FlexBox: Update the default value of FlexItem::alignSelf to match CSS implementations

BREAKING-CHANGES.txt

@@ -4,6 +4,29 @@ JUCE breaking changes
 develop
 =======
 
+Change
+------
+FlexItem::alignSelf now defaults to "autoAlign" rather than "stretch".
+
+Possible Issues
+---------------
+FlexBox layouts will be different in cases where FlexBox::alignItems is set to
+a value other than "stretch". This is because each FlexItem will now default
+to using the FlexBox's alignItems value. Layouts that explicitly set
+FlexItem::alignSelf on each item will not be affected.
+
+Workaround
+----------
+To restore the previous layout behaviour, set FlexItem::alignSelf to "stretch"
+on all FlexItems that would otherwise use the default value for alignSelf.
+
+Rationale
+---------
+The new behaviour more closely matches the behaviour of CSS FlexBox
+implementations. In CSS, "align-self" has an initial value of "auto", which
+computes to the parent's "align-items" value.
+
+
 Change
 ------
 Functions on AudioPluginInstance that can add parameters have been made

modules/juce_gui_basics/layout/juce_FlexItem.h

@@ -104,7 +104,7 @@ public:
         This determines the alignment of the item along the cross-axis (perpendicular to the direction
         of flow).
     */
-    AlignSelf alignSelf = AlignSelf::stretch;
+    AlignSelf alignSelf = AlignSelf::autoAlign;
 
     //==============================================================================
     /** This constant can be used for sizes to indicate that 'auto' mode should be used. */