grassleaff/Xoverdraw: Draw on screen with Xoverdraw, a SDL2 lightweight X11 screen annotation overlay written in C. It runs as a borderless, always-on-top, transparent window that lets you draw directly over whatever is on your screen.

grassleaff/Xoverdraw

Draw on screen with Xoverdraw, a SDL2 lightweight X11 screen annotation overlay written in C. It runs as a borderless, always-on-top, transparent window that lets you draw directly over whatever is on your screen.

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Makefile 2.2%

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grassleaff 4c3c40163d ADD: Implementing shape mode ("F" bind key)		2026年05月22日 09:21:28 -03:00
assets	Updating README.md with logo and some other changes	2026年04月30日 10:58:36 -03:00
src	ADD: Implementing shape mode ("F" bind key)	2026年05月22日 09:21:28 -03:00
.gitignore	FIX: Fix binary name + Installing assets/ system-wide on /usr/share/Xoverdraw/ to fix eraser circle cursor	2026年04月30日 16:10:14 -03:00
LICENSE	Initial commit	2026年04月30日 15:19:00 +02:00
Makefile	FIX: Fix binary name + Installing assets/ system-wide on /usr/share/Xoverdraw/ to fix eraser circle cursor	2026年04月30日 16:10:14 -03:00
README.md	ADD: Implementing shape mode ("F" bind key)	2026年05月22日 09:21:28 -03:00

README.md

accessibility text

A SDL2 lightweight X11 screen annotation overlay written in C. It runs as a borderless, always-on-top, transparent window that lets you draw directly over whatever is on your screen.

Dependencies

On Debian/Ubuntu:

sudo apt install build-essential pkg-config libsdl2-dev libsdl2-image-dev \
 libx11-dev libxrender-dev

Build & Run

make
./Xoverdraw

Controls

Input	Action
Left mouse button	Draw with brush
Right mouse button	Erase while held
`F`	Toggle shape mode
`Tab`	Cycle shape: rectangle, ellipse, line, arrow
`Shift` + `Tab`	Cycle shape backwards
`1` – `5`	Select color from palette
`[` / `]` or scroll wheel	Decrease / increase held tool size
`Shift` + size adjustment	Fine-tune size in increments of 1
`Z`	Undo last stroke or shape
`C`	Clear canvas
`O`	Toggle window opacity
`Esc` or `Q`	Quit

Configuration

All user-tweakable options live in src/include/config.h. After editing, rebuild with:

make clean && make

The following settings are available:

Constant	Description
`XOVERDRAW_INITIAL_BRUSH_SIZE`	Starting brush radius (default: `5`)
`XOVERDRAW_INITIAL_ERASER_SIZE`	Starting eraser radius (default: `50`)
`XOVERDRAW_MIN_TOOL_SIZE` / `MAX`	Allowed size range (default: `2` – `120`)
`XOVERDRAW_TOOL_SIZE_STEP`	Size increment per keypress/scroll (default: `2`)
`XOVERDRAW_DEFAULT_BRUSH_COLOR_INDEX`	Index into the palette for the initial color
`XOVERDRAW_PALETTE`	Five RGBA colors: red, green, blue, yellow, white
`XOVERDRAW_WINDOW_OPACITY`	Normal window opacity (default: `1.0`)
`XOVERDRAW_DIMMED_WINDOW_OPACITY`	Dimmed opacity toggled with `O` (default: `0.42`)
`XOVERDRAW_CURSOR_*`	Brush cursor appearance (color, shadow, crosshair geometry)
`XOVERDRAW_SHAPE_CURSOR_*`	Shape cursor dimensions
`XOVERDRAW_ERASER_CURSOR_*`	Eraser cursor appearance (color, shadow, thickness, smoothing)
`XOVERDRAW_ERASER_CURSOR_IMAGE`	Path to the PNG used as the eraser cursor overlay

X11 Transparency

Real window transparency on X11 requires two things:

A 32-bit ARGB visual, which Xoverdraw selects automatically via SDL_HINT_VIDEO_X11_WINDOW_VISUALID.
An active compositor such as picom, mutter, kwin, or the XFCE compositor.

Without a compositor, ARGB windows typically render as solid black. Xoverdraw prints a warning to stderr when it detects this situation.