Ensure initial PTY size matches Terminal (if any)

If a PTY has a terminal_path set to a valid Terminal, then ensure that
the initial cols and rows of PTY match the cols and rows of the Terminal
when calling fork() or open(), otherwise PTY will output wrong-sized
data for the Terminal until resized.

Fixes #56.

test/platform/unix/unix.test.gd

@@ -167,6 +167,61 @@ class Helper:
 		return {rows = int(size.x), cols = int(size.y)}
 
 
+class TestPTYSize:
+	extends "res://addons/gut/test.gd"
+	# Tests to check that psuedoterminal size (as reported by the stty command)
+	# matches the size of the Terminal node. Uses various scene tree layouts with
+	# Terminal and PTY nodes in different places.
+	# See: https://github.com/lihop/godot-xterm/issues/56
+
+	const PTY := preload("res://addons/godot_xterm/pty.gd")
+	const Terminal := preload("res://addons/godot_xterm/terminal.gd")
+
+	var pty: PTY
+	var terminal: Terminal
+	var scene: Node
+	var regex := RegEx.new()
+
+	func before_all():
+		regex.compile(".*rows (?<rows>[0-9]+).*columns (?<columns>[0-9]+).*")
+
+	func before_each():
+		scene = add_child_autofree(preload("res://test/scenes/pty_and_terminal.tscn").instance())
+
+	func test_correct_stty_reports_correct_size():
+		for s in [
+			"PTYChild",
+			"PTYSiblingAbove",
+			"PTYSiblingBelow",
+			"PTYCousinAbove",
+			"PTYCousinBelow",
+			"PTYCousinAbove2",
+			"PTYCousinBelow2"
+		]:
+			pty = scene.get_node(s).find_node("PTY")
+			terminal = scene.get_node(s).find_node("Terminal")
+
+			pty.call_deferred("fork", OS.get_environment("SHELL"))
+			pty.call_deferred("write", "stty -a | head -n1\n")
+			var output := ""
+			while not "rows" in output and not "columns" in output:
+				output = (yield(pty, "data_received")).get_string_from_utf8()
+			var regex_match = regex.search(output)
+			var stty_rows = int(regex_match.get_string("rows"))
+			var stty_cols = int(regex_match.get_string("columns"))
+
+			assert_eq(
+				stty_rows,
+				terminal.rows,
+				"Expected stty to report correct number of rows for layout '%s'" % s
+			)
+			assert_eq(
+				stty_cols,
+				terminal.cols,
+				"Expected stty to report correct number of columns for layout '%s'" % s
+			)
+
+
 class LinuxHelper:
 	extends Helper