, month);

    /*Add two data series*/
    lv_chart_series_t * ser1 = lv_chart_add_series(chart, lv_palette_lighten(LV_PALETTE_GREEN, 2), LV_CHART_AXIS_PRIMARY_Y);
    lv_chart_series_t * ser2 = lv_chart_add_series(chart, lv_palette_darken(LV_PALETTE_GREEN, 2), LV_CHART_AXIS_PRIMARY_Y);

    /*Set the next points on 'ser1'*/
    uint32_t i;
    for(i = 0; i < 12; i++) {
        lv_chart_set_next_value(chart, ser1, lv_rand(10, 60));
        lv_chart_set_next_value(chart, ser2, lv_rand(50, 90));
    }
    lv_chart_refresh(chart); /*Required after direct set*/
}

#endif

Show the value of the pressed points

#include "../../lv_examples.h"
#if LV_USE_CHART && LV_BUILD_EXAMPLES

static void event_cb(lv_event_t * e)
{
    lv_event_code_t code = lv_event_get_code(e);
    lv_obj_t * chart = lv_event_get_target(e);

    if(code == LV_EVENT_VALUE_CHANGED) {
        lv_obj_invalidate(chart);
    }
    if(code == LV_EVENT_REFR_EXT_DRAW_SIZE) {
        int32_t * s = lv_event_get_param(e);
        *s = LV_MAX(*s, 20);
    }
    else if(code == LV_EVENT_DRAW_POST_END) {
        int32_t id = lv_chart_get_pressed_point(chart);
        if(id == LV_CHART_POINT_NONE) return;

        LV_LOG_USER("Selected point %d", (int)id);

        lv_chart_series_t * ser = lv_chart_get_series_next(chart, NULL);
        while(ser) {
            lv_point_t p;
            lv_chart_get_point_pos_by_id(chart, ser, id, &p);

            int32_t * y_array = lv_chart_get_y_array(chart, ser);
            int32_t value = y_array[id];

            char buf[16];
            lv_snprintf(buf, sizeof(buf), LV_SYMBOL_DUMMY"$%d", value);

            lv_draw_rect_dsc_t draw_rect_dsc;
            lv_draw_rect_dsc_init(&draw_rect_dsc);
            draw_rect_dsc.bg_color = lv_color_black();
            draw_rect_dsc.bg_opa = LV_OPA_50;
            draw_rect_dsc.radius = 3;
            draw_rect_dsc.bg_image_src = buf;
            draw_rect_dsc.bg_image_recolor = lv_color_white();

            lv_area_t a;
            a.x1 = chart->coords.x1 + p.x - 20;
            a.x2 = chart->coords.x1 + p.x + 20;
            a.y1 = chart->coords.y1 + p.y - 30;
            a.y2 = chart->coords.y1 + p.y - 10;

            lv_layer_t * layer = lv_event_get_layer(e);
            lv_draw_rect(layer, &draw_rect_dsc, &a);

            ser = lv_chart_get_series_next(chart, ser);
        }
    }
    else if(code == LV_EVENT_RELEASED) {
        lv_obj_invalidate(chart);
    }
}

/**
 * Show the value of the pressed points
 */
void lv_example_chart_3(void)
{
    /*Create a chart*/
    lv_obj_t * chart;
    chart = lv_chart_create(lv_screen_active());
    lv_obj_set_size(chart, 200, 150);
    lv_obj_center(chart);

    lv_obj_add_event_cb(chart, event_cb, LV_EVENT_ALL, NULL);
    lv_obj_refresh_ext_draw_size(chart);

    /*Zoom in a little in X*/
    //    lv_chart_set_scale_x(chart, 800);

    /*Add two data series*/
    lv_chart_series_t * ser1 = lv_chart_add_series(chart, lv_palette_main(LV_PALETTE_RED), LV_CHART_AXIS_PRIMARY_Y);
    lv_chart_series_t * ser2 = lv_chart_add_series(chart, lv_palette_main(LV_PALETTE_GREEN), LV_CHART_AXIS_PRIMARY_Y);
    uint32_t i;
    for(i = 0; i < 10; i++) {
        lv_chart_set_next_value(chart, ser1, lv_rand(60, 90));
        lv_chart_set_next_value(chart, ser2, lv_rand(10, 40));
    }
}

#endif

Recolor bars based on their value

#include "../../lv_examples.h"

#if LV_USE_CHART && LV_DRAW_SW_COMPLEX && LV_BUILD_EXAMPLES

static void draw_event_cb(lv_event_t * e)
{
    lv_draw_task_t * draw_task = lv_event_get_draw_task(e);
    lv_draw_dsc_base_t * base_dsc = draw_task->draw_dsc;

    if(base_dsc->part != LV_PART_ITEMS) {
        return;
    }

    lv_draw_fill_dsc_t * fill_dsc = lv_draw_task_get_fill_dsc(draw_task);
    if(fill_dsc) {
        lv_obj_t * chart = lv_event_get_target(e);
        int32_t * y_array = lv_chart_get_y_array(chart, lv_chart_get_series_next(chart, NULL));
        int32_t v = y_array[base_dsc->id2];

        uint32_t ratio = v * 255 / 100;
        fill_dsc->color = lv_color_mix(lv_palette_main(LV_PALETTE_GREEN), lv_palette_main(LV_PALETTE_RED), ratio);
    }
}

/**
 * Recolor the bars of a chart based on their value
 */
void lv_example_chart_4(void)
{
    /*Create a chart1*/
    lv_obj_t * chart = lv_chart_create(lv_screen_active());
    lv_chart_set_type(chart, LV_CHART_TYPE_BAR);
    lv_chart_set_point_count(chart, 24);
    lv_obj_set_style_pad_column(chart, 2, 0);
    lv_obj_set_size(chart, 260, 160);
    lv_obj_center(chart);

    lv_chart_series_t * ser = lv_chart_add_series(chart, lv_color_hex(0xff0000), LV_CHART_AXIS_PRIMARY_Y);
    lv_obj_add_event_cb(chart, draw_event_cb, LV_EVENT_DRAW_TASK_ADDED, NULL);
    lv_obj_add_flag(chart, LV_OBJ_FLAG_SEND_DRAW_TASK_EVENTS);

    uint32_t i;
    for(i = 0; i < 24; i++) {
        lv_chart_set_next_value(chart, ser, lv_rand(10, 90));
    }
}

#endif

Faded area line chart with custom division lines

#include "../../lv_examples.h"

#if LV_USE_CHART && LV_DRAW_SW_COMPLEX && LV_BUILD_EXAMPLES

static void hook_division_lines(lv_event_t * e);
static void add_faded_area(lv_event_t * e);
static void draw_event_cb(lv_event_t * e);

/**
 * Add a faded area effect to the line chart and make some division lines ticker
 */
void lv_example_chart_5(void)
{
    /*Create a chart*/
    lv_obj_t * chart = lv_chart_create(lv_screen_active());
    lv_chart_set_type(chart, LV_CHART_TYPE_LINE);   /*Show lines and points too*/
    lv_obj_set_size(chart, 200, 150);
    lv_obj_set_style_pad_all(chart, 0, 0);
    lv_obj_set_style_radius(chart, 0, 0);
    lv_obj_center(chart);

    lv_chart_set_div_line_count(chart, 5, 7);

    lv_obj_add_event_cb(chart, draw_event_cb, LV_EVENT_DRAW_TASK_ADDED, NULL);
    lv_obj_add_flag(chart, LV_OBJ_FLAG_SEND_DRAW_TASK_EVENTS);

    lv_chart_series_t * ser = lv_chart_add_series(chart, lv_palette_main(LV_PALETTE_RED), LV_CHART_AXIS_PRIMARY_Y);

    uint32_t i;
    for(i = 0; i < 10; i++) {
        lv_chart_set_next_value(chart, ser, lv_rand(10, 80));
    }
}

static void draw_event_cb(lv_event_t * e)
{
    lv_draw_task_t * draw_task = lv_event_get_draw_task(e);
    lv_draw_dsc_base_t * base_dsc = draw_task->draw_dsc;

    if(base_dsc->part == LV_PART_ITEMS && draw_task->type == LV_DRAW_TASK_TYPE_LINE) {
        add_faded_area(e);

    }
    /*Hook the division lines too*/
    if(base_dsc->part == LV_PART_MAIN && draw_task->type == LV_DRAW_TASK_TYPE_LINE) {
        hook_division_lines(e);
    }
}

static void add_faded_area(lv_event_t * e)
{
    lv_obj_t * obj = lv_event_get_target(e);

    lv_draw_task_t * draw_task = lv_event_get_draw_task(e);
    lv_draw_dsc_base_t * base_dsc = draw_task->draw_dsc;

    const lv_chart_series_t * ser = lv_chart_get_series_next(obj, NULL);

    /*Draw a triangle below the line witch some opacity gradient*/
    lv_draw_line_dsc_t * draw_line_dsc = draw_task->draw_dsc;
    lv_draw_triangle_dsc_t tri_dsc;

    lv_draw_triangle_dsc_init(&tri_dsc);
    tri_dsc.p[0].x = draw_line_dsc->p1.x;
    tri_dsc.p[0].y = draw_line_dsc->p1.y;
    tri_dsc.p[1].x = draw_line_dsc->p2.x;
    tri_dsc.p[1].y = draw_line_dsc->p2.y;
    tri_dsc.p[2].x = draw_line_dsc->p1.y < draw_line_dsc->p2.y ? draw_line_dsc->p1.x : draw_line_dsc->p2.x;
    tri_dsc.p[2].y = LV_MAX(draw_line_dsc->p1.y, draw_line_dsc->p2.y);
    tri_dsc.bg_grad.dir = LV_GRAD_DIR_VER;

    int32_t full_h = lv_obj_get_height(obj);
    int32_t fract_uppter = (int32_t)(LV_MIN(draw_line_dsc->p1.y, draw_line_dsc->p2.y) - obj->coords.y1) * 255 / full_h;
    int32_t fract_lower = (int32_t)(LV_MAX(draw_line_dsc->p1.y, draw_line_dsc->p2.y) - obj->coords.y1) * 255 / full_h;
    tri_dsc.bg_grad.stops[0].color = ser->color;
    tri_dsc.bg_grad.stops[0].opa = 255 - fract_uppter;
    tri_dsc.bg_grad.stops[0].frac = 0;
    tri_dsc.bg_grad.stops[1].color = ser->color;
    tri_dsc.bg_grad.stops[1].opa = 255 - fract_lower;
    tri_dsc.bg_grad.stops[1].frac = 255;

    lv_draw_triangle(base_dsc->layer, &tri_dsc);

    /*Draw rectangle below the triangle*/
    lv_draw_rect_dsc_t rect_dsc;
    lv_draw_rect_dsc_init(&rect_dsc);
    rect_dsc.bg_grad.dir = LV_GRAD_DIR_VER;
    rect_dsc.bg_grad.stops[0].color = ser->color;
    rect_dsc.bg_grad.stops[0].frac = 0;
    rect_dsc.bg_grad.stops[0].opa = 255 - fract_lower;
    rect_dsc.bg_grad.stops[1].color = ser->color;
    rect_dsc.bg_grad.stops[1].frac = 255;
    rect_dsc.bg_grad.stops[1].opa = 0;

    lv_area_t rect_area;
    rect_area.x1 = (int32_t)draw_line_dsc->p1.x;
    rect_area.x2 = (int32_t)draw_line_dsc->p2.x - 1;
    rect_area.y1 = (int32_t)LV_MAX(draw_line_dsc->p1.y, draw_line_dsc->p2.y) - 1;
    rect_area.y2 = (int32_t)obj->coords.y2;
    lv_draw_rect(base_dsc->layer, &rect_dsc, &rect_area);
}

static void hook_division_lines(lv_event_t * e)
{
    lv_draw_task_t * draw_task = lv_event_get_draw_task(e);
    lv_draw_dsc_base_t * base_dsc = draw_task->draw_dsc;
    lv_draw_line_dsc_t * line_dsc = draw_task->draw_dsc;

    /*Vertical line*/
    if(line_dsc->p1.x == line_dsc->p2.x) {
        line_dsc->color  = lv_palette_lighten(LV_PALETTE_GREY, 1);
        if(base_dsc->id1 == 3) {
            line_dsc->width = 2;
            line_dsc->dash_gap = 0;
            line_dsc->dash_width = 0;
        }
        else {
            line_dsc->width = 1;
            line_dsc->dash_gap = 6;
            line_dsc->dash_width = 6;
        }
    }
    /*Horizontal line*/
    else {
        if(base_dsc->id1 == 2) {
            line_dsc->width  = 2;
            line_dsc->dash_gap  = 0;
            line_dsc->dash_width  = 0;
        }
        else {
            line_dsc->width = 2;
            line_dsc->dash_gap  = 6;
            line_dsc->dash_width  = 6;
        }

        if(base_dsc->id1 == 1  || base_dsc->id1 == 3) {
            line_dsc->color  = lv_palette_main(LV_PALETTE_GREEN);
        }
        else {
            line_dsc->color  = lv_palette_lighten(LV_PALETTE_GREY, 1);
        }
    }
}

#endif

Show cursor on the clicked point

#include "../../lv_examples.h"
#if LV_USE_CHART && LV_BUILD_EXAMPLES

static lv_obj_t * chart;
static lv_chart_series_t * ser;
static lv_chart_cursor_t * cursor;

static void value_changed_event_cb(lv_event_t * e)
{
    static int32_t last_id = -1;
    lv_obj_t * obj = lv_event_get_target(e);

    last_id = lv_chart_get_pressed_point(obj);
    if(last_id != LV_CHART_POINT_NONE) {
        lv_chart_set_cursor_point(obj, cursor, NULL, last_id);
    }
}

/**
 * Show cursor on the clicked point
 */
void lv_example_chart_6(void)
{
    chart = lv_chart_create(lv_screen_active());
    lv_obj_set_size(chart, 200, 150);
    lv_obj_align(chart, LV_ALIGN_CENTER, 0, -10);

    //    lv_chart_set_axis_tick(chart, LV_CHART_AXIS_PRIMARY_Y, 10, 5, 6, 5, true, 40);
    //    lv_chart_set_axis_tick(chart, LV_CHART_AXIS_PRIMARY_X, 10, 5, 10, 1, true, 30);

    lv_obj_add_event_cb(chart, value_changed_event_cb, LV_EVENT_VALUE_CHANGED, NULL);
    lv_obj_refresh_ext_draw_size(chart);

    cursor = lv_chart_add_cursor(chart, lv_palette_main(LV_PALETTE_BLUE), LV_DIR_LEFT | LV_DIR_BOTTOM);

    ser = lv_chart_add_series(chart, lv_palette_main(LV_PALETTE_RED), LV_CHART_AXIS_PRIMARY_Y);
    uint32_t i;
    for(i = 0; i < 10; i++) {
        lv_chart_set_next_value(chart, ser, lv_rand(10, 90));
    }

    //    lv_chart_set_scale_x(chart, 500);

    lv_obj_t * label = lv_label_create(lv_screen_active());
    lv_label_set_text(label, "Click on a point");
    lv_obj_align_to(label, chart, LV_ALIGN_OUT_TOP_MID, 0, -5);
}

#endif

Scatter chart

#include "../../lv_examples.h"
#if LV_USE_CHART && LV_BUILD_EXAMPLES

static void draw_event_cb(lv_event_t * e)
{
    lv_draw_task_t * draw_task = lv_event_get_draw_task(e);
    lv_draw_dsc_base_t * base_dsc = draw_task->draw_dsc;
    if(base_dsc->part == LV_PART_INDICATOR) {
        lv_obj_t * obj = lv_event_get_target(e);
        lv_chart_series_t * ser = lv_chart_get_series_next(obj, NULL);
        lv_draw_rect_dsc_t * rect_draw_dsc = draw_task->draw_dsc;
        uint32_t cnt = lv_chart_get_point_count(obj);

        /*Make older value more transparent*/
        rect_draw_dsc->bg_opa = (LV_OPA_COVER *  base_dsc->id2) / (cnt - 1);

        /*Make smaller values blue, higher values red*/
        int32_t * x_array = lv_chart_get_x_array(obj, ser);
        int32_t * y_array = lv_chart_get_y_array(obj, ser);
        /*dsc->id is the tells drawing order, but we need the ID of the point being drawn.*/
        uint32_t start_point = lv_chart_get_x_start_point(obj, ser);
        uint32_t p_act = (start_point + base_dsc->id2) % cnt; /*Consider start point to get the index of the array*/
        lv_opa_t x_opa = (x_array[p_act] * LV_OPA_50) / 200;
        lv_opa_t y_opa = (y_array[p_act] * LV_OPA_50) / 1000;

        rect_draw_dsc->bg_color = lv_color_mix(lv_palette_main(LV_PALETTE_RED),
                                               lv_palette_main(LV_PALETTE_BLUE),
                                               x_opa + y_opa);
    }
}

static void add_data(lv_timer_t * timer)
{
    LV_UNUSED(timer);
    lv_obj_t * chart = timer->user_data;
    lv_chart_set_next_value2(chart, lv_chart_get_series_next(chart, NULL), lv_rand(0, 200), lv_rand(0, 1000));
}

/**
 * A scatter chart
 */
void lv_example_chart_7(void)
{
    lv_obj_t * chart = lv_chart_create(lv_screen_active());
    lv_obj_set_size(chart, 200, 150);
    lv_obj_align(chart, LV_ALIGN_CENTER, 0, 0);
    lv_obj_add_event_cb(chart, draw_event_cb, LV_EVENT_DRAW_TASK_ADDED, NULL);
    lv_obj_add_flag(chart, LV_OBJ_FLAG_SEND_DRAW_TASK_EVENTS);
    lv_obj_set_style_line_width(chart, 0, LV_PART_ITEMS);   /*Remove the lines*/

    lv_chart_set_type(chart, LV_CHART_TYPE_SCATTER);

    lv_chart_set_range(chart, LV_CHART_AXIS_PRIMARY_X, 0, 200);
    lv_chart_set_range(chart, LV_CHART_AXIS_PRIMARY_Y, 0, 1000);

    lv_chart_set_point_count(chart, 50);

    lv_chart_series_t * ser = lv_chart_add_series(chart, lv_palette_main(LV_PALETTE_RED), LV_CHART_AXIS_PRIMARY_Y);
    uint32_t i;
    for(i = 0; i < 50; i++) {
        lv_chart_set_next_value2(chart, ser, lv_rand(0, 200), lv_rand(0, 1000));
    }

    lv_timer_create(add_data, 100, chart);
}

#endif

API

lv_chart.h