OpenCPN Developer Manual

Plugin Installer Source Code Adaptation.

A plugin which has not been adapted to the plugin manager needs some modifications to work. This page tries to describe these changes in short.

  • Use API 16: Update the source code to use API 16.

  • Use GetPluginDataDir() to locate plugins data directory

  • Review data directory usages

These changes should be enough for most plugins. However, more complicated plugins might need to consider the more complete list available in the installer documentation.

Changes associated with API 16

  • The plugin api reference is changed from opencpn_plugin_110 to opencpn_plugin_116.

Change needed for the managed process

  • GetPluginDataDir() is used instead of *GetpSharedDataLocation().

Review data directory usages

A plugin is related to two different data directories:

  • The installation directory, handled by the installer. This is a read-only directory preloaded with data from the plugin. It is owned by the installer and plugin must not change this data. The path is retrieved using GetPluginDataDir().

  • The plugin’s private data directory. This is a directory created within the configuration directory, used for persistent plugin data. The base directory is retrieved using getpPrivateApplicationDataLocation()

See the installer docs to see the actual paths for these directories on different platforms.

There has been multiple bugs related to plugins which have been writing data into the installation directory. Such usage must be patched to work properly with the installer. This is not a new requirement, but the installer is overall more picky.

Addition for MacOSX

  • wxInitAllImageHandlers(): Ensures the png image is recognised on the Mac

TideFinder_pi::TideFinder_pi(void *ppimgr) :opencpn_plugin_116 (ppimgr) \{ // Create the PlugIn icons initialize_images();

  wxFileName fn;

  auto path = GetPluginDataDir("TideFinder_pi");
  fn.SetPath(path);
  fn.AppendDir("data");
  fn.SetFullName("tidefinder_panel_icon.png");

  path = fn.GetFullPath();

  wxInitAllImageHandlers();

  wxLogDebug(wxString("Using icon path: ") + path);
  if (!wxImage::CanRead(path)) {
      wxLogDebug("Initiating image handlers.");
      wxInitAllImageHandlers();
  }
  wxImage panelIcon(path);
  if (panelIcon.IsOk())
      m_panelBitmap = wxBitmap(panelIcon);
  else
      wxLogWarning("TideFinder panel icon has NOT been loaded");

  m_bShowTideFinder = false;

}