feat(simulator) add glfw3 backend

CMakeLists.txt

@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.10)
 project(lvgl)
 
-foreach(BACKEND_NAME "SDL" "LINUX_DRM" "LINUX_FBDEV" "X11" "WAYLAND")
+foreach(BACKEND_NAME "SDL" "LINUX_DRM" "LINUX_FBDEV" "X11" "WAYLAND" "OPENGLES")
     execute_process(COMMAND "scripts/backend_conf.sh" ${BACKEND_NAME} OUTPUT_VARIABLE IS_BACKEND_ENABLED)
     set("LV_USE_${BACKEND_NAME}" ${IS_BACKEND_ENABLED})
 endforeach()
@@ -65,6 +65,16 @@ elseif (LV_USE_LINUX_FBDEV)
     add_executable(lvglsim ${SIM_SRC} src/backends/fbdev.c)
     target_link_libraries(lvglsim lvgl lvgl::examples lvgl::demos lvgl::thorvg m pthread)
 
+elseif (LV_USE_OPENGLES)
+
+    find_package(PkgConfig REQUIRED)
+    pkg_check_modules(GLFW3 REQUIRED glfw3)
+    pkg_check_modules(GLEW REQUIRED glew)
+
+    add_executable(lvglsim ${SIM_SRC} src/backends/glfw3.c)
+    target_link_libraries(lvglsim lvgl lvgl::examples lvgl::demos lvgl::thorvg
+        m pthread ${GLFW3_LIBRARIES} ${GLEW_LIBRARIES})
+
 endif()
 
 add_custom_target (run COMMAND ${EXECUTABLE_OUTPUT_PATH}/lvglsim DEPENDS lvglsim)

src/backends/glfw3.c

@@ -0,0 +1,55 @@
+/**
+ * @file glfw3.c
+ *
+ * The backend for the glfw3 library
+ *
+ */
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+#include "lvgl/lvgl.h"
+#include "settings.h"
+#include "util.h"
+
+void lv_linux_disp_init(void)
+{
+    lv_glfw_texture_t *window_texture;
+    lv_indev_t *mouse;
+    lv_display_t *disp_texture;
+    uint32_t disp_texture_id;
+    lv_obj_t *cursor_obj;
+
+    /* create a window and initialize OpenGL */
+    lv_glfw_window_t * window = lv_glfw_window_create(window_width, window_height, true);
+
+    /* create a display that flushes to a texture */
+    disp_texture = lv_opengles_texture_create(window_width, window_height);
+    lv_display_set_default(disp_texture);
+
+    /* add the texture to the window */
+    disp_texture_id = lv_opengles_texture_get_texture_id(disp_texture);
+    window_texture = lv_glfw_window_add_texture(window, disp_texture_id,
+            window_width, window_height);
+
+    /* get the mouse indev of the window texture */
+    mouse = lv_glfw_texture_get_mouse_indev(window_texture);
+
+    /* add a cursor to the mouse indev */
+    LV_IMAGE_DECLARE(mouse_cursor_icon);
+    cursor_obj = lv_image_create(lv_screen_active());
+    lv_image_set_src(cursor_obj, &mouse_cursor_icon);
+    lv_indev_set_cursor(mouse, cursor_obj);
+}
+
+void lv_linux_run_loop(void)
+{
+    uint32_t idle_time;
+
+    /* Handle LVGL tasks */
+    while (true) {
+
+        idle_time = lv_timer_handler(); /* Returns the time to the next timer execution */
+        usleep(idle_time * 1000);
+    }
+}

src/backends/settings.h

@@ -13,6 +13,7 @@
 #if LV_USE_SDL == 0 && \
     LV_USE_WAYLAND == 0 && \
     LV_USE_LINUX_DRM == 0 && \
+    LV_USE_OPENGLES == 0 && \
     LV_USE_LINUX_FBDEV == 0
 
 #error Unsupported configuration - Please select at least one backend in lv_conf.h