Property values for two-sided doors to make them interconnect with the map at runtime.

• §2. Door direction
• §4. Door to
• §6. Found in

§1. The I6 implementation of two-way doors is quite complicated; see the Inform Designer's Manual, fourth edition (the "DM4") for explanations, but basically it means giving instances of such doors three low-level properties —

• ● door_dir, the map direction through the door;
• ● door_to, the room on the other side;
• ● found_in, the two rooms in which the door is located.

We continue to use that implementation because there is no pressing reason to change it: I7 authors are never even aware of how this is all done, and do not have to see or think about these properties.

§2. Door direction.

typedef struct door_dir_notice {
    struct inter_name *ddn_iname;
    struct instance *door;
    struct instance *R1;
    struct instance *D1;
    struct instance *D2;
    CLASS_DEFINITION
} door_dir_notice;

parse_node *RTDoors::door_dir_for_2_sided(instance *I, instance *R1, instance *D1,
    instance *D2) {
    door_dir_notice *notice = CREATE(door_dir_notice);
    notice->ddn_iname =
        Hierarchy::make_iname_in(TSD_DOOR_DIR_FN_HL, RTInstances::package(I));
    notice->door = I;
    notice->R1 = R1;
    notice->D1 = D1;
    notice->D2 = D2;
    text_stream *desc = Str::new();
    WRITE_TO(desc, "door_dir for "); Instances::write(desc, I);
    Sequence::queue(&RTDoors::door_dir_agent, STORE_POINTER_door_dir_notice(notice), desc);
    return Rvalues::from_iname(notice->ddn_iname);
}

• The structure door_dir_notice is private to this section.

§3. So, then, this is a function: see the DM4 for specification.

void RTDoors::door_dir_agent?Usage of RTDoors::door_dir_agent:
§2(compilation_subtask *t) {
    door_dir_notice *notice = RETRIEVE_POINTER_door_dir_notice(t->data);
    packaging_state save = Functions::begin(notice->ddn_iname);
    local_variable *loc = LocalVariables::new_internal_commented(I"loc", I"room of actor");
    inter_symbol *loc_s = LocalVariables::declare(loc);
    EmitCode::inv(STORE_BIP);
    EmitCode::down();
        EmitCode::ref_symbol(K_value, loc_s);
        EmitCode::val_iname(K_value, Hierarchy::find(LOCATION_HL));
    EmitCode::up();

    EmitCode::inv(IF_BIP);
    EmitCode::down();
        EmitCode::inv(EQ_BIP);
        EmitCode::down();
            EmitCode::val_symbol(K_value, loc_s);
            EmitCode::val_iname(K_value, Hierarchy::find(THEDARK_HL));
        EmitCode::up();
        EmitCode::code();
        EmitCode::down();
            EmitCode::inv(STORE_BIP);
            EmitCode::down();
                EmitCode::ref_symbol(K_value, loc_s);
                EmitCode::val_iname(K_value, Hierarchy::find(REAL_LOCATION_HL));
            EmitCode::up();
        EmitCode::up();
    EmitCode::up();

    EmitCode::inv(IF_BIP);
    EmitCode::down();
        EmitCode::inv(EQ_BIP);
        EmitCode::down();
            EmitCode::val_symbol(K_value, loc_s);
            EmitCode::val_iname(K_value, RTInstances::value_iname(notice->R1));
        EmitCode::up();
        EmitCode::code();
        EmitCode::down();
            EmitCode::inv(RETURN_BIP);
            EmitCode::down();
                EmitCode::val_iname(K_value,
                    RTInstances::value_iname(Map::get_value_of_opposite_property(notice->D1)));
            EmitCode::up();
        EmitCode::up();
    EmitCode::up();

    EmitCode::inv(RETURN_BIP);
    EmitCode::down();
        EmitCode::val_iname(K_value,
            RTInstances::value_iname(Map::get_value_of_opposite_property(notice->D2)));
    EmitCode::up();

    Functions::end(save);
}

§4. Door to.

typedef struct door_to_notice {
    struct inter_name *dtn_iname;
    struct instance *door;
    struct instance *R1;
    struct instance *R2;
    CLASS_DEFINITION
} door_to_notice;

parse_node *RTDoors::door_to_for_2_sided(instance *I, instance *R1, instance *R2) {
    door_to_notice *notice = CREATE(door_to_notice);
    notice->dtn_iname =
        Hierarchy::make_iname_in(TSD_DOOR_TO_FN_HL, RTInstances::package(I));
    notice->door = I;
    notice->R1 = R1;
    notice->R2 = R2;
    text_stream *desc = Str::new();
    WRITE_TO(desc, "door_to for "); Instances::write(desc, I);
    Sequence::queue(&RTDoors::door_to_agent, STORE_POINTER_door_to_notice(notice), desc);
    return Rvalues::from_iname(notice->dtn_iname);
}

• The structure door_to_notice is private to this section.

§5. Another function: see the DM4 for specification.

void RTDoors::door_to_agent?Usage of RTDoors::door_to_agent:
§4(compilation_subtask *t) {
    door_to_notice *notice = RETRIEVE_POINTER_door_to_notice(t->data);
    packaging_state save = Functions::begin(notice->dtn_iname);
    local_variable *loc = LocalVariables::new_internal_commented(I"loc", I"room of actor");
    inter_symbol *loc_s = LocalVariables::declare(loc);
    EmitCode::inv(STORE_BIP);
    EmitCode::down();
        EmitCode::ref_symbol(K_value, loc_s);
        EmitCode::val_iname(K_value, Hierarchy::find(LOCATION_HL));
    EmitCode::up();

    EmitCode::inv(IF_BIP);
    EmitCode::down();
        EmitCode::inv(EQ_BIP);
        EmitCode::down();
            EmitCode::val_symbol(K_value, loc_s);
            EmitCode::val_iname(K_value, Hierarchy::find(THEDARK_HL));
        EmitCode::up();
        EmitCode::code();
        EmitCode::down();
            EmitCode::inv(STORE_BIP);
            EmitCode::down();
                EmitCode::ref_symbol(K_value, loc_s);
                EmitCode::val_iname(K_value, Hierarchy::find(REAL_LOCATION_HL));
            EmitCode::up();
        EmitCode::up();
    EmitCode::up();

    EmitCode::inv(IF_BIP);
    EmitCode::down();
        EmitCode::inv(EQ_BIP);
        EmitCode::down();
            EmitCode::val_symbol(K_value, loc_s);
            EmitCode::val_iname(K_value, RTInstances::value_iname(notice->R1));
        EmitCode::up();
        EmitCode::code();
        EmitCode::down();
            EmitCode::inv(RETURN_BIP);
            EmitCode::down();
                EmitCode::val_iname(K_value, RTInstances::value_iname(notice->R2));
            EmitCode::up();
        EmitCode::up();
    EmitCode::up();

    EmitCode::inv(RETURN_BIP);
    EmitCode::down();
        EmitCode::val_iname(K_value, RTInstances::value_iname(notice->R1));
    EmitCode::up();

    Functions::end(save);
}

§6. Found in. And this is a two-element array, simply giving the two rooms R1 and R2 which the door is found in:

parse_node *RTDoors::found_in_for_2_sided(instance *I, instance *R1, instance *R2) {
    package_request *PR =
        Hierarchy::package_within(INLINE_PROPERTIES_HAP, RTInstances::package(I));
    inter_name *S = Hierarchy::make_iname_in(INLINE_PROPERTY_HL, PR);
    packaging_state save = EmitArrays::begin_inline(S, K_value);
    EmitArrays::iname_entry(RTInstances::value_iname(R1));
    EmitArrays::iname_entry(RTInstances::value_iname(R2));
    EmitArrays::end(save);
    return Rvalues::from_iname(S);
}