| Pic.Free | Part of Pic module |
| Syntax | Pic.Free (picID : int)
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| Description | Pic.Free is used to release the memory allocated by
Pic.New. It frees up the memory allocated to the parameter
picID. This means that picID can not be used in a
Draw.Pic or Draw.Save procedure after Pic.Free
is called. Turing has a limited number of pictures that are available at any one time (approximately 1,000). A program that continuously allocates pictures (using Pic.New or Pic.FileNew) will eventually fail if it does not free the pictures using Pic.Free. As well, if a program allocates hundreds of pictures and does not free any of them, the memory devoted to the pictures will not be freed and eventually the program may exhaust the memory on the machine.
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| Details | If Pic.Free is passed an invalid picture ID, a fatal error
occurs. If the Pic.Free call fails for other (non-fatal)
reasons, Error.Last will return a non-zero value indicating
the reason for the failure. Error.LastMsg will return a string
which contains the textual version of the error.
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| Example | The program animates a picture moving across a background. Each
time the picture is about to move to a new location, a picture of
the background at that location is taken. When the picture is to be
moved to the next location, the background picture is drawn over top
of the picture, thus "erasing" it. The Pic.Free command frees
up each background picture once it is no longer in use. Without it,
the program would use up all the picture identifiers and crash after
one or two moves across the window. The animation in the example flickers slightly. See View.Update for information on how to produce flicker-free animation.
var picID, bgID : int
var x, y, c, direction : int
% Create the picture being moved
Draw.FillBox (50, 50, 150, 150, brightred)
Draw.FillStar (50, 50, 150, 150, brightgreen)
Draw.FillOval (100, 100, 30, 30, brightblue)
picID := Pic.New (50, 50, 150, 150)
% Create a background
for i : 1 .. 1000
x := Rand.Int (0, maxx)
y := Rand.Int (0, maxy)
c := Rand.Int (9, 15) % Use bright colors
Draw.FillBox (x, y, x + 30, y + 30, c)
end for
x := 1
y := 100
direction := 1
% Main loop
loop
% Take a picture of the background
bgID := Pic.New (x, y, x + 100, y + 100)
Pic.Draw (picID, x, y, picCopy) % Draw the picture
delay (20) % Delay 20 milliseconds
Pic.Draw (bgID, x, y, picCopy) % Draw the background over the picture
Pic.Free (bgID) % Free the background
if x <= 0 or (x + 100) >= maxx then
direction := -direction
end if
x += direction
end loop
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| Execute | |
| Status | Exported qualified. This means that you can only call the function by calling Pic.Free, not by calling Free.
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