Introduce a 'System' theme to the styles.

Setting the theme to System chooses either the light or dark theme
based on the system theme colors. However, when reading the value of
the theme property, the value is never System, but the actual theme.

[ChangeLog][Controls][Material] Added Material.System theme enum value,
that can be used to let the Material style choose either the light or
dark theme based on the system theme colors.
[ChangeLog][Controls][Universal] Added Universal.System theme enum value,
that can be used to let the Universal style choose either the light or
dark theme based on the system theme colors.

Change-Id: Ibfc9f01953cb8322b64d59413cfbaef9d4bb28fd
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

1 files changed, 3 insertions, 3 deletions

diff --git a/src/imports/controls/doc/src/qtquickcontrols2-styles.qdoc b/src/imports/controls/doc/src/qtquickcontrols2-styles.qdoc
index 5ea56c49..d2c4c5f3 100644
--- a/src/imports/controls/doc/src/qtquickcontrols2-styles.qdoc
+++ b/src/imports/controls/doc/src/qtquickcontrols2-styles.qdoc
@@ -101,15 +101,15 @@
     of the methods described earlier) and certain style-specific attributes. The following
     example specifies that the preferred style is the Material style. Furthermore, when the
     application is run with the Material style, its theme is light and the accent color is
-    brown. However, if the application is run with the Universal style instead, the theme
-    is dark and the accent color is red.
+    brown. However, if the application is run with the Universal style instead, the accent
+    color is red and the appropriate theme is chosen based on the system theme colors.
 
     \code
     [Controls]
     Style=Material
 
     [Universal]
-    Theme=Dark
+    Theme=System
     Accent=Red
 
     [Material]