-Fixed screen capture for viewports, added a screen capture demo, fixes #1529

viewport/screen_capture/engine.cfg

@@ -0,0 +1,8 @@
+[application]
+
+name="Screen Capturing"
+main_scene="res://screen_capture.scn"
+
+[display]
+
+stretch_mode="2d"

viewport/screen_capture/screen_capture.gd

@@ -0,0 +1,27 @@
+
+extends Control
+
+# member variables here, example:
+# var a=2
+# var b="textvar"
+
+func _ready():
+	# Initialization here
+	pass
+
+
+
+
+func _on_button_pressed():
+	get_viewport().queue_screen_capture()
+	#let two frames pass to make sure the screen was aptured
+	yield(get_tree(),"idle_frame")
+	yield(get_tree(),"idle_frame")
+	#retrieve the captured image
+	var img = get_viewport().get_screen_capture()
+	#create a texture for it
+	var tex = ImageTexture.new()
+	tex.create_from_image(img)
+	#set it to the capture node
+	get_node("capture").set_texture(tex)
+	pass # replace with function body