[LVGL 9.0] Image rotation will not work properly if the image is partially updated

Sheng_LIANG · May 7, 2024, 6:56am

Description

What MCU/Processor/Board and compiler are you using?

PC Simulator

What LVGL version are you using?

V9.0

What do you want to achieve?

Using a separated thread to draw a custom image using lvgl canvas.
Rotate the custom image and draw it on the screen when LV_EVENT_DRAW_MAIN event is received.

What have you tried so far?

I found the image rotation can work if I use lv_obj_invalidate() without specify the area (which means the whole object will be redraw). However, I use lv_obj_invalidate(lv_area_t*) to specify the updated area, the updated area will not be rotated.

Code to reproduce

The following is the code of main function.
/* lvgl initialization code /
…
/ lvgl initialization code */

lv_delay_set_cb(SDL_Delay);
BaseWindow * baseWindow = new BaseWindow();
lv_thread_t thread;
lv_thread_init(&thread, LV_THREAD_PRIO_MID, mainThread, 0, baseWindow);
baseWindow->load();

/*Handle LVGL tasks*/
while (1) {
    baseWindow->lock();
    int timeTillNext = lv_timer_handler();
    baseWindow->unlock();
    lv_delay_ms(timeTillNext);
}

The following is the code of mainThread
static void mainThread(void* args) {
BaseWindow* win = (BaseWindow*) args;

lv_obj_t *canvas = lv_canvas_create(lv_obj_create(nullptr));
lv_canvas_set_draw_buf(canvas, win->getBuffer());
lv_canvas_fill_bg(canvas,  lv_color_white(), LV_OPA_COVER);

int counter = 0;

while(true) {
    win->lock();
    lv_layer_t layer;

    lv_canvas_init_layer(canvas, &layer);

    lv_draw_rect_dsc_t rect_dsc;
    lv_area_t rect_area = {700, 300, 900, 500};
    lv_draw_rect_dsc_init(&rect_dsc);

    rect_dsc.bg_color = lv_color_white();
    lv_draw_rect(&layer, &rect_dsc, &rect_area);

    lv_draw_arc_dsc_t arc_dsc;
    lv_draw_arc_dsc_init(&arc_dsc);

    arc_dsc.center.x = 800;
    arc_dsc.center.y = 400;
    arc_dsc.color = lv_color_make(0, 255, 255);
    arc_dsc.width = 10;
    arc_dsc.start_angle = 0 + counter;
    arc_dsc.end_angle = 280;
    arc_dsc.radius = 100;
    arc_dsc.rounded = 1;

    lv_draw_arc(&layer, &arc_dsc);

    lv_draw_label_dsc_t label_dsc;
    lv_draw_label_dsc_init(&label_dsc);

    char textBuf[255] = {0};
    lv_snprintf(textBuf, 255, "Hello world %d \n", counter);

    label_dsc.color = lv_color_make(255, 0, 0);
    label_dsc.text = textBuf;

    lv_area_t area;
    area.x1 = 100;
    area.x2 = 400;
    area.y1 = 100;
    area.y2 = 400;

    lv_draw_rect(&layer, &rect_dsc, &area);
    lv_draw_label(&layer, &label_dsc, &area);

    lv_canvas_finish_layer(canvas, &layer);
    win->invalidate(&area);
    win->invalidate(&rect_area);
    win->unlock();

    counter++;

    if(counter > 50)
        counter = 0;
    lv_delay_ms(100);
}

}

The following is the code of event handler LV_EVENT_DRAW_MAIN
void onDraw(lv_layer_t* layer) {
lv_draw_image_dsc_t drawImageDsc;
lv_area_t area = {0, 0, getWidth(), getHeight()};
lv_draw_image_dsc_init(&drawImageDsc);

    lv_draw_buf_to_image(m_drawbuffer, &m_content);

    drawImageDsc.src = &m_content;
    drawImageDsc.pivot.x = LV_HOR_RES / 2;
    drawImageDsc.pivot.y = LV_VER_RES / 2;
    drawImageDsc.rotation = 45;
    lv_draw_image(layer, &drawImageDsc, &area);
}

Screenshot and/or video

The incorrect result.

The expected result.