Add example for TimeFrameUnion and properly use the parameters struct (#3179)

data/assets/examples/timeframe/union.asset

@@ -0,0 +1,40 @@
+-- This example creates a union out of two simpler TimeFrameIntervals and uses it for a
+-- SceneGraphNode. The first TimeFrameInterval covers January 1st, 2000 and the second
+-- TimeFrameInterval covers March 1st, 2002. The resulting TimeFrameUnion will cover both
+-- January 1st, 2000 and March 1st, 2002.
+
+local Node = {
+  Identifier = "TimeFrameUnion_Example",
+  TimeFrame = {
+    Type = "TimeFrameUnion",
+    TimeFrames = {
+      -- The first TimeFrameInterval for the first day
+      {
+        Type = "TimeFrameInterval",
+        Start = "2000 JAN 01 00:00:00.000",
+        End = "2000 JAN 01 23:59:59.999"
+      },
+      -- The second TimeFrameInterval for the second day
+      {
+        Type = "TimeFrameInterval",
+        Start = "2002 MAR 01 00:00:00.000",
+        End = "2002 MAR 01 23:59:59.999"
+      }
+    }
+  },
+  Renderable = {
+    Type = "RenderableCartesianAxes"
+  },
+  GUI = {
+    Name = "TimeFrameUnion",
+    Path = "/Examples"
+  }
+}
+
+asset.onInitialize(function()
+  openspace.addSceneGraphNode(Node)
+end)
+
+asset.onDeinitialize(function()
+  openspace.removeSceneGraphNode(Node)
+end)

modules/base/timeframe/timeframeunion.cpp

@@ -40,6 +40,12 @@ namespace {
         openspace::properties::Property::Visibility::AdvancedUser
     };
 
+    // This TimeFrame class will accept the union of all passed-in TimeFrames. This means
+    // that this TimeFrame will be active if at least one of the child TimeFrames is
+    // active and it will be inactive if none of the child TimeFrames are active.
+    //
+    // This can be used to create more complex TimeFrames that are made up of several,
+    // simpler TimeFrames themselves.
     struct [[codegen::Dictionary(TimeFrameUnion)]] Parameters {
         // [[codegen::verbatim(TimeFramesInfo.description)]]
         std::vector<ghoul::Dictionary> timeFrames
@@ -51,7 +57,7 @@ namespace {
 namespace openspace {
 
 documentation::Documentation TimeFrameUnion::Documentation() {
-    return codegen::doc<Parameters>("base_time_frame_union");
+    return codegen::doc<Parameters>("base_timeframe_union");
 }
 
 bool TimeFrameUnion::isActive(const Time& time) const {
@@ -64,21 +70,15 @@ bool TimeFrameUnion::isActive(const Time& time) const {
 }
 
 TimeFrameUnion::TimeFrameUnion(const ghoul::Dictionary& dictionary) {
-    // I don't know how we can actually help the reference attribute properly. Since the
-    // Parameter list only contains the monostate, there is no need to actually create
-    // the object here
-    codegen::bake<Parameters>(dictionary);
+    const Parameters p = codegen::bake<Parameters>(dictionary);
 
-    const ghoul::Dictionary frames =
-        dictionary.value<ghoul::Dictionary>(TimeFramesInfo.identifier);
-
-    for (const std::string_view k : frames.keys()) {
-        const ghoul::Dictionary& subDictionary = frames.value<ghoul::Dictionary>(k);
-        _timeFrames.push_back(TimeFrame::createFromDictionary(subDictionary));
+    for (size_t i = 0; i < p.timeFrames.size(); i++) {
+        const ghoul::Dictionary& frame = p.timeFrames[i];
+        _timeFrames.push_back(TimeFrame::createFromDictionary(frame));
         TimeFrame& subFrame = *_timeFrames.back();
-        subFrame.setIdentifier(std::string(k));
-        subFrame.setGuiName(std::string(k));
-        subFrame.setDescription(std::string(k));
+        subFrame.setIdentifier(std::format("{}", i));
+        subFrame.setGuiName(std::format("{}", i));
+        subFrame.setDescription(std::format("{}", i));
         addPropertySubOwner(*_timeFrames.back());
     }
 }