Document expose event behavior

Document that "visible"-but-obscured windows may not
get expose events for various audiences: QTestLib
users, platform plugin authors and on the QExposeEvent
itself. QWindow::exposeEvent() already has this documented
and is not changed.

Task-number: QTBUG-50414
Change-Id: I91042e8b1c70e48f10e692b2e80367d242a8ccbe
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 11 insertions, 0 deletions

diff --git a/src/testlib/qtestcase.qdoc b/src/testlib/qtestcase.qdoc
index 1b1a8b6007..2d1e27ec40 100644
--- a/src/testlib/qtestcase.qdoc
+++ b/src/testlib/qtestcase.qdoc
@@ -1084,6 +1084,10 @@
     This is mainly useful for asynchronous systems like X11, where a window will be mapped to screen some
     time after being asked to show itself on the screen.
 
+    Note that a window that is mapped to screen may still not be considered exposed if the window client
+    area is completely covered by other windows, or if the window is otherwise not visible. This function
+    will then time out when waiting for such a window.
+
     \sa QTest::qWaitForWindowActive(), QWindow::isExposed()
 */
 
@@ -1106,6 +1110,13 @@
     This is mainly useful for asynchronous systems like X11, where a window will be mapped to screen some
     time after being asked to show itself on the screen.
 
+    Note that a window that is mapped to screen may still not be considered exposed if the window client
+    area is completely covered by other windows, or if the window is otherwise not visible. This function
+    will then time out when waiting for such a window.
+
+    A specific configuration where this happens is when using QGLWidget as a viewport widget on macOS:
+    The viewport widget gets the expose event, not the parent widget.
+
     \sa QTest::qWaitForWindowActive()
 */