From f75816a33a322f519b05dd4146bfe5f7a593efe0 Mon Sep 17 00:00:00 2001
From: Eike Hein <hein@kde.org>
Date: Sun, 3 Dec 2017 07:12:46 +0900
Subject: [PATCH] Initialize scale factor to the last scale factor set on any
 instance

Summary:
Plasma::Svg initializes SvgPrivate::scaleFactor to 1.0. On systems with
a higher value for Units:devicePixelRatio, that means Svg::setScaleFactor
gets called with a different value right after instanciation and a fair
amount of work is done twice.

This patch introduces a static SvgPrivate::s_lastScaleFactor,
initialized to 1.0 but updated in Svg::setScaleFactor.
SvgPrivate::scaleFactor is then initialized to the static every time
its instanciated. That means after the first time Svg::setScaleFactor
is called with e.g. 2.0, subsequent Svg instances get initialized
with 2.0.

This ends up shaving a decent amount of time off of startup on scaled
systems.

Reviewers: #plasma, davidedmundson, broulik

Subscribers: plasma-devel, #frameworks

Tags: #plasma, #frameworks

Differential Revision: https://phabricator.kde.org/D9119
---
 src/plasma/private/svg_p.h | 1 +
 src/plasma/svg.cpp         | 4 +++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/plasma/private/svg_p.h b/src/plasma/private/svg_p.h
index 1ad666f30..84b41ecfa 100644
--- a/src/plasma/private/svg_p.h
+++ b/src/plasma/private/svg_p.h
@@ -97,6 +97,7 @@ public:
 
     static QHash<QString, SharedSvgRenderer::Ptr> s_renderers;
     static QWeakPointer<Theme> s_systemColorsCache;
+    static qreal s_lastScaleFactor;
 
     Svg *q;
     QWeakPointer<Theme> theme;
diff --git a/src/plasma/svg.cpp b/src/plasma/svg.cpp
index 33bb94975..5118501e8 100644
--- a/src/plasma/svg.cpp
+++ b/src/plasma/svg.cpp
@@ -146,7 +146,7 @@ SvgPrivate::SvgPrivate(Svg *svg)
       colorGroup(Plasma::Theme::NormalColorGroup),
       lastModified(0),
       devicePixelRatio(1.0),
-      scaleFactor(1.0),
+      scaleFactor(s_lastScaleFactor),
       status(Svg::Status::Normal),
       multipleImages(false),
       themed(false),
@@ -700,6 +700,7 @@ void SvgPrivate::colorsChanged()
 
 QHash<QString, SharedSvgRenderer::Ptr> SvgPrivate::s_renderers;
 QWeakPointer<Theme> SvgPrivate::s_systemColorsCache;
+qreal SvgPrivate::s_lastScaleFactor = 1.0;
 
 Svg::Svg(QObject *parent)
     : QObject(parent),
@@ -746,6 +747,7 @@ void Svg::setScaleFactor(qreal ratio)
     }
 
     d->scaleFactor = floor(ratio);
+    d->s_lastScaleFactor = d->scaleFactor;
     //not resize() because we want to do it unconditionally
     QRectF rect;