- Protect AddClip(), RemoveClip(), update_open_clips(), sort_clips(), sort_effects() methods with mutex, making them thread safe

- Refactor sorting of clips & effects, and only sort these arrays when the arrays change (instead of each call to GetFrame)
- Cache max timeline duration, and make Timeline::GetMaxTime() thread safe
- New multi-threaded unit tests, which are designed to verify no seg faults on multi-threaded calls to Timeline::GetFrame(), Timeline::AddClip(), and Timeline::RemoveClip()
- New public Timeline::SortTimeline() method which is called by child Clips automatically, when certain properties are changed

src/ClipBase.cpp

@@ -11,9 +11,55 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 
 #include "ClipBase.h"
+#include "Timeline.h"
 
 using namespace openshot;
 
+// Set position on timeline (in seconds)
+void ClipBase::Position(float value) {
+
+	position = value;
+
+	if (ParentTimeline()) {
+		// Resort timeline items (internal clips/effects arrays)
+		Timeline *parentTimeline = (Timeline *) ParentTimeline();
+		parentTimeline->SortTimeline();
+	}
+}
+
+// Set layer of clip on timeline (lower number is covered by higher numbers)
+void ClipBase::Layer(int value) {
+	layer = value;
+
+	if (ParentTimeline()) {
+		// Resort timeline items (internal clips/effects arrays)
+		Timeline *parentTimeline = (Timeline *) ParentTimeline();
+		parentTimeline->SortTimeline();
+	}
+}
+
+// Set start position (in seconds) of clip (trim start of video)
+void ClipBase::Start(float value) {
+	start = value;
+
+	if (ParentTimeline()) {
+		// Resort timeline items (internal clips/effects arrays)
+		Timeline *parentTimeline = (Timeline *) ParentTimeline();
+		parentTimeline->SortTimeline();
+	}
+}
+
+// Set end position (in seconds) of clip (trim end of video)
+void ClipBase::End(float value) {
+	end = value;
+
+	if (ParentTimeline()) {
+		// Resort timeline items (internal clips/effects arrays)
+		Timeline *parentTimeline = (Timeline *) ParentTimeline();
+		parentTimeline->SortTimeline();
+	}
+}
+
 // Generate Json::Value for this object
 Json::Value ClipBase::JsonValue() const {