reduced calls to SDL_GetTicks to speed things up

src/animated.cpp

@@ -21,6 +21,15 @@
 #include "util.hpp"
 #include "serialization/string_utils.hpp"
 
+namespace {
+	int current_ticks = 0;
+}
+
+void new_animation_frame()
+{
+	current_ticks = SDL_GetTicks();
+}
+
 template<typename T, typename T_void_value>
 const T animated<T,T_void_value>::void_value_ = T_void_value()();
 
@@ -94,7 +103,7 @@ void animated<T,T_void_value>::start_animation(int start_frame, int cycles, int
 {
 	started_ = true;
 	start_frame_ = start_frame;
-	start_ticks_ = real_start_ticks_ = current_time_ = SDL_GetTicks() * acceleration;
+	start_ticks_ = real_start_ticks_ = current_time_ = current_ticks * acceleration;
 	cycles_ = cycles;
 	current_cycle_ = 0;
 	acceleration_ = acceleration;
@@ -120,7 +129,7 @@ void animated<T,T_void_value>::update_current_frame()
 
 	frame_changed_ = false;
 	// Always update current_time_, for the animation_time functions to work.
-	current_time_ = SDL_GetTicks() * acceleration_;
+	current_time_ = current_ticks * acceleration_;
 	if(!started_)
 		return;
 
@@ -218,7 +227,7 @@ template<typename T,  typename T_void_value>
 int animated<T,T_void_value>::get_animation_time() const
 {
 	if(does_not_change_)
-		return SDL_GetTicks() * acceleration_ - real_start_ticks_ + start_frame_;
+		return current_ticks * acceleration_ - real_start_ticks_ + start_frame_;
 
 	return current_time_ - real_start_ticks_ + start_frame_;
 }

src/animated.hpp

@@ -17,6 +17,8 @@
 #include <string>
 #include <vector>
 
+void new_animation_frame();
+
 template<typename T>
 class void_value
 {

src/display.cpp

@@ -2062,6 +2062,7 @@ void display::invalidate_unit()
 
 void display::invalidate_animations()
 {
+	new_animation_frame();
 	bool animate_flags = false;
 	gamemap::location topleft;
 	gamemap::location bottomright;