fix(flex): use min size when item is set to grow and parent is LV_SIZE_CONTENT (#8806)

Co-authored-by: cubic-dev-ai[bot] <191113872+cubic-dev-ai[bot]@users.noreply.github.com>
Co-authored-by: André <andre_miguel_costa@hotmail.com>

docs/src/common-widget-features/layouts/flex.rst

@@ -204,6 +204,30 @@ You can force Flex to put an item into a new line with
     Learn more about `CSS Flexbox`_.
 
 
+Edge cases and notes
+--------------------
+
+The following behaviors clarify interactions between flex grow, wrapping and size constraints:
+
+- Grow with LV_SIZE_CONTENT parent: If a flex container's size on the main axis is
+   :c:macro:`LV_SIZE_CONTENT` and it contains items with non-zero grow, the grown items
+   initially use their own minimum size when determining the container's content size.
+   If the container has min/max constraints that force a concrete size, the remaining
+   space is then distributed among grow items (respecting each item's min/max).
+
+- Wrapping with grow: For :cpp:enumerator:`LV_FLEX_FLOW_ROW_WRAP` and
+   :cpp:enumerator:`LV_FLEX_FLOW_COLUMN_WRAP`, wrapping is used as expected even when the
+   object is grown in the same direction and its size in that direction is
+   :c:macro:`LV_SIZE_CONTENT`. In this case the :c:macro:`LV_SIZE_CONTENT` constraint is
+   ignored to be consistent with how the object size is calculated, and the grown size is used.
+
+- Min/max as content or percent: Item min/max width/height can be set to
+   :c:macro:`LV_SIZE_CONTENT` or :cpp:expr:`LV_PCT(x)`. These constraints are respected
+   during grow and wrapping and can clamp size of grown items.
+
+- Gaps with zero-size grow: Padding/gap is still applied even if a grown item ends up
+   with zero size on the main axis; this matches CSS flex behavior.
+
 
 .. _flex_examples:
 

docs/src/common-widget-features/layouts/grid.rst

@@ -199,6 +199,15 @@ The columns will be placed from right to left.
 
 
 
+Edge cases and notes
+--------------------
+
+- Min/max as content or percent: Child Widgets can set min/max width/height to
+  :c:macro:`LV_SIZE_CONTENT` or :cpp:expr:`LV_PCT(x)`. These constraints are respected
+  when computing :c:macro:`LV_GRID_CONTENT` tracks (tracks sized to their largest
+  child) and when distributing space to FR-unit tracks.
+
+
 .. admonition::  Further Reading
 
     - Learn more about `CSS Grid`_ layout.

docs/src/common-widget-features/layouts/overview.rst

@@ -64,6 +64,7 @@ LVGL can be freely extended by a custom layout like this:
    ...
 
    MY_LAYOUT = lv_layout_register(my_layout_update, &user_data);
+   lv_layout_set_min_size_cb(MY_LAYOUT, my_layout_get_min_size); /* Optional */
 
    ...
 
@@ -72,6 +73,10 @@ LVGL can be freely extended by a custom layout like this:
        /* Will be called automatically if it's required to reposition/resize the children of "widget" */
    }
 
+The min size callback is optional and can be used to precompute the minimum size of all the children in
+the layout before sizing and positioning them. This is useful for layouts like flex that need to know
+the minimum size of children to properly calculate the grow size of the children.
+
 Custom style properties can be added which can be retrieved and used in the update
 callback. For example: