[platforms] Call setSoftWareCursor in init instead of ctor

Summary:
Platform::setSoftWareCursor creates connections to the Cursor in order
to trigger repaints whenever the cursor position changes. The Cursor is
created before Platform::init is called, but after the Platform is
created. Thus the call needs to happen in init, otherwise the cursor
is not rendered correctly.

BUG: 356328
FIXED-IN: 5.7.0

Reviewers: #kwin, #plasma_on_wayland

Subscribers: plasma-devel, kwin

Tags: #plasma_on_wayland, #kwin

Differential Revision: https://phabricator.kde.org/D2025

plugins/platforms/fbdev/fb_backend.cpp

@@ -38,7 +38,6 @@ namespace KWin
 FramebufferBackend::FramebufferBackend(QObject *parent)
     : Platform(parent)
 {
-    setSoftWareCursor(true);
 }
 
 FramebufferBackend::~FramebufferBackend()
@@ -61,6 +60,7 @@ QPainterBackend *FramebufferBackend::createQPainterBackend()
 
 void FramebufferBackend::init()
 {
+    setSoftWareCursor(true);
     LogindIntegration *logind = LogindIntegration::self();
     auto takeControl = [logind, this]() {
         if (logind->hasSessionControl()) {

plugins/platforms/virtual/virtual_backend.cpp

@@ -42,7 +42,6 @@ VirtualBackend::VirtualBackend(QObject *parent)
             qDebug() << "Screenshots saved to: " << m_screenshotDir->path();
         }
     }
-    setSoftWareCursor(true);
     setSupportsPointerWarping(true);
 }
 
@@ -50,6 +49,7 @@ VirtualBackend::~VirtualBackend() = default;
 
 void VirtualBackend::init()
 {
+    setSoftWareCursor(true);
     m_size = initialWindowSize();
     setReady(true);
     waylandServer()->seat()->setHasPointer(true);