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Handling Time

Time in DSFML

Just like the SFML implementation of time, DSFML doesn't impose a specific unit or type for time values, like always being a float for seconds or long for milliseconds and leaving it up to the programmer to convert as needed. It instead provides a struct, Time, that wraps this functionality.

The Time struct contains a relative time value or time span. It's exclusively a value used to represent a certain amount of time, as opposed to a full-on date-time class.

Converting Time

A Time object can be created from any of the source units: seconds, milliseconds, or microseconds. There is a (non-member) function to turn each of them into a Time:

Time t1 = microseconds(42000000);
auto t2 = milliseconds(42000);
auto t3 = seconds(42);

Note how all three of these times are equal.

Similarly, a Time object can be converted back to either seconds, milliseconds, or microseconds:

Time  time = ...;

long  usec = time.asMicroseconds();
int   msec = time.asMilliseconds();
float sec  = time.asSeconds();

Playing With Time Values

Time is just an amount of time, so it supports arithmetic operations such as addition, subtraction, comparison, etc. Times can also be negative.

Time t1 = seconds(42);
auto t2 = t1 * 2;
auto t3 = t1 + t2;
auto t4 = -t3;

bool b1 = (t1 == t2);
bool b2 = (t3 > t4);

Measuring Time

Now that we've seen how to manipulate time values with DSFML, let's see how to do something that almost every program needs: measuring the time elapsed.

DSFML, like SFML, has a very simple class for measuring time: Clock. It only has two methods: getElapsedTime(), to retrieve the time elapsed since the clock started, and restart(), to restart the clock.

Clock clock = new Clock(); // starts the clock
Time elapsed1 = clock.getElapsedTime();
Time elapsed2 = clock.getElapsedTime();

Note that restart() also returns the elapsed time, so that you can avoid the slight gap that would exist if you had to call getElapsedTime() 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 clock = new Clock();
while (window.isOpen())
    Time elapsed = clock.restart();