From e4456347c498bffbda1b4b458482b27014a34fe2 Mon Sep 17 00:00:00 2001
From: Vlad Zagorodniy <vladzzag@gmail.com>
Date: Sun, 21 Apr 2019 00:52:15 +0300
Subject: [PATCH] Fix corner screen glows that suddenly pop up

Summary:
Depending on how pointer approaches a screen corner, the maximum
distance between two may be smaller than 2 * edgeDistance. This can
happen for example when approaching the corner along of any two adjacent
screen edges.

As a result, the calculated factor can be anywhere between 0 and 0.5
when pointer enters approachGeometry(). This change adjusts calculation
of the factor, so it always ranges from 0 to 1 no matter how the pointer
approaches corners.

Reviewers: #kwin, davidedmundson

Reviewed By: #kwin, davidedmundson

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D20707
---
 screenedge.cpp | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/screenedge.cpp b/screenedge.cpp
index e232c21a80..847628da6f 100644
--- a/screenedge.cpp
+++ b/screenedge.cpp
@@ -616,20 +616,21 @@ void Edge::updateApproaching(const QPoint &point)
     if (approachGeometry().contains(point)) {
         int factor = 0;
         const int edgeDistance = m_edges->cornerOffset();
-        // manhattan length for our edge
-        const int cornerDistance = 2*edgeDistance;
+        auto cornerDistance = [=](const QPoint &corner) {
+            return qMax(qAbs(corner.x() - point.x()), qAbs(corner.y() - point.y()));
+        };
         switch (border()) {
         case ElectricTopLeft:
-            factor = (point.manhattanLength()<<8) / cornerDistance;
+            factor = (cornerDistance(approachGeometry().topLeft())<<8) / edgeDistance;
             break;
         case ElectricTopRight:
-            factor = ((point - approachGeometry().topRight()).manhattanLength()<<8) / cornerDistance;
+            factor = (cornerDistance(approachGeometry().topRight())<<8) / edgeDistance;
             break;
         case ElectricBottomRight:
-            factor = ((point - approachGeometry().bottomRight()).manhattanLength()<<8) / cornerDistance;
+            factor = (cornerDistance(approachGeometry().bottomRight())<<8) / edgeDistance;
             break;
         case ElectricBottomLeft:
-            factor = ((point - approachGeometry().bottomLeft()).manhattanLength()<<8) / cornerDistance;
+            factor = (cornerDistance(approachGeometry().bottomLeft())<<8) / edgeDistance;
             break;
         case ElectricTop:
             factor = (qAbs(point.y() - approachGeometry().y())<<8) / edgeDistance;