[RESOLVED] KeyUp or KeyDown? : What to consider when choosing.

[webbiz]

This is one of those questions where I'd like the experts to please express their thoughts on.


The action in question: This will trigger the ZOOM IN or OUT of my price chart.

Now, I already have the code in two test buttons. A "+" button, and a "-" button.

I'll be deleting these buttons because the action to ZOOM IN will be activated by pressing the "-" key. The ZOOM OUT will be the "+" key.

Now all I have to do is choose:

The KeyDown event or the KeyUp event.

Note: No other key will be held down or pressed in conjunction. Just a quick click of the "+" or "-" key will do the trick.


How does one normally decide and based on what conditions?

TIA

[VanGoghGaming]

When you keep a key pressed the "KeyDown" event starts repeating itself, while the "KeyUp" event requires separate keystrokes every time.

Of course there's also the "KeyPress" event which combines the two, so it's up to you which one you prefer.

[baka]

Dim LastKey%

Private Sub Form_KeyDown(KeyCode As Integer, Shift As Integer)
    If KeyCode = LastKey Then Exit Sub
    LastKey = KeyCode
    Debug.Print "KeyDown: " & KeyCode
End Sub

Private Sub Form_KeyUp(KeyCode As Integer, Shift As Integer)
    LastKey = 0
End Sub

if don't like the repeat thing while also want to have the "Down" as the trigger not the "Up", u can do something like this.

[webbiz]

@VanGoghGaming @baka

Your responses make the answer clear.

In my current task, I prefer that the action occurs once and that another press is required if you want to do again.

So the 'repeating' part tells me to go with KeyUP when repeating is not what you want...OR...

If you just have to have KeyDown (for whatever reason), check if that key was already pressed last time and get out of dodge.

Thanks!

[dilettante]

I always start assuming I want KeyPress. If that doesn't work for my purpose at hand I consider KeyUp. In rare cases I might choose KeyDown, but mainly to cancel a key.

Each has its uses and limitations.

[Zvoni]

What VanGogh said for KeyDown.
Usually the decision is, if you want to validate the pressed key before displaying it, which wouldn't be the case for you.

On a sidenote: You might think about evaluating the Shift-Key.
Zoom-In is "-".
"-" individually is, say, zoom in by 5%
SHIFT+"-" is zoom-in, say, 25%
ALT+"-" is zoom-in, say, 50%

[webbiz]

What VanGogh said for KeyDown.
Usually the decision is, if you want to validate the pressed key before displaying it, which wouldn't be the case for you.

On a sidenote: You might think about evaluating the Shift-Key.
Zoom-In is "-".
"-" individually is, say, zoom in by 5%
SHIFT+"-" is zoom-in, say, 25%
ALT+"-" is zoom-in, say, 50%

That's a good idea if I had more increments.

But in my project case, it's about 2 presses to get to maximum display, and about 4 presses for the most zoomed-in.

So adding Shift would be overkill.

If the increments were smaller and more of them, then I could see using 'Shift' to make bigger jumps.