Windowkeyword

Sets new view coordinates mapping for current viewport

Syntax

Window [ [Screen] ( x1, y1 )-( x2, y2 ) ]

Description

Window is used to define a new coordinates system. (x1, y1) and (x2, y2) are the new coordinates to be mapped to the opposite corners of the current viewport; all future coordinates passed to graphics primitive statements will be affected by this new mapping. If Screen is omitted, the new coordinates system will be Cartesian, that is, with y coordinates increasing from bottom to top. Call Window with no argument to disable the coordinates transformation.

FreeBASIC's current behavior is to keep track of the corners of the Window, rather than a specific coordinate mapping. This means that the coordinate mapping can change after calls to View.
The Window corners are also currently taken into account when working on image buffers, so when a Window is in effect, the coordinate mapping will be different from image to image.

When there is no Window in effect, there is no coordinate mapping in effect, so the effective coordinate system is constant, independent of image buffer sizes or View coordinates (if any).

Remarks

Differences from QB

QBASIC preserves the coordinate mapping after subsequent calls to VIEW.
FreeBASIC's current behavior is to preserve the WINDOW coordinates after calls to VIEW, or when working on images, meaning that the coordinate mapping may undergo scaling/translations. (If a WINDOW hasn't been set, there is no coordinate mapping, and so it doesn't change after calls to VIEW.) The behavior may change in future, but consistent behavior can be be assured over inconstent viewport coordinates by re-calling WINDOW when you change the VIEW.

Example

'' The program shows how changing the view coordinates mapping for the current viewport changes the size of a figure drawn on the screen.

'' The effect is one of zooming in and out:

''   - As the viewport coordinates get smaller, the figure appears larger on the screen, until parts of it are finally clipped,

''        because they lie outside the window.

''   - As the viewport coordinates get larger, the figure appears smaller on the screen.



Declare Sub Zoom (ByVal X As Integer)

Dim As Integer X = 500, Xdelta = 50



Screen 12

Do

  Do While X < 525 And X > 50

    X += Xdelta                      '' Change window size.

    Zoom(X)

    If Inkey <> "" Then Exit Do, Do  '' Stop if key pressed.

    Sleep 100

  Loop

  X -= Xdelta

  Xdelta *= -1                       '' Reverse size change.

Loop



Sub Zoom (ByVal X As Integer)

  Window (-X,-X)-(X,X)               '' Define new window.

  ScreenLock

  Cls

  Circle (0,0), 60, 11, , , 0.5, F   '' Draw ellipse with x-radius 60.

  ScreenUnlock

End Sub

Screen 13



'' define clipping area

View ( 10, 10 ) - ( 310, 150 ), 1, 15    



'' set view coordinates

Window ( -1, -1 ) - ( 1, 1 )             



'' Draw X axis

Line (-1,0)-(1,0),7

Draw String ( 0.8, -0.1 ), "X"



'' Draw Y axis

Line (0,-1)-(0,1),7

Draw String ( 0.1, 0.8 ), "Y"



Dim As Single x, y, s



'' compute step size (corresponds to a step of 1 pixel on x coordinate)

s = 2 / PMap( 1, 0 )



'' plot the function

For x = -1 To 1 Step s

  y = x ^ 3

  PSet( x, y ), 14

Next x



'' revert to screen coordinates

Window



'' remove the clipping area

View



'' draw title

Draw String ( 120, 160 ), "Y = X ^ 3"



Sleep

Reference

Documented in KeyPgWindow.html