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Lobster boat and the big ocean, Ogunquit, Maine, 1998-06-08.

Quirks to be aware of

  1. Graphs actually begin a little bit earlier than the nominal start time so that the specified start will appear immediately to the right of the labels for the depth axis instead of being obscured by them.
  2. The effective end time for graph and clock modes is entirely determined by the start time, the width, and the aspect.  If an end time is also specified by the user, it is ignored.
  3. XTide uses shorter descriptions for the tide events listed across the bottom caption line in tide graphs whenever the descriptions get to be longer than the timestamps.  Consequently, changing the time format setting to something more concise causes the descriptions to get shorter too, which is what you want.  However, this behavior can result in cosmetic inconsistencies; e.g., with default settings, "Mark Rising" is matched by "Mark" instead of "Mark Falling," because the one additional letter puts it over.
  4. The -o command line switch causes output to be appended to the specified file instead of overwriting it as is the generally accepted custom.
  5. While XTide-specific command-line arguments can be concatenated with their switches or not, the arguments to standard X11 switches sometimes must be separate to work.  Affected switches include -display, -fn, and -geometry.
  6. What XTide does about minimum current events at subordinate stations might not be what you expect.  See Appendix B for details.

Known limitations

  1. RGB color specs (rgb:N/N/N) in sizes other than 24 bits (rgb:hh/hh/hh) generally will not work.
  2. All timestamps have a precision of plus or minus one minute.
  3. XTide locates tide events to an accuracy of plus or minus one minute.  This refers only to the prediction model, not to how well the model agrees with reality.
  4. URLs assigned to specific locations by the xttpd web server are rather transient and will change whenever the harmonics files are updated.  The xttpd web space will remain internally consistent, but hyperlinks from outside pages will be screwed.
  5. The time scale for stations claiming to be in UTC is not strictly speaking UTC since it does not implement leap seconds.
  6. If a subordinate station has absurd offsets that cause low tides to become higher than high tides, the upper and lower bounds reported by stats mode may be incorrect.
  7. When specifying location names on the command line, multiple data sets having the same name cannot be distinguished, and it is not deterministic which one you will get.
  8. XTide is untested and probably dysfunctional on any platform where time_t is a non-integral type.  It would probably still work with --enable-time-workaround.
  9. XTide assumes that the first 256 characters of every font agree with ISO-8859-1 (except under DOS).
  10. Semitransparent style makes no sense in formats that don't support opacity (text and PseudoColor X-windows).

Known bugs

  1. If the control panel is resized, dismissed, and then shown again, its buttons are missing.  Cause of bug:  Don't know.  Workaround:  Close the control panel using the window manager (e.g., hit the × in the upper right corner) and then show it again.  The control panel retains its new size but the buttons reappear.
  2. Some of the dialog windows cause harmless but annoying toolkit warnings when you dismiss them.  Cause of bug:  Don't understand what the toolkit grabs are doing.  Workaround:  Ignore warnings.
  3. Line width in line graphs isn't maintained when the slope of the graph becomes drastic.  Cause of bug:  Need better algorithm for drawing line graphs.  Workaround:  Set the aspect higher.
  4. Buttons will sometimes shift out from under the mouse pointer and get "stuck on."  Cause of bug:  (1) button moves due to changing geometry of other things in the box, leading to (2) button shifts out from under the pointer, which triggers (3) bug in Athena Widgets where the button release event gets lost.  Workaround:  As needed, click on the stuck button to un-stick it.  This problem can be prevented in the control panel by specifying a monospace font with the -fn switch, which avoids (1).  The bug is less likely in other windows.
  5. The analog tide clock icon flashes when it updates, and doesn't update at all under some window managers.  Alternate symptom:  Tide clocks crash the window manager at random.  Cause of bug:  Window managers don't expect icons to keep changing and aren't designed to handle it properly.  Workaround:  Use a window manager that doesn't suck.
  6. Dialog boxes don't behave like you would expect when you hit the Enter key.  Cause of bug:  Athena widgets use multi-line buffers even for one-line fields.  Workaround:  Don't hit Enter.
  7. Syslog messages generated by xttpd have timestamps in UTC or random time zones instead of local time, which is highly confusing in a log that is otherwise in local time.  Cause of bug:  Design defect of syslog():  Every program logs in whatever time zone it happens to be using at the time instead of a standard zone.  XTide needs to adopt the time zone of each station to generate predictions for it.  Workaround:  none.
  8. The location chooser depends on a station naming convention to determine which stations are currents.  If that convention is not followed, dots may be drawn in the wrong color.  Cause of bug:  Design defect of libtcd:  libtcd doesn't let you know whether you are looking at a tide station or a current station until after you load it.  Workaround:  Ensure that "Current" appears in the station name if it's a current, and not otherwise.
  9. When XTide is linked with Xaw3d or Xaw3dXft, text dialog boxes reachable from the Options menu (save filename, mark level, aspect) and control panel may have 2-color bitmap borders instead of gray-shaded borders.  Cause of bug:  For reasons unknown, the "threeD" widget owned by asciiTextWidget is inaccessible from the application level, preventing XTide from setting its beNiceToColormap resource to False.  Workaround:  Add XTide*beNiceToColormap: False to ~/.Xresources.
  10. When XTide is linked with Xaw3dXft and the X server's DPI is set to a value much greater than 96, lines of text in the location list window overlap each other.  Cause of bug:  Faulty implementation of list widget in Xaw3dXft.  Workaround:  Don't link with Xaw3dXft or don't use high values for DPI.

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