1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
|
Handling time
=============
.. contents:: :local:
Time in pySFML
--------------
Unlike many other libraries where time is an int number of milliseconds, or a
float number of seconds, pySFML doesn't impose any specific unit or type for
time values. Instead it leaves this choice to the user through a flexible
:class:`.Time`. All pySFML classes and functions that manipulate time values
use this class.
:class:`.Time` wraps a relative time value (in other words, a time span). It is
not a date-time class which would represent the current
year/month/day/hour/minute/second, it's just a value that represents a certain
amount of time, and how to interpret it depends on the context where it is used.
Converting time
---------------
A :class:`.Time` value can be constructed from different source units: seconds,
milliseconds and microseconds. There is a (non-member) function to turn each of
them into a :class:`.Time`: ::
t1 = sf.microseconds(10000)
t2 = sf.milliseconds(10)
t3 = sf.seconds(0.01)
Note that these three times are all equal.
Similarly, a :class:`.Time` can be converted back to either seconds,
milliseconds or microseconds: ::
time = ...
usec = time.microseconds # long
msec = time.milliseconds # int
sec = time.seconds # float
Playing with time values
------------------------
:class:`.Time` is just an amount of time, so it supports arithmetic operations
such as addition, subtraction, comparison, etc. Times can also be negative.
t1 = ...
t2 = t1 * 2
t3 = t1 + t2
t4 = -t3
b1 = t1 == t2
b2 = t3 > t4
Measuring time
--------------
Now that we've seen how to manipulate time values with pySFML, let's see how to
do something that almost every program needs: measuring the time elapsed.
pySFML has a very simple class for measuring time: :class:`.Clock`. It only has
two members: :attr:`.elapsed_time`, to retrieve the time elapsed since the
clock started, and :meth:`.restart`, to restart the clock. ::
clock = sf.Clock() # starts the clock
# ...
elapsed1 = clock.elapsed_time
print(elapsed1.seconds)
clock.restart()
# ...
elapsed2 = clock.elapsed_time
print(elapsed2.seconds)
Note that restart also returns the elapsed time, so that you can avoid the
slight gap that would exist if you had to call :attr:`.elapsed_time`
explicitly before restart.
Here is an example that uses the time elapsed at each iteration of the game
loop to update the game logic::
clock = sf.Clock()
while window.is_open:
elapsed = clock.restart()
update_game(elapsed)
#...
|
