Baji_Rtc_Toy/managed_components/lvgl__lvgl/docs/layouts/grid.md

Grid

Overview

The Grid layout is a subset of CSS Flexbox.

It can arrange items into a 2D "table" that has rows or columns (tracks). The item can span through multiple columns or rows. The track's size can be set in pixel, to the largest item (LV_GRID_CONTENT) or in "Free unit" (FR) to distribute the free space proportionally.

To make an object a grid container call lv_obj_set_layout(obj, LV_LAYOUT_GRID).

Note that the grid layout feature of LVGL needs to be globally enabled with LV_USE_GRID in lv_conf.h.

Terms

• tracks: the rows or columns
• free unit (FR): if set on track's size is set in FR it will grow to fill the remaining space on the parent.
• gap: the space between the rows and columns or the items on a track

Simple interface

With the following functions you can easily set a Grid layout on any parent.

Grid descriptors

First you need to describe the size of rows and columns. It can be done by declaring 2 arrays and the track sizes in them. The last element must be LV_GRID_TEMPLATE_LAST.

For example:

static lv_coord_t column_dsc[] = {100, 400, LV_GRID_TEMPLATE_LAST};   /*2 columns with 100 and 400 ps width*/
static lv_coord_t row_dsc[] = {100, 100, 100, LV_GRID_TEMPLATE_LAST}; /*3 100 px tall rows*/

To set the descriptors on a parent use lv_obj_set_grid_dsc_array(obj, col_dsc, row_dsc).

Besides simple settings the size in pixel you can use two special values:

• LV_GRID_CONTENT set the width to the largest children on this track
• LV_GRID_FR(X) tell what portion of the remaining space should be used by this track. Larger value means larger space.

Grid items

By default, the children are not added to the grid. They need to be added manually to a cell.

To do this call lv_obj_set_grid_cell(child, column_align, column_pos, column_span, row_align, row_pos, row_span).

column_align and row_align determine how to align the children in its cell. The possible values are:

• LV_GRID_ALIGN_START means left on a horizontally and top vertically. (default)
• LV_GRID_ALIGN_END means right on a horizontally and bottom vertically
• LV_GRID_ALIGN_CENTER simply center

colum_pos and row_pos means the zero based index of the cell into the item should be placed.

colum_span and row_span means how many tracks should the item involve from the start cell. Must be > 1.

Grid align

If there are some empty space the track can be aligned several ways:

• LV_GRID_ALIGN_START means left on a horizontally and top vertically. (default)
• LV_GRID_ALIGN_END means right on a horizontally and bottom vertically
• LV_GRID_ALIGN_CENTER simply center
• LV_GRID_ALIGN_SPACE_EVENLY items are distributed so that the spacing between any two items (and the space to the edges) is equal. Not applies to track_cross_place.
• LV_GRID_ALIGN_SPACE_AROUND items are evenly distributed in the track with equal space around them. Note that visually the spaces aren’t equal, since all the items have equal space on both sides. The first item will have one unit of space against the container edge, but two units of space between the next item because that next item has its own spacing that applies. Not applies to track_cross_place.
• LV_GRID_ALIGN_SPACE_BETWEEN items are evenly distributed in the track: first item is on the start line, last item on the end line. Not applies to track_cross_place.

To set the track's alignment use lv_obj_set_grid_align(obj, column_align, row_align).

Style interface

All the Grid related values are style properties under the hood and you can use them similarly to any other style properties. The following Grid related style properties exist:

• GRID_COLUMN_DSC_ARRAY
• GRID_ROW_DSC_ARRAY
• GRID_COLUMN_ALIGN
• GRID_ROW_ALIGN
• GRID_CELL_X_ALIGN
• GRID_CELL_COLUMN_POS
• GRID_CELL_COLUMN_SPAN
• GRID_CELL_Y_ALIGN
• GRID_CELL_ROW_POS
• GRID_CELL_ROW_SPAN

Internal padding

To modify the minimum space Grid inserts between objects, the following properties can be set on the Grid container style:

• pad_row Sets the padding between the rows.
• pad_column Sets the padding between the columns.

Other features

RTL

If the base direction of the container is set to LV_BASE_DIR_RTL, the meaning of LV_GRID_ALIGN_START and LV_GRID_ALIGN_END is swapped. I.e. START will mean right-most.

The columns will be placed from right to left.

Example

.. include:: ../../examples/layouts/grid/index.rst

API

.. doxygenfile:: lv_grid.h
  :project: lvgl