mirror of
https://github.com/lvgl/lvgl.git
synced 2025-01-14 06:42:58 +08:00
84 lines
4.1 KiB
Markdown
84 lines
4.1 KiB
Markdown
```eval_rst
|
|
.. include:: /header.rst
|
|
:github_url: |github_link_base|/widgets/core/label.md
|
|
```
|
|
# Label (lv_label)
|
|
|
|
## Overview
|
|
A label is the basic object type that is used to display text.
|
|
|
|
## Parts and Styles
|
|
- `LV_PART_MAIN` ut uses all the typical background properties and the text properties. The padding values can be used to add space between the text and the background.
|
|
|
|
## Usage
|
|
|
|
### Set text
|
|
You can set the text on a label at runtime with `lv_label_set_text(label, "New text")`.
|
|
It will allocate a buffer dynamically, and the provided string will be copied into that buffer.
|
|
Therefore, you don't need to keep the text you pass to `lv_label_set_text` in scope after that function returns.
|
|
|
|
With `lv_label_set_text_fmt(label, "Value: %d", 15)` printf formatting can be used to set the text.
|
|
|
|
Labels are able to show text from a static character buffer. To do so, use `lv_label_set_text_static(label, "Text")`.
|
|
In this case, the text is not stored in the dynamic memory and the given buffer is used directly instead.
|
|
This means that the array can't be a local variable which goes out of scope when the function exits.
|
|
Constant strings are safe to use with `lv_label_set_text_static` (except when used with `LV_LABEL_LONG_DOT`, as it modifies the buffer in-place), as they are stored in ROM memory, which is always accessible.
|
|
|
|
### New line
|
|
|
|
New line characters are handled automatically by the label object. You can use `\n` to make a line break. For example: `"line1\nline2\n\nline4"`
|
|
|
|
### Long modes
|
|
By default, the width and height of the label is set to `LV_SIZE_CONTENT`therefore the size of the label is automatically expands to the text size.
|
|
Otherwise, if the width or height is explicitly set (useing e.g.`lv_obj_set_width` or a layout), the lines wider than the label's width can be manipulated according to several long mode policies.
|
|
Similary, the policies can be applied if the height of the text is greater than the height of the label.
|
|
- `LV_LABEL_LONG_WRAP` Wrap too long lines. If the height is `LV_SIZE_CONTENT` the label's height will be expanded, elst the text will be clipped. (Default)
|
|
- `LV_LABEL_LONG_DOT` Replaces the last 3 characters from bottom right corner of the label with dots (`.`)
|
|
- `LV_LABEL_LONG_SCROLL` If the text is wider than the label scroll it horizontally back and forth. If it's higher, scroll vertically. Only one direction is scrolled and horizontal scrolling has higher precedence.
|
|
- `LV_LABEL_LONG_SCROLL_CIRCULAR` If the text is wider than the label scroll it horizontally continously. If it's higher, scroll vertically. Only one direction is scrolled and horizontal scrolling has higher precedence.
|
|
- `LV_LABEL_LONG_CLIP` Simply clip the parts of the text outside of the label.
|
|
|
|
You can specify the long mode with `lv_label_set_long_mode(label, LV_LABEL_LONG_...)`
|
|
|
|
Note that `LV_LABEL_LONG_DOT` manipulates the text buffer in-place in order to add/remove the dots.
|
|
When `lv_label_set_text` or `lv_label_set_array_text` are used, a separate buffer is allocated and this implementation detail is unnoticed.
|
|
This is not the case with `lv_label_set_text_static`. The buffer you pass to `lv_label_set_text_static` must be writable if you plan to use `LV_LABEL_LONG_DOT`.
|
|
|
|
### Text recolor
|
|
In the text, you can use commands to recolor parts of the text. For example: `"Write a #ff0000 red# word"`.
|
|
This feature can be enabled individually for each label by `lv_label_set_recolor()` function.
|
|
|
|
### Very long texts
|
|
LVGL can efficiently handle very long (e.g. > 40k characters) by saving some extra data (~12 bytes) to speed up drawing. To enable this feature, set `LV_LABEL_LONG_TXT_HINT 1` in `lv_conf.h`.
|
|
|
|
### Symbols
|
|
The labels can display symbols alongside letters (or on their own). Read the [Font](/overview/font) section to learn more about the symbols.
|
|
|
|
## Events
|
|
No special event's are send by the Label.
|
|
|
|
Learn more about [Events](/overview/event).
|
|
|
|
## Keys
|
|
No *Keys* are processed by the object type.
|
|
|
|
Learn more about [Keys](/overview/indev).
|
|
|
|
## Example
|
|
|
|
```eval_rst
|
|
|
|
.. include:: ../../../examples/widgets/label/index.rst
|
|
|
|
```
|
|
|
|
## API
|
|
|
|
```eval_rst
|
|
|
|
.. doxygenfile:: lv_label.h
|
|
:project: lvgl
|
|
|
|
```
|
|
|