无法在Smalltalk Pharo 2中多次查看键盘事件

2023年12月11日 246次阅读

我想查看键盘事件,根据Sensor的文档,我可以在不使用peekKeyboardEvent从队列中删除事件的情况下执行此操作,但是它似乎不起作用.

这有效：

"Show that a single event can be checked multiple times"
Transcript clear; show: 'Type something... '; flush.
(Delay forSeconds: 2) wait.
5 timesRepeat: [  
    Transcript show: (Sensor peekEvent); cr
]

输出：

Type something... #(2 48243801 5 2 8 0 0 1)
#(2 48243801 5 2 8 0 0 1)
#(2 48243801 5 2 8 0 0 1)
#(2 48243801 5 2 8 0 0 1)
#(2 48243801 5 2 8 0 0 1)

但这不是：

"Show that a single keyboard event can be checked multiple times"
Transcript clear; show: 'Type something... '; flush.
(Delay forSeconds: 2) wait.
5 timesRepeat: [  
    Transcript show: (Sensor peekKeyboardEvent); cr
]

输出：

Type something... #(2 48205144 97 0 0 97 0 1)
nil
nil
nil
nil

还有一个问题：为什么Transcript flush不会导致输出立即出现？它仅在脚本运行后出现.

最佳答案 首先,pharo是一个快速移动的目标,因此最好分辨出哪个版本.

找到答案的最佳方法是浏览代码.我将在当前的开发pharo 3.0中展示这一点
如果浏览peekKeyboardEvent的实现者(选择它然后Alt m),你会在InputEventSensor中找到一个版本：

peekKeyboardEvent
    "Allows for use of old Sensor protocol to get at the keyboard,
    as when running kbdTest or the InterpreterSimulator in Morphic"

    ^eventQueue findFirst: [:buf | self isKbdEvent: buf]

如果您分析对eventQueue的inst var引用

initialize
        "Initialize the receiver"
        super initialize.
        eventQueue := WaitfreeQueue new.
        ...snip...

然后浏览WaitfreeQueue(选择它然后Alt b)

findFirst: aBlock
    "Note, this method only for backward compatibility. It duplicating the semantics of #nextOrNilSuchThat: completely.
    Use #nextOrNilSuchThat: instead "

    ^ self nextOrNilSuchThat: aBlock

然后：

nextOrNilSuchThat: aBlock
    "Fetch an object from queue that satisfies aBlock, skipping (but not removing) any intermediate objects.
    If no object has been found, answer <nil> and leave me intact.

    NOTA BENE:  aBlock can contain a non-local return (^).
    Found item is removed from queue    .

    If queue currently in the middle of extraction by other process, don't wait and return <nil> immediately"
    ...snip...

你可以信任评论,或者自己在代码中验证,这种方法正在消耗事件而不是偷看.

因此,这种民意调查风格似乎确实已被弃用并且在法律上失去了支持

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