docs/src/widgets/textarea.rst
.. _lv_textarea:
Overview
The Text Area is a :ref:base_widget with a :ref:lv_label and a cursor on
it. Text or characters can be added to it. Long lines are wrapped and when the
text becomes long enough, the Text Area can be scrolled.
One-line mode and password modes are supported.
.. _lv_textarea_parts_and_styles:
Parts and Styles
LV_PART_MAIN The background of the Text Area; uses the
:ref:typical background style properties <typical bg props> and the text related
style properties including text_align to align the text to the left,
right or center.LV_PART_SCROLLBAR The scrollbar that is shown when the text is
longer than its height.LV_PART_SELECTED Determines the style of the :ref:selected text <lv_label_text_selection>. Only text_color and
bg_color style properties can be used. bg_color should be set
directly on the label of the Text Area.LV_PART_CURSOR Marks the position where the characters are
inserted. The cursor's area is always the bounding box of the current
character. A block cursor can be created by adding a background color
and background opacity to :cpp:enumerator:LV_PART_CURSOR\ 's style. To create
a "bar" cursor leave the cursor transparent and set a left border. The
anim_time style property sets the cursor's blink time.LV_PART_TEXTAREA_PLACEHOLDER Unique to Text Area; allows styling
the :ref:placeholder text <textarea_placeholder_text>... _lv_textarea_usage:
Usage
You can insert text or characters to the current cursor's position with:
lv_textarea_add_char(textarea, 'c')lv_textarea_add_text(textarea, "insert this text")To add wide characters like 'á', 'ß' or CJK characters, use
:cpp:expr:lv_textarea_add_text(textarea, "á").
:cpp:expr:lv_textarea_set_text(textarea, "New text") replaces all existing text
with "New text".
.. _textarea_placeholder_text:
Placeholder text is text that is displayed when the Text Area is empty. This can be a handy way to provide the end user with a hint about what to type there.
Specify placeholder text using
:cpp:expr:lv_textarea_set_placeholder_text(textarea, "Placeholder text").
To delete the character to the left of the current cursor position, use
:cpp:expr:lv_textarea_delete_char(textarea).
To delete to the right, use :cpp:expr:lv_textarea_delete_char_forward(textarea)
The cursor position can be modified programmatically using
:cpp:expr:lv_textarea_set_cursor_pos(textarea, cursor_pos) where cursor_pos is
the zero-based index of the character the cursor should be placed in front of.
:cpp:enumerator:LV_TEXTAREA_CURSOR_LAST can be passed to mean "after the
last character"
You can move the cursor one character-position (or line) at a time with
lv_textarea_cursor_right(textarea)lv_textarea_cursor_left(textarea)lv_textarea_cursor_up(textarea)lv_textarea_cursor_down(textarea)If :cpp:expr:lv_textarea_set_cursor_click_pos(textarea, true) is applied, the
cursor will jump to the position where the Text Area was clicked.
The cursor is normally always visible. It can be a good idea to style it
to be visible only in :cpp:enumerator:LV_STATE_FOCUSED state. See :ref:styles
for more information about how to do this.
The Text Area can be configured to keep all text on a single line with
:cpp:expr:lv_textarea_set_one_line(textarea, true). In this mode:
The Text Area supports password mode which can be enabled with
:cpp:expr:lv_textarea_set_password_mode(textarea, true).
By default, if the • (Bullet, U+2022 <https://www.fileformat.info/info/unicode/char/2022/index.htm>__)
character exists in the font, the entered characters are converted to it after
a configurable delay after each new character is entered. If • does not
exist in the font, * will be used. You can override the default
"masking" character with :cpp:expr:lv_textarea_set_password_bullet(textarea, str)
where str is a NUL-terminated C string. Example:
.. code-block:: c
lv_textarea_set_password_bullet(textarea, "x");
In password mode :cpp:expr:lv_textarea_get_text(textarea) returns the actual
text entered, not the bullet characters.
The visibility time can be adjusted with :c:macro:LV_TEXTAREA_DEF_PWD_SHOW_TIME in lv_conf.h.
You can set a list of accepted characters with
:cpp:expr:lv_textarea_set_accepted_chars(textarea, list) or
:cpp:expr:lv_textarea_set_accepted_chars_static(textarea, list) where list is a
pointer to a NUL-terminated string, or NULL to accept all characters. Characters
entered not in this list will be ignored.
.. code-block:: c
lv_textarea_set_accepted_chars(textarea, "0123456789.+-");
The maximum number of characters can be limited using
:cpp:expr:lv_textarea_set_max_length(textarea, max_char_num).
If the text in the Text Area is very long (e.g. > 20k characters), scrolling and
drawing might be slow. However, by setting :c:macro:LV_LABEL_LONG_TXT_HINT in
lv_conf.h to a non-zero value, the performance with long text is significantly
improved. It does this by saving some additional information about the current
vertical position of the text shown. With this mode configured, scrolling and drawing
is as fast as with "normal" short text. The cost is 12 extra bytes per label in RAM.
This value is set to 1 by default. If you do not use long text, you can save
12 bytes per label by setting it to 0.
If :c:macro:LV_LABEL_TEXT_SELECTION is set to a non-zero value in lv_conf.h,
some additional functionality (and 8 bytes per label) are added to Label Widgets
and Text Area Widgets, and text-selection functionality is automated in Text Area
Widgets. (If you do not use selected text in your application, you can save 8 bytes
per label in RAM by setting that macro to equate to 0.)
Any part of the text can be selected if enabled with
:cpp:expr:lv_textarea_set_text_selection(textarea, true). This works much like
when you select text on your PC by clicking and dragging with your mouse or other
pointer input device. If you pass false to this function to disable text
selection, any text selected time of the call will be de-selected.
Shift+click and keyboard-only text selection with Shift+Arrow keys is expected to be added in the future.
If you need to programmatically deal with selected text, in addition to the
:cpp:expr:lv_textarea_set_text_selection(textarea, enable) function, the following
is your tool set for doing so. (ta_label is a pointer to the Text Area's
Label retrieved with ta_label = lv_textarea_get_label(textarea);.)
lv_textarea_get_text_selection(textarea) tells whether text selection is enabled.lv_textarea_text_is_selected(textarea) tells whether any text is currently selected.lv_textarea_clear_selection(textarea) clears current text selection.lv_label_set_text_selection_start(ta_label, index) where index is
the zero-based index of the first character of the selected text.
Pass :c:macro:LV_DRAW_LABEL_NO_TXT_SEL to specify no text selected.lv_label_set_text_selection_end(ta_label, index) where index is
the zero-based index of the character just after the selected text.
Pass :c:macro:LV_DRAW_LABEL_NO_TXT_SEL to specify no text selected.lv_label_get_text_selection_start(ta_label) zero-based index of the
first character of the selected text.
:c:macro:LV_DRAW_LABEL_NO_TXT_SEL indicates no text selected.lv_label_get_text_selection_end(ta_label) zero-based index of the
character just after the selected text.
:c:macro:LV_DRAW_LABEL_NO_TXT_SEL indicates no text selected.Normally you won't need these since Text Area automates the text selection process, but if you do need to change the selection programmatically, the above are your tools to do so.
.. _lv_textarea_events:
Events
LV_EVENT_INSERT Sent right before a character or text is
inserted. The event parameter is the text about to be inserted.
:cpp:expr:lv_textarea_set_insert_replace(textarea, "New text") can be called
from within that event to replace the text to be inserted. The contents of the
buffer passed must be survive long enough for the call to lv_timer_handler()
that is driving the event to return (after which the Text Area's label will have
copied the text). So it should not be a local buffer (created on the stack)
where its contents will be destroyed before that happens. Passing "" means "do
not insert anything".LV_EVENT_VALUE_CHANGED Sent when the content of the Text Area
has changed.LV_EVENT_READY Sent when :cpp:enumerator:LV_KEY_ENTER is
pressed (or sent) to a one-line Text Area... admonition:: Further Reading
Learn more about :ref:`lv_obj_events` emitted by all Widgets.
Learn more about :ref:`events`.
.. _lv_textarea_keys:
Keys
LV_KEY_UP/DOWN/LEFT/RIGHT Move the cursorAny character Add the character to the current cursor position.. admonition:: Further Reading
Learn more about :ref:`indev_keys`.
.. _lv_textarea_example:
Examples
.. include:: /examples/widgets/textarea/index.rst
.. _lv_textarea_api:
API