st-graphics

This is a fork of st that implements a subset of kitty graphics protocol.

I've recently switched to XRender for displaying images. There might be issues, try the legacy branch graphics-legacy if you encounter any.

If you want this formatted as a single patch, take the last commit from this branch: graphics-squashed.

This repository also includes a simple script to display images icat-mini.sh. Note: to make it work in tmux you need to enable pass-through sequences, i.e. add something like this to your .tmux.conf:

set -gq allow-passthrough all

You also need to make sure that tmux supports 24-bit colors and that it knows that the client terminal supports 24-bit colors (you may need to install the st terminfo entry on all systems that you use, including remote ones).

Installation

As usual, copy config.def.h to config.h, modify it according to your needs, run make install or DESTDIR=/some/prefix make install.

In addition to the standard st dependencies (X11, fontconfig, freetype2), you will need imlib2 and zlib for the graphics module.

Configuration

This fork includes some seemingly unrelated changes, like anysize and underline color and style. You may want to tweak them too if you don't like the defaults. See also patch compatibility.

You may want to change the graphics-related shortcuts and image size limits (see config.def.h).

Default shortcuts:

• Ctrl+Shift+RightClick to preview the clicked image in feh.
• Ctrl+Shift+MiddleClick to see debug info (image id, placement id, etc).
• Ctrl+Shift+F1 to toggle graphics debug mode. It has three states: 1) no debugging; 2) show general info and print logs to stderr; 3) print logs and show bounding boxes.
• Ctrl+Shift+F6 to dump the state of all images to stderr.
• Ctrl+Shift+F7 to unload all images from ram (but the cache in /tmp will be preserved).
• Ctrl+Shift+F8 to toggle image display.

Features

Originally I implemented it to prototype the Unicode placeholder feature (which is now included in the kitty graphics protocol). Classic placements were retrofitted later, and under the hood they are implemented via the same placeholder mechanism. This means that a cell may be occupied only by one placement. It is the main reason why some things don't work or work a bit differently.

Here is the list of supported (✅ ), unsupported (❌), and non-standard (⚡) features.

• Uploading:
  • Formats:
    • ✅ PNG (f=100)
    • ✅ RGB, RGBA (f=24, f=32)
    • ✅ Compression with zlib (o=z)
    • ⚡ jpeg. Actually any format supported by imlib2 should work. The key value is the same as for png (f=100).
  • Transmission mediums:
    • ✅ Direct (t=d)
    • ✅ File (t=f)
    • ✅ Temporary file (t=t)
    • ❌ Shared memory object (t=s)
  • ❌ Size and offset specification (S and O keys)
  • ✅ Image numbers
  • ✅ Responses
  • ✅ Transmit and display (a=T)
• Placement:
  • ✅ Classic placements (but see the note above)
  • ✅ Unicode placeholders
  • ✅ Placement IDs
  • ❌ NOTE: Placement IDs must be 24-bit (between 1 and 16777215).
  • ✅ Cursor movement policies C=1 and C=0
  • ✅ Source rectangle (x, y, w, h)
  • ✅ The number of rows/columns (r, c)
  • ❌ Cell offsets (X, Y)
  • ❌ z-index. Classic placements will erase old placements and the text on overlap.
  • ❌ Relative placements (P, Q, H, V)
• Deletion:
  • ✅ Deletion of image data when the specifier is uppercase
  • ✅ All visible classic placements (d=a)
  • ✅ By image id/number and placement id (d=i, d=n)
  • ❌ By position (specifiers c, p, q, x, y, z)
  • ❌ Animation frames (d=f)
• ❌ Animation - completely unsupported

Things I have tested

Apps that seem to work

• Kitty's icat (including from within tmux).
• termpdf
• ranger - I had to explicitly set TERM=kitty. This should be fixed in ranger of course.
• tpix
• pixcat (modulo some unsupported keys that are currently ignored).
• viu - I had to explicitly set TERM=kitty.
• timg - I had to explicitly pass -pk (i.e. timg -pk <image>). If your timg is fresh enough, it even works in tmux!

Apps that sort of work

• hologram.nvim - There are some glitches, like erasure of parts of the status line.

Apps that don't work

• termvisage - seems to erase cells containing the image after image placement. In kitty this has no effect on classic placements because they aren't attached to cells, but in st-graphics classic placements are implemented on top of Unicode placements, so they get erased.

Patch compatibility

This fork includes some patches and features that are not graphics-related per se, but are hard to disentangle from the graphics implementation:

• Anysize - this patch is applied and on by default. If you want the "expected" anysize behavior (no centering), set anysize_halign and anysize_valign to zero in config.h.
• Support for several XTWINOPS control sequences to query information that is sometimes required for image display (like cell size in pixels).
• Support for decoration (underline) color and style. The decoration color is used to specify the placement id in Unicode placeholders, so it's hard to make them separate. The behavior of the underline is different from the upstream st: it's drawn behind the text and the thickness depends on the font size. You may need to tweak the code in xdrawglyphfontspecs in x.c if you don't like it.

Patches that I have tried to apply together with graphics:

• Boxdraw - seems to work, applied with minimal conflicts, see this branch.
• Scrollback - quite a few conflicts, but easy to resolve. Seems to work but more testing may be needed. See this branch.
• Alpha - works. Check out the graphics-with-alpha branch where the alpha is adjustable with Ctrl-Shift-[ and Ctrl-Shift-].
• Background Image - seems to work, see this branch.