[Needs Review] implementing backward compatible follow multi-target

example/allfeature/camera_controls.gui_script

@@ -55,7 +55,7 @@ end
 
 local function post_follow_message(self)
 	msg.post(CAMERA_ID, "follow", {
-		target = "/player",
+		target = {"/player2", "/player"},
 		lerp = self.lerp,
 		offset = self.camera_offset,
 		horizontal = self.follow_horizontal,

example/allfeature/example.collection

@@ -282,3 +282,43 @@ embedded_instances {
     z: 1.0
   }
 }
+embedded_instances {
+  id: "player2"
+  data: "embedded_components {\n"
+  "  id: \"sprite\"\n"
+  "  type: \"sprite\"\n"
+  "  data: \"tile_set: \\\"/example/assets/examples.atlas\\\"\\n"
+  "default_animation: \\\"hitman1_gun\\\"\\n"
+  "material: \\\"/builtins/materials/sprite.material\\\"\\n"
+  "blend_mode: BLEND_MODE_ALPHA\\n"
+  "\"\n"
+  "  position {\n"
+  "    x: -83.0\n"
+  "    y: -220.0\n"
+  "    z: 0.0\n"
+  "  }\n"
+  "  rotation {\n"
+  "    x: 0.0\n"
+  "    y: 0.0\n"
+  "    z: 0.0\n"
+  "    w: 1.0\n"
+  "  }\n"
+  "}\n"
+  ""
+  position {
+    x: 414.889
+    y: 640.951
+    z: 1.0
+  }
+  rotation {
+    x: 0.0
+    y: 0.0
+    z: 0.0
+    w: 1.0
+  }
+  scale3 {
+    x: 1.0
+    y: 1.0
+    z: 1.0
+  }
+}

orthographic/camera.lua

@@ -42,6 +42,7 @@ local v4_tmp = vmath.vector4()
 local v3_tmp = vmath.vector3()
 
 local cameras = {}
+local targets = {}
 
 --- projection providers (projectors)
 -- a mapping of id to function to calculate and return a projection matrix
@@ -193,6 +194,30 @@ local function calculate_view(camera, camera_world_pos, offset)
 	return view
 end
 
+--- Return target tables
+function M.get_targets()
+	return targets
+end
+
+--- Set targets
+-- @param message_targets
+function M.set_targets(message_targets)
+	targets = {}
+	if type(message_targets) == "table" then
+		for i = 1, #message_targets do
+			if type(message_targets[i]) == "string" then
+				table.insert(targets, hash(message_targets[i]))
+			else
+				table.insert(targets, message_targets[i])
+			end
+		end
+	elseif type(message_targets) == "string" then
+		table.insert(targets, hash(message_targets))
+	else
+		table.insert(targets, message_targets)
+	end
+end
+
 
 --- Initialize a camera
 -- Note: This is called automatically from the init() function of the camera.script
@@ -249,9 +274,12 @@ function M.update(camera_id, dt)
 	if follow_enabled then
 		local follow_horizontal = go.get(camera.url, "follow_horizontal")
 		local follow_vertical = go.get(camera.url, "follow_vertical")
-		local follow = go.get(camera.url, "follow_target")
 		local follow_offset = go.get(camera.url, "follow_offset")
-		local target_world_pos = go.get_world_position(follow) + follow_offset
+		local target_world_pos = go.get_world_position(targets[1])
+		for i = 2, #targets do
+			target_world_pos = target_world_pos + go.get_world_position(targets[i])
+		end
+		target_world_pos = target_world_pos / #targets + follow_offset
 		local new_pos
 		local deadzone_top = go.get(camera.url, "deadzone_top")
 		local deadzone_left = go.get(camera.url, "deadzone_left")

orthographic/camera.script

@@ -42,13 +42,26 @@ local ZOOM_TO = hash("zoom_to")
 local USE_PROJECTION = hash("use_projection")
 
 local function position_on_follow(self)
-	local target_position = go.get_position(self.follow_target)
+	local targets = camera.get_targets()
 	local camera_position = go.get_position()
-	target_position.z = camera_position.z
+	local target_position
+	if #targets == 0 then
+		target_position = camera_position
+	else
+		target_position = vmath.vector3()
+		for i = 1, #targets do
+			target_position = target_position + go.get_position(targets[i])
+		end
+		target_position = target_position / #targets
+		target_position.z = camera_position.z
+	end
 	go.set_position(target_position)
 end
 
 function init(self)
+	if self.follow then
+		camera.set_targets(self.follow_target)
+	end
 	camera.init(go.get_id(), msg.url(), { zoom = self.zoom })
 	if self.enabled then
 		camera.update(go.get_id(), 0)
@@ -97,7 +110,7 @@ function on_message(self, message_id, message, sender)
 		if message.vertical == nil then message.vertical = true end
 		self.follow_horizontal = message.horizontal
 		self.follow_vertical = message.vertical
-		self.follow_target = type(message.target) == "string" and hash(message.target) or message.target
+		camera.set_targets(message.target)
 		self.follow_lerp = message.lerp or 1
 		self.follow_offset = message.offset or vmath.vector3()
 		self.follow_immediately = message.immediate