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>

Xi/xiproperty.c

@@ -49,7 +49,8 @@ static struct dev_properties
     Atom type;
     char *name;
 } dev_properties[] = {
-    {0, XI_PROP_ENABLED}
+    {0, XI_PROP_ENABLED},
+    {0, XATOM_FLOAT}
 };
 
 static long XIPropHandlerID = 1;
@@ -137,6 +138,58 @@ XIPropToInt(XIPropertyValuePtr val, int *nelem_return, int **buf_return)
     return Success;
 }
 
+/**
+ * Convert the given property's value(s) into @nelem_return float values and
+ * store them in @buf_return. If @nelem_return is larger than the number of
+ * values in the property, @nelem_return is set to the number of values in the
+ * property.
+ *
+ * If *@buf_return is NULL and @nelem_return is 0, memory is allocated
+ * automatically and must be freed by the caller.
+ *
+ * Possible errors returned:
+ * Success
+ * BadMatch ... Wrong atom type, atom is not XA_FLOAT
+ * BadValue ... Wrong format, format is not 32
+ * BadAlloc ... NULL passed as buffer and allocation failed.
+ * BadLength ... @buff is NULL but @nelem_return is non-zero.
+ *
+ * @param val The property value
+ * @param nelem_return The maximum number of elements to return.
+ * @param buf_return Pointer to an array of at least @nelem_return values.
+ * @return Success or the error code if an error occured.
+ */
+_X_EXPORT int
+XIPropToFloat(XIPropertyValuePtr val, int *nelem_return, float **buf_return)
+{
+    int i;
+    float *buf;
+
+    if (!val->type || val->type != XIGetKnownProperty(XATOM_FLOAT))
+        return BadMatch;
+
+    if (val->format != 32)
+        return BadValue;
+    if (!*buf_return && *nelem_return)
+        return BadLength;
+
+    buf = *buf_return;
+
+    if (!buf && !(*nelem_return))
+    {
+        buf = xcalloc(val->size, sizeof(float));
+        if (!buf)
+            return BadAlloc;
+        *buf_return = buf;
+        *nelem_return = val->size;
+    } else if (val->size < *nelem_return)
+        *nelem_return = val->size;
+
+    for (i = 0; i < val->size && i < *nelem_return; i++)
+           buf[i] = ((float*)val->data)[i];
+
+    return Success;
+}
 
 /**
  * Init those properties that are allocated by the server and most likely used

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"