[effects/blur] Disable texture cache on Wayland

Summary:
It is known to create problems especially on multi-screen and is not as
important on Wayland as it used to be on X11 thanks to things like
buffer age and in general better rendering.

Test Plan: Opened the config module and verified that the option is
hidden

Reviewers: #kwin, #plasma

Subscribers: plasma-devel, kwin

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D9879

effects/blur/CMakeLists.txt

@@ -12,6 +12,7 @@ target_link_libraries(kwin_blur_config
     KF5::ConfigWidgets
     KF5::I18n
     KF5::Service
+    KF5::WindowSystem
 )
 
 kcoreaddons_desktop_to_json(kwin_blur_config blur_config.desktop SERVICE_TYPES kcmodule.desktop)

effects/blur/blur.cpp

@@ -118,7 +118,7 @@ void BlurEffect::reconfigure(ReconfigureFlags flags)
     if (shader)
         shader->setRadius(radius);
 
-    m_shouldCache = BlurConfig::cacheTexture();
+    m_shouldCache = effects->waylandDisplay() ? false : BlurConfig::cacheTexture();
 
     windows.clear();
 

effects/blur/blur_config.cpp

@@ -25,6 +25,7 @@
 #include <kwineffects_interface.h>
 #include <KAboutData>
 #include <KPluginFactory>
+#include <KWindowSystem>
 
 K_PLUGIN_FACTORY_WITH_JSON(BlurEffectConfigFactory,
                            "blur_config.json",
@@ -37,6 +38,9 @@ BlurEffectConfig::BlurEffectConfig(QWidget *parent, const QVariantList &args)
     : KCModule(KAboutData::pluginData(QStringLiteral("blur")), parent, args)
 {
     ui.setupUi(this);
+    if (KWindowSystem::isPlatformWayland()) {
+        ui.kcfg_CacheTexture->setVisible(false);
+    }
     BlurConfig::instance(KWIN_CONFIG);
     addConfig(BlurConfig::self(), this);