a little tutorial STEP by STEP on scrolling in 2D graphic mode

[TempodiBasic]

Hi friends
I want to share these basical knowledges about scrolling background in graphic mode using  the powerful _PUTIMAGE.
It is a basical 2D graphic mode 32bit.

I post the following 6 QB64pe code examples that start from a backgroung scrolling to right and leaving a black screen to arrive to a background scrolling in the 4 directions of a bidimensional field in which the user can start/stop the scrolling, change the directions of the scrolling and quit the program.

If you want to see the final result you must run the STEP 6. 
If you want follow the tutorial you must go step by step from 1 to 6.

Happy enjoyment  with this code.

STEP 1

Code: (Select All)

 
Rem Demonstration of scrolling towards right or left of the background
Rem  STEP 1 a background scrolling towards right in loop
' Global variables' declaration
Dim Back As Long, Scr As Long, x As Integer, y As Integer, w As Integer, h As Integer
Dim i As Integer, k As String
_Title " Demo of background scrolling: step 1" ' title on the titlebar of the application
' variables' initialization
w = 800: h = 600
y = 1
x = 1
Scr = _NewImage(w, h, 32)
Back = _NewImage(w, h, 32)
Screen Scr ' it creates window of the application
_Dest Back ' it sets the surface as destination of graphic output
' it draws a gradient background by using a FOR loop with graphic instructions (LINE and _RGBA)
For i = 1 To 10
    Line ((w / 10) * (i - 1), y)-((w / 10) * (i + 1), h), _RGBA32(1 + (i - 1) * (255 / 10), 127, 127, 255), BF
Next i
_Dest 0 ' it sets the surface of destination of graphic output as the window of the application
 
' it manages the keyboard input of user and the scrolling towards right of background
While k <> "Q"
    k = UCase$(InKey$) ' it takes the input from keyboard
    Cls 'it clears previous screen
    _PutImage (x, y), Back, Scr 'it paints screen now
    _PrintString (1, 1), "Press Q to quit program" ' it shows instruction for user on the screen
    x = x + 1 'it calculates the new position where starting to paint background, it is towards right
    _Display ' it forces hardware to show image
    _Limit 100 ' it reduces the number of cycles of CPU used by this application
Wend
 
End

STEP 2

Code: (Select All)

 
Rem Demonstration of scrolling towards right or left of the background
Rem  STEP 2 a background scrolling towards right in loop
' Global variables' declaration
Dim Back As Long, Scr As Long, x As Integer, y As Integer, w As Integer, h As Integer
Dim i As Integer, k As String
_Title " Demo of background scrolling: step 2" ' title on the titlebar of the application
' variables' initialization
w = 800: h = 600
y = 1
x = 1
Scr = _NewImage(w, h, 32)
Back = _NewImage(w, h, 32)
Screen Scr ' it creates window of the application
_Dest Back ' it sets the surface as destination of graphic output
' it draws a gradient background by using a FOR loop with graphic instructions (LINE and _RGBA)
For i = 1 To 10
    Line ((w / 10) * (i - 1), y)-((w / 10) * (i + 1), h), _RGBA32(1 + (i - 1) * (255 / 10), 127, 127, 255), BF
Next i
_Dest 0 ' it sets the surface of destination of graphic output as the window of the application
 
' it manages the keyboard input of user and the scrolling towards right of background
While k <> "Q"
    k = UCase$(InKey$) ' it takes the input from keyboard
    Cls 'it clears previous screen
    _PutImage (x, y), Back, Scr 'it paints screen now
    _PrintString (1, 1), "Press Q to quit program, A to restart" ' it shows instruction for user on the screen
    x = x + 1 'it calculates the new position where starting to paint background, it is towards right
    If k = "A" Then x = 1 ' it corrects x when user restarts
    _Display ' it forces hardware to show image
    _Limit 100 ' it reduces the number of cycles of CPU used by this application
Wend
 
End

STEP 3

Code: (Select All)

 
Rem Demonstration of scrolling towards right or left of the background
Rem  STEP 3 a background scrolling towards right in loop
' Global variables' declaration
Dim Back As Long, Scr As Long, x As Integer, y As Integer, w As Integer, h As Integer
Dim i As Integer, k As String
_Title " Demo of background scrolling: step 3" ' title on the titlebar of the application
' variables' initialization
w = 800: h = 600
y = 1
x = 1
Scr = _NewImage(w, h, 32)
Back = _NewImage(w, h, 32)
Screen Scr ' it creates window of the application
_Dest Back ' it sets the surface as destination of graphic output
' it draws a gradient background by using a FOR loop with graphic instructions (LINE and _RGBA)
For i = 1 To 10
    Line ((w / 10) * (i - 1), y)-((w / 10) * (i + 1), h), _RGBA32(1 + (i - 1) * (255 / 10), 127, 127, 255), BF
Next i
_Dest 0 ' it sets the surface of destination of graphic output as the window of the application
 
' it manages the keyboard input of user and the scrolling towards right of background
While k <> "Q"
    k = UCase$(InKey$) ' it takes the input from keyboard
    Cls 'it clears previous screen
    _PutImage (x, y), Back, Scr 'it paints screen now
    _PutImage (x - w, y), Back, Scr ' it completes the background on the left side
    _PrintString (1, 1), "Press Q to quit program" ' it shows instruction for user on the screen
    x = x + 1 'it calculates the new position where starting to paint background, it is towards right
    If x > w Then x = 1 ' it corrects x when is over
    _Display ' it forces hardware to show image
    _Limit 100 ' it reduces the number of cycles of CPU used by this application
Wend
 
End

STEP 4

Code: (Select All)

 
Rem Demonstration of scrolling towards right or left of the background
Rem  STEP 4 a background scrolling towards right in loop
' Global variables' declaration
Dim Back As Long, Scr As Long, x As Integer, y As Integer, w As Integer, h As Integer
Dim i As Integer, k As String, S As Integer
_Title " Demo of background scrolling: step 4" ' title on the titlebar of the application
' variables' initialization
w = 800: h = 600
y = 1
x = 1
Scr = _NewImage(w, h, 32)
Back = _NewImage(w, h, 32)
S = 1
Screen Scr ' it creates window of the application
_Dest Back ' it sets the surface as destination of graphic output
' it draws a gradient background by using a FOR loop with graphic instructions (LINE and _RGBA)
For i = 1 To 10
    Line ((w / 10) * (i - 1), y)-((w / 10) * (i + 1), h), _RGBA32(1 + (i - 1) * (255 / 10), 127, 127, 255), BF
Next i
_Dest 0 ' it sets the surface of destination of graphic output as the window of the application
 
' it manages the keyboard input of user and the scrolling towards right of background
While k <> "Q"
    k = UCase$(InKey$) ' it takes the input from keyboard
    Cls 'it clears previous screen
    _PutImage (x, y), Back, Scr 'it paints screen now
    _PutImage (x - w, y), Back, Scr ' it completes the background on the left side
    _PrintString (1, 1), "Press Q to quit program, S to stop/start demo" ' it shows instruction for user on the screen
    If k = "S" Then If S > 0 Then S = -1 Else S = 1 ' it starts/stops the scrolling to right
    If S > 0 Then x = x + 1 'it calculates the new position where starting to paint background, it is towards right
    If x > w Then x = 1 ' it corrects x when is over
    _Display ' it forces hardware to show image
    _Limit 100 ' it reduces the number of cycles of CPU used by this application
Wend
 
End

STEP 5

Code: (Select All)

 
Rem Demonstration of scrolling towards right or left of the background
Rem  STEP 5 a background scrolling towards right /left in loop
' Global variables' declaration
Dim Back As Long, Scr As Long, x As Integer, y As Integer, w As Integer, h As Integer
Dim i As Integer, k As String, S As Integer, d As Integer
_Title " Demo of background scrolling: step 5" ' title on the titlebar of the application
' variables' initialization
w = 800: h = 600
y = 1
x = 1
Scr = _NewImage(w, h, 32)
Back = _NewImage(w, h, 32)
S = 1
d = 1
Screen Scr ' it creates window of the application
_Dest Back ' it sets the surface as destination of graphic output
' it draws a gradient background by using a FOR loop with graphic instructions (LINE and _RGBA)
For i = 1 To 10
    Line ((w / 10) * (i - 1), y)-((w / 10) * (i + 1), h), _RGBA32(1 + (i - 1) * (255 / 10), 127, 127, 255), BF
Next i
_Dest 0 ' it sets the surface of destination of graphic output as the window of the application
 
' it manages the keyboard input of user and the scrolling towards right of background
While k <> "Q"
    k = UCase$(InKey$) ' it takes the input from keyboard
    Cls 'it clears previous screen
    _PutImage (x, y), Back, Scr 'it paints screen now
    _PutImage (x - w, y), Back, Scr ' it completes the background on the left side
    _PrintString (1, 1), "Press Q to quit program, S to stop/start demo, R to reverse direction" ' it shows instruction for user on the screen
    If k = "S" Then If S > 0 Then S = -1 Else S = 1 ' it starts/stops the scrolling to right
    If k = "R" Then d = d * -1 ' it changes the direction of scrolling +1 = to right / -1 = to left
    If S > 0 Then x = x + d 'it calculates the new position where starting to paint background, it is towards right
    If d > 0 And x > w Then x = 1 ' it corrects x when is over w and scrolling is to right
    If d < 0 And x < 1 Then x = w ' it corrects x when is under 1 and scrolling is to left
    _Display ' it forces hardware to show image
    _Limit 100 ' it reduces the number of cycles of CPU used by this application
Wend
 
End

STEP 6

Code: (Select All)

 
Rem Demonstration of scrolling towards right or left of the background
Rem  STEP 6 a background scrolling towards right /left & down/up in loop
' Global variables' declaration
Dim Back As Long, Scr As Long, x As Integer, y As Integer, w As Integer, h As Integer
Dim i As Integer, k As String, dx As Integer, dy As Integer, O As Integer, V As Integer, S As Integer
_Title " Demo of background scrolling: step 6" ' title on the titlebar of the application
' variables' initialization
w = 800: h = 600
y = 1
x = 1
Scr = _NewImage(w, h, 32)
Back = _NewImage(w, h, 32)
dx = 1
dy = 1
S = 1
O = 1
V = 1
Randomize Timer ' it starts the random generator of number
Screen Scr ' it creates window of the application
_Dest Back ' it sets the surface as destination of graphic output
' it draws a background by using a FOR loop with graphic instructions (LINE and _RGBA)
For i = 1 To 100
    Line ((Rnd * (780) + 10), Rnd * (580) + 10)-(Rnd * (780) + 10, Rnd * (580) + 10), _RGBA32(Rnd * (255), Rnd * (255), Rnd * (255), 255), B
Next i
_Dest 0 ' it sets the surface of destination of graphic output as the window of the application
 
' it manages the keyboard input of user and the scrolling background
While k <> "Q"
    k = UCase$(InKey$) ' it takes the input from keyboard
    Cls 'it clears previous screen
    _PutImage (x, y), Back, Scr 'it paints screen now
    _PutImage (x - w, y), Back, Scr ' it completes the background on the left side
    _PutImage (x, y - h), Back, Scr ' it completes the background on the upper side
    _PutImage (x - w, y - h), Back, Scr ' it completes the background on the upper side
    _PrintString (1, 1), "Press Q to quit program, S to stop/start demo, R to reverse directions" ' it shows instruction for user on the screen
    _PrintString (1, 20), " O stop/start horizontal scrolling, V stop/start vertical scrolling"
 
    ' it starts/stops the scrolling
    If k = "S" Then S = S * -1
    If k = "R" Then
        ' it changes only scrolling activated
        If O > 0 Then dx = dx * -1
        If V > 0 Then dy = dy * -1
        ' it changes the direction of scrolling +1 = to right to bottom/ -1 = to left to up
    End If
    If k = "O" Then O = O * -1 'it sets the status of horizontal scrolling
    If k = "V" Then V = V * -1 ' it sets the status of vertical scrolling
 
 
    If S > 0 And O > 0 Then x = x + dx ' it scrolls only horizontal
    If S > 0 And V > 0 Then y = y + dy ' it scrolls only vertical
    If dx > 0 And x > w Then x = 1 ' it corrects x when it is over w and scrolling is to right
    If dx < 0 And x < 1 Then x = w ' it corrects x when it is under 1 and scrolling is to left
    If dy > 0 And y > h Then y = 1 ' it corrects y when it is over h and scrolling is to down
    If dy < 0 And y < 1 Then y = h ' it corrects when it is under 1 and scrolling is to up
    _Display ' it forces hardware to show image
    _Limit 100 ' it reduces the number of cycles of CPU used by this application
Wend
 
End

Thanks for feedbacks

[bplus]

It'd be MUCH better if your backround was HUGE and didn't all fit in the viewing screen like they do in those games that travel the kingdom collecting magic potions, fighting monsters and rescuing damsels in distress or those space games that travel the universe collecting technology, fighting aliens and rescuing planets in jeopardy of alien invasion.

You know like the tutorial Fellippe did.

[TempodiBasic]

Hi Bplus
yes the tecnique to use a BIG scenario and a LITTLER camera that shows only a piece of the scenario on the screen is very smart and useful.
Just like the code written by Fellippe in that game online via TCP/IP.  A clone of Among Us.
I remember C&C and AOE as famous prototypes. Very smart also the use of the fog to not discover all the map in a look.
Here a oltragious example

Code: (Select All)

 
Rem demonstration of scrolling of a camera (little view) on a scenario (Total view)
 
' global variables
Dim Scenario As Long, Camera As Long
Dim d As Integer, x As Integer, y As Integer, Sw As Integer, Sh As Integer, Cw As Integer, Ch As Integer
Dim k As String
' initialization
Sw = 1200
Sh = 800
Cw = 200
Ch = 200
x = 1
y = 1
k = ""
Randomize Timer
Scenario = _NewImage(Sw, Sh, 32)
Camera = _NewImage(Cw, Ch, 32)
Screen Camera
_FullScreen
_Title "A demonstration of scrolling of a camera on a scenario"
 
' creating the scenario
_Dest Scenario
For a = 1 To 100
    Line (Rnd * Sw, Rnd * Sh)-(Rnd * Sw, Rnd * Sh), _RGBA32(Rnd * 255, Rnd * 255, Rnd * 255, 255), B
Next a
_Dest Scr
 
While k <> "Q"
 
    k = UCase$(InKey$)
    If k = "W" Then y = y - 1
    If k = "S" Then y = y + 1
    If k = "A" Then x = x - 1
    If k = "D" Then x = x + 1
 
    If x < 1 Then x = 1
    If x > (Sw - Cw) Then x = Sw - Cw
    If y < 1 Then y = 1
    If y > (Sh - Ch) Then y = Sh - Ch
    Cls
    _PutImage (1, 1), Scenario, Camera, (x, y)-(Cw + x, Ch + y)
    _PrintString (1, 1), "Use WASD to move camera"
    _PrintString (1, 180), "Q to quit"
    _Display
 
Wend
End

The tecnique showed in this tutorial is for background like dino run,  moon racer, car racing game, or infinite pacman labyrinth or infinite frogger. Over this image of background it must be painted the hero, the obstacles, the enemies etc etc all objects variable for position, for movement and dimensions.
But that is another tutorial.

[bplus]

Background image BIGGER than the display screen:

Code: (Select All)

_Title "Image bigger than screen" ' b+ 2024-12-30
Randomize Timer
Screen _NewImage(800, 600, 32)
_ScreenMove 100, 20

Dim bg&
bgw = 2400
bgh = 600
bg& = _NewImage(bgw, bgh, 32)
_Dest bg&
For i = 1 To 100
    Line (Rnd * bgw, Rnd * bgh)-Step(Rnd * 100 + 50, Rnd * 75 + 25), _RGB32(Rnd * 255, Rnd * 255, Rnd * 255), BF
Next
_Dest 0
d = 1
While _KeyDown(27) = 0
    Cls
    k$ = UCase$(InKey$)
    If k$ = "A" Then d = -1
    If k$ = "D" Then d = 1
    If d Then
        If le + 800 > bgw Then
            d = -d
            te = bgw - le
            _PutImage (0, 0)-(te, bgh), bg&, 0, (bgw - te, 0)-(bgw, bgh)
            _PutImage (te, 0)-(800, bgh), bg&, 0, (0, 0)-(800 - te, bgh)
            Beep
        Else
            _PutImage (0, 0)-(800, bgh), bg&, 0, (le, 0)-(le + 800, bgh)
        End If
    End If
    le = le + d
    If le < 0 Then le = 0: d = -d: Beep
    _Display
    _Limit 120
Wend

This is just left and right, A and D, maybe @TempodiBasic can add up and down?

[SMcNeill]

I've got a boatload of programs with the background image being bigger than the visible screen, and which scroll up/down.  It's a common technique which I use for quickly and easily making a scrollable screen with more information than what you can normally find on a single page.

Make a background image 32000 pixels tall, print/draw all you want on it, and then display your _Height from StartY to StartY + _Height to put the portion of the image on the screen that you want.

Bonus points involved if you include a slider on the side which you can use for navigation as well. 

[TempodiBasic]

Background image BIGGER than the display screen:

Code: (Select All)

_Title "Image bigger than screen" ' b+ 2024-12-30
Randomize Timer
Screen _NewImage(800, 600, 32)
_ScreenMove 100, 20

Dim bg&
bgw = 2400
bgh = 600
bg& = _NewImage(bgw, bgh, 32)
_Dest bg&
For i = 1 To 100
    Line (Rnd * bgw, Rnd * bgh)-Step(Rnd * 100 + 50, Rnd * 75 + 25), _RGB32(Rnd * 255, Rnd * 255, Rnd * 255), BF
Next
_Dest 0
d = 1
While _KeyDown(27) = 0
    Cls
    k$ = UCase$(InKey$)
    If k$ = "A" Then d = -1
    If k$ = "D" Then d = 1
    If d Then
        If le + 800 > bgw Then
            d = -d
            te = bgw - le
            _PutImage (0, 0)-(te, bgh), bg&, 0, (bgw - te, 0)-(bgw, bgh)
            _PutImage (te, 0)-(800, bgh), bg&, 0, (0, 0)-(800 - te, bgh)
            Beep
        Else
            _PutImage (0, 0)-(800, bgh), bg&, 0, (le, 0)-(le + 800, bgh)
        End If
    End If
    le = le + d
    If le < 0 Then le = 0: d = -d: Beep
    _Display
    _Limit 120
Wend

This is just left and right, A and D, maybe @TempodiBasic can add up and down?

@Bplus
Hi man
so you're using filled rectangles into your BIGGER image!
And what? Do you like put the scrolling working in automation, it does not matter about user input! 
These concepts are over mine knowledge so I cannot UP/DOWN scrolling.
Buuut if you add this you can add to this  scrolling  the stop & go feature like the ecological car.

Code: (Select All)

 
S = 1
while _keydown(27) = 0
...
...
IF k$ = "S" THEN S = S * -1
...
....
...
IF S>0 THEN le = le +d
...
...
wend

[Petr]

I use a different solution. If the screen resolution is, for example, 800x600 and the displayed object has coordinates 9000, 320, then it does not meet the conditions and is not displayed. Anything that is in the range 0 - 800 and 0 - 600 meets them and is therefore visible.

Here is an example. Let's say you need to display a higher resolution image on an 800x600 screen. Just use what _PutImage can do by itself and take advantage of the fact that things outside the visible area are not rendered.
In the program, use the left, right, up, down arrows and the mouse wheel to zoom.
Also try inserting any other image instead of _ScreenImage. It will work the same.

Code: (Select All)

 
Dim As Long MX, MY, LB, RB, Imag
 
Imag = _ScreenImage
Screen _NewImage(800, 600, 32)
Z = 799
RatioY = _Height / _Width
 
Do Until k& = 27
    k& = _KeyHit
    GetMouse MX, MY, LB, RB, MWH
    Select Case k&
        Case 18432: Y = Y - 10
        Case 20480: Y = Y + 10
        Case 19200: X = X - 10
        Case 19712: X = X + 10
    End Select
    Z = Z + MWH
    Cls
    _PutImage (0, 0)-(799, 599), Imag, 0, (X, Y)-(X + Z, Y + Z * RatioY)
    _Display
    _Limit 30
Loop
 
Sub GetMouse (MX As Long, MY As Long, LB As Long, RB As Long, MWH As Single)
    omwh = MWH
    Do While _MouseInput
        MWH = MWH + 10 * _MouseWheel
    Loop
    If omwh - MWH = 0 Then MWH = 0
    MX = _MouseX
    MY = _MouseY
    LB = _MouseButton(1)
    RB = _MouseButton(2)
End Sub

[SMcNeill]

Just a copy/paste from elsewhere, as this topic has fragmented into a couple of different spots now. It's still the same stuff; just directed to different people at this point.

Since you guys are all having fun with this, here's a Steve Simple version of screen scrolling at work.   Just use the mouse and watch what happens!

Code: (Select All)

Screen _NewImage(800, 600, 32) 'the screen that the user is going to see
Background = _NewImage(800 * 3, 600 * 3, 32) 'my background which is 3 times larger than my screen
_Dest Background
_PrintMode _KeepBackground

'Create a background which we can scroll and view via the mouse
For x = 0 To 2
    For y = 0 To 2
        Line (x * 800, y * 600)-Step(800, 600), _RGB(x * 127.5, y * 127.5, Rnd * 256), BF 'draw each quadrent a different color
        For i = 0 To 37
            text$ = "QUADRENT" + Str$(y * 3 + x + 1) + ": LINE #" + Str$(i)
            _PrintString (x * 800, y * 600 + i * _FontHeight), text$
        Next
    Next
Next

StartX = 800: StartY = 600
_MouseMove 400, 300 'center the mouse before we start scrolling like crazy
_Delay .2 'give the mouse time to move to the proper position for starting
Do
    While _MouseInput: Wend
    'If the mouse is near an edge, then change the starting points to reflect the scrolling
    If _MouseX < 20 Then StartX = StartX - (20 - _MouseX): If StartX < 0 Then StartX = 0
    If _MouseX > 779 Then StartX = StartX + (_MouseX - 779): If StartX > 1600 Then StartX = 1600
    If _MouseY < 20 Then StartY = StartY - (20 - _MouseY): If StartY < 0 Then StartY = 0
    If _MouseY > 579 Then StartY = StartY + (_MouseY - 579): If StartY > 1200 Then StartY = 1200
    _PutImage (0, 0)-Step(800, 600), Background, 0, (StartX, StartY)-Step(800, 600)
    _Display
    _Limit 60
Loop Until _MouseButton(1) Or _MouseButton(2) 'press a mouse button to end
System

Note: The closer your mouse gets to the edge, the faster the scrolling. Advance your pointer slowly towards the edge and watch as the scroll speed increases and decreases as you approach the edge more.

[Pete]

Now let's see a SCREEN 0 example!!!

Actually that's the one thing I haven't yet coded in SCREEN 0, a lateral scroll routine. The IDE uses one, which I presume is written in SCREEN 0.

Hmm, with arrays it's pretty easy...

Use arrow left and right keys to laterally scroll the text on the screen.

Code: (Select All)

ReDim l$(20)
For h = 1 To 20
    For i = 1 To Rnd * 50 + 60
        j = Int(Rnd * 10 + 48)
        l$ = l$ + Chr$(j)
        If Int(Rnd * 7) = 1 And Right$(l$, 1) <> " " Then l$ = l$ + " "
    Next
    l$(h) = l$: l$ = ""
Next
k = 1
Do
    For i = 1 To 20
        Locate i, 1:
        a$ = Space$(_Width)
        Mid$(a$, 1) = Mid$(l$(i), k, _Width)
        Print a$;
    Next
    Do
        _Limit 60
        b$ = InKey$
        Select Case b$
            Case Chr$(27): End
            Case Chr$(0) + "K"
                If k > 0 Then k = k - 1: Exit Do
            Case Chr$(0) + "M"
                k = k + 1: Exit Do
        End Select
    Loop
Loop

Now if the text is a single variable with line breaks, that would require a slightly different approach.

Code: (Select All)

Width 80, 25
_ScreenMove _Middle
For h = 1 To 20
    For i = 1 To Rnd * 50 + 60
        j = Int(Rnd * 10 + 48)
        a$ = a$ + Chr$(j)
        If Int(Rnd * 7) = 1 And Right$(a$, 1) <> " " Then a$ = a$ + " "
    Next
    a$ = a$ + Chr$(13) + Chr$(10)
Next
Rem a$ = _Clipboard$
Do
    seed = 1
    For i = 1 To 20
        Locate i, 1
        a1$ = Mid$(a$, seed, _Width + k)
        If k < InStr(a1$ + Chr$(13), Chr$(13)) Then a1$ = Mid$(a1$, k + 1) Else a1$ = ""
        If InStr(a1$, Chr$(13)) Then a1$ = Mid$(a1$, 1, InStr(a1$, Chr$(13)) - 1)
        x$ = Space$(_Width)
        Mid$(x$, 1) = a1$
        Print x$;
        seed = InStr(seed, a$, Chr$(13)) + 2
    Next
    Do
        _Limit 60
        b$ = InKey$
        Select Case b$
            Case Chr$(27): End
            Case Chr$(0) + "K"
                If k > 0 Then k = k - 1: Exit Do
            Case Chr$(0) + "M"
                k = k + 1: Exit Do
        End Select
    Loop
Loop

Anyway, not goof proofed so if you remove the remark at the _clipboard option just be sure you copy enough text to cover 20 or more lines. This is just what I would start out with a s way of displaying and horizontally scrolling text in SCREEN 0.

Pete

[TempodiBasic]

Now let's see a SCREEN 0 example!!!

Actually that's the one thing I haven't yet coded in SCREEN 0, a lateral scroll routine. The IDE uses one, which I presume is written in SCREEN 0.

Hmm, with arrays it's pretty easy...

Use arrow left and right keys to laterally scroll the text on the screen.

Code: (Select All)

ReDim l$(20)
For h = 1 To 20
    For i = 1 To Rnd * 50 + 60
        j = Int(Rnd * 10 + 48)
        l$ = l$ + Chr$(j)
        If Int(Rnd * 7) = 1 And Right$(l$, 1) <> " " Then l$ = l$ + " "
    Next
    l$(h) = l$: l$ = ""
Next
k = 1
Do
    For i = 1 To 20
        Locate i, 1:
        a$ = Space$(_Width)
        Mid$(a$, 1) = Mid$(l$(i), k, _Width)
        Print a$;
    Next
    Do
        _Limit 60
        b$ = InKey$
        Select Case b$
            Case Chr$(27): End
            Case Chr$(0) + "K"
                If k > 0 Then k = k - 1: Exit Do
            Case Chr$(0) + "M"
                k = k + 1: Exit Do
        End Select
    Loop
Loop

Now if the text is a single variable with line breaks, that would require a slightly different approach.

Code: (Select All)

Width 80, 25
_ScreenMove _Middle
For h = 1 To 20
    For i = 1 To Rnd * 50 + 60
        j = Int(Rnd * 10 + 48)
        a$ = a$ + Chr$(j)
        If Int(Rnd * 7) = 1 And Right$(a$, 1) <> " " Then a$ = a$ + " "
    Next
    a$ = a$ + Chr$(13) + Chr$(10)
Next
Rem a$ = _Clipboard$
Do
    seed = 1
    For i = 1 To 20
        Locate i, 1
        a1$ = Mid$(a$, seed, _Width + k)
        If k < InStr(a1$ + Chr$(13), Chr$(13)) Then a1$ = Mid$(a1$, k + 1) Else a1$ = ""
        If InStr(a1$, Chr$(13)) Then a1$ = Mid$(a1$, 1, InStr(a1$, Chr$(13)) - 1)
        x$ = Space$(_Width)
        Mid$(x$, 1) = a1$
        Print x$;
        seed = InStr(seed, a$, Chr$(13)) + 2
    Next
    Do
        _Limit 60
        b$ = InKey$
        Select Case b$
            Case Chr$(27): End
            Case Chr$(0) + "K"
                If k > 0 Then k = k - 1: Exit Do
            Case Chr$(0) + "M"
                k = k + 1: Exit Do
        End Select
    Loop
Loop

Anyway, not goof proofed so if you remove the remark at the _clipboard option just be sure you copy enough text to cover 20 or more lines. This is just what I would start out with a s way of displaying and horizontally scrolling text in SCREEN 0.

Pete

Hi Pete
your scrolling in SCREEN 0 is very interesting. As I have seen it I remembered when I saw for the first time the Text-windows in Turbo Pascal 6.0 in which you can scroll to right and to bottom beyond the text in the window.
So you bring me to imagine a demo
here it is

Code: (Select All)

 
 
Width 80, 25 ' screen 0 only text 80 columns for 25 rows
_ControlChr Off
_Title "Scrolling text in SCREEN 0 with arrow keys"
Dim Row As String, Text(1 To 40) As String, cText(1 To 255, 1 To 40) As Integer, a As Integer, b As Integer, R As Integer, C As Integer
' initialization
 
' it builds a string of 255 characters
For a = 1 To 255
    Row = Row + Chr$(a)
Next a
' it builds  40 rows of 255 characters for row
For a = 1 To 40
    Text(a) = Right$(Row, a + 10) + Left$(Row, 255 - a - 10)
    For b = 1 To 255
        cText(b, a) = (b * a) Mod 7
    Next b
Next a
 
Row = ""
R = 1
C = 1
While Row <> "Q"
    Row = UCase$(InKey$)
 
    If Row = Chr$(0) + "H" Then R = R - 1
    If Row = Chr$(0) + "P" Then R = R + 1
 
    If Row = Chr$(0) + "K" Then C = C - 1
    If Row = Chr$(0) + "M" Then C = C + 1
 
    Cls , 0
    For a = 0 To 24
        Locate a + 1, 1
        If (a + R) < 41 And (a + R) > 0 Then
            For b = 1 To 80
                If (C + b - 1 < 256) And (C + b - 1 > 0) Then
                    Color , cText(C + b - 1, a + R)
                    Print Mid$(Text(a + R), C + b - 1, 1);
                Else
                    Color , 0
                    Print " ";
                End If
 
            Next b
        End If
    Next
    _Display
    _Limit 100
Wend
End

I hope you don't mind