Rockchip Linux LVGL и галерея OpenGL(ES)

<SDK>/buildroot/configs/rockchip/gui/lvgl/
├── lvgl_drm.config         # symlink to V8
├── lvgl_rkadk.config       # symlink to V8
├── lvgl_sdl.config         # symlink to V8
├── music.config            # Music DEMO from LVGL team
├── rk_demo.config          # DEMO from Rockchip team
├── v8                      # configurations for LVGL V8
│   ├── base.config         # basic configurations for LVGL
│   ├── lvgl_drm.config     # DRM configurations
│   ├── lvgl_rkadk.config   # RKADK configurations
│   └── lvgl_sdl.config     # SDL configurations
├── v9                      # configurations for LVGL V9
│   ├── base.config
│   ├── lvgl_drm.config
│   ├── lvgl_rkadk.config
│   └── lvgl_sdl.config
└── widgets.config          # Widgets DEMO from LVGL team

$ cat buildroot/configs/rockchip_rk3308_bs_32_ia_release_defconfig | grep lvgl
# select a backend
#include "gui/lvgl/lvgl_drm.config"
# select a demo
#include "gui/lvgl/rk_demo.config"

BR2_PACKAGE_SDL2=y
BR2_PACKAGE_SDL2_OPENGLES=y
# Use wayland backend. Depends on your environment
BR2_PACKAGE_SDL2_WAYLAND=y

BR2_PACKAGE_LV_DRIVERS_USE_OPENGL=y

cd buildroot
source envsetup.sh
# choose your board defconfig
# Compile these three package in version 8
make lvgl lv_drivers lvgl_demo -j20
# Compile these two package in version 9
make lvgl lvgl_demo -j20

cd buildroot
# Compile these three package in version 8
make lvgl-reconfigure lv_drivers-reconfigure lvgl_demo-reconfigure -j20
# Compile these two package in version 9
make lvgl-reconfigure lvgl_demo-reconfigure -j20

app/lvgl_demo/
├── cJSON   # cJSON source code
├── common  # common widgets
├── gallery # gallery application
├── lv_demo # basic demos
├── lvgl8   # API porting for V8
├── lvgl9   # API porting for V9
├── rk_demo
│   ├── asr                 # ASR function
│   ├── furniture_control
│   ├── home                # home page
│   ├── include             # head files
│   ├── intercom_homepage
│   │   ├── intercom_call
│   │   └── video_monitor
│   ├── layout              # layout widgets
│   ├── resource            # pictures, fonts
│   ├── rockit              # rockit adaptions
│   ├── setting             # system setting page
│   ├── smart_home
│   └── wifibt              # rkwifibt adaptions
├── sys     # timestamp, cpu information, soc information, etc.
└── tools   # coding style formater

/* <SDK>/app/lvgl_demo/lv_demo/main.c */
...
int main(int argc, char **argv)
{
    lv_port_init();

    /* DEMO UI initialization */
#if LV_USE_DEMO_WIDGETS
    lv_demo_widgets();
#elif LV_USE_DEMO_BENCHMARK
    lv_demo_benchmark();
#elif LV_USE_DEMO_MUSIC
    lv_demo_music();
#endif
    while (!quit)
    {
        /* call the task handler, all events, rendering,
         * display will be done in this function
         */
        lv_task_handler();
        usleep(100);
    }

    return 0;
}

/* <SDK>/app/lvgl_demo/lvgl8/lv_port_init.c */
/* touch screen rotation */
/* 0, 90, 180, 270 */
static int g_indev_rotation = 0;
/* display rotation */
/* 0, 90, 180, 270 */
static int g_disp_rotation = 0;

void lv_port_init(void)
{
    /* Start of any LVGL applications */
    lv_init();

    /* display initialization */
    lv_port_disp_init(0, 0, g_disp_rotation);
    /* touch screen initialization */
    lv_port_indev_init(g_indev_rotation);
}

/* <SDK>/app/lvgl_demo/lvgl9/lv_port_init.c */
/* touch screen rotation */
/* 0, 90, 180, 270 */
static int g_indev_rotation = 0;
/* display rotation */
/* 0, 90, 180, 270 */
static int g_disp_rotation = 0;
/* log level */
static int log_level = LV_LOG_LEVEL_WARN;
...
void lv_port_init(void)
{
    const char *buf;

    /* Start of any LVGL applications */
    lv_init();

    /* update log level bt getenv */
    buf = getenv("LV_DEBUG");
    if (buf)
        log_level = buf[0] - '0';
    /* setting log callback */
    lv_log_register_print_cb(print_cb);
    /* setting systick callback */
    lv_tick_set_cb(lv_systick);
    /* setting delay callback */
    lv_delay_set_cb(lv_sysdelay);

    /* display initialization */
    lv_port_disp_init(0, 0, g_disp_rotation);
    /* touch screen initialization */
    lv_port_indev_init(g_indev_rotation);
}

lv_drivers/sdl/gl/
├── gl.c                // APIs implementation
├── gl.h                // APIs and external structure definition
├── mat.c               // Matrix function implementation
├── mat.h               // Matrix function definition
└── shaders             // OpenGL shaders
    ├── bgra_cube.frag  // BGRA cube fragment shader
    ├── bgra.frag       // BGRA 2D picture fragment shader
    ├── common.vert     // common vertex shader
    ├── cube.vert       // cube vertex shader
    ├── default.vert    // 2D picture vertex shader
    ├── rgba_cube.frag  // RGBA cube fragment shader
    └── rgba.frag       // RGBA 2D picture fragment shader

enum {
    LV_GL_FMT_ALPHA,
    LV_GL_FMT_LUMINANCE,
    LV_GL_FMT_LUMINANCE_ALPHA,
    LV_GL_FMT_INTENSITY,
    LV_GL_FMT_RGB,
    LV_GL_FMT_RGBA,
    LV_GL_FMT_BGRA,
};

enum {
    GL_TEX_TYPE_2D,
    GL_TEX_TYPE_CUBE,
};

enum {
    CUBE_LEFT,
    CUBE_RIGHT,
    CUBE_TOP,
    CUBE_BOTTOM,
    CUBE_FRONT,
    CUBE_BACK,
};

typedef struct {
    /* the address of image */
    const void *pixels;
    /* image format */
    int format;
    /* width */
    int w;
    /* height */
    int h;
} lv_gl_img_t;

typedef struct {
    /* width */
    int w;
    /* height */
    int h;
} lv_gl_size_t;

typedef struct {
    /* GPU texture object */
    GLuint gl_tex;
    /* GPU Frame Buffer Object */
    GLuint FBO;
    /* Texture size. For 2D textures, only the first set of sizes is valid.
     * A cube has 6 faces and 6 sets of size information. */
    lv_gl_size_t size[6];
    /* Texture format */
    int format;
    /* Object type, 2D or CUBE */
    int type;
    /* refrence count */
    int ref_cnt;
} lv_gl_tex_t;

typedef struct {
    float x, y, z;
} lv_gl_vec_t;

typedef struct {
    /* width */
    int w;
    /* height */
    int h;
    /* reverse y, just keep it 0 */
    int reverse_y;
    /* bound textures */
    lv_gl_tex_t *tex;
    /* rendering rectangle */
    SDL_Rect r;
    /* viewport rectangle */
    SDL_Rect view;
    /* crop rectagnle */
    SDL_Rect crop;
    /* The viewport area needs to be updated.
     * It is used internally and can be ignored by the application.
     */
    int view_dirty;
    /* The crop area needs to be updated.
     * It is used internally and can be ignored by the application.
     */
    int crop_dirty;
    /* enable crop */
    int crop_en;
} lv_gl_base_t;

typedef struct {
    lv_gl_base_t base;
    /* GPU Vertex Array Object */
    GLuint VAO;
    /* GPU Vertex Buffer Object */
    GLuint VBO;
    /* Output type, default GL_TEXTURE_2D.
     * If you need to render on a cube,
     * specify the rendered surface through this variable.
     */
    int out_type;
    /* Manually specify the coordinates of the four vertices of
     * a 2D object. The default vertex is full screen (note that
     * it is the view size of the framebuffer, not the screen size,
     * and the two may not be equal). Then set the scale, offset
     * and other attributes to perform matrix transformation.
     * You can also freely specify vertex coordinates through this attribute.
     * However, it is not recommended to use both methods together,
     * as the transformations involved are more complicated and
     * it is difficult to estimate the final effect by manual calculation.
     * The range of x, y, and z is [-1, 1]
     */
    lv_gl_vec_t p[4];
    /* Manually specify the reference range of the texture,
     * which is used when only part of the texture slice is needed.
     */
    SDL_Rect tp;

    /* global alpha */
    float alpha;
    /*
     * The order of the following transformations is:
     * pos * offset * scale * self_rot * view_rot * perspective * move
     * Calculate from left to right.
     * The perspective is the view transformation to achieve
     * the effect of near big and far small.
     */
    /* Scaling in three axes */
    lv_gl_vec_t scale;
    /* Offset in three axes */
    lv_gl_vec_t offset;
    /* Roration in three axes */
    lv_gl_vec_t self_rot;
    /* Viewport rotation in three axes */
    lv_gl_vec_t view_rot;
    /* Movements in three axes */
    lv_gl_vec_t move;
} lv_gl_obj_t;

gallery/
├── anims                   // animations
│   ├── cube_flip.c         // cube flip
│   ├── cube_flip.h
│   ├── cube_lyric.c        // cube lyric rendering
│   ├── cube_lyric.h
│   ├── cube_rotate.c       // cube rotate
│   ├── cube_rotate.h
│   ├── fade_out.c          // picture fade out
│   ├── fade_out.h
│   ├── fade_slide_out.c    // picture slide and fade out
│   ├── fade_slide_out.h
│   ├── fold.c              // picture fold
│   ├── fold.h
│   ├── photo_stream.c      // photo stream
│   ├── photo_stream.h
│   ├── roller.c            // picture rollering preview
│   ├── roller.h
│   ├── slide_out.c         // picture slide out
│   ├── slide_out.h
│   ├── stiker.c            // picture stiker testing
│   └── stiker.h
├── CMakeLists.txt
├── gallery.c               // UI entry
├── gallery.h
├── main.c                  // application entry
├── main.h
└── pics                    // picture resources

// gallery.c

/* Define the characters in cube lyric rendering demo, two lines for one surface */
static char *lyric[]...

/* The texture objects */
lv_gl_tex_t *tex_cube;
lv_gl_tex_t *tex_2d[6];
lv_gl_tex_t *tex_roller;
lv_gl_tex_t *tex_fb;

/* The rendering objects */
lv_gl_obj_t *obj_fb;
lv_gl_obj_t *obj_img0;
lv_gl_obj_t *obj_img1;
lv_gl_obj_t *obj_cube;
lv_gl_obj_t *obj_fold[4];
lv_gl_obj_t *obj_roller_items[6];
lv_gl_obj_t *obj_roller;
/* The lyric_row array used in cube lyric rendering demo. */
lyric_row *obj_lyrics;

/* Viewport size, equal to the screen size minus the button matrix size. */
SDL_Rect view;

/* Screen size */
SDL_Rect screen;

/* Indicates whether the current animation is playing */
int animing = 0;

/* Font imported from ttf file */
lv_ft_info_t ttf_main;

/* lvgl screen object */
lv_obj_t *scr;
/* lvgl image object */
lv_obj_t *img1;
/* lvgl image object */
lv_obj_t *img2;
/* lvgl object, animation area */
lv_obj_t *anim_area;
/* lvgl button matrix object */
lv_obj_t *btn_mat;
/* lvgl slider object */
lv_obj_t *slider;
/* lvgl object, photo stream container */
lv_obj_t *photo_box;
/* lvgl image objects for photo stream */
lv_obj_t *photos[6];

/* lvgl animations */
static lv_anim_t anims[]...

/* label texts for button matrix */
static const char *btnm_map[]...

/* event callback of button matrix */
static void event_handler(lv_event_t * e)

/* font initialization */
static void font_init(void)

/* create canvas, rendering texts to pictures */
static label_canvas *create_canvas(lv_color_t color, lv_font_t *font)

/* rendering texts to pictures and import to a GPU texture object */
static lv_gl_obj_t *utf8_to_obj(lv_gl_obj_t *parent, label_canvas *lc, char *text)

/* common animation start callback */
void common_anim_start(void)

/* texture object initialization */
static void tex_init(void)

/* UI entry */
void gallery(void)

// gallery.h
typedef struct
{
    /* Specify the text font and color */
    lv_draw_label_dsc_t label_dsc;
    /* buffer for canvas */
    lv_img_dsc_t *img_dsc;
    /* lvgl canvas object */
    lv_obj_t *canvas;
} label_canvas;

typedef struct {
    /* GPU rendering object */
    lv_gl_obj_t **objs;
    /* charactor length */
    int len;
} lyric_row;

 /* anims/cube_flip.c */
/*
 * Define three additional sub-animations.
 * The application divides the complete animation into 4 steps, each rotating 90 degrees
 * The first animation is defined in anims/cube_flip.h, from 0 degrees to 90 degrees
 * The first sub-animation rotates from 90 degrees to 180 degrees
 * The second sub-animation goes from 180 degrees to 270 degrees
 * The third sub-animation goes from 270 degrees to 360 degrees
 * Each sub-animation has act_time = -1000 set to achieve a 1s interval
 * between each action
 */
static lv_anim_t sub_anims[]...
/* Set viewport for all cube animations */
SDL_Rect cube_view;
/* Set the zoom effect according to the current animation progress */
#define ZOOM_IN ...
/* Cube animation rendering callback, for all cube animations */
void anim_cube_render(void)
/*
 * Cube animation start callback, for all cube animations
 * Modify the view to a specific value in the start callback,
 * First, take the side with smaller width and height in the default view
 * for example, if the width is smaller than the height, take the width.
 * And divide this value by 0.57 and plus 2 as the width and height of the new view
 * (the view needs to be square, otherwise subsequent transformations may be abnormal).
 * Since the distance from the center of the cube to any corner is d=sqrt(3)/2*a
 * a is the side length and is equal to 2.0 (the coordinate system is
 * [-1, -1, -1]-[1, 1, 1])
 * Therefore, in order to ensure that no matter how the cube is rotated,
 * any corner will not exceed the coordinate system, that is,
 * d should always be less than 1.0.
 * Then choose a scaling factor of 0.57. sqrt(3)/2*a*0.57=0.9873
 * plus 2 is just an empirical value, which ensures that the cube slightly exceeds the
 * screen and leaves no gaps on the left and right.
 * It can be removed according to actual application conditions
 */
void anim_cube_start(lv_anim_t *a)
/* Start callback */
void anim_cube_flip_start(lv_anim_t *a)
/* Animation callback, set the Y-axis rotation angle and scaling ratio
 * according to the current animation progress
 */
void anim_cube_flip(void *var, int32_t v)
/* End callback, determine the current animation segment according to
 * the value of a->var, and execute the next animation segment or end it
 */
void anim_cube_flip_end(lv_anim_t *a)

/* anims/cube_rotate.c */
/* start callback, just call anim_cube_start */
void anim_cube_rotate_start(lv_anim_t *a)
/* Animation callback, set the scale to 0.57 (see the previous section for the reason),
 * and set the rotation angle of the X and Y axes according to the animation progress */
void anim_cube_rotate(void *var, int32_t v)
/* End callback, restore animation flag, and restore progress bar */
void anim_cube_rotate_end(lv_anim_t *a)

/* anims/cube_lyric.c */
/*
 * Define two additional sub-animations. In the application, each rotation and
 * each line of text rendering is divided into sub-animations to complete.
 * The animation starts from the left, and the main animation completes the two
 * lines of drawing on the left.
 * After the main animation is completed, enable the first rotation sub-animation,
 * rotating from left to right
 * After the rotation is completed, enable the first rendering sub-animation and
 * complete the drawing of the two lines on the right surface.
 * After drawing is completed, enable the second rotation sub-animation,
 * and repeat this cycle until all 6 surfaces are drawn.
 */
static lv_anim_t sub_anims[]...
/* Indicates the number of characters in the current line being drawn. */
static int line;
static int row;
static int col;
/*
 * The rendering callback is different from the ordinary cube.
 * It has an extra step of drawing on the cube, so it has an independent callback.
 * In this callback:
 * The first step is to set the cube as a framebuffer, which means that all
 * subsequent rendering will be drawn onto the cube.
 * The second step is to draw the current character
 * The third step is to reset the framebuffer, which means that subsequent rendering
 * is directly displayed on the screen
 * The fourth step is to render the cube to the screen
 */
void anim_cube_lyric_render(void)
/*
 * The starting callback first calls the cube general starting callback and
 * sets the rendering callback to anim_cube_lyric_render
 * Then rotate the cube to the left to facilitate subsequent animation
 */
void anim_cube_lyric_start(lv_anim_t *a)
/* Draw animation callback, update character index according to current progress,
 * trigger rendering */
void anim_cube_lyric(void *var, int32_t v)
/* Rotation animation callback, rotate the cube to the appropriate face according
 * to the current progress */
void anim_cube_lyric_sub(void *var, int32_t v)
/* The rotation animation ends callback. According to the length of the next line
 * of text, the drawing animation duration is updated (calculated as 300ms per word)
 * and the drawing animation is started.*/
void anim_cube_lyric_sub_end(lv_anim_t *a)
/*
 * Callback when the animation ends. The number of lines increases by one each time
 * the animation is finished.
 * If the number of lines is an odd number, it means that there is still one line that
 * has not been displayed. According to the length of the next line of text,
 * the duration of the drawing animation is updated (calculated at 300ms per word),
 * and the drawing animation is started.
 * If the number of rows is even, it means that the current page has been drawn,
 * than start the rotation animation.
 * If all 12 lines are drawn, end the animation
 * The DEMO has 12 rows in total, 2 rows per page. If you plan for other numbers of
rows,
 * the logic will be different.
 */
void anim_cube_lyric_end(lv_anim_t *a)

/* anims/fold.c */
/* Rendering callback.
 * The application divides the two images into four parts (each is divided into two
 * parts, left and right), so four rendering calls are made in the rendering callback.
*/
static void anim_fold_render(void)
/*
 * Start callback
 * 1 Set the view to 480x480 (picture size, optional, adjust according to
 *   actual situation)
 * 2 Reset the scale parameters of the 4 render objects according to the new view
 * 3 Divide the image into 4 parts, obj_fold[0] is the left half of image 1,
 *   obj_fold[1] is the right half of image 1, and so on.
 * 4 Set the render callback
 */
void anim_fold_start(lv_anim_t *a)
/*
 * Animation callbacks
 * The requirement for using rotation transformation is relatively complex,
 * because the rotation axis is constantly changing, and the rotation angle needs to be
 * inferred based on the offset value. Therefore, it is achieved by directly setting the
 * vertex coordinates. It only needs to continuously update the X-axis coordinates of
 * each vertex of the four objects in the animation callback. The two points on the
right
 * of obj_fold[0] and the two points on the left of obj_fold[1] are fixedly folded
inward
 * and unchanged. Therefore, the X coordinates of these four points do not need to be
 * changed, and only the Z coordinates need to be set to negative values (currently set
 * to 0~-0.2, adjusted according to the effect). The perspective transformation in the
 * vertex shader will automatically transform the effect of near large and far small.
 */
void anim_fold(void *var, int32_t v)
/* End callback */
void anim_fold_end(lv_anim_t *a)

/* anims/roller.c */
/* Rendering callback, render 6 pictures in sequence */
void anim_roller_render(void)
/*
 * Start callback
 * 1 Set the view to 2000x2000. Because it involves rotation, in order to avoid the
image
 *   exceeding the coordinates and causing cropping and loss of the screen, set it to a
 *   large value.
 * 2 Recalculate the size of the rendered object according to the new view, and set
 *   the Z axis offset to 0.20785, so that the image is a certain distance from the
 *   center, thus forming a barrel shape. The Z axis calculation is a simple Pythagorean
 *   theorem, sqrt(240^2 - 120^2) / 2000 * 2.0 = 0.20785, the image width is 240 (see
the
 *   image below), and since it is a hexagon, a simple sqrt(240^2 - 120^2) can calculate
 *   the distance from each face to the center. 2000 is the view size, and the scale
 *   ratio is calculated from it, and then multiplied by the range 2.0 (coordinates
 *   -1.0~1.0) to get the offset value. If it is not a hexagon, you need to calculate
the
 *   distance in other ways, and the way to calculate the scale ratio and offset value
 *   remains unchanged.
 * 3 Set the X-axis rotation to 30 and the Z-axis rotation to 15. In order to have a
 *   tilt effect, set them as needed.
 */
void anim_roller_start(lv_anim_t *a)
/* Animation callback. Add the rotation value to the Y axis of each image.
 * The first image is 0 degrees plus the rotation value, the second image is 60 degrees
 * plus the rotation value, and so on. */
void anim_roller(void *var, int32_t v)
/* End callback */
void anim_roller_end(lv_anim_t *a)

/* anims/stiker.c */
/*
 * Rendering callback
 * 1 Set obj_fb as framebuffer
 * 2 Clear obj_fb with color(0.0, 0.0, 0.0, 1.0) because we need the alpha of framebuffer
 *   always be 1.0 before each rendering
 * 3 Rendering obj_img1 to obj_fb as a backgroud
 * 4 Rendering obj_img0 to obj_fb as a stiker
 * 5 Reset to default framebuffer, rendering obj_fb to screen
 * In actual use, the two images can be rendered directly to the screen.
 * The DEMO is just to show the rendering function and framebuffer function.
 */
static void anim_stiker_render(void)
/* Start callback. Set the coordinates of the texture to 0,0 and call lv_gl_obj_move
 * to update the parameter values.
 */
void anim_stiker_start(lv_anim_t *a)
/* Animation callback. Set the coordinates according to the current animation progress,
 * and call lv_gl_obj_move to update the parameter values.
 */
void anim_stiker(void *var, int32_t v)
/* End callback */
void anim_stiker_end(lv_anim_t *a)

/* anims/slide_out.c */
/* Calls the common start callback and sets the animation area to be visible */
void anim_slide_out_start(lv_anim_t *a)
/* Animation callback, updates the X coordinates of the two images */
void anim_slide_out(void *var, int32_t v)
/* End callback */
void anim_slide_out_end(lv_anim_t *a)

/* anims/fade_out.c */
/* Calls the common start callback and sets the animation area to be visible */
void anim_fade_out_start(lv_anim_t *a)
/* Animation callback, updates the transparency of the two images */
void anim_fade_out(void *var, int32_t v)
/* End callback */
void anim_fade_out_end(lv_anim_t *a)

/* anims/fade_slide_out.c */
/* Calls the common start callback and sets the animation area to be visible */
void anim_fade_slide_out_start(lv_anim_t *a)
/* Animation callback, updates the X coordinates of the two images and the
 * transparency of first image according to the current animation progress */
void anim_fade_slide_out(void *var, int32_t v)
/* End callback */
void anim_fade_slide_out_end(lv_anim_t *a)

/* anims/photo_stream.c */
/* image height */
static int32_t img_h = 480;
/* image gap */
static int32_t gap_h = 20;
/*
 * Calculate the maximum Y coordinate based on the image height, image gap,
 * and number of images
 * max_y = n * img_h + (n - 1) * gap_h
 */
static int32_t max_y;
/*
 * Boundary value, used to reset to the top of the photo stream and continue
 * looping after the image reaches max_y
 * boundary = n * img_h + n * gap_h
 * Since the image needs to return to the top after the loop and needs to be
 * spaced from the first image, boundary has one more gap_h than max_y.
 */
static int32_t boundary;
/* Update image coordinates regularly */
static lv_timer_t *timer;
/* The coordinate offset increased by the timer*/
static int32_t timer_ofs = 0;
/* The coordinate offset increased by the last touch */
static int32_t touch_ofs_s = 0;
/* The coordinate offset increased by this touch */
static int32_t touch_ofs = 0;
/* Update and check the Y coordinate of the image to achieve animation effect */
static void update_y(void)
/* Timer callback */
static void lv_timer_cb(lv_timer_t *timer)
/*
 * Touch callback
 * LV_EVENT_PRESSED: Pause the timer and get the coordinates of the pressed
 * LV_EVENT_PRESSING: Get the current touch coordinates, compare with the pressed
 * coordinates, add touch_ofs_s to calculate the offset value and update the coordinates
 * LV_EVENT_RELEASED: Re-enable the timer and record the touch offset to touch_ofs_s
 * The reason for dividing into three offsets is to ensure the continuity of the
 * animation coordinates when the touch is pressed and released,
 * and to avoid coordinate shifting.
 */
static void touch_handler(lv_event_t * e)
/* Stop photo stream */
void anim_photo_stream_stop(void)
/* Initialize the photo stream, create a timer, calculate max_y, boundary, etc. */
void anim_photo_stream_start(lv_anim_t *a)
/* Animation callback
 * In fact, the photo stream is implemented using a timer and has nothing to do
 * in animation callback. The animation callback is used here just to unify the
 * interface and facilitate embedding into the DEMO framework.
 * The actual application development can just use the timer callback.
 */
void anim_photo_stream(void *var, int32_t v)
void anim_photo_stream_end(lv_anim_t *a)