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examples/calculator: Add an LVGL touchscreen calculator.

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Add a calculator example that can run as either a built-in application or loadable module. It uses configurable framebuffer and touchscreen paths, reserves the nxstore supervisor bar, and exits cooperatively on SIGTERM.

Validate display, touchscreen, and signal-handler setup before entering the LVGL loop. Reset static state on every invocation so built-in relaunches behave like fresh module loads.

Assisted-by: OpenAI Codex:gpt-5.6-sol
Signed-off-by: aviralgarg05 <gargaviral99@gmail.com>
This commit is contained in:
aviralgarg05 2026-07-12 16:01:18 +05:30
parent 79daf2c5a9
commit 9372de597b
5 changed files with 647 additions and 0 deletions
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37
examples/calculator/CMakeLists.txt Normal file
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# ##############################################################################
# apps/examples/calculator/CMakeLists.txt
#
# SPDX-License-Identifier: Apache-2.0
#
# Licensed to the Apache Software Foundation (ASF) under one or more contributor
# license agreements. See the NOTICE file distributed with this work for
# additional information regarding copyright ownership. The ASF licenses this
# file to you under the Apache License, Version 2.0 (the "License"); you may not
# use this file except in compliance with the License. You may obtain a copy of
# the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations under
# the License.
#
# ##############################################################################
if(CONFIG_EXAMPLES_CALCULATOR)
nuttx_add_application(
NAME
calc
PRIORITY
${CONFIG_EXAMPLES_CALCULATOR_PRIORITY}
STACKSIZE
${CONFIG_EXAMPLES_CALCULATOR_STACKSIZE}
MODULE
${CONFIG_EXAMPLES_CALCULATOR}
DEPENDS
lvgl
SRCS
calculator_main.c)
endif()

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examples/calculator/Kconfig Normal file
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#
# For a description of the syntax of this configuration file,
# see the file kconfig-language.txt in the NuttX tools repository.
#
menuconfig EXAMPLES_CALCULATOR
tristate "Calculator"
default n
depends on GRAPHICS_LVGL && INPUT_TOUCHSCREEN
---help---
Enable the simple LVGL touchscreen calculator example.
if EXAMPLES_CALCULATOR
config EXAMPLES_CALCULATOR_PRIORITY
int "calculator task priority"
default 100
config EXAMPLES_CALCULATOR_STACKSIZE
int "calculator stack size"
default 16384
config EXAMPLES_CALCULATOR_INPUT_DEVPATH
string "Touchscreen device path"
default "/dev/input0"
---help---
The path to the touchscreen device. Default: "/dev/input0"
config EXAMPLES_CALCULATOR_FBDEVPATH
string "Framebuffer device path"
default "/dev/fb0"
---help---
The path to the framebuffer device. Default: "/dev/fb0"
endif # EXAMPLES_CALCULATOR

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examples/calculator/Make.defs Normal file
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############################################################################
# apps/examples/calculator/Make.defs
#
# SPDX-License-Identifier: Apache-2.0
#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements. See the NOTICE file distributed with
# this work for additional information regarding copyright ownership. The
# ASF licenses this file to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance with the
# License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
#
############################################################################
ifneq ($(CONFIG_EXAMPLES_CALCULATOR),)
CONFIGURED_APPS += $(APPDIR)/examples/calculator
endif

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examples/calculator/Makefile Normal file
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############################################################################
# apps/examples/calculator/Makefile
#
# SPDX-License-Identifier: Apache-2.0
#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements. See the NOTICE file distributed with
# this work for additional information regarding copyright ownership. The
# ASF licenses this file to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance with the
# License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
#
############################################################################
include $(APPDIR)/Make.defs
PROGNAME = calc
PRIORITY = $(CONFIG_EXAMPLES_CALCULATOR_PRIORITY)
STACKSIZE = $(CONFIG_EXAMPLES_CALCULATOR_STACKSIZE)
MODULE = $(CONFIG_EXAMPLES_CALCULATOR)
MAINSRC = calculator_main.c
include $(APPDIR)/Application.mk

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examples/calculator/calculator_main.c Normal file
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/****************************************************************************
* apps/examples/calculator/calculator_main.c
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/boardctl.h>
#include <lvgl/lvgl.h>
#include <system/nxstore_chrome.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#undef NEED_BOARDINIT
#if defined(CONFIG_BOARDCTL) && !defined(CONFIG_NSH_ARCHINIT)
# define NEED_BOARDINIT 1
#endif
#define CALC_DISPLAY_MAX 16
/****************************************************************************
* Private Data
****************************************************************************/
/* Set only by quit_signal_handler(), an async-signal-safe flag - the
* actual shutdown happens from the main loop, a known-safe point,
* rather than from the handler itself. See games/NXDoom's
* i_install_quit_signal()/i_poll_quit_signal() for the same pattern:
* an external supervisor (nxstore) has no in-app quit path to drive,
* so it can only ask this process to exit from the outside via
* SIGTERM.
*/
static volatile sig_atomic_t g_quit_requested;
static lv_obj_t *g_display;
static char g_display_buf[CALC_DISPLAY_MAX + 1] = "0";
static double g_accumulator;
static char g_pending_op;
static bool g_start_new_entry = true;
/****************************************************************************
* Private Functions
****************************************************************************/
static void quit_signal_handler(int signo)
{
(void)signo;
g_quit_requested = 1;
}
/* nxstore's own "Close" bar is confined to the top 36px of the display
* so it can coexist with full-screen children like this one - a
* convention that only works if the child app leaves that strip alone.
* This app's display/keypad fill the entire canvas, so nxstore's bar
* gets overdrawn as soon as this screen loads. Give the calculator its
* own close affordance instead: tapping it just sets the same quit flag
* SIGTERM does, so nxstore's nxstore_poll_running_app() sees the process
* exit on its own and returns to the app list automatically.
*/
static void close_event_cb(lv_event_t *e)
{
UNUSED(e);
g_quit_requested = 1;
}
static void calc_update_display(void)
{
lv_label_set_text(g_display, g_display_buf);
}
static void calc_set_display_number(double value)
{
snprintf(g_display_buf, sizeof(g_display_buf), "%.10g", value);
calc_update_display();
}
static double calc_apply(double a, double b, char op, bool *ok)
{
*ok = true;
switch (op)
{
case '+':
return a + b;
case '-':
return a - b;
case '*':
return a * b;
case '/':
if (b == 0)
{
*ok = false;
return 0;
}
return a / b;
default:
return b;
}
}
static void calc_clear(void)
{
g_accumulator = 0;
g_pending_op = 0;
g_start_new_entry = true;
snprintf(g_display_buf, sizeof(g_display_buf), "0");
calc_update_display();
}
static void calc_handle_digit(char digit)
{
size_t len;
if (g_start_new_entry)
{
g_display_buf[0] = '\0';
g_start_new_entry = false;
}
if (strcmp(g_display_buf, "0") == 0)
{
g_display_buf[0] = '\0';
}
len = strlen(g_display_buf);
if (len + 1 >= sizeof(g_display_buf))
{
/* Display is already at capacity - drop the keypress rather than
* overflow g_display_buf or silently truncate mid-number.
*/
return;
}
g_display_buf[len] = digit;
g_display_buf[len + 1] = '\0';
calc_update_display();
}
static void calc_handle_point(void)
{
size_t len;
if (g_start_new_entry)
{
snprintf(g_display_buf, sizeof(g_display_buf), "0");
g_start_new_entry = false;
}
if (strchr(g_display_buf, '.') != NULL)
{
return;
}
len = strlen(g_display_buf);
if (len + 1 >= sizeof(g_display_buf))
{
return;
}
g_display_buf[len] = '.';
g_display_buf[len + 1] = '\0';
calc_update_display();
}
static void calc_handle_op(char op)
{
double current = atof(g_display_buf);
bool ok;
if (g_pending_op != 0)
{
g_accumulator = calc_apply(g_accumulator, current, g_pending_op, &ok);
if (!ok)
{
snprintf(g_display_buf, sizeof(g_display_buf), "Error");
calc_update_display();
g_pending_op = 0;
g_start_new_entry = true;
return;
}
}
else
{
g_accumulator = current;
}
g_pending_op = op;
g_start_new_entry = true;
calc_set_display_number(g_accumulator);
}
static void calc_handle_equals(void)
{
double current = atof(g_display_buf);
bool ok;
if (g_pending_op == 0)
{
g_accumulator = current;
}
else
{
g_accumulator = calc_apply(g_accumulator, current, g_pending_op, &ok);
if (!ok)
{
snprintf(g_display_buf, sizeof(g_display_buf), "Error");
calc_update_display();
g_pending_op = 0;
g_start_new_entry = true;
return;
}
}
g_pending_op = 0;
g_start_new_entry = true;
calc_set_display_number(g_accumulator);
}
static void button_event_cb(lv_event_t *e)
{
FAR const char *code = lv_event_get_user_data(e);
switch (code[0])
{
case 'C':
calc_clear();
break;
case '.':
calc_handle_point();
break;
case '=':
calc_handle_equals();
break;
case '+':
case '-':
case '*':
case '/':
calc_handle_op(code[0]);
break;
default:
calc_handle_digit(code[0]);
break;
}
}
static lv_obj_t *make_button(lv_obj_t *parent, FAR const char *label,
FAR const char *code, uint32_t color)
{
lv_obj_t *btn;
lv_obj_t *btn_label;
btn = lv_obj_create(parent);
lv_obj_set_style_radius(btn, 10, 0);
lv_obj_set_style_bg_color(btn, lv_color_hex(color), 0);
lv_obj_set_style_bg_color(btn, lv_color_hex(0xffffff),
LV_STATE_PRESSED);
lv_obj_set_style_bg_opa(btn, LV_OPA_30, LV_STATE_PRESSED);
lv_obj_set_style_border_width(btn, 0, 0);
lv_obj_clear_flag(btn, LV_OBJ_FLAG_SCROLLABLE);
lv_obj_add_flag(btn, LV_OBJ_FLAG_CLICKABLE);
btn_label = lv_label_create(btn);
lv_label_set_text(btn_label, label);
lv_obj_set_style_text_color(btn_label, lv_color_hex(0xffffff), 0);
lv_obj_center(btn_label);
lv_obj_add_event_cb(btn, button_event_cb, LV_EVENT_CLICKED,
(void *)code);
return btn;
}
/****************************************************************************
* Public Functions
****************************************************************************/
int main(int argc, FAR char *argv[])
{
lv_nuttx_dsc_t info;
lv_nuttx_result_t result;
lv_obj_t *screen;
lv_obj_t *grid;
lv_obj_t *close_btn;
lv_obj_t *close_label;
struct sigaction sa;
int32_t display_height;
int32_t display_width;
static const char *const keys[5][4] =
{
{ "7", "8", "9", "/" },
{ "4", "5", "6", "*" },
{ "1", "2", "3", "-" },
{ "C", "0", ".", "+" },
{ "=", "=", "=", "=" },
};
static const int32_t col_dsc[] =
{
LV_GRID_FR(1), LV_GRID_FR(1), LV_GRID_FR(1), LV_GRID_FR(1),
LV_GRID_TEMPLATE_LAST
};
static const int32_t row_dsc[] =
{
LV_GRID_FR(1), LV_GRID_FR(1), LV_GRID_FR(1), LV_GRID_FR(1),
LV_GRID_FR(1), LV_GRID_TEMPLATE_LAST
};
g_quit_requested = 0;
g_display_buf[0] = '0';
g_display_buf[1] = '\0';
g_accumulator = 0;
g_pending_op = 0;
g_start_new_entry = true;
memset(&sa, 0, sizeof(sa));
sa.sa_handler = quit_signal_handler;
sigemptyset(&sa.sa_mask);
if (sigaction(SIGTERM, &sa, NULL) < 0)
{
LV_LOG_ERROR("calculator: failed to install SIGTERM handler");
return 1;
}
if (lv_is_initialized())
{
LV_LOG_ERROR("LVGL already initialized! aborting.");
return -1;
}
#ifdef NEED_BOARDINIT
boardctl(BOARDIOC_INIT, 0);
#endif
lv_init();
lv_nuttx_dsc_init(&info);
info.fb_path = CONFIG_EXAMPLES_CALCULATOR_FBDEVPATH;
info.input_path = CONFIG_EXAMPLES_CALCULATOR_INPUT_DEVPATH;
lv_nuttx_init(&info, &result);
if (result.disp == NULL)
{
LV_LOG_ERROR("calculator: LVGL display init failed!");
lv_nuttx_deinit(&result);
lv_deinit();
return 1;
}
if (result.indev == NULL)
{
LV_LOG_ERROR("calculator: touchscreen init failed!");
lv_nuttx_deinit(&result);
lv_deinit();
return 1;
}
display_width = lv_display_get_horizontal_resolution(result.disp);
display_height = lv_display_get_vertical_resolution(result.disp);
if (display_width <= 0 || display_height <= NXSTORE_BAR_HEIGHT)
{
LV_LOG_ERROR("calculator: display is too small");
lv_nuttx_deinit(&result);
lv_deinit();
return 1;
}
screen = lv_obj_create(NULL);
lv_obj_set_size(screen, display_width,
display_height - NXSTORE_BAR_HEIGHT);
lv_obj_set_pos(screen, 0, NXSTORE_BAR_HEIGHT);
lv_obj_set_style_bg_color(screen, lv_color_hex(0x101827), 0);
lv_obj_set_style_border_width(screen, 0, 0);
lv_obj_clear_flag(screen, LV_OBJ_FLAG_SCROLLABLE);
g_display = lv_label_create(screen);
lv_obj_set_width(g_display, LV_PCT(90));
lv_obj_set_style_text_font(g_display, &lv_font_montserrat_20, 0);
lv_obj_set_style_text_color(g_display, lv_color_hex(0xffffff), 0);
lv_obj_set_style_text_align(g_display, LV_TEXT_ALIGN_RIGHT, 0);
lv_label_set_text(g_display, g_display_buf);
lv_obj_align(g_display, LV_ALIGN_TOP_MID, 0, 48);
close_btn = lv_obj_create(screen);
lv_obj_set_size(close_btn, 36, 36);
lv_obj_align(close_btn, LV_ALIGN_TOP_RIGHT, -8, 8);
lv_obj_set_style_radius(close_btn, 8, 0);
lv_obj_set_style_bg_color(close_btn, lv_color_hex(0xf0554c), 0);
lv_obj_set_style_bg_color(close_btn, lv_color_hex(0xb03830),
LV_STATE_PRESSED);
lv_obj_set_style_border_width(close_btn, 0, 0);
lv_obj_clear_flag(close_btn, LV_OBJ_FLAG_SCROLLABLE);
lv_obj_add_flag(close_btn, LV_OBJ_FLAG_CLICKABLE);
close_label = lv_label_create(close_btn);
lv_label_set_text(close_label, LV_SYMBOL_CLOSE);
lv_obj_set_style_text_color(close_label, lv_color_hex(0xffffff), 0);
lv_obj_clear_flag(close_label, LV_OBJ_FLAG_CLICKABLE);
lv_obj_center(close_label);
lv_obj_add_event_cb(close_btn, close_event_cb, LV_EVENT_CLICKED, NULL);
grid = lv_obj_create(screen);
lv_obj_set_size(grid, LV_PCT(90), LV_PCT(70));
lv_obj_align(grid, LV_ALIGN_BOTTOM_MID, 0, -16);
lv_obj_set_style_bg_opa(grid, LV_OPA_TRANSP, 0);
lv_obj_set_style_border_width(grid, 0, 0);
lv_obj_set_style_pad_all(grid, 4, 0);
lv_obj_set_style_pad_gap(grid, 8, 0);
lv_obj_clear_flag(grid, LV_OBJ_FLAG_SCROLLABLE);
lv_obj_set_grid_dsc_array(grid, col_dsc, row_dsc);
lv_obj_set_layout(grid, LV_LAYOUT_GRID);
for (int row = 0; row < 5; row++)
{
for (int col = 0; col < 4; col++)
{
FAR const char *code = keys[row][col];
uint32_t color = 0x2a3648;
lv_obj_t *btn;
if (row == 4)
{
/* Single wide "=" button spans the whole row - only
* instantiate it once, on the first column.
*/
if (col > 0)
{
continue;
}
}
if (strchr("+-*/=", code[0]) != NULL)
{
color = 0x3d8bff;
}
else if (code[0] == 'C')
{
color = 0xf0554c;
}
btn = make_button(grid, code, code, color);
if (row == 4)
{
lv_obj_set_grid_cell(btn, LV_GRID_ALIGN_STRETCH, 0, 4,
LV_GRID_ALIGN_STRETCH, row, 1);
}
else
{
lv_obj_set_grid_cell(btn, LV_GRID_ALIGN_STRETCH, col, 1,
LV_GRID_ALIGN_STRETCH, row, 1);
}
}
}
lv_screen_load(screen);
while (!g_quit_requested)
{
uint32_t idle;
idle = lv_timer_handler();
/* Minimum sleep of 1ms */
idle = idle ? idle : 1;
usleep(idle * 1000);
}
lv_nuttx_deinit(&result);
lv_deinit();
return 0;
}