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docs(layers): clarify how to control Widget layering (#9379)

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Co-authored-by: cubic-dev-ai[bot] <191113872+cubic-dev-ai[bot]@users.noreply.github.com>
This commit is contained in:
Victor Wheeler
2025-12-20 00:08:14 -07:00
committed by GitHub
parent e60b27c62c
commit 949e69a3d0
1 changed files with 21 additions and 15 deletions
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docs/src/common-widget-features/layers.rst
+17 -11
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@@ -7,9 +7,10 @@ Layers
When the term "layer" is used in LVGL documentation, it may refer to one of several When the term "layer" is used in LVGL documentation, it may refer to one of several
things: things:
1. for Widgets, the :ref:`layers_creation` creates a natural layering of Widgets; 1. For Widgets, the :ref:`layers_creation` creates a natural layering (Z-order) of
2. in the context of pixel rendering (drawing), there are :ref:`draw_layers`; Widgets sharing the same parent.
3. permanent :ref:`display_screen_layers` are part of each :ref:`display` object. 2. In the context of pixel rendering (drawing), there are :ref:`draw_layers`.
3. Permanent :ref:`display_screen_layers` are part of each :ref:`display` object.
#1 is covered below. #2 and #3 are covered in :ref:`draw_layers` and #1 is covered below. #2 and #3 are covered in :ref:`draw_layers` and
:ref:`display_screen_layers` respectively. :ref:`display_screen_layers` respectively.
@@ -59,17 +60,21 @@ its children.
Changing Order Changing Order
-------------- --------------
There are three explicit ways to bring a Widget to the foreground: There are three explicit ways to change a Widget's layer position (Z-order) among
Widgets that share the same parent:
- Use :cpp:expr:`lv_obj_move_to_index(widget, idx)` to move a Widget to a given index in the order of children. - Use :cpp:expr:`lv_obj_move_to_index(widget, idx)` to move a Widget to a new index.
- ``0``: background :0: Background
- ``child_num - 1``: foreground :child_count - 1: Foreground
- ``< 0``: count from the top, to move forward (up): :cpp:expr:`lv_obj_move_to_index(widget, lv_obj_get_index(widget) - 1)` :< 0: Count down from the top (-1 = topmost).
:lv_obj_get_index(widget) - 1: Move down 1 layer.
- Use :cpp:expr:`lv_obj_swap(widget1, widget2)` to swap the relative layer position of two Widgets. :lv_obj_get_index(widget) + 1: Move up 1 layer.
- When :cpp:expr:`lv_obj_set_parent(widget, new_parent)` is used, ``widget`` will be on the foreground of ``new_parent``.
- Use :cpp:expr:`lv_obj_swap(widget1, widget2)` to swap the layer positions (Z-orders)
of the two Widgets.
- When :cpp:expr:`lv_obj_set_parent(widget, new_parent)` is used, ``widget`` will
become the foremost child of ``new_parent``.
@@ -79,6 +84,7 @@ API
*** ***
.. API equals: .. API equals:
lv_obj_get_index
lv_obj_move_to_index lv_obj_move_to_index
lv_obj_swap lv_obj_swap
lv_obj_set_parent lv_obj_set_parent