Add UiNode class for UI rendering

Author: Baptistegrn

std/ui.das

@@ -0,0 +1,38 @@
+options gen2
+
+require node
+require grngame_renderer
+
+class UiNode : Node {
+    center: bool
+    flip_x: bool
+    alpha: int
+    rotation: int
+    coeff: int
+
+    def UiNode(ui_name: string, w: int, h: int, is_center: bool) {
+        Node`Node(self, ui_name)
+        self.coeff = 1
+        self.center = is_center
+        self.flip_x = false
+        self.alpha = 255
+        self.rotation = 0
+    }
+
+    def get_draw_position() : float2 {
+        if (center) {
+            //todo center position
+            return position
+        }
+        return position
+    }
+
+    def override render() {
+        super.render()
+        if (alpha == 0) {
+            return
+        }
+        var draw_pos = get_draw_position()
+        draw(name, draw_pos.x, draw_pos.y,coeff, flip_x, rotation, alpha)
+    }
+}