feat: add system time offset setting (#6139)

* Add setting for system time offset

Add a setting to displace citra system time by days, hours, minutes
or seconds
Add UI for the setting which is only visible when clock is set to
system time
Change core/settings.h to include the setting

* Add system time offset to kernel

Actually makes use of the time offset.

* Fix time offset calculatioon in core/movie.cpp

* Replace C++20 chrono::days with seconds

Hopefully fixes the build.

src/core/hle/kernel/shared_page.cpp

@@ -45,6 +45,16 @@ static std::chrono::seconds GetInitTime() {
         std::tm* now_tm = std::localtime(&now_time_t);
         if (now_tm && now_tm->tm_isdst > 0)
             now = now + std::chrono::hours(1);
+
+        // add the offset
+        s64 init_time_offset = Settings::values.init_time_offset;
+        long long days_offset = init_time_offset / 86400;
+        long long days_offset_in_seconds = days_offset * 86400; // h/m/s truncated
+        unsigned long long seconds_offset =
+            std::abs(init_time_offset) - std::abs(days_offset_in_seconds);
+
+        now = now + std::chrono::seconds(seconds_offset);
+        now = now + std::chrono::seconds(days_offset_in_seconds);
         return std::chrono::duration_cast<std::chrono::seconds>(now.time_since_epoch());
     }
     case Settings::InitClock::FixedTime:

src/core/movie.cpp

@@ -601,9 +601,17 @@ void Movie::PrepareForPlayback(const std::string& movie_file) {
 }
 
 void Movie::PrepareForRecording() {
-    init_time = (Settings::values.init_clock == Settings::InitClock::SystemTime
-                     ? Common::Timer::GetTimeSinceJan1970().count()
-                     : Settings::values.init_time);
+    if (Settings::values.init_clock == Settings::InitClock::SystemTime) {
+        long long init_time_offset = Settings::values.init_time_offset;
+        long long days_offset = init_time_offset / 86400;
+        unsigned long long seconds_offset =
+            std::abs(init_time_offset) - std::abs(days_offset * 86400);
+
+        init_time =
+            Common::Timer::GetTimeSinceJan1970().count() + seconds_offset + (days_offset * 86400);
+    } else {
+        init_time = Settings::values.init_time;
+    }
 }
 
 Movie::ValidationResult Movie::ValidateMovie(const std::string& movie_file) const {

src/core/settings.h

@@ -163,6 +163,7 @@ struct Values {
     int region_value;
     InitClock init_clock;
     u64 init_time;
+    s64 init_time_offset;
 
     // Renderer
     bool use_gles;