kdesktop: better support for old-school multihead setupsFat-Zer/fix/kdesktop-multihead

This fixes several issues on "old-school multihead" X11 setups (with
several screens per display i.e. when DISPLAY has form ":x.y"
also known as "TDE_MULTIHEAD" or "Zaphode mode"). Also it slightly
enhances functionality for more common xinerama setups. In particular:
* fixed an issue where on primary screen wallpaper is getting rendered
  for both secondary and primary on certain kdesktop configurations.
* fixed an issue on walpaper config dialog where previews for two
  monitors were displayed overlapped.
* update preview in config dialog in case a monitor gets
  connected/disconnected.
* some minor whitespace cleanup.

1 files changed, 6 insertions, 1 deletions

diff --git a/kcontrol/background/bgrender.cpp b/kcontrol/background/bgrender.cpp
index 522065711..650dc63a2 100644
--- a/kcontrol/background/bgrender.cpp
+++ b/kcontrol/background/bgrender.cpp
@@ -1206,7 +1206,12 @@ void KVirtualBGRenderer::initRenderers()
 
     m_bCommonScreen = m_pConfig->readBoolEntry("CommonScreen", _defCommonScreen);
 
-    m_numRenderers = m_bDrawBackgroundPerScreen ? TDEApplication::desktop()->numScreens() : 1;
+    if (m_bDrawBackgroundPerScreen && TDEApplication::desktop()->isVirtualDesktop()) {
+        m_numRenderers = TDEApplication::desktop()->numScreens();
+    } else {
+        m_numRenderers = 1;
+    }
+
     if (m_numRenderers < 2) {
         // Only one screen is currently available; deactivate per-screen rendering but do not overwrite multi-screen settings
         m_bDrawBackgroundPerScreen = false;