added delay to legacy updates to fix lag, and prevented mouse from selecting unmapped windows

CMakeLists.txt

 endif()
 
 if ( NOT SLOP_LEGACY_MODE )
-    set(SLOP_LEGACY_MODE FALSE CACHE BOOL "Legacy mode requires the XShape extension, is laggy, isn't guaranteed to be invisible on shutdown, isn't guaranteed to support opacity, and doesn't support custom shaders. Though it still might be desired since it doesn't require OpenGL to use.")
+    set(SLOP_LEGACY_MODE FALSE CACHE BOOL "Legacy mode requires the XShape extension, is laggy, isn't guaranteed to be invisible on shutdown, isn't guaranteed to support opacity, doesn't support custom shaders, and requires C++11 for the sleep_for functions. Though it still might be desired since it doesn't require OpenGL to use.")
 endif()
 
 project(slop)
     find_package(XExt REQUIRED)
     include_directories(${XEXT_INCLUDE_DIR})
     target_link_libraries(${EXECUTABLE_NAME} ${XEXT_LIBRARIES})
+    set_property(TARGET ${EXECUTABLE_NAME} PROPERTY CXX_STANDARD 11)
+    set_property(TARGET ${EXECUTABLE_NAME} PROPERTY CXX_STANDARD_REQUIRED ON)
 else()
     find_package(GLX REQUIRED)
     find_package(OpenGL REQUIRED)

src/mouse.cpp

         if ( children[i] == ignoreWindow ) {
             continue;
         }
+        XWindowAttributes attr;         
+        XGetWindowAttributes( x11->display, children[i], &attr );
+        if ( attr.map_state != IsViewable ) {
+            continue;
+        }
         glm::vec4 rect = getWindowGeometry(children[i], false);
         float a = pos.x - rect.x;
         float b = pos.y - rect.y;

src/xslop.cpp

         memory.draw( fake );
 
         // X11 explodes if we update as fast as possible, here's a tiny sleep.
-        //std::this_thread::sleep_for(std::chrono::milliseconds(10));
         XFlush(x11->display);
+        std::this_thread::sleep_for(std::chrono::milliseconds(10));
 
         // Then we draw the framebuffer to the screen
         if ( keyboard->anyKeyDown() || mouse->getButton( 3 ) ) {