lvgl/docs/widgets/core/btnmatrix.md

```eval_rst
.. include:: /header.rst 
:github_url: |github_link_base|/widgets/btnmatrix.md
```
# Button matrix (lv_btnmatrix)

## Overview

The Button Matrix objects can display multiple buttons in rows and columns.

The Button matrix object is very light weighted because the buttons are not created just virtually drawn on the fly.
This way, 1 button use only 8 extra bytes instead of the ~100-150 byte size of a normal [Button](/widgets/core/btn) object and other ~100 byte for the size of the [Label](/widgets/core/label) object.

The Button matrix is added to the deafult group (if it is set). Besides the Button matrix is an editable object to allow selecting and clicing the buttons with encoder navigation too.

## Parts and Styles
- `LV_PART_MAIN` The bacground of the button matrix. It uses the typical background style properties. `pad_row` and `pad_column` sets the space between the buttons.
- `LV_PART_ITEMS` The buttons and they all use the text and typical background style properties expect translations and transformations. 

## Usage

### Button's text
There is a text on each button. To specify them a descriptor string array, called *map*, needs to be used.
The map can be set with `lv_btnmatrix_set_map(btnm, my_map)`.
The declaration of a map should look like `const char * map[] = {"btn1", "btn2", "btn3", NULL}`.
Note that, the last element has to be `NULL` or an empty string (`""`)!  

Use `"\n"` in the map  to make **line break**. E.g. `{"btn1", "btn2", "\n", "btn3", ""}`. Each line's buttons have their width calculated automatically.
So in the example the first row will have 2 buttons each with 50% width and a second row with 1 button having 100% width.

### Control buttons
The buttons' width can be set relative to the other button in the same row with `lv_btnmatrix_set_btn_width(btnm, btn_id, width)`
E.g. in a line with two buttons: *btnA, width = 1* and *btnB, width = 2*, *btnA* will have 33 % width and *btnB* will have 66 % width. 
It's similar to how the [`flex-grow`](https://developer.mozilla.org/en-US/docs/Web/CSS/flex-grow) property works in CSS.
The width's value mus be in the \[1..7\] range and the deafult width is 1.

In addition to the width, each button can be customized with the following parameters:
- `LV_BTNMATRIX_CTRL_HIDDEN` Makes a button hidden (hidden buttons still take up space in the layout, they are just not visible or clickable)
- `LV_BTNMATRIX_CTRL_NO_REPEAT` Disable repeating when the button is long pressed
- `LV_BTNMATRIX_CTRL_DISABLED` Makes a button disabled Like `LV_STATE_DISABLED` on normal objects
- `LV_BTNMATRIX_CTRL_CHECKABLE` Enable toggling of a button. I.e. `LV_STATE_CHECHED` will be added/removed as the button is clicked
- `LV_BTNMATRIX_CTRL_CHECKED` MAke the button checked. It will use the `LV_STATE_CHECHKED` styles.
- `LV_BTNMATRIX_CTRL_CLICK_TRIG` Enabled: send LV_EVENT_VALUE_CHANGE on CLICK, Disabled: send LV_EVENT_VALUE_CHANGE on PRESS*/
- `LV_BTNMATRIX_CTRL_RECOLOR` Enable recoloring of button texts with `#`. E.g. `"It's #ff0000 red#"`
- `LV_BTNMATRIX_CTRL_CUSTOM_1` Custom free to use flag
- `LV_BTNMATRIX_CTRL_CUSTOM_2` Custom free to use flag

By deafult all flags are disabled.

To set or clear a button's control attribute, use `lv_btnmatrix_set_btn_ctrl(btnm, btn_id, LV_BTNM_CTRL_...)` and 
`lv_btnmatrix_clear_btn_ctrl(btnm, btn_id, LV_BTNMATRIX_CTRL_...)` respectively. More `LV_BTNM_CTRL_...` values can be OR-ed

To set/clear the same control attribute for all buttons of a button matrix, use `lv_btnmatrix_set_btn_ctrl_all(btnm, btn_id, LV_BTNM_CTRL_...)` and 
`lv_btnmatrix_clear_btn_ctrl_all(btnm, btn_id, LV_BTNMATRIX_CTRL_...)`.

The set a control map for a button matrix (similarly to the map for the text), use `lv_btnmatrix_set_ctrl_map(btnm, ctrl_map)`.
An element of `ctrl_map` should look like `ctrl_map[0] = width | LV_BTNM_CTRL_NO_REPEAT |  LV_BTNM_CTRL_CHECHKABLE`. 
The number of elements should be equal to the number of buttons (excluding newlines characters).

### One check
The "One check" feature can be enabled with `lv_btnmatrix_set_one_check(btnm, true)` to allow only one button to be checked at once.

## Events
- `LV_EVENT_VALUE_CHANGED` Sent when a button is pressed/released or repeated after long press. The event paramter is set to the ID of the pressed/released button.
- `LV_EVENT_DRAW_PART_BEGIN` and `LV_EVENT_DRAW_PART_END` are sent for both the main and the items (buttons) parts to allow hooking the drawing. 
The for more detail on the main part see the [Base object](/widgets/obj#events)'s documentation.
For the buttons the following fields are used: `clip_area`, `draw_area`, `rect_dsc`, `rect_dsc`, `part`, `id` (index of the button being drawn). 

`lv_btnmatrix_get_selected_btn(btnm)` returns the index of the lastly pressed, released or focused button or `LV_BTNMATRIX_BTN_NONE` if no such button.

`lv_btnmatrix_get_btn_text(btnm, btn_id)` returns a pointer to the text of `btn_id`th button.

Learn more about [Events](/overview/event).

## Keys
- `LV_KEY_RIGHT/UP/LEFT/RIGHT` To navigate among the buttons to select one
- `LV_KEY_ENTER` To press/release the selected button

Learn more about [Keys](/overview/indev).

## Example

```eval_rst

.. include:: ../../../examples/widgets/btnmatrix/index.rst

```

## API

```eval_rst

.. doxygenfile:: lv_btnmatrix.h
  :project: lvgl

```