configure - add warning when enabling xcb

diff --git a/configure.ac b/configure.ac
index 0751b39..a939879 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -4042,3 +4042,27 @@ if test "x${have_systemd_pkg}" = "xyes" -a "x${want_systemd}" = "xno"; then
    echo "                ||----w |"
    echo "                ||     ||"
 fi
+
+if test "x${with_x11}" = "xxcb"; then
+   echo "_____________________________________________________________________"
+   echo "!!-- WARNING --!!"
+   echo "_____________________________________________________________________"
+   echo "You have chosen to use XCB instead of Xlib. It is a myth that XCB"
+   echo "is amazingly faster than Xlib (when used sensibly). It can be"
+   echo "faster in a few corner cases on startup of an app, but it comes"
+   echo "with many downsides. One of those is more complex code inside"
+   echo "ecore_x, which is far less tested in XCB mode than Xlib. Also"
+   echo "the big catch is that OpenGL suppot basically requires Xlib anyway"
+   echo "so if you want OpenGL in X11, you need Xlib regardless and so you"
+   echo "gain nothing really in terms of speed and no savings in memory"
+   echo "because Xlib is still linked, loaded and used, BUT instead you"
+   echo "have OpenGL drivers working with an hybrid XCB/Xlib (mostly XCB)"
+   echo "toolkit and this is basically never tested by anyone working on"
+   echo "the OpenGL drivers, so you will have bugs. Do not enable XCB"
+   echo "and use OpenGL. XCB is only useful if you wish to shave a few Kb"
+   echo "off the memory footprint of a whole system and live with less"
+   echo "tested code, and possibly unimplemented features in ecore_x. To"
+   echo "remove the XCB setup, remove the --with-x11=xcb optiomn to"
+   echo "configure."
+   echo "_____________________________________________________________________"
+fi