Don't snap to auto-hidden panels

Summary:
When moving windows we don't want to snap against not visible windows
like auto-hidden panels.

BUG: 365892
FIXED-IN: 5.8.4

Test Plan: So far only auto-test, manual test will follow.

Reviewers: #kwin, #plasma

Subscribers: plasma-devel, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D3225

autotests/integration/move_resize_window_test.cpp

@@ -664,7 +664,6 @@ void MoveResizeWindowTest::testAdjustClientGeometryOfAutohidingX11Panel()
     QVERIFY(panelHiddenSpy.wait());
 
     // now try to snap again
-    QEXPECT_FAIL("", "BUG 365892", Continue);
     QCOMPARE(Workspace::self()->adjustClientPosition(testWindow, targetPoint, false), targetPoint);
 
     // and destroy the panel again

geometry.cpp

@@ -527,6 +527,8 @@ QPoint Workspace::adjustClientPosition(AbstractClient* c, QPoint pos, bool unres
                     continue;
                 if ((*l)->isMinimized())
                     continue; // is minimized
+                if (!(*l)->isShown(false))
+                    continue;
                 if ((*l)->tabGroup() && (*l) != (*l)->tabGroup()->current())
                     continue; // is not active tab
                 if (!((*l)->isOnDesktop(c->desktop()) || c->isOnDesktop((*l)->desktop())))