demo: lvgl: Add lvgl sample to draw touch events on the screen

This is a small lvgl touch demo application featuring
functionality to "draw" on the the screen.
This can be useful to test touch input functionality
during board setup.

Signed-off-by: Martin Kiepfer <mrmarteng@teleschirm.org>

samples/modules/lvgl/touch_draw/CMakeLists.txt

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+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(lvgl_touch_draw)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

samples/modules/lvgl/touch_draw/README.rst

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+.. zephyr:code-sample:: lvgl-touch-draw
+   :name: LVGL touch draw demo
+   :relevant-api: display_interface input_interface
+
+   Allow "drawing" on the screen with use of a touch input
+
+Overview
+********
+
+This sample application features drawing functionality based on touch input.
+Received touch input will be drawn onto the surface of the screen.
+This feature can be generally helpful for testing proper functionality of the
+touch interface.
+
+When the board features a user-button (``sw0``) pushing this button will clear
+the screen again.
+
+Requirements
+************
+
+This demo requires a board or a shield with a display and touch-input device,
+for example:
+
+- :ref:`m5stack_core2`
+
+Please make sure (:dtcompatible:`zephyr,lvgl-pointer-input`) is defined in
+device tree.
+
+Memory requirements
+===================
+The sample application requires an LVGL memory pool of at least 32 kBytes.
+
+Building and Running
+********************
+
+Example building for :ref:`m5stack_core2`:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/modules/lvgl/touch_draw
+   :board: m5stack_core2
+   :goals: build flash
+
+References
+**********
+
+.. target-notes::
+
+.. _LVGL Web Page: https://lvgl.io/

samples/modules/lvgl/touch_draw/boards/m5stack_core2.conf

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+# SPDX-License-Identifier: Apache-2.0
+
+CONFIG_MAIN_STACK_SIZE=4096

samples/modules/lvgl/touch_draw/boards/m5stack_stamps3.conf

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+# SPDX-License-Identifier: Apache-2.0
+
+CONFIG_MAIN_STACK_SIZE=4096

samples/modules/lvgl/touch_draw/prj.conf

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+CONFIG_MAIN_STACK_SIZE=2048
+
+CONFIG_COMMON_LIBC_MALLOC=y
+CONFIG_COMMON_LIBC_MALLOC_ARENA_SIZE=-1
+
+CONFIG_DISPLAY=y
+CONFIG_DISPLAY_LOG_LEVEL_ERR=y
+
+CONFIG_LOG=y
+CONFIG_SHELL=y
+
+CONFIG_INPUT=y
+
+CONFIG_LVGL=y
+CONFIG_LV_Z_MEM_POOL_HEAP_LIB_C=y
+CONFIG_LV_USE_LOG=y
+CONFIG_LV_FONT_MONTSERRAT_14=y

samples/modules/lvgl/touch_draw/sample.yaml

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+sample:
+  description: LVGL touch draw demo
+  name: LVGL touch draw
+common:
+  modules:
+    - lvgl
+  harness: none
+  tags:
+    - samples
+    - display
+    - touch
+    - gui
+    - lvgl
+tests:
+  sample.display.lvgl.touch_draw:
+    filter: dt_chosen_enabled("zephyr,display") and dt_chosen_enabled("zephyr,lvgl-pointer-input")
+    min_flash: 250
+    min_ram: 32

samples/modules/lvgl/touch_draw/src/main.c

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+/*
+ * Copyright (c) 2024 Martin Kiepfer <mrmarteng@teleschirm.org>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/device.h>
+#include <zephyr/devicetree.h>
+#include <zephyr/drivers/display.h>
+#include <zephyr/drivers/gpio.h>
+#include <stdlib.h>
+#include <lvgl.h>
+#include <stdio.h>
+#include <string.h>
+#include <zephyr/kernel.h>
+#include <lvgl_input_device.h>
+
+#define LOG_LEVEL CONFIG_LOG_DEFAULT_LEVEL
+#include <zephyr/logging/log.h>
+LOG_MODULE_REGISTER(app);
+
+struct pressing_callback_context {
+	lv_obj_t *canvas;
+	lv_indev_t *indev;
+};
+
+#ifdef CONFIG_GPIO
+struct button_callback_context {
+	struct gpio_callback callback;
+	lv_obj_t *canvas;
+};
+static struct gpio_dt_spec button_gpio = GPIO_DT_SPEC_GET_OR(DT_ALIAS(sw0), gpios, {0});
+
+static void button_isr_callback(const struct device *port, struct gpio_callback *cb, uint32_t pins)
+{
+	ARG_UNUSED(port);
+	ARG_UNUSED(pins);
+
+	struct button_callback_context *ctx =
+		CONTAINER_OF(cb, struct button_callback_context, callback);
+
+	lv_canvas_fill_bg(ctx->canvas, lv_color_black(), LV_OPA_TRANSP);
+}
+#endif /* CONFIG_GPIO */
+
+static void lv_draw_pressing_callback(lv_event_t *e)
+{
+	lv_point_t point;
+	lv_draw_rect_dsc_t dsc;
+	struct pressing_callback_context *ctx = e->user_data;
+
+	lv_indev_get_point(ctx->indev, &point);
+
+	lv_draw_rect_dsc_init(&dsc);
+	dsc.bg_color = lv_palette_main(LV_PALETTE_GREY);
+	dsc.border_width = 0U;
+	dsc.outline_color = lv_palette_main(LV_PALETTE_GREY);
+	dsc.outline_width = 3U;
+	dsc.outline_pad = 0U;
+	dsc.outline_opa = LV_OPA_COVER;
+	dsc.radius = 5U;
+
+	lv_canvas_draw_rect(ctx->canvas, point.x, point.y, 10U, 10U, &dsc);
+}
+
+int main(void)
+{
+	const struct device *display_dev;
+	const struct device *pointer_dev;
+	lv_obj_t *touch_label;
+	struct pressing_callback_context pressing_cb_ctx;
+#ifdef CONFIG_GPIO
+	struct button_callback_context btn_cb_ctx;
+#endif
+
+	display_dev = DEVICE_DT_GET(DT_CHOSEN(zephyr_display));
+	if (!device_is_ready(display_dev)) {
+		LOG_ERR("Device not ready, aborting test");
+		return -ENODEV;
+	}
+
+	pointer_dev = DEVICE_DT_GET(DT_COMPAT_GET_ANY_STATUS_OKAY(zephyr_lvgl_pointer_input));
+	if (!device_is_ready(pointer_dev)) {
+		LOG_ERR("Device not ready, aborting test");
+		return -ENODEV;
+	}
+	pressing_cb_ctx.indev = lvgl_input_get_indev(pointer_dev);
+
+	/**
+	 * The required canvas buf size is calculated by
+	 * (lv_img_color_format_get_px_size(cf) * width) / 8 * height)
+	 * 2 bpp are used here to reduce overall memory requirements
+	 **/
+	lv_opa_t *mask_map = malloc(LV_VER_RES * LV_HOR_RES * sizeof(lv_opa_t) / 4U);
+	if (mask_map == NULL) {
+		LOG_ERR("Allocating canvas layer failed. Please review LVGL mem pool size.");
+		return -ENOMEM;
+	}
+
+	/* Create canvas layer for "drawing" touch events */
+	pressing_cb_ctx.canvas = lv_canvas_create(lv_scr_act());
+	lv_canvas_set_buffer(pressing_cb_ctx.canvas, mask_map, LV_HOR_RES, LV_VER_RES,
+			     LV_IMG_CF_ALPHA_2BIT);
+	lv_canvas_fill_bg(pressing_cb_ctx.canvas, lv_color_black(), LV_OPA_TRANSP);
+	lv_obj_center(pressing_cb_ctx.canvas);
+	lv_obj_add_event_cb(lv_scr_act(), lv_draw_pressing_callback, LV_EVENT_PRESSING,
+			    &pressing_cb_ctx);
+
+	/* Create label with "touch me" text */
+	touch_label = lv_label_create(lv_scr_act());
+	lv_label_set_text(touch_label, "touch me!");
+	lv_obj_align(touch_label, LV_ALIGN_CENTER, 0, 0);
+
+#ifdef CONFIG_GPIO
+	if (gpio_is_ready_dt(&button_gpio)) {
+		int err;
+
+		err = gpio_pin_configure_dt(&button_gpio, GPIO_INPUT);
+		if (err) {
+			LOG_ERR("Failed to configure button gpio: %d", err);
+			return -EIO;
+		}
+
+		gpio_init_callback(&btn_cb_ctx.callback, button_isr_callback, BIT(button_gpio.pin));
+		btn_cb_ctx.canvas = pressing_cb_ctx.canvas;
+
+		err = gpio_add_callback(button_gpio.port, &btn_cb_ctx.callback);
+		if (err) {
+			LOG_ERR("Failed to add button callback: %d", err);
+			return -EIO;
+		}
+
+		err = gpio_pin_interrupt_configure_dt(&button_gpio, GPIO_INT_EDGE_TO_ACTIVE);
+		if (err) {
+			LOG_ERR("Failed to configure button callback: %d", err);
+			return -EIO;
+		}
+	}
+#endif /* CONFIG_GPIO */
+
+	lv_task_handler();
+	display_blanking_off(display_dev);
+
+	while (true) {
+		lv_task_handler();
+		k_sleep(K_MSEC(10));
+	}
+}