# Barcode (/libs/barcode)
The LVGL Barcode utility enables you to generate Code-128 bar codes. It uses the
[code128](https://github.com/fhunleth/code128) library by
[fhunleth](https://github.com/fhunleth).
Usage [#usage]
Set to `1` in `lv_conf.h`.
Use to create a barcode object, and use
to set the data to encode.
Call to adjust scaling,
call and
adjust colors. Call to set the bar code's
orientation.
By default, encoding is used
and strips `[FCN1]` and spaces. Optionally use
to set
.
These can all be called in any order, before or after the data. The Widget keeps a copy of
the data - costing its length in bytes - so any change, including a resize, regenerates the
bars automatically.
Update mode [#update-mode]
Every change except the colors regenerates the bars.
chooses when:
* `LV_BARCODE_UPDATE_MODE_IMMEDIATE` (default) regenerates inside the setter.
* `LV_BARCODE_UPDATE_MODE_DEFERRED` marks the bars out of date instead, so several changes
collapse into one regeneration. Call when done - it
regenerates from the stored data and returns the result.
```c title=" " lineNumbers=1
lv_barcode_set_update_mode(barcode, LV_BARCODE_UPDATE_MODE_DEFERRED);
lv_barcode_set_scale(barcode, 2);
lv_barcode_set_direction(barcode, LV_DIR_VER);
lv_barcode_render(barcode); /* generate once, here, and get the result */
```
Forgetting that call still gives the right bitmap - the redraw fills the bars in and warns -
but the work lands on that refresh and no caller is left to see a failure.
Two things to know about deferred mode:
* The canvas is resized in the setter in both modes, because the draw pass cannot
reallocate it. Only the fill is deferred.
* obeys the mode too, so in deferred mode its return
value reports only the resize.
Switching back to `LV_BARCODE_UPDATE_MODE_IMMEDIATE` while out of date also regenerates, but
that setter returns `void`, so a failure is only logged. Render first to get the result.
Detecting a failed regeneration [#detecting-a-failed-regeneration]
returns its result, and so does
in immediate mode. The rest cannot: the property
setters return `void`, resizes happen in an event handler, and a deferred fill happens in
the draw pass. covers those:
```c title=" " lineNumbers=1
lv_obj_set_height(barcode, 0); /* leaves no room for a horizontal barcode */
if(!lv_barcode_is_render_valid(barcode)) {
/* the bitmap is blank; give the object a height */
}
```
It is also `false` before any data is set. A failure is not retried every redraw - only a
change makes the Widget try again, and that change sets the flag back to `true` before the
new attempt runs. So `true` means "no known failure", not "the bitmap is up to date"; in
deferred mode a pending regeneration is also `true`.
Notes [#notes]
* It is best not to manually set the width of the barcode, because when
the width of the Widget is lower than the width of the barcode, the
display will be incomplete due to truncation.
* A horizontal barcode is as tall as the Widget and a vertical one as wide, so that
dimension must be set. Until it is, nothing can be generated - but the data is
remembered, so the barcode appears once the Widget has a size.
* The scale adjustment can only be an integer multiple, for example,
means 2x scaling.
* The direction setting can be or .
* Changing the color (dark or light) only updates the palette, so it is cheap
and never regenerates the bars.
Example [#example]
Create a Barcode [#create-a-barcode]