Xi: add XATOM_FLOAT to server-defined properties.

This property is used to denote type float for input properties. Such
properties can be accessed easily through the XIPropToFloat() function.

Code originally written by Simon Thum.

Signed-off-by: Peter Hutterer <peter.hutterer@redhat.com>

include/exevents.h

@@ -257,4 +257,10 @@ extern _X_EXPORT int XIPropToInt(
         int **buf_return
 );
 
+extern _X_EXPORT int XIPropToFloat(
+        XIPropertyValuePtr val,
+        int *nelem_return,
+        float **buf_return
+);
+
 #endif /* EXEVENTS_H */

include/xserver-properties.h

@@ -26,6 +26,10 @@
 #ifndef _XSERVER_PROPERTIES_H_
 #define _XSERVER_PROPERTIES_H_
 
+/* Type for a 4 byte float. Storage format IEEE 754 in client's default
+ * byte-ordering. */
+#define XATOM_FLOAT "FLOAT"
+
 /* BOOL. 0 - device disabled, 1 - device enabled */
 #define XI_PROP_ENABLED      "Device Enabled"