### Preferences

The Preferences window contains user-controlled options for how fv behaves and looks. Click on one of the labeled tabs to bring up one of the following sets of options...

- App
  - List FITS files only: If turned on, only FITS file will be listed in the file-selection-dialog.
  - Show Desktop Manager: Turn desktop manger on/off.
  - Window Management: Select one of the following behaviors.
    - Leave existing windows open when opening new one
      All the opened windows will be kept on the desktop.
    - Hide existing windows open when opening new one
      Only keep one window of a kind on the desktop. e.g. if displaying a header, will hide all the other header windows. All the hidden windows are listed in the desktop manager.
    - Close existing windows open when opening new one
      Will close all the existing fv windows of the same kind. Will ask to save any change made.
    - Html Browser (Unix only)
      Web browser setting. User can specify which browser to use to display web pages. If it is required in fv or Hera operation and user has not specified his/her perference, "netscape" will be substitued in the entry provided. On Windows, this option will not be displayed since the default browser will be opened via Windows "start" command.
- Keywords
  - Write History Keywords: If turned on, a HISTORY keyword (with date and user name) is written in the header unit when a change to the extension is saved.
  - Auto-reformat Keys: If enabled, all the keywords inserted/changed in the Header window will be reformatted to a fixed format. When disabled, keyword entries will be written exactly as you type them.
  - Protect required keys: If enabled, you will not be able to modify required keywords such as BITPIX, NAXIS, TFORM, etc, or insert keywords within the initial set of required keywords.
  - Checksum Updates: When turned on, fv will update checksum keywords in an extension's header when modifying the extension.
- Tables
  - ASCII Column Justification: Choose whether you'd like ASCII columns to be left or right justified.
- Graphs
  - Auto-Plot Primary Image: When on, the primary image of a FITS file will be automatically plotted when the file is opened.
  - Use WCS Info: fv can choose to either use or ignore any WCS (World Coordinate System) keywords in the FITS file when creating a graph. With WCS Info turned off, graphs will be created using pixel coordinates.
  - Image Viewer: Select whether images should be display using POW (included with fv) or or DS9 (products of the Harvard SAO/HEAD R&D group). When user selects DS9 on Windows platform, Preference will give user the ability to supply (or to correct) DS9 and XPA library path.
  - Graph Size: Select the default graph size to use (in screen pixels) when creating a new graph (image or curve) using POW. Sizes are given as "width x height".

    Click on "Configure..." to modify the graph size list.

    To delete one of more size(s), on the "fv: Graph Size" top panel, click the button in front of the selection (could click on more than one selection.) And then click on "Delete" to delete the selection(s).

    To add a new graph size, on the "fv: Graph Size" bottom panel, input new width and height. The new size (in width x height) will show up on top of "Available Graph Size" if it is a new one.

    Click "OK" or "Cancel" to exit.

- Colors
  - Click on the appropriate button to change the color of the background/foreground/Active background/Active foreground/Check button.
  - Use Up/Down arrow to change the font size. Fv panels will be rendered with new font size once "Save" is clicked.

  Click the Save button to permanently save your preferences. Location of saved preference:

  - UNIX: saved in ~/.fvrc;
  - Windows: saved in <Installed fv Root>\lib\fv\fv.ini;
  - Mac OS: saved in the Preferences folder as fv Preferences.

  Go to About fv.