Add operator< for VerticalPosition.

2 files changed, 34 insertions, 0 deletions

diff --git a/src/vertical_position.cc b/src/vertical_position.cc
index cdf0b6c..37930d0 100644
--- a/src/vertical_position.cc
+++ b/src/vertical_position.cc
@@ -21,6 +21,29 @@
 
 using namespace sub;
 
+float
+VerticalPosition::fraction_from_screen_top () const
+{
+	if (!reference || (!proportional && !line)) {
+		return 0;
+	}
+
+	float const prop = proportional ? proportional.get() : (float (line.get()) / lines.get ());
+	
+	switch (reference.get ()) {
+	case TOP_OF_SCREEN:
+		return prop;
+	case CENTRE_OF_SCREEN:
+		return prop + 0.5;
+	case BOTTOM_OF_SCREEN:
+		return 1 - prop;
+	case TOP_OF_SUBTITLE:
+		return prop;
+	}
+
+	return 0;
+}
+
 bool
 VerticalPosition::operator== (VerticalPosition const & other) const
 {
@@ -32,3 +55,11 @@ VerticalPosition::operator== (VerticalPosition const & other) const
 
 	return false;
 }
+
+bool
+VerticalPosition::operator< (VerticalPosition const & other) const
+{
+	return fraction_from_screen_top() < other.fraction_from_screen_top();
+}
+
+	
diff --git a/src/vertical_position.h b/src/vertical_position.h
index 77b0675..9f04056 100644
--- a/src/vertical_position.h
+++ b/src/vertical_position.h
@@ -41,6 +41,9 @@ public:
 	boost::optional<VerticalReference> reference;
 	
 	bool operator== (VerticalPosition const & other) const;
+	bool operator< (VerticalPosition const & other) const;
+
+	float fraction_from_screen_top () const;
 };
 	
 }