Graphic Undo/redo

[Peter Redei]

I am missing the GRAPHIC UNDO and GRAPHIC REDO statements
I am sure we can implement it with a workaround. Has anybody done that?

Thanks,

Peter Redei

[Arie Verheul]

Graphic Set Mix ?

For certain purposes Graphic Set Mix may do the job.
It is especially useful for moving selectboxes or crosshairs over the screen.

Arie Verheul

   
[FONT="Courier New"][SIZE="3"]#Dim All
   
Function PBMain
    
    Local hWnd As Dword
    
    Graphic Window "",200,200,200,200 To hWnd
    Graphic Attach hWnd,0
    Graphic Color %white,%black
    Graphic Clear
    
    Graphic Box (80,80)-(120,120)
    
    Sleep 2000
   
    Graphic Set Mix %mix_xorsrc
    
    Graphic Box (50,50)-(150,150),20,%blue,%red
    
    Sleep 2000
    
    Graphic Box (50,50)-(150,150),20,%blue,%red
    
    Sleep 2000    
    
End Function[/SIZE][/FONT]

[Peter Redei]

Thanks Arie. Using mix can indeed result in a variety of effects, but I cannot see how it can be used for undo/redo. My first choice for undo/redo would be using GRAPHIC GET BITS TO sPrior to save the image to sPrior string and on Undo using GRAPHIC SET BITS sPrior followed with GRAPHIC REDRAW. This is actually working nicely.


Peter Redei

[Aslan Babakhanov]

Never did it, but you can implement a kind of "layer" technology

You need to save the portion of window with graphics before any graphics
operations. It is possible by saving them to BMP in temp folder and restoring when needed.Here is a pseudocode

   '.. in your application
   ' this is our procedure to save a portion/window etc.. 
   ' before any graphical operation  
   PSAVE_UNDO (grHwn, UndoPageCounter)  
   GRAPHIC LINE ...
   GRAPHIC PRINT ... 
   ..etc
   ' now save for redo
   PSAVE_REDO (grHwn, RedoPageCounter)  ' save after graphics operations
   INCR UndoPageCounter: MAXUNDO = UndoPageCounter
   INCR RedoPageCounter: MAXREDO = RedoPageCounter
   ..
   ..
   '------------------
   ' UNDO action
   '------------------
   DECR UndoPageCounter
   DECR RedoPageCounter
   IF UndoPageCounter <=1 THEN UndoPageCounter = 1
   IF RedoPageCounter <=1 THEN RedoPageCounter = 1
       PLOAD_UNDO (gwHwn, UndoPageCounter)
   ..
   ..
   '------------------ 
   ' REDO action
   '------------------
   INCR UndoPageCounter
   INCR RedoPageCounter
   IF UndoPageCounter >= MAXUNDO THEN UndoPageCounter >= MAXUNDO
   IF RedoPageCounter >= MAXREDO THEN RedoPageCounter >= MAXREDO
       PLOAD_REDO (gwHwn, RedoPageCounter)


 SUB PSAVE_REDO (gwHwn, c)
    GRAPHIC ATTACH gwHwn
    GRAPHIC SAVE "redo" & LTRIM$(STR$(c)) & ".bmp"
 ....
 SUB PSAVE_UNDO (gwHwn, c)
    GRAPHIC ATTACH gwHwn
    GRAPHIC SAVE "undo" & LTRIM$(STR$(c)) & ".bmp"
 ....
 SUB PLOAD_UNDO (gwHwn, c)
    GRAPHIC ATTACH gwHwn
    GRAPHIC BITMAP LOAD  "undo" & LTRIM$(STR$(c)) & ".bmp" ....
 ....
 SUB PLOAD_REDO (gwHwn, c)
    GRAPHIC ATTACH gwHwn
     GRAPHIC BITMAP LOAD "redo" & LTRIM$(STR$(c)) & ".bmp"

ghHwn - is the handle of graphics window you want to undo/redo

Not tested - but this should work
Also, you need to define the number and type of graphical operations to be stored as a one layer.

[Peter Redei]

Thanks Aslan. You are right in creating layers. You do not need to save bitmaps though, GRAPHIC GET/SET BITS offers better option. Here is a pseudo version:

GLOBAL sGraphic_Undo() AS STRING
GLOBAL sGraphic_Redo() AS STRING    
function PBMAIN()
     ClearLayers
     'whenever the cancas changes call SaveGRAPHIC
     'call UndoGRAPHIC to restore the prior canvas
     'call RedoGRAPHIC to redo after undo
end function
SUB AddLayer(BYVAL sLayer AS STRING)

    ARRAY INSERT sGraphic_Undo(0), sLayer

END SUB
SUB UndoGRAPHIC()
    LOCAL sPrior AS STRING
    IF LEN(sGraphic_Undo(0)) THEN
        GRAPHIC GET BITS TO sPrior
        ARRAY INSERT sGraphic_Redo(0), sPrior
        GRAPHIC SET BITS sGraphic_Undo(0)
        GRAPHIC REDRAW
        ARRAY DELETE sGraphic_Undo(0)
    ELSE
        REDIM sGraphic_Undo(0 TO 11)
    END IF
    
END SUB

SUB RedoGRAPHIC()
    LOCAL sPrior AS STRING
    IF LEN(sGraphic_Redo(0)) THEN
        SaveGRAPHIC
        GRAPHIC SET BITS sGraphic_Redo(0)
        GRAPHIC REDRAW
        ARRAY DELETE sGraphic_Redo(0)
     ELSE
        REDIM sGraphic_Redo(0 TO 11)
    END IF
END SUB

SUB ClearLayers()
    REDIM sGraphic_Undo(0 TO 11)
    REDIM sGraphic_Redo(0 TO 11)
END SUB
SUB SaveGRAPHIC()
    LOCAL sPrior AS STRING
    GRAPHIC GET BITS TO sPrior:AddLayer sPrior
END SUB

Thanks,


Peter Redei