[effects/wobblywindows] Draw clients below opaque wobbly windows

Summary:
Given that wobbly windows effect takes optimized render path, it needs
to clear the clip region of about to be transformed opaque window.

BUG: 411092
FIXED-IN: 5.17.0

Reviewers: #kwin, davidedmundson

Reviewed By: #kwin, davidedmundson

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D23774

effects/wobblywindows/wobblywindows.cpp

@@ -249,6 +249,10 @@ void WobblyWindowsEffect::prePaintWindow(EffectWindow* w, WindowPrePaintData& da
         bool stop = false;
         qreal updateTime = time;
 
+        // We have to reset the clip region in order to render clients below
+        // opaque wobbly windows.
+        data.clip = QRegion();
+
         while (!stop && (updateTime > maxTime)) {
 #if defined VERBOSE_MODE
             qCDebug(KWINEFFECTS) << "loop time " << updateTime << " / " << time;