Grid

Overview

The Grid layout is a subset of CSS Grid.

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 int32_t column_dsc[] = {100, 400, LV_GRID_TEMPLATE_LAST};   /*2 columns with 100 and 400 ps width*/
static int32_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 size to fit the largest child 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 column_pos and row_pos means the zero based index of the cell into the item should be placed.

column_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).

Sub grid

If you set the column and/or row grid descriptors of a widget to NULL it will use the grid descriptor(s) from it's parent. For example if you create a grid item on 2..6 columns and 1..3 rows of the parent, the grid item will see 5 columns and 4 rows with the corresponding track size from the parent.

This way even if a wrapper item is used on the grid and can be made "transparent" from the grid's point of view.

Limitations:

  • The sub grid is resolved only in one level depth. That is a grid can have a sub grid children, but a sub grid can't have an other sub grid.

  • LV_GRID_CONTENT tracks on the are not handled in the sub grid, only in the its own grid.

The sub grid feature works the same as in CSS. For further reference see this description.

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

A simple grid

C code  

 View on GitHub
#include "../../lv_examples.h"
#if LV_USE_GRID && LV_BUILD_EXAMPLES

/**
 * A simple grid
 */
void lv_example_grid_1(void)
{
    static int32_t col_dsc[] = {70, 70, 70, LV_GRID_TEMPLATE_LAST};
    static int32_t row_dsc[] = {50, 50, 50, LV_GRID_TEMPLATE_LAST};

    /*Create a container with grid*/
    lv_obj_t * cont = lv_obj_create(lv_screen_active());
    lv_obj_set_style_grid_column_dsc_array(cont, col_dsc, 0);
    lv_obj_set_style_grid_row_dsc_array(cont, row_dsc, 0);
    lv_obj_set_size(cont, 300, 220);
    lv_obj_center(cont);
    lv_obj_set_layout(cont, LV_LAYOUT_GRID);

    lv_obj_t * label;
    lv_obj_t * obj;

    uint32_t i;
    for(i = 0; i < 9; i++) {
        uint8_t col = i % 3;
        uint8_t row = i / 3;

        obj = lv_button_create(cont);
        /*Stretch the cell horizontally and vertically too
         *Set span to 1 to make the cell 1 column/row sized*/
        lv_obj_set_grid_cell(obj, LV_GRID_ALIGN_STRETCH, col, 1,
                             LV_GRID_ALIGN_STRETCH, row, 1);

        label = lv_label_create(obj);
        lv_label_set_text_fmt(label, "c%d, r%d", col, row);
        lv_obj_center(label);
    }
}

#endif

Demonstrate cell placement and span

C code  

 View on GitHub
#include "../../lv_examples.h"
#if LV_USE_GRID && LV_BUILD_EXAMPLES

/**
 * Demonstrate cell placement and span
 */
void lv_example_grid_2(void)
{
    static int32_t col_dsc[] = {70, 70, 70, LV_GRID_TEMPLATE_LAST};
    static int32_t row_dsc[] = {50, 50, 50, LV_GRID_TEMPLATE_LAST};

    /*Create a container with grid*/
    lv_obj_t * cont = lv_obj_create(lv_screen_active());
    lv_obj_set_grid_dsc_array(cont, col_dsc, row_dsc);
    lv_obj_set_size(cont, 300, 220);
    lv_obj_center(cont);

    lv_obj_t * label;
    lv_obj_t * obj;

    /*Cell to 0;0 and align to to the start (left/top) horizontally and vertically too*/
    obj = lv_obj_create(cont);
    lv_obj_set_size(obj, LV_SIZE_CONTENT, LV_SIZE_CONTENT);
    lv_obj_set_grid_cell(obj, LV_GRID_ALIGN_START, 0, 1,
                         LV_GRID_ALIGN_START, 0, 1);
    label = lv_label_create(obj);
    lv_label_set_text(label, "c0, r0");

    /*Cell to 1;0 and align to to the start (left) horizontally and center vertically too*/
    obj = lv_obj_create(cont);
    lv_obj_set_size(obj, LV_SIZE_CONTENT, LV_SIZE_CONTENT);
    lv_obj_set_grid_cell(obj, LV_GRID_ALIGN_START, 1, 1,
                         LV_GRID_ALIGN_CENTER, 0, 1);
    label = lv_label_create(obj);
    lv_label_set_text(label, "c1, r0");

    /*Cell to 2;0 and align to to the start (left) horizontally and end (bottom) vertically too*/
    obj = lv_obj_create(cont);
    lv_obj_set_size(obj, LV_SIZE_CONTENT, LV_SIZE_CONTENT);
    lv_obj_set_grid_cell(obj, LV_GRID_ALIGN_START, 2, 1,
                         LV_GRID_ALIGN_END, 0, 1);
    label = lv_label_create(obj);
    lv_label_set_text(label, "c2, r0");

    /*Cell to 1;1 but 2 column wide (span = 2).Set width and height to stretched.*/
    obj = lv_obj_create(cont);
    lv_obj_set_size(obj, LV_SIZE_CONTENT, LV_SIZE_CONTENT);
    lv_obj_set_grid_cell(obj, LV_GRID_ALIGN_STRETCH, 1, 2,
                         LV_GRID_ALIGN_STRETCH, 1, 1);
    label = lv_label_create(obj);
    lv_label_set_text(label, "c1-2, r1");

    /*Cell to 0;1 but 2 rows tall (span = 2).Set width and height to stretched.*/
    obj = lv_obj_create(cont);
    lv_obj_set_size(obj, LV_SIZE_CONTENT, LV_SIZE_CONTENT);
    lv_obj_set_grid_cell(obj, LV_GRID_ALIGN_STRETCH, 0, 1,
                         LV_GRID_ALIGN_STRETCH, 1, 2);
    label = lv_label_create(obj);
    lv_label_set_text(label, "c0\nr1-2");
}

#endif

Demonstrate grid's -free unit-

C code  

 View on GitHub
#include "../../lv_examples.h"
#if LV_USE_GRID && LV_BUILD_EXAMPLES

/**
 * Demonstrate grid's "free unit"
 */
void lv_example_grid_3(void)
{
    /*Column 1: fix width 60 px
     *Column 2: 1 unit from the remaining free space
     *Column 3: 2 unit from the remaining free space*/
    static int32_t col_dsc[] = {60, LV_GRID_FR(1), LV_GRID_FR(2), LV_GRID_TEMPLATE_LAST};

    /*Row 1: fix width 50 px
     *Row 2: 1 unit from the remaining free space
     *Row 3: fix width 50 px*/
    static int32_t row_dsc[] = {50, LV_GRID_FR(1), 50, LV_GRID_TEMPLATE_LAST};

    /*Create a container with grid*/
    lv_obj_t * cont = lv_obj_create(lv_screen_active());
    lv_obj_set_size(cont, 300, 220);
    lv_obj_center(cont);
    lv_obj_set_grid_dsc_array(cont, col_dsc, row_dsc);

    lv_obj_t * label;
    lv_obj_t * obj;
    uint32_t i;
    for(i = 0; i < 9; i++) {
        uint8_t col = i % 3;
        uint8_t row = i / 3;

        obj = lv_obj_create(cont);
        /*Stretch the cell horizontally and vertically too
         *Set span to 1 to make the cell 1 column/row sized*/
        lv_obj_set_grid_cell(obj, LV_GRID_ALIGN_STRETCH, col, 1,
                             LV_GRID_ALIGN_STRETCH, row, 1);

        label = lv_label_create(obj);
        lv_label_set_text_fmt(label, "%d,%d", col, row);
        lv_obj_center(label);
    }
}

#endif

Demonstrate track placement

C code  

 View on GitHub
#include "../../lv_examples.h"
#if LV_USE_GRID && LV_BUILD_EXAMPLES

/**
 * Demonstrate track placement
 */
void lv_example_grid_4(void)
{
    static int32_t col_dsc[] = {60, 60, 60, LV_GRID_TEMPLATE_LAST};
    static int32_t row_dsc[] = {45, 45, 45, LV_GRID_TEMPLATE_LAST};

    /*Add space between the columns and move the rows to the bottom (end)*/

    /*Create a container with grid*/
    lv_obj_t * cont = lv_obj_create(lv_screen_active());
    lv_obj_set_grid_align(cont, LV_GRID_ALIGN_SPACE_BETWEEN, LV_GRID_ALIGN_END);
    lv_obj_set_grid_dsc_array(cont, col_dsc, row_dsc);
    lv_obj_set_size(cont, 300, 220);
    lv_obj_center(cont);

    lv_obj_t * label;
    lv_obj_t * obj;
    uint32_t i;
    for(i = 0; i < 9; i++) {
        uint8_t col = i % 3;
        uint8_t row = i / 3;

        obj = lv_obj_create(cont);
        /*Stretch the cell horizontally and vertically too
         *Set span to 1 to make the cell 1 column/row sized*/
        lv_obj_set_grid_cell(obj, LV_GRID_ALIGN_STRETCH, col, 1,
                             LV_GRID_ALIGN_STRETCH, row, 1);

        label = lv_label_create(obj);
        lv_label_set_text_fmt(label, "%d,%d", col, row);
        lv_obj_center(label);
    }
}

#endif

Demonstrate column and row gap

C code  

 View on GitHub
#include "../../lv_examples.h"
#if LV_USE_GRID && LV_BUILD_EXAMPLES

static void row_gap_anim(void * obj, int32_t v)
{
    lv_obj_set_style_pad_row(obj, v, 0);
}

static void column_gap_anim(void * obj, int32_t v)
{
    lv_obj_set_style_pad_column(obj, v, 0);
}

/**
 * Demonstrate column and row gap
 */
void lv_example_grid_5(void)
{

    /*60x60 cells*/
    static int32_t col_dsc[] = {60, 60, 60, LV_GRID_TEMPLATE_LAST};
    static int32_t row_dsc[] = {45, 45, 45, LV_GRID_TEMPLATE_LAST};

    /*Create a container with grid*/
    lv_obj_t * cont = lv_obj_create(lv_screen_active());
    lv_obj_set_size(cont, 300, 220);
    lv_obj_center(cont);
    lv_obj_set_grid_dsc_array(cont, col_dsc, row_dsc);

    lv_obj_t * label;
    lv_obj_t * obj;
    uint32_t i;
    for(i = 0; i < 9; i++) {
        uint8_t col = i % 3;
        uint8_t row = i / 3;

        obj = lv_obj_create(cont);
        lv_obj_set_grid_cell(obj, LV_GRID_ALIGN_STRETCH, col, 1,
                             LV_GRID_ALIGN_STRETCH, row, 1);
        label = lv_label_create(obj);
        lv_label_set_text_fmt(label, "%d,%d", col, row);
        lv_obj_center(label);
    }

    lv_anim_t a;
    lv_anim_init(&a);
    lv_anim_set_var(&a, cont);
    lv_anim_set_values(&a, 0, 10);
    lv_anim_set_repeat_count(&a, LV_ANIM_REPEAT_INFINITE);

    lv_anim_set_exec_cb(&a, row_gap_anim);
    lv_anim_set_duration(&a, 500);
    lv_anim_set_playback_duration(&a, 500);
    lv_anim_start(&a);

    lv_anim_set_exec_cb(&a, column_gap_anim);
    lv_anim_set_duration(&a, 3000);
    lv_anim_set_playback_duration(&a, 3000);
    lv_anim_start(&a);
}

#endif

Demonstrate RTL direction on grid

C code  

 View on GitHub
#include "../../lv_examples.h"
#if LV_USE_GRID && LV_BUILD_EXAMPLES

/**
 * Demonstrate RTL direction on grid
 */
void lv_example_grid_6(void)
{

    static int32_t col_dsc[] = {60, 60, 60, LV_GRID_TEMPLATE_LAST};
    static int32_t row_dsc[] = {45, 45, 45, LV_GRID_TEMPLATE_LAST};

    /*Create a container with grid*/
    lv_obj_t * cont = lv_obj_create(lv_screen_active());
    lv_obj_set_size(cont, 300, 220);
    lv_obj_center(cont);
    lv_obj_set_style_base_dir(cont, LV_BASE_DIR_RTL, 0);
    lv_obj_set_grid_dsc_array(cont, col_dsc, row_dsc);

    lv_obj_t * label;
    lv_obj_t * obj;
    uint32_t i;
    for(i = 0; i < 9; i++) {
        uint8_t col = i % 3;
        uint8_t row = i / 3;

        obj = lv_obj_create(cont);
        /*Stretch the cell horizontally and vertically too
         *Set span to 1 to make the cell 1 column/row sized*/
        lv_obj_set_grid_cell(obj, LV_GRID_ALIGN_STRETCH, col, 1,
                             LV_GRID_ALIGN_STRETCH, row, 1);

        label = lv_label_create(obj);
        lv_label_set_text_fmt(label, "%d,%d", col, row);
        lv_obj_center(label);
    }
}

#endif

API

lv_grid.h