Module Graphics

Raised by the functions below when they encounter an error.

Show the graphics window or switch the screen to graphic mode. The graphics window is cleared and the current point is set to (0, 0). The string argument is used to pass optional information on the desired graphics mode, the graphics window size, and so on. Its interpretation is implementation-dependent. If the empty string is given, a sensible default is selected.

Delete the graphics window or switch the screen back to text mode.

Set the title of the graphics window.

Resize and erase the graphics window.

Erase the graphics window.

See Graphics.size_y.

Return the size of the graphics window. Coordinates of the screen pixels range over 0 .. size_x()-1 and 0 .. size_y()-1. Drawings outside of this rectangle are clipped, without causing an error. The origin (0,0) is at the lower left corner. Some implementation (e.g. X Windows) represent coordinates by 16-bit integers, hence wrong clipping may occur with coordinates below -32768 or above 32676.

A color is specified by its R, G, B components. Each component is in the range 0..255. The three components are packed in an int: 0xRRGGBB, where RR are the two hexadecimal digits for the red component, GG for the green component, BB for the blue component.

rgb r g b returns the integer encoding the color with red component r, green component g, and blue component b. r, g and b are in the range 0..255.

Set the current drawing color.

See Graphics.foreground.

Default background and foreground colors (usually, either black foreground on a white background or white foreground on a black background). Graphics.clear_graph fills the screen with the background color. The initial drawing color is foreground.

Plot the given point with the current drawing color.

Plot the given points with the current drawing color.

Return the color of the given point in the backing store (see "Double buffering" below).

Position the current point.

rmoveto dx dy translates the current point by the given vector.

Return the abscissa of the current point.

Return the ordinate of the current point.

Return the position of the current point.

Draw a line with endpoints the current point and the given point, and move the current point to the given point.

Draw a line with endpoints the current point and the current point translated of the given vector, and move the current point to this point.

curveto b c d draws a cubic Bezier curve starting from the current point to point d, with control points b and c, and moves the current point to d.

draw_rect x y w h draws the rectangle with lower left corner at x,y, width w and height h. The current point is unchanged. Raise Invalid_argument if w or h is negative.

draw_poly_line points draws the line that joins the points given by the array argument. The array contains the coordinates of the vertices of the polygonal line, which need not be closed. The current point is unchanged.

draw_poly polygon draws the given polygon. The array contains the coordinates of the vertices of the polygon. The current point is unchanged.

draw_segments segments draws the segments given in the array argument. Each segment is specified as a quadruple (x0, y0, x1, y1) where (x0, y0) and (x1, y1) are the coordinates of the end points of the segment. The current point is unchanged.

draw_arc x y rx ry a1 a2 draws an elliptical arc with center x,y, horizontal radius rx, vertical radius ry, from angle a1 to angle a2 (in degrees). The current point is unchanged. Raise Invalid_argument if rx or ry is negative.

draw_ellipse x y rx ry draws an ellipse with center x,y, horizontal radius rx and vertical radius ry. The current point is unchanged. Raise Invalid_argument if rx or ry is negative.

draw_circle x y r draws a circle with center x,y and radius r. The current point is unchanged. Raise Invalid_argument if r is negative.

Set the width of points and lines drawn with the functions above. Under X Windows, set_line_width 0 selects a width of 1 pixel and a faster, but less precise drawing algorithm than the one used when set_line_width 1 is specified. Raise Invalid_argument if the argument is negative.

See Graphics.draw_string.

Draw a character or a character string with lower left corner at current position. After drawing, the current position is set to the lower right corner of the text drawn.

Set the font used for drawing text. The interpretation of the argument to set_font is implementation-dependent.

Set the character size used for drawing text. The interpretation of the argument to set_text_size is implementation-dependent.

Return the dimensions of the given text, if it were drawn with the current font and size.

fill_rect x y w h fills the rectangle with lower left corner at x,y, width w and height h, with the current color. Raise Invalid_argument if w or h is negative.

Fill the given polygon with the current color. The array contains the coordinates of the vertices of the polygon.

Fill an elliptical pie slice with the current color. The parameters are the same as for Graphics.draw_arc.

Fill an ellipse with the current color. The parameters are the same as for Graphics.draw_ellipse.

Fill a circle with the current color. The parameters are the same as for Graphics.draw_circle.

The abstract type for images, in internal representation. Externally, images are represented as matrices of colors.

In matrices of colors, this color represent a 'transparent' point: when drawing the corresponding image, all pixels on the screen corresponding to a transparent pixel in the image will not be modified, while other points will be set to the color of the corresponding point in the image. This allows superimposing an image over an existing background.

Convert the given color matrix to an image. Each sub-array represents one horizontal line. All sub-arrays must have the same length; otherwise, exception Graphic_failure is raised.

Convert an image to a color matrix.

Draw the given image with lower left corner at the given point.

Capture the contents of a rectangle on the screen as an image. The parameters are the same as for Graphics.fill_rect.

create_image w h returns a new image w pixels wide and h pixels tall, to be used in conjunction with blit_image. The initial image contents are random, except that no point is transparent.

blit_image img x y copies screen pixels into the image img, modifying img in-place. The pixels copied are those inside the rectangle with lower left corner at x,y, and width and height equal to those of the image. Pixels that were transparent in img are left unchanged.

To report events.

To specify events to wait for.

Wait until one of the events specified in the given event list occurs, and return the status of the mouse and keyboard at that time. If Poll is given in the event list, return immediately with the current status. If the mouse cursor is outside of the graphics window, the mouse_x and mouse_y fields of the event are outside the range 0..size_x()-1, 0..size_y()-1. Keypresses are queued, and dequeued one by one when the Key_pressed event is specified and the Poll event is not specified.

Loop before exiting the program, the list given as argument is the list of handlers and the events on which these handlers are called. To exit cleanly the loop, the handler should raise Exit. Any other exception will be propagated outside of the loop.

Return the position of the mouse cursor, relative to the graphics window. If the mouse cursor is outside of the graphics window, mouse_pos() returns a point outside of the range 0..size_x()-1, 0..size_y()-1.

Return true if the mouse button is pressed, false otherwise.

Wait for a key to be pressed, and return the corresponding character. Keypresses are queued.

Return true if a keypress is available; that is, if read_key would not block.

sound freq dur plays a sound at frequency freq (in hertz) for a duration dur (in milliseconds).

By default, drawing takes place both on the window displayed on screen, and in a memory area (the 'backing store'). The backing store image is used to re-paint the on-screen window when necessary.

To avoid flicker during animations, it is possible to turn off on-screen drawing, perform a number of drawing operations in the backing store only, then refresh the on-screen window explicitly.

auto_synchronize false turns on-screen drawing off. All subsequent drawing commands are performed on the backing store only.

auto_synchronize true refreshes the on-screen window from the backing store (as per synchronize), then turns on-screen drawing back on. All subsequent drawing commands are performed both on screen and in the backing store.

The default drawing mode corresponds to auto_synchronize true.

Synchronize the backing store and the on-screen window, by copying the contents of the backing store onto the graphics window.

Set display mode on or off. When turned on, drawings are done in the graphics window; when turned off, drawings do not affect the graphics window. This occurs independently of drawing into the backing store (see the function Graphics.remember_mode below). Default display mode is on.

Set remember mode on or off. When turned on, drawings are done in the backing store; when turned off, the backing store is unaffected by drawings. This occurs independently of drawing onto the graphics window (see the function Graphics.display_mode above). Default remember mode is on.