[X11] Question about TouchCancel event like ACTION_CANCEL in android

강정현 jhyuni.kang at samsung.com
Wed Apr 15 23:50:41 PDT 2015

Hello, Peter Hutterer.


I’m planning to add a “Event cancel”(Touch Cancel?) event in x11

Like below article I want to send a event to apps for notification about
current events are canceled!.


How/What I doing for this job?

I need your advise. Please give me your help.


Thanks and regards,

Jeonghyun Kang.


From: 강정현 [mailto:jhyuni.kang at samsung.com] 
Sent: Wednesday, April 15, 2015 7:39 PM
To: 'xorg-devel at lists.x.org'
Subject: [X11] Question about TouchCancel event like ACTION_CANCEL in


Hello, Dears.

I send this email again. Because of HTML (not text)


I'm planning to add a touch cancel event(like ACTION_CANCEL in Android) in
X11 protocol.


So I invested XI events and I found a variable named "flags" in DeviceEvent

The "flags" variable can get values like below.



(defined in XI2.h)

/* Device event flags (common) */

/* Device event flags (key events only) */

#define XIKeyRepeat                             (1 << 16)

/* Device event flags (pointer events only) */

#define XIPointerEmulated                       (1 << 16)

/* Device event flags (touch events only) */

#define XITouchPendingEnd                       (1 << 16)

#define XITouchEmulatingPointer                 (1 << 17)



So I think how about insert "Device event flags" for a touch cancel event
like below.

#define XITouchCancel  (1 << 18)


#define XIPointerCancel (1 << 18)

we can distinguish Normal touch events and a touch cancel event using
XITouchCancel definition.


Another way is make new events: struct TouchCancelEvent( have a type


Each method has its advantages and disadvantages.


So I hope to hear opinions.

Would you give me some advice or opinion?


I will wait your reply.

Best regards,

Jeonghyun Kang.


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