---
name: "katarakt"
section: "1"
platform: "linux"
package: "katarakt"
version: "0.2-4+b1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/katarakt"
---

# katarakt(1)

a simple PDF viewer with three layouts

## NAME

katarakt - a simple PDF viewer with three layouts

## SYNOPSIS

**katarakt** (\[*OPTIONS*\] *FILE*\|(-u *URL*))\*

## DESCRIPTION

It’s a PDF viewer. It views PDFs.

There are currently three layouts. The *single layout* is very simple and only supports scrolling on a per page basis. As the name suggests the current page is displayed in the center and zoomed to fit the window. It is active by default.

The *grid layout* is much more advanced and offers continuous (smooth, per pixel) scrolling, zooming and adjusting the column count. Pages keep their correct relative size and are shown in a grid.

The *presenter layout* is for giving a presentation. It opens a second window, to be viewed on the projector, and shows the current and next slide in the main window.

For every file passed on the command line a separate process is spawned.

## OPTIONS

- **-u**, **--url**

  Instead of opening a local document, download it from the given URL.

- **-p**, **--page** *NUM*

  Start on page *NUM*.

- **-f**, **--fullscreen**

  Start in fullscreen mode.

- **-q**, **--quit** *true*\|*false*

  If true, quit on initialization failure. If false, show the window even if an error occured. Overrides the config option **quit\_on\_init\_fail**.

- **-s**, **--single-instance** *true*\|*false*

  If true, prevents opening the same document twice and focuses the existing instance. Overrides the config option **single\_instance\_per\_file**.

- **--write-default-config** *FILE*

  Write the built-in default configuration to *FILE* and exit. Hint: on unix systems, you can use *--write-defaults /dev/stdout* to print the defaults.

- **-v**, **--version**

  Print version information and exit.

- **-h**, **--help**

  Print help and exit.

## CONFIGURATION

Variables and key bindings can be changed by modifying the katarakt.ini file. By default it is read from *$XDG\_CONFIG\_HOME*.

Variables must be listed under the section "\[Settings\]", keys under section "\[Keys\]". Settings that are not present in the config file use the built-in default. For a list of all variables with a short explanation see below.

## KEY BINDINGS

**q**

Quit **katarakt**.

**1**

Switch to *single layout*. Views a single page at a time, scaled to fit the screen.

**2**

Switch to *grid layout*. Views pages in a continuous fashion, scaled to fit the window width. Supports zooming and multiple columns.

**3**

Switch to *presenter layout*. Views the current page and a smaller preview of the next page. Also, opens a second window that shows only the current page for displaying on a projector.

**Up**, **Down**, **Left**, **Right**, **k**, **j**, **h**, **l**

Move around (up/down/left/right).

**^u**, **^d**

Scroll up/down half the screen.

**BackSpace**, **Space**, **^b**, **^f**

Scroll up/down the screen. By default scrolls 90% to create an overlapping region.

**PgUp**, **PgDown**

Scroll up/down one page. Kind of swaps the pages in place.

**Home**, **End**, **g**, **G**

Go to the first/last page.

**^g**

Show *goto page* bar.

**/**

Show the search bar. Hitting **Esc** will hide the results, searching for an empty string will clear them. If the search term contains an uppercase letter the search is case sensitive ("smartcase"). If you search for the same term twice the next hit starting from the current view is selected.

**?**

Show the search bar. This next search will be backwards.

**n**, **N**

Focus next/previous search hit. This does not take the current view into account. For finding the next hit around the current view search for the same term again.

**^n**, **^N**

Focus next/previous search hit that is currently not visible.

**^o**, **^i**, **Alt-Left**, **Alt-Right**

Move backward/forward through the jump list. Entries are added automatically when jumping.

**m**

Manually add the current page to the jump list.

**-**, **+**, **=**

Adjust zoom level (*grid layout* only).

**z**

Reset zoom level to default, i.e. fit width (*grid layout* only).

**\[**, **\]**

Adjust column count (*grid layout* only).

**{**, **}**

Adjust the column the first page will be displayed in. Useful for reading in a book layout with a cover page (*grid layout* only).

**,**, **.**

Rotate pages left/right.

**t**

Toggle the page number display in the bottom right corner.

**i**

Toggle between normal and inverted color rendering.

**^c**

Copy the current selection to the global clipboard.

**v**

Swap the mouse buttons for selection and panning. The the left mouse button’s current operation is indicated by the mouse cursor.

**f**

Toggle fullscreen.

**r**

Reload the document. This can also be achieved by sending SIGUSR1 to the process. **katarakt** reloads automatically if the opened file has changed.

**o**

Open a different document; shows a file dialog.

**s**

Show a file dialog to save the current document.

**F9**

Toggle the table of contents.

**x**

Toggle freezing the slide currently displayed in the projector window. When frozen, scrolling only affects the main window.

## VARIABLES

*string* **default\_layout**

single: The layout on startup. Possible values: *single*, *grid*, *presenter*.

*string* **background\_color**

0xDF202020: Background color in ARGB Format. Alpha only works when using a compositor.

*string* **background\_color\_fullscreen**

0xFF000000: Fullscreen background color in ARGB Format.

*string* **unrendered\_page\_color**

0x40FFFFFF: Color that gets drawn instead of a page that hasn’t been rendered yet. If colors are inverted, this gets inverted as well.

*int* **click\_link\_button**

1: The mouse button used for clicking links. Buttons 1-5 are supported.

*int* **drag\_view\_button**

2: The mouse button used for scrolling the view. Double-clicking this button centers the view around the location of the click. This is especially useful when using many columns to get an overview. Resets the column count to 1.

*int* **select\_text\_button**

1: The mouse button used for text selection. Double- and triple-clicking are supported to select with word/line granularity.

*int* **hide\_mouse\_timeout**

2000: The delay in milliseconds after which the mouse cursor is hidden. Set to 0 to disable.

*int* **smooth\_scroll\_delta**

30: Pixel offset when moving around.

*float* **screen\_scroll\_factor**

0\.9: Factor for scrolling the screen. Should be \<= 1 to create an overlapping region.

*float* **jump\_padding**

0\.2: Distance from the border of the screen to keep for jump targets, e.g. search hits. Moves the view so that search hits are centered more.

*int* **rect\_margin**

2: Number of pixels search rects are expanded by.

*int* **useless\_gap**

2: Gap between two pages in *grid layout* in pixels.

*int* **min\_zoom**

\-14: Smallest zoom value.

*int* **max\_zoom**

30: Biggest zoom value.

*float* **zoom\_factor**

0\.05: Influences the number of steps between min and max.

*int* **min\_page\_width**

50: Pages can not be smaller than this.

*bool* **quit\_on\_init\_fail**

false: If true, quit katarakt if the document fails to open.

*bool* **single\_instance\_per\_file**

false: If set and katarakt is called with a file that is already shown in another katarakt instance, then the other katarakt window is activated instead.

*string* **stylesheet**

See http://doc.qt.io/qt-4.8/stylesheet.html. It can be overridden via Qt’s **-stylesheet** command line option. The following example changes the *goto page* bar:

```
stylesheet="
GotoLine {
        margin: 0px;
        padding: 4px;
        border-top-right-radius: 6px;
        border-top: 1px solid black;
        border-right: 1px solid black;
}"
```

*string* **page\_overlay\_text**

Page %1/%2: The text in the bottom right corner.

*string* **icon\_theme**

The name of your icon theme. Fill in if auto detection fails.

*int* **prefetch\_count**

4: Number of pages exceeding the currently visible ones to render, back- and forwards respectively.

*float* **inverted\_color\_contrast**

0\.5: the contrast when using inverted colors to avoid too much brightness.

*float* **inverted\_color\_brightening**

0\.15: amount of brightening when using inverted colors to shift black to gray.

*int* **mouse\_wheel\_factor**

120: QT delta for turning the mouse wheel 1 click. Shouldn’t need to be touched.

*bool* **thumbnail\_filter**

true: Enables the higher quality downsampling filter for thumbnails.

*int* **thumbnail\_size**

32: One dimension of square thumbnails saved at run-time for every page that was once rendered.

## COMMUNITY

Feel free to join the IRC channel *#katarakt* on freenode.

## AUTHOR

**katarakt** is written by Philipp Erhardt.

## RESOURCES

GitLab: https://gitlab.cs.fau.de/Qui\_Sum/katarakt