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The Graphics window

The Graphics window is the drawing surface for the turtles.

BUTTON? (BUTTONP)

Reports the state of a mouse button.

Syntax

BUTTON?
(BUTTON? button)

Description

BUTTON? reports the state of a mouse button. BUTTON? reports TRUE when the left button is depressed or FALSE when the button is not depressed. Is used with an additional input, the input is 1 for the left button, 2 for the middle button, and 3 for the right button.

See also MOUSE.

Example

TO CHASE
    SETPOS MOUSE
    IF BUTTON? [STOP]
    CHASE
END
CHASE

CLEAN

Erases the graphics pane.

Syntax

CLEAN

Description

CLEAN erases the current Graphics window but does not affect the heading or position of the turtle. See also CLEARSCREEN and DRAW.

Example

HOME
SETPC "RED
SETH 20
FD 50
CLEAN
FD 50

CLEARSCREEN (CS)

Erases the graphics pane and homes the turtle.

Syntax

CLEARSCREEN

Description

CLEARSCREEN erases the current Graphics window, deletes all control widgets, returns the turtle to the center of the window, and sets the turtle's heading to 0. CLEARSCREEN does not affect the pen state or window colors. See also CLEAN and DRAW.

Example

HOME
SETPC "RED
SETH 20
FD 50
CLEARSCREEN
FD 50

DRAW

Clears the current graphics window and resets all attached turtles.

Syntax

DRAW

Description

DRAW prepares the current Graphics window for drawing by doing the following:

  • Clears the window.
  • Deletes all control widgets.
  • Resets all attached turtles to their default values.
  • Sets turtle 0 to be the active turtle.
  • Homes the turtle.
  • Shows the turtle.
  • Puts the pen down.
  • Sets the window to WRAP mode.

See also CLEARSCREEN and CLEAN.

Example

TELL 0 HOME
RT 22 FD 10000
DRAW

EXTENT

Reports the extent of the current Graphics window.

Syntax

EXTENT

Description

EXTENT reports a list containing the X and Y extents of the current Graphics window, based on the extent settings of the first active turtle. In the default state, where one turtle step corresponds to one screen pixel, the extents are both zero.

For a detailed explanation of the window extent, see SETEXTENT.

See also SETEXTENT, WRAP, and FENCE.

Example

EXTENT
Result: [0 0]

FENCE

Fences all turtles inside the drawing borders.

Syntax

FENCE

Description

FENCE prevents the turtle from moving beyond the edge of the Graphics drawing borders. If you try to move the turtle outside the borders, it moves to the drawing border and stops.

See also WRAP and WINDOW.

Example

HOME
SETH 20
FENCE
FD 1000

GRID

Sets the size of the graphics grid.

Syntax

GRID size

Description

GRID sets the horizontal and vertical scales of the Graphics window grid to its input.

See also GRIDON and GRIDOFF.

Example

GRIDON
GRID 50
GRID 100

GRIDOFF

Hides the grid of the Graphics window.

Syntax

GRIDOFF

Description

GRIDOFF makes a visible grid in the Graphics window invisible.

See also GRIDON and GRID.

Example

GRIDON
GRIDOFF

GRIDON

Displays the grid of the Graphics window.

Syntax

GRIDON
(GRIDON [horizontal vertical])

Description

GRIDON makes a grid visible in the Graphics window. By default, the scale of the grid is 100 pixels on each axis.

The scale of the grid may be changed by supplying GRIDON with a list containing the desired horizontal and vertical scales for the grid and putting GRIDON and its argument in parentheses.

See also GRIDOFF and GRID.

Example

(GRIDON [150 50])
 GRIDON

LOADPIC

Loads a picture as background picture.

Syntax

LOADPIC filename.ext
(LOADPIC filename.ext TRUE)

Description

LOADPIC loads the file from the cloud to the current graphics canvas. The file is loaded as a bit map that fills the current viewport. If no extension is given to the filename, the picture format that is loaded is the format specified in the built-in variable :PICTURE.FORMAT. If the file has a different extension, then the extension must be specified in the LOADPIC command.

If the last input to LOADPIC is TRUE, LOADPIC loads multiple copies of the image instead and fills the entire graphics screen with these copies (it tiles the images).

MOUSE

Reports the position of the mouse cursor.

Syntax

MOUSE

Description

MOUSE reports the coordinates of the position of the mouse pointer as a list of two numbers representing the x coordinate and the y coordinate. The coordinates are relative to the center of the Graphics window. See also BUTTON?.

Example

TO CHASE
    SETPOS MOUSE
    IF BUTTON? [STOP]
    CHASE
END
CHASE

MOUSESHAPE

Reports the shape of the mouse cursor.

Syntax

MOUSESHAPE

Description

MOUSESHAPE reports the number of the current mouse pointer shape as defined with the SETMOUSESHAPE command. On startup, the mouse shape is 1.

Example

MOUSESHAPE

SAVEPIC

Saves the contents of the Graphics window.

Syntax

SAVEPIC filename.ext
SAVEPIC type-decriptors
(SAVEPIC)
(SAVEPIC filename.ext "windowname)

Description

SAVEPIC saves the contents of the current Graphics window into a bitmap file on disk. SAVEPIC uses the boundaries of the current drawing area. If no extension is given to the filename, the picture format that is saved is the format specified in the built-in variable :PICTURE.FORMAT. If you want a different format than the default, then the extension must be specified in the SAVEPIC command. SAVEPIC can save into several different formats; see :PICTURE.FORMAT for a list of supported formats.

SAVEPIC displays a File Open dialog if it is called without any inputs, or if the input is a list of file type descriptors. For a description of file type descriptors, see the OPEN command. Clicking the Cancel button in a File Save dialog causes the SAVEPIC command to return.

Example

SAVEPIC "Sample

SETEXTENT

Set the extent of the current Graphics window.

Syntax

SETEXTENT extent
SETEXTENT [xExtent yExtent]
(SETEXTENT)

Description

SETEXTENT defines the coordinate mapping mode in terms of turtle steps. The default is an extent value of zero, which means the coordinate system has an aspect ratio of 1:1 regardless of the window size. Painting outside the window in WINDOW mode is possible and the drawings become visible when the window is made larger.

If a different extent is defined, the coordinate system is mapped to the size given regardless of the window size. If an extent value of 200 is set, the coordinates range from -200 to +200. Scaling is performed automatically to fit within the window. It is possible to set different extents for the X and Y coordinates by using a two-element list as input. (SETEXTENT) resets the extent to 1:1 mapping.

Note that each individual turtle, control, or bitmap may have its own screen extent. Thus the lines drawn by different turtles for the same number of turtle steps may be of different lengths if their extents are not the same.

See also EXTENT, SETORIGIN and ORIGIN.

Example

ASK 0 [SETEXTENT 100 PENUP SETX -25 PENDOWN]
ASK 1 [SETEXTENT 50 PENUP SETX 25 PENDOWN]
TELL [0 1]
ST FORWARD 30

SETMOUSESHAPE

Sets the shape of the mouse cursor.

Syntax

SETMOUSESHAPE number
(SETMOUSESHAPE)

Description

SETMOUSESHAPE changes the shape of the mouse cursor when it is within the Graphics window. Its input is a number representing one of 23 available mouse shapes. When Logo starts, the mouse shape is 1. If SETMOUSESHAPE is enclosed in parentheses without inputs, shape 1 is used.

MOUSESHAPE reports the number of the current mouse shape.

Example

SETMOUSESHAPE 20

WINDOW

Removes the boundary for turtle movements.

Syntax

WINDOW

Description

WINDOW removes the boundaries from the turtle's field of movement. If the turtle moves beyond the borders of the Graphics drawing borders, it continues to move, but cannot be seen. The Graphics window becomes a small window overlooking the plane on which the turtle can travel.

See also FENCE and WRAP.

Example

HOME
SETH 20
WINDOW
FD 1500

WRAP

Lets the turtles wrap inside the window.

Syntax

WRAP

Description

WRAP maintains the turtle inside the Graphics drawing borders no matter how large a movement command is given. Any time the turtle moves off the window border, it wraps around the window and reappears on the opposite edge. When Logo starts up, the default window state is WRAP.

See also FENCE and WINDOW.

Example

HOME
SETH 20
WRAP
FD 1500