The Graphics window
The Graphics window is the drawing surface for the turtles.
BUTTON?
Also: 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
Also: 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.
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.
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.
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.
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.
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.
Example
HOME SETH 20 WRAP FD 1500