I must be missing something obvious with this code

[Dav]

I was adding a screen flipping effect to a program, and don't see why CLS is needed to remove the edge LINE before the last _PUTIMAGE is called.  I'm putimaging the whole screen at the end, shouldn't that remove the LINE?

- Dav

Code: (Select All)

'==============

'FLIPSCREENHZ.BAS

'==============



Screen _NewImage(1000, 700, 32)



'=== draw stuff

For t = 1 To 50

    Line (Rnd * _Width, Rnd * _Height)-Step(15 + (Rnd * 100), 15 + (Rnd * 100)), _RGB(Rnd * 255, Rnd * 255, Rnd * 255), BF

    Circle (Rnd * _Width, Rnd * _Height), 15 + (Rnd * 100), _RGB(Rnd * 255, Rnd * 255, Rnd * 255)

Next



Locate 12, 12: Print "PRESS ANY KEY TO FILP ME";

'kep pressing any key to flip screen

'ESC exits



Do

    a$ = Input$(1)

    If a$ = Chr$(27) Then End



    FlipScreen



Loop



Sub FlipScreen



    'Flips current screen horizontally



    displayStatus%% = _AutoDisplay 'get current display status



    _Display 'turn off auto screen updates



    scrn& = _CopyImage(_Display)



    x1 = 0: x2 = _Width

    y1 = 0: y2 = _Height



    Do

        'draw screen image

        Cls: _PutImage (x1, y1)-(x2, y2), scrn&



        'draw edge line around it for extra effect

        Line (x1, y1)-(x2, y2), _RGB(128, 128, 128), B



        x1 = x1 + 45: If x1 > _Width Then x1 = _Width

        x2 = x2 - 45: If x2 < 0 Then x2 = 0



        _Display

        _Limit 30

    Loop Until x1 = _Width And x2 = 0



    'Shouldn't _PUTIMAGE below fit the whole screen and remove the edge LINE without needing CLS?

    'CLS



    _PutImage (_Width, 0)-(0, _Height), scrn&

    _Display

    _FreeImage scrn&



    If displayStatus%% = -1 Then _AutoDisplay 'restore previous



End Sub

[SMcNeill]

Set a variable W and H and make them = Width - 1 and Height - 1.

Your screen dimensions are 0 to Width - 1, not 0 to Width.  

[Dav]

Set a variable W and H and make them = Width - 1 and Height - 1.

Your screen dimensions are 0 to Width - 1, not 0 to Width.  

Ahhh,  Thanks, Steve.

Woo hoo!  I won the idiot of the day award before 9:30am.   

- Dav

[PhilOfPerth]

Set a variable W and H and make them = Width - 1 and Height - 1.

Your screen dimensions are 0 to Width - 1, not 0 to Width.  

Ahhh,  Thanks, Steve.

Woo hoo!  I won the idiot of the day award before 9:30am.   

- Dav

Ok, I'll return my cup; I'll miss it though. 

[JRace]

The off-by-one error is so common that the ISO has considered making it a required standard error.

[TerryRitchie]

The off-by-one error is so common that the ISO has considered making it a required standard error.

If I had a dollar for every time the off by one error has befuddled me I would be funding flights on a SpaceX Dragon.

[Dimster]

Steve could likely listen to your car engine and diagnosis an efficiency just by the sound. In fact, I suspect there are a lot of engine whispers on this forum.

[TerryRitchie]

Steve could likely listen to your car engine and diagnosis an efficiency just by the sound. In fact, I suspect there are a lot of engine whispers on this forum.

My grandpa (a life-long farmer) definitely had this skill. His Chalmers, Masseys, Fords, and Olivers always ran in perfect condition. Hell, the Alliis Chalmers he used as a cultivator and you had to hand crank that puppy. More than once that damn thing kicked back on me and sent me flying.

[Pete]

Wait, I missed out on the Idiot of the Day award? Dammit, now I'll have to figure out when the next competition starts!

Pete