asked on

undo

i give my users the ability to stamp a picture on a main stage.

i want them to be able to undo the last 5 possible stamps.

each stamp is a paintpicture event:

e.g. picture1.paintpicture image1.picture, x, y

is there some type of memory logic that i use to store each of the five last events in memory.

thanks in advance.

AzraSound

Just a simple stack implementation. When adding an item, push it onto the top of the stack, when undoing, remove the top item and point to the next item on the stack. You could achieve this with a simple array, e.g.,

Private m_picStack(1 To 5) As StdPicture
Private m_intStackPointer As Integer

Sub Push()
Dim i As Integer

If m_intStackPointer = 5 Then
'move all items down a position
For i = 2 To 5
m_picStack(i - 1) = m_picStack(i)
Next
m_picStack(5) = Image1.Picture
Else
m_intStackPointer = m_intStackPointer + 1
m_picStack(m_intStackPointer) = Image1.Picture
End If
End Sub

Function Pop() As StdPicture
Pop = m_picStack(m_intStackPointer)
m_intStackPointer = m_intStackPointer - 1
End Function

ameba

"Command" design patterns provide a convenient way to store and execute an Undo function. Each command object can remember what it just did and restore that state when
requested to do so.
You must keep a single sequential list of the commands that have been executed, and each command has to keep a list of its executions... etc. piece of cake ;-)

Richie_Simonetti

Hearing...

eyemag

ASKER

azrasound-

i tried implementing with a picturebox and no luck. could you give me a full example.

thanks, if i need to increase the points let me know

ASKER CERTIFIED SOLUTION

inthedark

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inthedark

? = '

Sorry there were a few typos where width and heigh got mixed up but if you need any further help with the concept I would be happy to help.

dekeldate

listening...

mcoop

I must admit I was wondering which way this would go, and my feelings go with [inthedark], because the structures that you tend to deal with in VB are often not conducive to 'just removing the last opration'

I have done something similar - and [inthedark]'s method seems to just 'work more often'... however the original 'stack' approach is the textbook answer, it requires that you maintain more info off the stack to recover the actual 'state of play' - as opposed to simply repeating the process from the most recent 'convenient' starting point.... of course you should also consider keeping more than one recent re-entry point for multiple undo operations.... altogether not an easy answer !!

Richie_Simonetti

But Ark codes should works (i mean, stdpicture approach)!

DanRollins

Moderator, my recommended disposition is:

Accept inthedark's comment(s) as an answer.

DanRollins -- EE database cleanup volunteer

Richie_Simonetti

In a last case. a split between inthedark and ark should be nice.
Cheers

AzraSound

AzraSound = Ark

Richie_Simonetti

Sorry, i did it again, i meant Azra and inthedark.

DanRollins

Thanks for the input. Modified recommendation:

Split points between inthedark and AzraSound

DanRollins -- EE database cleanup volunteer

Netminder

Per recommendation, force-accepted.

Netminder
CS Moderator

AzraSound: points for you at https://www.experts-exchange.com/questions/20341070/For-AzraSound-re-various.html