1# Button matrix (lv_btnmatrix)
2
3## Overview
4
5The Button Matrix object is a lightweight way to display multiple buttons in rows and columns. Lightweight because the buttons are not actually created but just virtually drawn on the fly. This way, one button use only eight extra bytes of memory instead of the ~100-150 bytes a normal [Button](/widgets/core/btn) object plus the 100 or so bytes for the [Label](/widgets/core/label) object.
6
7The Button matrix is added to the default group (if one is set). Besides the Button matrix is an editable object to allow selecting and clicking the buttons with encoder navigation too.
8
9## Parts and Styles
10- `LV_PART_MAIN` The background of the button matrix, uses the typical background style properties. `pad_row` and `pad_column` sets the space between the buttons.
11- `LV_PART_ITEMS` The buttons all use the text and typical background style properties except translations and transformations.
12
13## Usage
14
15### Button's text
16There is a text on each button. To specify them a descriptor string array, called *map*, needs to be used.
17The map can be set with `lv_btnmatrix_set_map(btnm, my_map)`.
18The declaration of a map should look like `const char * map[] = {"btn1", "btn2", "btn3", NULL}`.
19Note that the last element has to be either `NULL` or an empty string (`""`)!
20
21Use `"\n"` in the map to insert a **line break**. E.g. `{"btn1", "btn2", "\n", "btn3", ""}`. Each line's buttons have their width calculated automatically.
22So in the example the first row will have 2 buttons each with 50% width and a second row with 1 button having 100% width.
23
24### Control buttons
25The buttons' width can be set relative to the other button in the same row with `lv_btnmatrix_set_btn_width(btnm, btn_id, width)`
26E.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.
27It's similar to how the [`flex-grow`](https://developer.mozilla.org/en-US/docs/Web/CSS/flex-grow) property works in CSS.
28The width must be in the \[1..15\] range and the default width is 1.
29
30In addition to the width, each button can be customized with the following parameters:
31- `LV_BTNMATRIX_CTRL_HIDDEN` Makes a button hidden (hidden buttons still take up space in the layout, they are just not visible or clickable)
32- `LV_BTNMATRIX_CTRL_NO_REPEAT` Disable repeating when the button is long pressed
33- `LV_BTNMATRIX_CTRL_DISABLED` Makes a button disabled Like `LV_STATE_DISABLED` on normal objects
34- `LV_BTNMATRIX_CTRL_CHECKABLE` Enable toggling of a button. I.e. `LV_STATE_CHECHED` will be added/removed as the button is clicked
35- `LV_BTNMATRIX_CTRL_CHECKED` Make the button checked. It will use the `LV_STATE_CHECHKED` styles.
36- `LV_BTNMATRIX_CTRL_CLICK_TRIG` Enabled: send LV_EVENT_VALUE_CHANGE on CLICK, Disabled: send LV_EVENT_VALUE_CHANGE on PRESS
37- `LV_BTNMATRIX_CTRL_POPOVER` Show the button label in a popover when pressing this key
38- `LV_BTNMATRIX_CTRL_RECOLOR` Enable recoloring of button texts with `#`. E.g. `"It's #ff0000 red#"`
39- `LV_BTNMATRIX_CTRL_CUSTOM_1` Custom free to use flag
40- `LV_BTNMATRIX_CTRL_CUSTOM_2` Custom free to use flag
41
42By default, all flags are disabled.
43
44To set or clear a button's control attribute, use `lv_btnmatrix_set_btn_ctrl(btnm, btn_id, LV_BTNM_CTRL_...)` and
45`lv_btnmatrix_clear_btn_ctrl(btnm, btn_id, LV_BTNMATRIX_CTRL_...)` respectively. More `LV_BTNM_CTRL_...` values can be OR-ed
46
47To set/clear the same control attribute for all buttons of a button matrix, use `lv_btnmatrix_set_btn_ctrl_all(btnm, LV_BTNM_CTRL_...)` and
48`lv_btnmatrix_clear_btn_ctrl_all(btnm, LV_BTNMATRIX_CTRL_...)`.
49
50The set a control map for a button matrix (similarly to the map for the text), use `lv_btnmatrix_set_ctrl_map(btnm, ctrl_map)`.
51An element of `ctrl_map` should look like `ctrl_map[0] = width | LV_BTNM_CTRL_NO_REPEAT |  LV_BTNM_CTRL_CHECHKABLE`.
52The number of elements should be equal to the number of buttons (excluding newlines characters).
53
54### One check
55The "One check" feature can be enabled with `lv_btnmatrix_set_one_checked(btnm, true)` to allow only one button to be checked at a time.
56
57## Events
58- `LV_EVENT_VALUE_CHANGED` Sent when a button is pressed/released or repeated after long press. The event parameter is set to the ID of the pressed/released button.
59- `LV_EVENT_DRAW_PART_BEGIN` and `LV_EVENT_DRAW_PART_END` are sent for the following types:
60    - `LV_BTNMATRIX_DRAW_PART_BTN` The individual buttons.
61        - `part`: `LV_PART_ITEMS`
62        - `id`:index of the button being drawn
63        - `draw_area`: the area of teh button
64        - `rect_dsc`
65
66See the events of the [Base object](/widgets/obj) too.
67
68`lv_btnmatrix_get_selected_btn(btnm)` returns the index of the most recently released or focused button or `LV_BTNMATRIX_BTN_NONE` if no such button.
69
70`lv_btnmatrix_get_btn_text(btnm, btn_id)` returns a pointer to the text of `btn_id`th button.
71
72Learn more about [Events](/overview/event).
73
74## Keys
75- `LV_KEY_RIGHT/UP/LEFT/RIGHT` To navigate among the buttons to select one
76- `LV_KEY_ENTER` To press/release the selected button
77
78Learn more about [Keys](/overview/indev).
79
80## Example
81
82```eval_rst
83
84.. include:: ../../../examples/widgets/btnmatrix/index.rst
85
86```
87
88## API
89
90```eval_rst
91
92.. doxygenfile:: lv_btnmatrix.h
93  :project: lvgl
94
95```
96