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+# Displays
+
+``` important:: The basic concept of a *display* in LVGL is explained in the [Porting](/porting/display) section. So before reading further, please read the [Porting](/porting/display) section first.
+```
+
+## Multiple display support
+
+In LVGL you can have multiple displays, each with their own driver and objects. The only limitation is that every display needs to have the same color depth (as defined in `LV_COLOR_DEPTH`).
+If the displays are different in this regard the rendered image can be converted to the correct format in the drivers `flush_cb`.
+
+Creating more displays is easy: just initialize more display buffers and register another driver for every display.
+When you create the UI, use `lv_disp_set_default(disp)` to tell the library on which display to create objects.
+
+Why would you want multi-display support? Here are some examples:
+- Have a "normal" TFT display with local UI and create "virtual" screens on VNC on demand. (You need to add your VNC driver).
+- Have a large TFT display and a small monochrome display.
+- Have some smaller and simple displays in a large instrument or technology.
+- Have two large TFT displays: one for a customer and one for the shop assistant.
+
+### Using only one display
+Using more displays can be useful but in most cases it's not required. Therefore, the whole concept of multi-display handling is completely hidden if you register only one display.
+By default, the last created (and only) display is used.
+
+`lv_scr_act()`, `lv_scr_load(scr)`, `lv_layer_top()`, `lv_layer_sys()`, `LV_HOR_RES` and `LV_VER_RES` are always applied on the most recently created (default) display.
+If you pass `NULL` as `disp` parameter to display related functions the default display will usually be used.
+E.g. `lv_disp_trig_activity(NULL)` will trigger a user activity on the default display. (See below in [Inactivity](#Inactivity)).
+
+### Mirror display
+
+To mirror the image of a display to another display, you don't need to use multi-display support. Just transfer the buffer received in `drv.flush_cb` to the other display too.
+
+### Split image
+You can create a larger virtual display from an array of smaller ones. You can create it as below:
+1. Set the resolution of the displays to the large display's resolution.
+2. In `drv.flush_cb`, truncate and modify the `area` parameter for each display.
+3. Send the buffer's content to each real display with the truncated area.
+
+## Screens
+
+Every display has its own set of [screens](overview/object#screen-the-most-basic-parent) and the objects on each screen.
+
+Be sure not to confuse displays and screens:
+
+* **Displays** are the physical hardware drawing the pixels.
+* **Screens** are the high-level root objects associated with a particular display. One display can have multiple screens associated with it, but not vice versa.
+
+Screens can be considered the highest level containers which have no parent.
+A screen's size is always equal to its display and their origin is (0;0). Therefore, a screen's coordinates can't be changed, i.e. `lv_obj_set_pos()`, `lv_obj_set_size()` or similar functions can't be used on screens.
+
+A screen can be created from any object type but the two most typical types are [Base object](/widgets/obj) and [Image](/widgets/core/img) (to create a wallpaper).
+
+To create a screen, use `lv_obj_t * scr = lv_<type>_create(NULL, copy)`. `copy` can be an existing screen copied into the new screen.
+
+To load a screen, use `lv_scr_load(scr)`. To get the active screen, use `lv_scr_act()`. These functions work on the default display. If you want to specify which display to work on, use `lv_disp_get_scr_act(disp)` and `lv_disp_load_scr(disp, scr)`. A screen can be loaded with animations too. Read more [here](object.html#load-screens).
+
+Screens can be deleted with `lv_obj_del(scr)`, but ensure that you do not delete the currently loaded screen.
+
+### Transparent screens
+
+Usually, the opacity of the screen is `LV_OPA_COVER` to provide a solid background for its children. If this is not the case (opacity &lt; 100%) the display's background color or image will be visible.
+See the [Display background](#display-background) section for more details. If the display's background opacity is also not `LV_OPA_COVER` LVGL has no solid background to draw.
+
+This configuration (transparent screen and display) could be used to create for example OSD menus where a video is played on a lower layer, and a menu is overlayed on an upper layer.
+
+To handle transparent displays, special (slower) color mixing algorithms need to be used by LVGL so this feature needs to enabled with `LV_COLOR_SCREEN_TRANSP` in `lv_conf.h`.
+The Alpha channel of 32-bit colors will be 0 where there are no objects and 255 where there are solid objects.
+
+In summary, to enable transparent screens and displays for OSD menu-like UIs:
+- Enable `LV_COLOR_SCREEN_TRANSP` in `lv_conf.h`
+- Set the screen's opacity to `LV_OPA_TRANSP` e.g. with `lv_obj_set_style_local_bg_opa(lv_scr_act(), LV_OBJMASK_PART_MAIN, LV_STATE_DEFAULT, LV_OPA_TRANSP)`
+- Set the display opacity to `LV_OPA_TRANSP` with `lv_disp_set_bg_opa(NULL, LV_OPA_TRANSP);`
+
+## Features of displays
+
+### Inactivity
+
+A user's inactivity time is measured on each display. Every use of an [Input device](/overview/indev) (if [associated with the display](/porting/indev#other-features)) counts as an activity.
+To get time elapsed since the last activity, use `lv_disp_get_inactive_time(disp)`. If `NULL` is passed, the lowest inactivity time among all displays will be returned (**NULL isn't just the default display**).
+
+You can manually trigger an activity using `lv_disp_trig_activity(disp)`. If `disp` is `NULL`, the default screen will be used (**and not all displays**).
+
+### Background
+Every display has a background color, background image and background opacity properties. They become visible when the current screen is transparent or not positioned to cover the whole display.
+
+The background color is a simple color to fill the display. It can be adjusted with `lv_disp_set_bg_color(disp, color)`;
+
+The display background image is a path to a file or a pointer to an `lv_img_dsc_t` variable (converted image data) to be used as wallpaper. It can be set with `lv_disp_set_bg_image(disp, &my_img)`;
+If a background image is configured the background won't be filled with `bg_color`.
+
+The opacity of the background color or image can be adjusted with `lv_disp_set_bg_opa(disp, opa)`.
+
+The `disp` parameter of these functions can be `NULL` to select the default display.
+
+
+
+## API
+
+```eval_rst
+
+.. doxygenfile:: lv_disp.h
+  :project: lvgl
+
+```