XISelectEvent throws X Error: BadValue (integer out of range for operation)

Question

我正在尝试从 X11 读取事件，这是我的最小重现：

#include <X11/Xlib.h>
#include <X11/extensions/XInput2.h>
#include <dlfcn.h>
#include <stdlib.h>
#include <iostream>
#include <string.h>

int main() {
    if (getenv("DISPLAY") == NULL) return 1;

    void *x11 = dlopen("libX11.so.6", RTLD_GLOBAL | RTLD_LAZY);
    if (x11 == NULL) return 1;

    void *xInput2 = dlopen("libXi.so.6", RTLD_GLOBAL | RTLD_LAZY);
    if (xInput2 == NULL) return 1;

    // Check XInput2 functions are present, since libXi may contain XInput or XInput2.
    void *f = dlsym(xInput2, "XISelectEvents");
    if (f == NULL) return 1;

    // Load definitions
    dlsym(x11, "XOpenDisplay");
    dlsym(x11, "XDefaultRootWindow");
    dlsym(x11, "XQueryExtension");
    dlsym(x11, "XSync");
    dlsym(x11, "XNextEvent");
    dlsym(x11, "XSendEvent");
    dlsym(x11, "XFreeEventData");
    dlsym(x11, "XGetEventData");
    dlsym(xInput2, "XISelectEvents");

    Display *display = XOpenDisplay(NULL);
    if (display == NULL) return 1;

    int xiOpcode;
    int queryEvent;
    int queryError;
    XQueryExtension(display, "XInputExtension", &xiOpcode, &queryEvent, &queryError);

    Window root = XDefaultRootWindow(display);
    XIEventMask *xiMask = new XIEventMask;
    xiMask->deviceid = XIAllMasterDevices;
    xiMask->mask_len = XIMaskLen(XI_LASTEVENT);
    xiMask->mask = new unsigned char[xiMask->mask_len];

    XISetMask(xiMask->mask, XI_RawKeyPress);
    XISetMask(xiMask->mask, XI_RawKeyRelease);
    XISelectEvents(display, root, xiMask, 1);
    XSync(display, 0);

    delete [] xiMask->mask;
}

代码使用g++ test.cpp -lX11 -ldl -lXi

编译

它抛出以下错误：

X Error of failed request:  BadValue (integer parameter out of range for operation)
  Major opcode of failed request:  132 (XInputExtension)
  Minor opcode of failed request:  46 ()
  Value in failed request:  0xb
  Serial number of failed request:  14
  Current serial number in output stream:  15

我无法理解并对此做出反应，我们将不胜感激任何帮助。

我试过调试，发现错误正是在执行XISelectEvent时发生的。

Answer 1

我现在傻了，我忘了用new关键字在堆中分配的数组里面有垃圾

我不得不使用

memset(xiMask->mask, 0, xiMask->mask_len);

将数组中的所有值设置为0，然后根据需要开始设置每个元素的值。

更新：

我们可以使用 C++ 鲜为人知的特性，在单个表达式中使用 new T() 直接将最近分配的数组填充为 0。

这也是：

xiMask->mask = new unsigned char[xiMask->mask_len]();

XISelectEvent throws X Error: BadValue (integer out of range for operation)

XISelectEvent throws X Error: BadValue (integer out of range for operation)

c++

x11

xlib

xinput