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114 lines
4.8 KiB
Markdown
114 lines
4.8 KiB
Markdown
2 years ago
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# Meter (lv_meter)
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## Overview
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The Meter widget can visualize data in very flexible ways. In can show arcs, needles, ticks lines and labels.
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## Parts and Styles
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- `LV_PART_MAIN` The background of the Meter. Uses the typical background properties.
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- `LV_PART_TICK` The tick lines a labels using the *line* and *text* style properties.
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- `LV_PART_INDICATOR` The needle line or image using the *line* and *img* style properties, as well as the background properties to draw a square (or circle) on the pivot of the needles. Padding makes the square larger.
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- `LV_PART_ITEMS` The arcs using the *arc* properties.
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## Usage
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### Add a scale
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First a *Scale* needs to be added to the Meter with `lv_meter_scale_t * scale = lv_meter_add_scale(meter)`.
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The Scale has minor and major ticks and labels on the major ticks. Later indicators (needles, arcs, tick modifiers) can be added to the meter
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Any number of scales can be added to Meter.
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The minor tick lines can be configured with: `lv_meter_set_scale_ticks(meter, scale, tick_count, line_width, tick_length, ctick_olor)`.
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To add major tick lines use `lv_meter_set_scale_major_ticks(meter, scale, nth_major, tick_width, tick_length, tick_color, label_gap)`. `nth_major` to specify how many minor ticks to skip to draw a major tick.
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Labels are added automatically on major ticks with `label_gap` distance from the ticks with text proportionally to the values of the tick line.
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`lv_meter_set_scale_range(meter, scale, min, max, angle_range, rotation)` sets the value and angle range of the scale.
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### Add indicators
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Indicators need to be added to a Scale and their value is interpreted in the range of the Scale.
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All the indicator add functions return `lv_meter_indicator_t *`.
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#### Needle line
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`indic = lv_meter_add_needle_line(meter, scale, line_width, line_color, r_mod)` adds a needle line to a Scale. By default, the length of the line is the same as the scale's radius but `r_mod` changes the length.
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`lv_meter_set_indicator_value(meter, indic, value)` sets the value of the indicator.
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#### Needle image
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`indic = lv_meter_add_needle_img(meter, scale, img_src, pivot_x, pivot_y)` sets an image that will be used as a needle. `img_src` should be a needle pointing to the right like this `-O--->`.
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`pivot_x` and `pivot_y` sets the pivot point of the rotation relative to the top left corner of the image.
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`lv_meter_set_indicator_value(meter, inidicator, value)` sets the value of the indicator.
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#### Arc
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`indic = lv_meter_add_arc(meter, scale, arc_width, arc_color, r_mod)` adds and arc indicator. . By default, the radius of the arc is the same as the scale's radius but `r_mod` changes the radius.
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`lv_meter_set_indicator_start_value(meter, indic, value)` and `lv_meter_set_indicator_end_value(meter, inidicator, value)` sets the value of the indicator.
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#### Scale lines (ticks)
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`indic = lv_meter_add_scale_lines(meter, scale, color_start, color_end, local, width_mod)` adds an indicator that modifies the ticks lines.
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If `local` is `true` the ticks' color will be faded from `color_start` to `color_end` in the indicator's start and end value range.
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If `local` is `false` `color_start` and `color_end` will be mapped to the start and end value of the scale and only a "slice" of that color gradient will be visible in the indicator's start and end value range.
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`width_mod` modifies the width of the tick lines.
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`lv_meter_set_indicator_start_value(meter, inidicator, value)` and `lv_meter_set_indicator_end_value(meter, inidicator, value)` sets the value of the indicator.
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## Events
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- `LV_EVENT_DRAW_PART_BEGIN` and `LV_EVENT_DRAW_PART_END` is sent for the following types:
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- `LV_METER_DRAW_PART_ARC` The arc indicator
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- `part`: `LV_PART_ITEMS`
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- `sub_part_ptr`: pointer to the indicator
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- `arc_dsc`
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- `radius`: radius of the arc
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- `p1` center of the arc
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- `LV_METER_DRAW_PART_NEEDLE_LINE` The needle lines
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- `part`: `LV_PART_ITEMS`
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- `p1`, `p2` points of the line
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- `line_dsc`
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- `sub_part_ptr`: pointer to the indicator
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- `LV_METER_DRAW_PART_NEEDLE_IMG` The needle images
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- `part`: `LV_PART_ITEMS`
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- `p1`, `p2` points of the line
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- `img_dsc`
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- `sub_part_ptr`: pointer to the indicator
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- `LV_METER_DRAW_PART_TICK` The tick lines and labels
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- `part`: `LV_PART_TICKS`
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- `value`: the value of the line
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- `text`: `value` converted to decimal or `NULL` on minor lines
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- `label_dsc`: label draw descriptor or `NULL` on minor lines
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- `line_dsc`:
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- `id`: the index of the line
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See the events of the [Base object](/widgets/obj) too.
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Learn more about [Events](/overview/event).
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## Keys
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No keys are handled by the Meter widget.
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Learn more about [Keys](/overview/indev).
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## Example
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```eval_rst
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.. include:: ../../../examples/widgets/meter/index.rst
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```
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## API
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```eval_rst
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.. doxygenfile:: lv_meter.h
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:project: lvgl
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```
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