在CGEvent点击中获取修改键 [英] Obtaining modifier key pressed in CGEvent tap

问题描述

设置事件点击，我无法确定给定CGEvent的修饰符键。

  CGEventFlags flagsp指向; 
 
 flagsP = CGEventGetFlags（event）; 
 
 NSLog（@flags：0x％llX，flagsP）; 
 NSLog（@stored：0x％llX，kCGEventFlagMaskCommand）; 
 
 if（flagsP == kCGEventFlagMaskCommand）{
 NSLog（@command）; 
} 
  

鉴于上述代码段，第一个NSLog从第二个NSLog返回一个不同的值。当命令修改键被按下时，条件不会被触发，不要惊讶。

我需要确定是否按照给定的命令，备用，选项，控制或移位CGEvent。首先，我需要帮助才能理解为什么上述不起作用。

谢谢！

解决方案

这些是位掩码，它们将被逐个或并入到从 CGEventGetFlags （或自己创建一个事件时传递）的值。

由于没有单个位掩码将不等于多个位掩码的组合，因此您无法测试此处的相等性。您需要测试单个位的相等性。

要从组合位掩码中提取单个位掩码的值，请使用按位AND（ & ）运算符。然后，与您感兴趣的单位掩码进行比较：

  BOOL commandKeyIsPressed =（flagsP& kCGEventFlagMaskCommand）== kCGEventFlagMaskCommand; 
  

为什么两个？

<$在这种情况下，c $ c>& 表达式的计算结果与其操作数相同，即 CGEventFlags ，这可能不适合大小一个 BOOL ，这是一个已签名的char 。 == 表达式将其解析为1或0，这将适用于 BOOL 。

该问题的其他解决方案包括否定值两次（ !! ）并将变量声明为 bool 或 _Bool 而不是布尔值或 BOOL 。当你包含stdbool.h时，C99的 _Bool 类型（同义为 bool ）强制其值为1或0，就像 == 和 !! 解决方案一样。

Having setup an event tap, I'm not able to identify what modifier key was pressed given a CGEvent.

 CGEventFlags flagsP;

 flagsP=CGEventGetFlags(event);

 NSLog(@"flags: 0x%llX",flagsP);
 NSLog(@"stored: 0x%llX",kCGEventFlagMaskCommand);

 if (flagsP==kCGEventFlagMaskCommand) {
       NSLog(@"command pressed");
    }

Given the above snippet, the first NSLog returns a different value from the second NSLog. No surprise that the conditional is never triggered when the command modifier key is pressed.

I need to identify whether command, alternate, option, control or shift are pressed for a given CGEvent. First though, I need help to understand why the above isn't working.

Thanks!

解决方案

These are bit masks, which will be bitwise-ORed together into the value you receive from CGEventGetFlags (or pass when creating an event yourself).

You can't test equality here because no single bit mask will be equal to a combination of multiple bit masks. You need to test equality of a single bit.

To extract a single bit mask's value from a combined bit mask, use the bitwise-AND (&) operator. Then, compare that to the single bit mask you're interested in:

BOOL commandKeyIsPressed = (flagsP & kCGEventFlagMaskCommand) == kCGEventFlagMaskCommand;

Why both?

The & expression evaluates to the same type as its operands, which is CGEventFlags in this case, which may not fit in the size of a BOOL, which is a signed char. The == expression resolves that to 1 or 0, which is all that will fit in a BOOL.

Other solutions to that problem include negating the value twice (!!) and declaring the variable as bool or _Bool rather than Boolean or BOOL. C99's _Bool type (synonymized to bool when you include stdbool.h) forces its value to be either 1 or 0, just as the == and !! solutions do.

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