Change 2d transform snapping from floor to round

Two common problems have emerged as a result of transform snapping:
1) Camera jitter with a camera following a snapped object
2) Pixel gaps between e.g. a platform and a player, where a platform rounds down and a player rounds up

Using round seems to greatly reduce problems due to camera jitter. It also may prove better for  pixel gaps because pixel art is often designed on a grid, so whole numbers are too expected, which are unstable with floor().

scene/2d/animated_sprite.cpp

@@ -453,6 +453,8 @@ void AnimatedSprite::_notification(int p_what) {
 				ofs -= s / 2;
 
 			if (Engine::get_singleton()->get_snap_2d_transforms()) {
+				ofs = ofs.round();
+			} else if (Engine::get_singleton()->get_use_pixel_snap()) {
 				ofs = ofs.floor();
 			}
 			Rect2 dst_rect(ofs, s);

scene/2d/sprite.cpp

@@ -99,7 +99,10 @@ void Sprite::_get_rects(Rect2 &r_src_rect, Rect2 &r_dst_rect, bool &r_filter_cli
 	Point2 dest_offset = offset;
 	if (centered)
 		dest_offset -= frame_size / 2;
-	if (Engine::get_singleton()->get_use_pixel_snap()) {
+
+	if (Engine::get_singleton()->get_snap_2d_transforms()) {
+		dest_offset = dest_offset.round();
+	} else if (Engine::get_singleton()->get_use_pixel_snap()) {
 		dest_offset = dest_offset.floor();
 	}
 
@@ -378,7 +381,9 @@ Rect2 Sprite::get_rect() const {
 	Point2 ofs = offset;
 	if (centered)
 		ofs -= Size2(s) / 2;
-	if (Engine::get_singleton()->get_use_pixel_snap()) {
+	if (Engine::get_singleton()->get_snap_2d_transforms()) {
+		ofs = ofs.round();
+	} else if (Engine::get_singleton()->get_use_pixel_snap()) {
 		ofs = ofs.floor();
 	}
 

servers/visual/visual_server_canvas.cpp

@@ -100,7 +100,7 @@ void VisualServerCanvas::_render_canvas_item(Item *p_canvas_item, const Transfor
 	Rect2 rect = ci->get_rect();
 	Transform2D xform = ci->xform;
 	if (snap_2d_transforms) {
-		xform.elements[2] = xform.elements[2].floor();
+		xform.elements[2] = xform.elements[2].round();
 	}
 	xform = p_transform * xform;
 

servers/visual/visual_server_viewport.cpp

@@ -47,7 +47,7 @@ static Transform2D _canvas_get_transform(VisualServerViewport::Viewport *p_viewp
 
 		Transform2D c_xform = p_viewport->canvas_map[p_canvas->parent].transform;
 		if (snap) {
-			c_xform.elements[2] = c_xform.elements[2].floor();
+			c_xform.elements[2] = c_xform.elements[2].round();
 		}
 		xf = xf * c_xform;
 		scale = p_canvas->parent_scale;
@@ -55,7 +55,7 @@ static Transform2D _canvas_get_transform(VisualServerViewport::Viewport *p_viewp
 
 	Transform2D c_xform = p_canvas_data->transform;
 	if (snap) {
-		c_xform.elements[2] = c_xform.elements[2].floor();
+		c_xform.elements[2] = c_xform.elements[2].round();
 	}
 	xf = xf * c_xform;