Buffyboard

Buffyboard is a touch-enabled on-screen keyboard running on the Linux framebuffer. It's primarily intended for vampire hunting¹ but you can also use it as a general purpose keyboard.

Buffyboard uses lvgl for input processing and rendering. Key events are forwarded directly to the kernel via a uinput device. Since the latter emulates a hardware keyboard, the terminal keymap must match with Buffyboard's layout or else on-screen keys might not produce the correct result.

Status

While partially usable, buffyboard currently still is a work in progress.

What works

• On-screen keyboard control via mouse, trackpad or touchscreen
• Multi-layer keyboard layout including lowercase letters, uppercase letters, numbers and selected symbols (based on top three layers of squeekboard's US terminal layout)
• Key chords with one or more modifiers terminated by a single non-modifier (e.g. CTRL-c)
• Highlighting of active modifiers
• Automatic resizing (and later reset) of active VT to prevent overlap with keyboard

To do

• Support different screen rotations
• Eliminate libinput_multi.[ch] once support for multiple input devices has been upstreamed to lv_drivers (see lvgl/lv_drivers#151 and lvgl/lv_drivers#165)
• Add remaining layers from squeekboard's US terminal layout (symbols and actions)
• Warn about mismatches between on-screen keyboard layout and terminal keyboard layout
• Add squeekboard's FR terminal layout
• And, and, and ...

Development

Dependencies

• lvgl (git submodule / linked statically)
• lv_drivers (git submodule / linked statically)
• libinput
• evdev kernel module
• uinput kernel module

Building & running

For development and testing you can run the app in a VT. Usually sudo will be needed in order to access input device files.

$ make
$ sudo chvt 2
$ sudo ./buffyboard

Changing fonts

In order to work with lvgl, fonts need to be converted to C arrays. Buffyboard currently uses a combination of the Montserrat font for text and the FontAwesome font for pictograms. For both fonts only limited character ranges are included. To (re)generate the C file containing the combined font, run the following command

$ npx lv_font_conv --bpp 4 --size 32 --no-compress -o montserrat_extended_32.c --format lvgl \
    --font Montserrat-Regular.ttf \
      --range '0x0020-0x007F' \
      --range '0x00A0-0x00FF' \
      --range '0x0100-0x017F' \
      --range '0x2000-0x206F' \
      --range '0x20A0-0x20CF' \
    --font FontAwesome5-Solid+Brands+Regular.woff \
      --range '0xF001,0xF008,0xF00B,0xF00C,0xF00D,0xF011,0xF013,0xF015,0xF019,0xF01C,0xF021,0xF026,0xF027,0xF028,0xF03E,0xF0E0,0xF304,0xF043,0xF048,0xF04B,0xF04C,0xF04D,0xF051,0xF052,0xF053,0xF054,0xF067,0xF068,0xF06E,0xF070,0xF071,0xF074,0xF077,0xF078,0xF079,0xF07B,0xF093,0xF095,0xF0C4,0xF0C5,0xF0C7,0xF0C9,0xF0E7,0xF0EA,0xF0F3,0xF11C,0xF124,0xF158,0xF1EB,0xF240,0xF241,0xF242,0xF243,0xF244,0xF287,0xF293,0xF2ED,0xF55A,0xF7C2,0xF8A2' \
      --range '0xF35B'

The following is a summary of the meaning of the different unicode ranges used above

• Montserrat
  • Basic Latin (0x0020-0x007F)
  • Latin-1 supplement (0x00A0-0x00FF)
  • Latin extended A (0x0100-0x017F)
  • General punctuation (0x2000-0x206F)
  • Currency symbols (0x20A0-0x20CF)
• FontAwesome
  • Standard LV_SYMBOL_* glyphs (0xF001,0xF008,0xF00B,0xF00C,0xF00D,0xF011,0xF013,0xF015,0xF019,0xF01C,0xF021,0xF026,0xF027,0xF028,0xF03E,0xF0E0,0xF304,0xF043,0xF048,0xF04B,0xF04C,0xF04D,0xF051,0xF052,0xF053,0xF054,0xF067,0xF068,0xF06E,0xF070,0xF071,0xF074,0xF077,0xF078,0xF079,0xF07B,0xF093,0xF095,0xF0C4,0xF0C5,0xF0C7,0xF0C9,0xF0E7,0xF0EA,0xF0F3,0xF11C,0xF124,0xF158,0xF1EB,0xF240,0xF241,0xF242,0xF243,0xF244,0xF287,0xF293,0xF2ED,0xF55A,0xF7C2,0xF8A2)
  • arrow-alt-circle-up (0xF35B)

Changing layouts

Buffyboard uses squeekboard layouts converted to C via squeek2lvgl. To regenerate the layouts, run

$ ./regenerate-layouts.sh

from the root of the repository.

Acknowledgements

The lv_port_linux_frame_buffer project served as a starting point for the codebase.

The mouse cursor image was taken from lv_sim_emscripten.

Buffyboard was inspired by bakonyiferenc/fbkeyboard.

License

Buffyboard is licensed under the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

squeekboard and its keyboard layouts are licensed under the GNU General Public License version 3.0.

The Montserrat font is licensed under the Open Font License.

The FontAwesome font is licensed under the Open Font License version 1.1.

Footnotes

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1. If you still don't know what vampires have to do with all of this, the train of thought is: Linux framebuffer 👉 buffyboard 👉 ... wait for it ... 👉 Buffy the Vampire Slayer. There you have it. I never claimed I was funny. 😅 ↩︎