lvgl: add frame_incomplete information to display_write

In frames with multiple writes (officially supported through
`CONFIG_LV_Z_VDB_SIZE`) the display needs to be signalled that the
current frame is over and the content should be displayed.
This allows displays to present the UI without tearing artifacts.

Signed-off-by: Martin Stumpf <[email protected]>

Author: Finomnis

doc/releases/release-notes-4.1.rst

@@ -282,6 +282,9 @@ Trusted Firmware-M
 LVGL
 ****
 
+* Added ``frame_incomplete`` support to indicate whether a write is the last
+  write of the frame (:github:`81250`)
+
 Tests and Samples
 *****************
 

modules/lvgl/lvgl_display.c

@@ -25,6 +25,7 @@ void lvgl_flush_thread_entry(void *arg1, void *arg2, void *arg3)
 		k_msgq_get(&flush_queue, &flush, K_FOREVER);
 		data = (struct lvgl_disp_data *)flush.disp_drv->user_data;
 
+		flush.desc.frame_incomplete = !lv_disp_flush_is_last(flush.disp_drv);
 		display_write(data->display_dev, flush.x, flush.y, &flush.desc,
 			      flush.buf);
 
@@ -132,6 +133,7 @@ void lvgl_flush_display(struct lvgl_display_flush *request)
 	struct lvgl_disp_data *data =
 		(struct lvgl_disp_data *)request->disp_drv->user_data;
 
+	request->desc.frame_incomplete = !lv_disp_flush_is_last(request->disp_drv);
 	display_write(data->display_dev, request->x, request->y,
 		      &request->desc, request->buf);
 	lv_disp_flush_ready(request->disp_drv);

modules/lvgl/lvgl_display_mono.c

@@ -14,7 +14,6 @@ void lvgl_flush_cb_mono(lv_disp_drv_t *disp_drv, const lv_area_t *area, lv_color
 	uint16_t h = area->y2 - area->y1 + 1;
 	struct lvgl_disp_data *data = (struct lvgl_disp_data *)disp_drv->user_data;
 	const struct device *display_dev = data->display_dev;
-	struct display_buffer_descriptor desc;
 	const bool is_epd = data->cap.screen_info & SCREEN_INFO_EPD;
 	const bool is_last = lv_disp_flush_is_last(disp_drv);
 
@@ -29,10 +28,14 @@ void lvgl_flush_cb_mono(lv_disp_drv_t *disp_drv, const lv_area_t *area, lv_color
 		data->blanking_on = true;
 	}
 
-	desc.buf_size = (w * h) / 8U;
-	desc.width = w;
-	desc.pitch = w;
-	desc.height = h;
+	struct display_buffer_descriptor desc = {
+		.buf_size = (w * h) / 8U,
+		.width = w,
+		.pitch = w,
+		.height = h,
+		.frame_incomplete = !is_last,
+	};
+
 	display_write(display_dev, area->x1, area->y1, &desc, (void *)color_p);
 	if (data->cap.screen_info & SCREEN_INFO_DOUBLE_BUFFER) {
 		display_write(display_dev, area->x1, area->y1, &desc, (void *)color_p);