Class PropertyObject

Latest revision as of 19:22, 5 April 2021

• API Hierarchy
  • PropertyObject

This class provides an interface that allows an object to implement properties that can be saved or loaded to a session and edited by the user through a browser window in Surveyor. To enable this for an asset, it must inherit from PropertyObject (or from a derived child class such as ScenarioBehavior or MeshObject).

PropertyObject operates by way of a series of predefined callback methods which are designed to be overridden by the script writer to allow Trainz to access an object's properties. Properties are referred to in the class methods by their propertyID. Trainz determines this by reference to links in the object browser in the form live://property/propertyID.

When Trainz is saving a session, it asks each object to save its respective state into a Soup database. Trainz doesn't know what your object needs to save, but it does know that it can request an object's state via callbacks. Trainz relies on the script programmer to give careful thought to what data is needed to save and restore an objects state.

Depending on circumstances, not all callback methods have to be implemented. For example, you don't need to override GetPropertyElementList() if there are no list-selection properties.

[edit] Callback Sequences

The precise sequence of callback method calls will vary with the content of the browser and the user's input but the following gives a general idea:

• When the Property Browser is opened Trainz calls:
  • GetProperties() to read the current session data.
  • GetDescriptionHTML() to read the HTML code for the browser configuration window.
• When the user clicks on a URL, the propertyID is extracted from the link and these calls are made:
  • GetPropertyType() to establish the 'type' of the property is to be edited.
  • For "link" properties Trainz will call:
    • LinkPropertyValue(), which should respond and set the desired value
  • For "string", "int" and "float" properties:
    • GetPropertyValue() to establish the property's current value.
    • GetPropertyName() and/or GetPropertyDescription() to obtain display info for the UI.
    • Trainz then provides a pop-up edit box with a caption and current value filled in and waits for the user to edit the property, if desired.
  • For "list" properties:
    • GetPropertyName() and/or GetPropertyDescription() to obtain display info for the UI.
    • GetPropertyElementList() to obtain the list options to display to the player.
    • Trainz then provides a pop-up edit box with a caption and the list of options and waits for the user to edit the property, if desired.
  • For "map-object" and "asset-list" properties:
    • GetPropertyName() and/or GetPropertyDescription() to obtain display info for the UI.
    • Trainz displays a filterable list dialog to the player, showing a spinner while the search runs.
    • When a search completes, Trainz calls FilterPropertyElementList(), to allow the script to add/remove any custom entries.
• Once the user has carried out any edits:
  • The appropriate variant of SetPropertyValue() is called to update the value of the property.
  • GetDescriptionHTML() is called again to refresh the contents of the Browser window for any new configuration.
• When all edits are complete:
  • If the user confirms their changes and closes the dialog:
    • SetProperties() is called with the modified Soup to update the session database.
  • If the user cancels the changes:
    • SetProperties() is called with the original unaltered Soup to restore the script to it's original pre-edit state.

Throughout the above sequences Trainz is only concerned with the loading and saving of properties. Wherever a change in a property requires an update to the appearance of the object or to the contents of its variables it is the responsibility of the script writer to implement these changes at the appropriate time. In general changes should be implemented in SetProperties() since this will help to ensure that changes can be reversed if they are cancelled or when the game's UNDO command is invoked.

[edit] Save/Load

Scripted objects do not have their state automatically saved and restored. It is the responsibility of the individual scripts to save and restored any necessary state across a Surveyor save session/load session, or across a Driver save game/load game. This is implemented using the PropertyObject GetProperties() and SetProperties() functions. When saving, Trainz will ensure that GetProperties() has been called for every PropertyObject that is being saved. The Soup returned by this function is stored along with any native state for the object in question. When reloading, Trainz will first create the object and load the native state, then will call the SetProperties() function with the saved Soup which instructs the script to restore its state.

[edit] GetDescriptionHTML

Parameters

None

Return Value;

HTML formatted string to be loaded into the Property Browser.

Example Implementation

public string GetDescriptionHTML(void)
{
  StringTable strTable = GetAsset().GetStringTable();
  
  HTMLBuffer buffer = HTMLBufferStatic.Construct();
  buffer.Print("<html><body>");
  
  buffer.Escape(strTable.GetString("property_name_forename"));
  buffer.Print(": <a href=live://property/forename>");
  buffer.Escape(m_foreName);
  buffer.Print("</a><br>");
  buffer.Escape(strTable.GetString("property_name_surname"));
  buffer.Print(": <a href=live://property/forename>");
  buffer.Escape(m_surName);
  buffer.Print("</a><br>");
  buffer.Print("</body></html>");
  
  return buffer.AsString();
}

Description

This method is called by Trainz to retrieve HTML which a player can use to configure the objects properties. Any embedded properties should use the live://property/propertyID format, all player readable strings should be sourced from the asset string-table, and all player configurable values should be appropriately escaped to avoid HTML corruption.
The Trainz uses its Mini Browser to display the HTML. See the MiniBrowser page to find supported HTML elements.

[edit] GetProperties

Parameters

None

Return Value

Soup object containing data appropriate to represent the configured state of the object.

Example Implementation

public Soup GetProperties(void)
{
  Soup soup = inherited();
  soup.SetNamedTag("forename", m_foreName);
  soup.SetNamedTag("surname", m_surName);
  return soup;
}

Description

This method is used to save current properties into the session database. Care must be taken to ensure it writes data in the same tag format that SetProperties() is expecting. When overriding this method to handle your own properties, always call through to the overridden parent by using inherited().

[edit] SetProperties

Parameters

• soup = reference to soup to be saved to session.

Returned Value

None

Example Implementation

public void SetProperties(Soup soup)
{
  inherited(soup);
  m_foreName = soup.GetNamedTag("forename");
  m_surName = soup.GetNamedTag("surname");
}

Description

Restores object state with a Soup object returned from a previous call to GetProperties(). When overriding this method to handle your own properties, always call through to the overridden parent by using inherited(soup). This ensures that any data required by the parent class is appropriately set.

[edit] GetPropertyType

Parameters

• propertyID = Name of property.

Return Value

The type of the current property.

Example Implementation

string GetPropertyType(string propertyID)
{
  if (propertyID == "forename" or propertyID == "surname")
    return "string";
  
  return inherited(propertyID);
}

Description

This method is used by Trainz to determine the type of the named property. The supported types and their parameters are listed in the table below.

[edit] GetPropertyName

Parameters

• propertyID = Name of property.

Return Value

The name of the current property.

Example Implementation

string GetPropertyName(string propertyID)
{
  if (propertyID == "forename")
    return GetAsset().GetStringTable().GetString("property_name_forename");
  if (propertyID == "surname")
    return GetAsset().GetStringTable().GetString("property_name_surname");
  
  return inherited(propertyID);
}

[edit] GetPropertyDescription

Parameters

• propertyID = Name of property.

Return Value

Description to be used as a caption for the edit box presented to the user for a specific property.

Example Implementation

string GetPropertyDescription(string propertyID)
{
  if (propertyID == "forename")
    return GetAsset().GetStringTable().GetString("property_description_forename");
  if (propertyID == "surname")
    return GetAsset().GetStringTable().GetString("property_description_surname");
  
  return inherited(propertyID);
}

[edit] GetPropertyValue

Parameters

• propertyID = Name of property.

Returned Value

A string representation of the value of the current property.

Example Implementation

public string GetPropertyValue(string propertyID)
{
  if (propertyID == "forename")
    return m_foreName;
  if (propertyID == "surname")
    return m_foreName;
  
  return inherited(propertyID);
}

Description

Returns a string representation of the current value of the selected property, if possible. Where it is not possible to format a value into a string (such as with map-object and asset-list types) then any cached localised name may be returned, and native will attempt to find that object in any displayed list, etc.

[edit] LinkPropertyValue

Parameters

• propertyID = Name of property.

Returned Value

None

Example Implementation

void LinkPropertyValue(string propertyID)
{
  if (propertyID == "doors")
  {
    m_doorsOpen = !m_doorsOpen;
    SetMeshAnimationState("doors", m_doorsOpen);
    return;
  }
  
  inherited(propertyID);
}

Description

Called when the player clicks on a "link" property type. Link properties are most frequently used to toggle boolean values and selecting "radio" buttons.

[edit] GetPropertyElementList

Parameters

• propertyID = Name of property.

Returned Value

A string array to for the player to select a value from.

Example Implementation

public string[] GetPropertyElementList(string propertyID)
{
  if (propertyID == "mode")
  {
    StringTable strTable = GetAsset().GetStringTable();
    
    string[] result = new string[10];
    int i;
    for (i = 1; i < 10; ++i)
      result[i] = strTable.GetString("property_list_mode_" + i);
    
    return result;
  }
  
  return inherited(propertyID);
}

Description

Retrieves a list possible values for a named property. Used for the "list" type. The returned list should support localisation by using string-table entries where appropriate.

[edit] FilterPropertyElementList

Parameters

• propertyID = Name of property.
• listObjects = The list of objects about to be displayed.
• listNames = The names of the objects about to be displayed.

Returned Value

Whether the filter function has altered the list at all.

Example Implementation

public bool FilterPropertyElementList(string propertyID, GSObject[] listObjects, string[] listNames)
{
  if (propertyID == "object-list")
  {
    bool bDidChangeAnything = false;
    // Remove any already added objects from the list
    int i;
    for (i = 0; i < listObjects.size(); )
    {
      if (IsAlreadyInList(cast<GameObject>(listObjects[i])))
      {
        listObjects[i,i+1] = null;
        listNames[i,i+1] = null;
        bDidChangeAnything  = true;
      }
      else
      {
        ++i;
      }
    }
    
    return bDidChangeAnything;
  }
  
  return inherited(propertyID, listObjects, listNames);
}

Description

Used for "map-object" and "asset-list" types to allow the list to be filtered before display. This gives the script an opportunity to cull any inappropriate values (such as those already added) and/or add any custom entries (such as a "none" selection).

[edit] SetPropertyValue

Parameters

• propertyID = Name of property.
• value = string, int, float or object value to assign to the property.
• index = list types only, specifies the index of the selected item in the list.
• readableName = map-object and asset-list types only, specifies the localised name of the object/asset selected.

Return Value

None

Example Implementations

void SetPropertyValue(string propertyID, string value)
{
  if (propertyID == "forename")
  {
    m_foreName = value;
    return;
  }
  if (propertyID == "surname")
  {
    m_surName = value;
    return;
  }
  
  inherited(propertyID, value);
}

void SetPropertyValue(string propertyID, GSObject value, string readableName)
{
  if (propertyID == "junction")
  {
    m_junctionID = cast<GameObjectID>(value);
    m_junctionName = readableName;
    return;
  }
  if (propertyID == "sound-asset")
  {
    m_sound = cast<Asset>(value);
    m_soundName = readableName;
    return;
  }
  
  inherited(propertyID, value, readableName);
}

Description

Sets a new value for the named property. The variant called depends on the property type, as returned by GetPropertyType().

[edit] PropertyBrowserRefresh

Parameters

• browser = Reference to browser object displaying properties.

Returned Value

None

Description

A callback method which the script writer can override to specify tasks to be carried out whenever the Browser is refreshed.

[edit] SetPropertyHandler

Parameters

• handler = Handler to assign to this property object.

Returned Value

None

Description

Called to add a sub-handler property object to this object. The added HTMLPropertyHandler can then implement property lists, etc. This is useful for organising property values into groups. Several pre-defined HTMLPropertyHandler classes also already exist in the core Trainz scripts, which script programmers can use to save time and avoid code duplication.

[edit] GetPropertyHandler

Parameters

None

Returned Value

A reference to the current property handler for this object, or null if none has been set.

[edit] Categories