1```eval_rst 2.. include:: /header.rst 3:github_url: |github_link_base|/widgets/extra/chart.md 4``` 5# Chart (lv_chart) 6 7## Overview 8 9Charts 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. 10 11Charts can have: 12- division lines 13- 2 y axis 14- axis ticks and texts on ticks 15- cursors 16- scrolling and zooming 17 18## Parts and Styles 19- `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. 20- `LV_PART_SCROLLBAR` The scrollbar used if the chart is zoomed. See the [Base object](/widgets/obj)'s documentation for details. 21- `LV_PART_ITEMS` Refers to the line or bar series. 22 - Line chart: The *line* properties are used by the lines. `width`, `height`, `bg_color` and `radius` is used to set the appearance of points. 23 - Bar chart: The typical background properties are used to style the bars. 24- `LV_PART_INDICATOR` Refers to the points on line and scatter chart (small circles or squares). 25- `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. 26- `LV_PART_TICKS` *Line* and *Text* style properties are used to style the ticks 27 28## Usage 29 30 31### Chart type 32The following data display types exist: 33- `LV_CHART_TYPE_NONE` Do not display any data. Can be used to hide the series. 34- `LV_CHART_TYPE_LINE` Draw lines between the data points and/or points (rectangles or circles) on the data points. 35- `LV_CHART_TYPE_BAR` - Draw bars. 36- `LV_CHART_TYPE_SCATTER` - X/Y chart drawing point's and lines between the points. . 37 38You can specify the display type with `lv_chart_set_type(chart, LV_CHART_TYPE_...)`. 39 40 41### Data series 42You 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. 43`axis` can have the following values: 44- `LV_CHART_AXIS_PRIMARY_Y` Left axis 45- `LV_CHART_AXIS_SECONDARY_Y` Right axis 46- `LV_CHART_AXIS_PRIMARY_X` Bottom axis 47- `LV_CHART_AXIS_SECONDARY_X` Top axis 48 49 50`axis` tells which axis's range should be used te scale the values. 51 52`lv_chart_set_ext_y_array(chart, ser, value_array)` makes the chart use an external array for the given series. 53`value_array` should look like this: `lv_coord_t * value_array[num_points]`. The array size needs to be large enough to hold all the points of that series. 54The array's pointer will be saved in the chart so it needs to be global, static or dynamically allocated. 55Note: you should call `lv_chart_refresh(chart)` after the external data source has been updated to update the chart. 56 57The 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 array*s. 58 59For `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. 60 61### Modify the data 62You have several options to set the data of series: 631. Set the values manually in the array like `ser1->points[3] = 7` and refresh the chart with `lv_chart_refresh(chart)`. 642. Use `lv_chart_set_value_by_id(chart, ser, id, value)` where `id` is the index of the point you wish to update. 653. Use the `lv_chart_set_next_value(chart, ser, value)`. 664. Initialize all points to a given value with: `lv_chart_set_all_value(chart, ser, value)`. 67 68Use `LV_CHART_POINT_NONE` as value to make the library skip drawing that point, column, or line segment. 69 70For `LV_CHART_TYPE_SCATTER` type `lv_chart_set_value_by_id2(chart, ser, id, value)` and `lv_chart_set_next_value2(chart, ser, x_valuem y_value)` can be used as well. 71 72 73### Update modes 74`lv_chart_set_next_value` can behave in two ways depending on *update mode*: 75- `LV_CHART_UPDATE_MODE_SHIFT` Shift old data to the left and add the new one to the right. 76- `LV_CHART_UPDATE_MODE_CIRCULAR` - Add the new data in circular fashion, like an ECG diagram. 77 78The update mode can be changed with `lv_chart_set_update_mode(chart, LV_CHART_UPDATE_MODE_...)`. 79 80### Number of points 81The number of points in the series can be modified by `lv_chart_set_point_count(chart, point_num)`. The default value is 10. 82Note: 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. 83 84#### Handling large number of points 85On 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. 86If 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. 87 88### Vertical range 89You can specify the minimum and maximum values in y-direction with `lv_chart_set_range(chart, axis, min, max)`. 90`axis` can be `LV_CHART_AXIS_PRIMARY` (left axis) or `LV_CHART_AXIS_SECONDARY` (right axis). 91 92The value of the points will be scaled proportionally. The default range is: 0..100. 93 94### Division lines 95The number of horizontal and vertical division lines can be modified by `lv_chart_set_div_line_count(chart, hdiv_num, vdiv_num)`. 96The default settings are 3 horizontal and 5 vertical division lines. 97If 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. 98 99### Override default start point for series 100If 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 101index with the function `lv_chart_set_x_start_point(chart, ser, id)` where `id` is the new index position to start plotting from. 102 103Note that `LV_CHART_UPDATE_MODE_SHIFT` also changes the `start_point`. 104 105### Tick marks and labels 106Ticks and labels can be added to the axis with `lv_chart_set_axis_tick(chart, axis, major_len, minor_len, major_cnt, minor_cnt, label_en, draw_size)`. 107- `axis` can be `LV_CHART_AXIS_X/PRIMARY_Y/SECONDARY_Y` 108- `major_len` is the length of major ticks 109- `minor_len` is the length of minor ticks 110- `major_cnt` is the number of major ticks on the axis 111- `minor_cnt` in the number of minor ticks between two major ticks 112- `label_en` `true`: enable label drawing on major ticks 113- `draw_size` extra size required to draw the tick and labels (start with 20 px and increase if the ticks/labels are clipped) 114 115### Zoom 116The chart can be zoomed independently in x and y directions with `lv_chart_set_zoom_x(chart, factor)` and `lv_chart_set_zoom_y(chart, factor)`. 117If `factor` is 256 there is no zoom. 512 means double zoom, etc. Fractional values are also possible but < 256 value is not allowed. 118 119 120### Cursor 121 122A cursor can be added with `lv_chart_cursor_t * c1 = lv_chart_add_cursor(chart, color, dir);`. 123The 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. 124 125`lv_chart_set_cursor_pos(chart, cursor, &point)` sets the position of the cursor. 126`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. 127 128`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. 129 130`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. 131 132## Events 133- `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. 134- `LV_EVENT_DRAW_PART_BEGIN` and `LV_EVENT_DRAW_PART_END` are sent with the following types: 135 - `LV_CHART_DRAW_PART_DIV_LINE_INIT` Used before/after drawn the div lines to add masks to any extra drawings. The following fields are set: 136 - `part`: `LV_PART_MAIN` 137 - `line_dsc` 138 - `LV_CHART_DRAW_PART_DIV_LINE_HOR`, `LV_CHART_DRAW_PART_DIV_LINE_VER` Used for each horizontal and vertical division lines. 139 - `part`: `LV_PART_MAIN` 140 - `id`: index of the line 141 - `p1`, `p2`: points of the line 142 - `line_dsc` 143 - `LV_CHART_DRAW_PART_LINE_AND_POINT` Used on line and scatter charts for lines and points. 144 - `part`: `LV_PART_ITEMS` 145 - `id`: index of the point 146 - `value`: value of `id`th point 147 - `p1`, `p2`: points of the line 148 - `draw_area`: area of the point 149 - `line_dsc` 150 - `rect_dsc` 151 - `sub_part_ptr`: pointer to the series 152 - `LV_CHART_DRAW_PART_BAR` Used on bar charts for the rectangles. 153 - `part`: `LV_PART_ITEMS` 154 - `id`: index of the point 155 - `value`: value of `id`th point 156 - `draw_area`: area of the point 157 - `rect_dsc`: 158 - `sub_part_ptr`: pointer to the series 159 - `LV_CHART_DRAW_PART_CURSOR` Used on cursor lines and points. 160 - `part`: `LV_PART_CURSOR` 161 - `p1`, `p2`: points of the line 162 - `line_dsc` 163 - `rect_dsc` 164 - `draw_area`: area of the points 165 - `LV_CHART_DRAW_PART_TICK_LABEL` Used on tick lines and labels. 166 - `part`: `LV_PART_TICKS` 167 - `id`: axis 168 - `value`: value of the tick 169 - `text`: `value` converted to decimal or `NULL` for minor ticks 170 - `line_dsc`, 171 - `label_dsc`, 172 173See the events of the [Base object](/widgets/obj) too. 174 175Learn more about [Events](/overview/event). 176 177## Keys 178No *Keys* are processed by the object type. 179 180Learn more about [Keys](/overview/indev). 181 182## Example 183 184```eval_rst 185 186.. include:: ../../../examples/widgets/chart/index.rst 187 188``` 189 190## API 191 192```eval_rst 193 194.. doxygenfile:: lv_chart.h 195 :project: lvgl 196 197``` 198
