Timeline: Add id-lookup API and GetMaxFrame

include/Timeline.h

@@ -78,6 +78,21 @@ namespace openshot {
 			return false;
 	}};
 
+	/// Comparison method for finding the far end of the timeline, by locating
+	/// the Clip with the highest end-frame number using std::max_element
+	struct CompareClipEndFrames {
+		bool operator()(const openshot::Clip* lhs, const openshot::Clip* rhs) {
+			return (lhs->Position() + lhs->Duration())
+			    <= (rhs->Position() + rhs->Duration());
+	}};
+
+	/// Like CompareClipEndFrames, but for effects
+	struct CompareEffectEndFrames {
+		bool operator()(const openshot::EffectBase* lhs, const openshot::EffectBase* rhs) {
+			return (lhs->Position() + lhs->Duration())
+				<= (rhs->Position() + rhs->Duration());
+	}};
+
 	/**
 	 * @brief This class represents a timeline
 	 *
@@ -241,6 +256,18 @@ namespace openshot {
 		/// Return a list of clips on the timeline
 		std::list<openshot::Clip*> Clips() { return clips; };
 
+		/// Look up a single clip by ID
+		openshot::ClipBase* GetClip(const std::string& id);
+
+		/// Look up a clip effect by ID
+		openshot::EffectBase* GetClipEffect(const std::string& id);
+
+		/// Look up a timeline effect by ID
+		openshot::EffectBase* GetEffect(const std::string& id);
+
+		/// Look up the end frame number of the latest element on the timeline
+		int64_t GetMaxFrame();
+
 		/// Close the timeline reader (and any resources it was consuming)
 		void Close() override;
 

src/Timeline.cpp

@@ -263,6 +263,59 @@ void Timeline::RemoveClip(Clip* clip)
 	clips.remove(clip);
 }
 
+// Look up a clip
+openshot::ClipBase* Timeline::GetClip(const std::string& id)
+{
+	// Find the matching clip (if any)
+	for (const auto& clip : clips) {
+		if (clip->Id() == id) {
+			return clip;
+		}
+	}
+	return nullptr;
+}
+
+// Look up a timeline effect
+openshot::EffectBase* Timeline::GetEffect(const std::string& id)
+{
+	// Find the matching effect (if any)
+	for (const auto& effect : effects) {
+		if (effect->Id() == id) {
+			return effect;
+		}
+	}
+	return nullptr;
+}
+
+openshot::EffectBase* Timeline::GetClipEffect(const std::string& id)
+{
+	// Search all clips for matching effect ID
+	for (const auto& clip : clips) {
+		auto e = clip->GetEffect(id);
+		if (e != nullptr) {
+			return e;
+		}
+	}
+	return nullptr;
+}
+
+int64_t Timeline::GetMaxFrame() {
+	int64_t last_clip = 1;
+	int64_t last_effect = 1;
+
+	if (!clips.empty()) {
+		const auto max_clip = std::max_element(
+				clips.begin(), clips.end(), CompareClipEndFrames());
+		last_clip = (*max_clip)->Position() + (*max_clip)->Duration();
+	}
+	if (!effects.empty()) {
+		const auto max_effect = std::max_element(
+				effects.begin(), effects.end(), CompareEffectEndFrames());
+		last_effect = (*max_effect)->Position() + (*max_effect)->Duration();
+	}
+	return std::max(last_clip, last_effect);
+}
+
 // Apply a FrameMapper to a clip which matches the settings of this timeline
 void Timeline::apply_mapper_to_clip(Clip* clip)
 {