Workaround source compatibility issue introduced by xcb 1.9.3

Previous version of the struct:

typedef struct {
    uint8_t  response_type;  /**< Type of the response */
    uint8_t  pad0;           /**< Padding */
    uint16_t sequence;       /**< Sequence number */
    uint32_t length;
    uint16_t event_type;
    uint16_t pad1;
    uint32_t pad[5];         /**< Padding */
    uint32_t full_sequence;  /**< full sequence */
} xcb_ge_event_t;

New version of it:

typedef struct xcb_ge_event_t {
    uint8_t  response_type; /**<  */
    uint8_t  extension; /**<  */
    uint16_t sequence; /**<  */
    uint32_t length; /**<  */
    uint16_t event_type; /**<  */
    uint8_t  pad0[22]; /**<  */
    uint32_t full_sequence; /**<  */
} xcb_ge_event_t;

Changes are:
- "pad0" became "extension"
- "pad1" and "pad" became "pad0"

More details in https://bugs.freedesktop.org/show_bug.cgi?id=71502

Task-number: QTBUG-34748
Change-Id: Ibd801c11510f75fa82d5c14346b95236142487ac
Reviewed-by: Uli Schlachter <psychon@znc.in>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

1 files changed, 19 insertions, 3 deletions

diff --git a/src/plugins/platforms/xcb/qxcbconnection.cpp b/src/plugins/platforms/xcb/qxcbconnection.cpp
index cc8c42f96b..4d2735ca85 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection.cpp
@@ -1749,10 +1749,26 @@ bool QXcbConnection::xi2GetValuatorValueIfSet(void *event, int valuatorNum, doub
     return true;
 }
 
-bool QXcbConnection::xi2PrepareXIGenericDeviceEvent(xcb_ge_event_t *event, int opCode)
+// Starting from the xcb version 1.9.3 struct xcb_ge_event_t has changed:
+// - "pad0" became "extension"
+// - "pad1" and "pad" became "pad0"
+// New and old version of this struct share the following fields:
+// NOTE: API might change again in the next release of xcb in which case this comment will
+// need to be updated to reflect the reality.
+typedef struct qt_xcb_ge_event_t {
+    uint8_t  response_type;
+    uint8_t  extension;
+    uint16_t sequence;
+    uint32_t length;
+    uint16_t event_type;
+} qt_xcb_ge_event_t;
+
+bool QXcbConnection::xi2PrepareXIGenericDeviceEvent(xcb_ge_event_t *ev, int opCode)
 {
-    // xGenericEvent has "extension" on the second byte, xcb_ge_event_t has "pad0".
-    if (event->pad0 == opCode) {
+    qt_xcb_ge_event_t *event = (qt_xcb_ge_event_t *)ev;
+    // xGenericEvent has "extension" on the second byte, the same is true for xcb_ge_event_t starting from
+    // the xcb version 1.9.3, prior to that it was called "pad0".
+    if (event->extension == opCode) {
         // xcb event structs contain stuff that wasn't on the wire, the full_sequence field
         // adds an extra 4 bytes and generic events cookie data is on the wire right after the standard 32 bytes.
         // Move this data back to have the same layout in memory as it was on the wire