BAM: SCROLL statement "super-test"

[CharlieJV]

Hi Charlie, what you are doing in demo could easily be done by color shifting on a pallet.
The same could be done with text by position shifting start point of display for text.

Here is old demo in QB64:

Code: (Select All)

_Title "Color Cycle AKA Palette Shifting?" 'B+ 2019-04-13 trans from SdlBasic code

'color cycle test.sdlbas {B+=MGA 2016-06-04





Randomize Timer

'option qbasic

Const xmax = 400 '<==== drawing area width

Const ymax = 300 '<==== drawing area height

'setdisplay(xmax, ymax, 32, 1)

'setcaption("Color Cycle test.sdlbas")  '<===================== screen title

'autoback(-2)

Screen _NewImage(xmax, ymax, 32)



'dim common pal(16), cIndex=0

Dim Shared pal(16) As _Unsigned Long

Dim Shared cIndex As Integer



'QB colors approx

pal(0) = &HFF000000

pal(1) = &HFF000077

pal(2) = &HFFFF8866

pal(3) = &HFF008888

pal(4) = &HFF880000

pal(5) = &HFFFF8800

pal(6) = &HFF008800

pal(7) = &HFFBBBBBB

pal(8) = &HFF666666

pal(9) = &HFF0000FF

pal(10) = &HFF00FF00

pal(11) = &HFF00FFFF

pal(12) = &HFFFF0000

pal(13) = &HFFFF00FF

pal(14) = &HFFFFFF00

pal(15) = &HFFFFFFFF





While 1

    Cls

    For i = 0 To 15

        'simulate a Palette Shift by shifting the indexs to Palette calls

        Line (i * 20 + 40, 100)-Step(20, 100), pal((cIndex + i) Mod 16), BF

        cText xmax / 2, 50, 16, pal(15), "Index called:"

        cText i * 20 + 5 + 40, 70, 16, pal(15), Str$(i)

        cText xmax / 2, 220, 16, pal(15), "Shifted Index call:"

        cText i * 20 + 5 + 40, 240, 16, pal(15), Str$((cIndex + i) Mod 16)

    Next

    _Display

    _Limit 1

    'INPUT "Press enter for Palette shifting +1 "; wate$

    cIndex = (cIndex + 1) Mod 16 'color shift

Wend



Function ccycle (cNum)

    ccycle = pal((cIndex + cNum) Mod 16)

End Function



Sub cText (x, y, textHeight, K As _Unsigned Long, txt$)

    fg = _DefaultColor

    'screen snapshot

    cur& = _Dest

    I& = _NewImage(8 * Len(txt$), 16, 32)

    _Dest I&

    Color K, _RGBA32(0, 0, 0, 0)

    _PrintString (1, 1), txt$

    mult = textHeight / 16

    xlen = Len(txt$) * 8 * mult

    _PutImage (x - .5 * xlen + 1, y - .5 * textHeight + 1)-Step(xlen, textHeight), I&, cur&

    Color fg

    _FreeImage I&

End Sub

Of course this can be done without _PutImage by redrawing over same screen area each loop.

Maybe I am missing something?

That's flying right over my head.  I have no idea where you're going with that.

This is just to test the SCROLL statement to make sure each pixel is scrolling to the correct position, no matter what parameters get thrown at the statement.  Easier to identify the pixels using color.

SCROLL is about scrolling whatever happens to be on the screen.  All text and all graphics.  All pixels.

I think what you are writing about would only ever apply to the specific graphic used in this test case, but would not work with all cases of whatever is on the screen.