From 437a36a2bb86222f1c3d086c15a2f60eef898c1a Mon Sep 17 00:00:00 2001
From: David Edmundson <kde@davidedmundson.co.uk>
Date: Tue, 24 Apr 2018 23:20:14 +0200
Subject: [PATCH] [KScreen Effect] Fix fade to black

Summary:
When you have two windows ontop of each other and you turn them
transparent, evidently you'll be able to see through them.
Not only does it look unpolished if the desktop window flashes through
your windows, it can pose a privacy risk as you'd be able to briefly
look through the lock screen.

This patch fades apps to black intead of to transparent. As this looks
weird for panels, so windows are also faded to opaque (if relevant) at
the same rate.

BUG: 388384

Reviewers: #plasma, graesslin

Subscribers: luebking, plasma-devel, kwin, #kwin

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D9608
---
 effects/kscreen/kscreen.cpp | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/effects/kscreen/kscreen.cpp b/effects/kscreen/kscreen.cpp
index 2d167110b5..ee21ac5c20 100644
--- a/effects/kscreen/kscreen.cpp
+++ b/effects/kscreen/kscreen.cpp
@@ -105,19 +105,23 @@ void KscreenEffect::prePaintWindow(EffectWindow *w, WindowPrePaintData &data, in
 
 void KscreenEffect::paintWindow(EffectWindow *w, int mask, QRegion region, WindowPaintData &data)
 {
+    //fade to black and fully opaque
     switch (m_state) {
-    case StateFadingOut:
-        data.multiplyOpacity(1.0 - m_timeLine.currentValue());
-        break;
-    case StateFadedOut:
-        data.multiplyOpacity(0.0);
-        break;
-    case StateFadingIn:
-        data.multiplyOpacity(m_timeLine.currentValue());
-        break;
-    default:
-        // no adjustment
-        break;
+        case StateFadingOut:
+            data.setOpacity(data.opacity() + (1.0 - data.opacity()) * m_timeLine.currentValue());
+            data.multiplyBrightness(1.0 - m_timeLine.currentValue());
+            break;
+        case StateFadedOut:
+            data.multiplyOpacity(0.0);
+            data.multiplyBrightness(0.0);
+            break;
+        case StateFadingIn:
+            data.setOpacity(data.opacity() + (1.0 - data.opacity()) * (1.0 - m_timeLine.currentValue()));
+            data.multiplyBrightness(m_timeLine.currentValue());
+            break;
+        default:
+            // no adjustment
+            break;
     }
     effects->paintWindow(w, mask, region, data);
 }