Use runtime detection of XInput 2.1 to disable legacy wheel events

Ensure we fall back to using wheel button events if xinput 2.1
scroll events are not available. Handles lack of xinput 2.1
support in the server or in the input devices drivers.

Task-number: QTBUG-38169
Change-Id: Ie4ad9069f648d0ab02d8f9540ed01ad58fd9e9d8
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/src/plugins/platforms/xcb/qxcbconnection.cpp b/src/plugins/platforms/xcb/qxcbconnection.cpp
index f5f6c712c5..e3b81c2b40 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection.cpp
@@ -1791,6 +1791,19 @@ bool QXcbConnection::xi2GetValuatorValueIfSet(void *event, int valuatorNum, doub
     return true;
 }
 
+bool QXcbConnection::xi2GetButtonState(void *event, int buttonNum)
+{
+    xXIDeviceEvent *xideviceevent = static_cast<xXIDeviceEvent *>(event);
+    unsigned char *buttonsMaskAddr = (unsigned char*)&xideviceevent[1];
+
+    for (int i = 0; i < (xideviceevent->buttons_len * 4); i++) {
+        if (buttonNum < 8)
+            return (buttonsMaskAddr[i] & (1 << buttonNum));
+        buttonNum -= 8;
+    }
+    return false;
+}
+
 // Starting from the xcb version 1.9.3 struct xcb_ge_event_t has changed:
 // - "pad0" became "extension"
 // - "pad1" and "pad" became "pad0"