1 files changed, 77 insertions, 0 deletions
diff --git a/src/mbgl/util/transition.hpp b/src/mbgl/util/transition.hpp
new file mode 100644
index 0000000000..d6bbc9eba0
--- /dev/null
+++ b/src/mbgl/util/transition.hpp
@@ -0,0 +1,77 @@
+#ifndef MBGL_UTIL_TRANSITION
+#define MBGL_UTIL_TRANSITION
+
+#include <mbgl/util/noncopyable.hpp>
+#include <mbgl/util/time.hpp>
+
+namespace mbgl {
+namespace util {
+
+class transition : private noncopyable {
+public:
+    enum state {
+        running,
+        complete
+    };
+
+    inline transition(timestamp start_, timestamp duration_)
+        : start(start_),
+          duration(duration_) {}
+
+    inline float progress(timestamp now) const {
+        if (duration == 0) return 1;
+        if (start > now) return 0;
+
+        return (float)(now - start) / duration;
+    }
+
+    virtual state update(timestamp now) const = 0;
+    virtual ~transition();
+
+protected:
+    const timestamp start, duration;
+};
+
+template <typename T>
+class ease_transition : public transition {
+public:
+    ease_transition(T from_, T to_, T& value_, timestamp start_, timestamp duration_)
+        : transition(start_, duration_),
+          from(from_),
+          to(to_),
+          value(value_) {}
+
+    state update(timestamp now) const;
+
+private:
+    const T from, to;
+    T& value;
+
+};
+
+template <typename T>
+class timeout : public transition {
+public:
+    timeout(T final_value_, T& value_, timestamp start_, timestamp duration_)
+        : transition(start_, duration_),
+          final_value(final_value_),
+          value(value_) {}
+
+    state update(timestamp now) const {
+        if (progress(now) >= 1) {
+            value = final_value;
+            return complete;
+        } else {
+            return running;
+        }
+    }
+
+private:
+    const T final_value;
+    T& value;
+};
+
+}
+}
+
+#endif