extension.js

import * as Main from 'resource:///org/gnome/shell/ui/main.js';
import Meta from 'gi://Meta';
import Shell from 'gi://Shell';
import Clutter from 'gi://Clutter';
import GObject from 'gi://GObject';

import {Extension, gettext as _} from 'resource:///org/gnome/shell/extensions/extension.js';


const SHORTCUT = 'invert-window-shortcut';

export const InvertWindowEffect = GObject.registerClass(
class InvertWindowEffect extends Clutter.ShaderEffect {
	vfunc_get_static_shader_source() {
		return ' \
			uniform sampler2D tex; \
			void main() { \
				vec4 color = texture2D(tex, cogl_tex_coord_in[0].st); \
				if(color.a > 0.0) { \
					color.rgb /= color.a; \
				} \
				color.rgb = vec3(1.0, 1.0, 1.0) - color.rgb; \
				color.rgb *= color.a; \
				cogl_color_out = color * cogl_color_in; \
			} \
		';
	}

	vfunc_paint_target(...args) {
		this.set_uniform_value("tex", 0);
		super.vfunc_paint_target(...args);
	}
});


export default class InvertWindow extends Extension {
	toggle_effect() {
		global.get_window_actors().forEach(function(actor) {
			let meta_window = actor.get_meta_window();
			if(meta_window.has_focus()) {
				if(actor.get_effect('invert-color')) {
					actor.remove_effect_by_name('invert-color');
					delete meta_window._invert_window_tag;
				}
				else {
					let effect = new InvertWindowEffect();
					actor.add_effect_with_name('invert-color', effect);
					meta_window._invert_window_tag = true;
				}
			}
		}, this);
	}

	enable() {
		this._settings = this.getSettings();

		Main.wm.addKeybinding(
			SHORTCUT,
			this._settings,
			Meta.KeyBindingFlags.NONE,
			Shell.ActionMode.NORMAL,
			() => { this.toggle_effect(); }
		);

		global.get_window_actors().forEach(function(actor) {
			let meta_window = actor.get_meta_window();
			if(meta_window.hasOwnProperty('_invert_window_tag')) {
				let effect = new InvertWindowEffect();
				actor.add_effect_with_name('invert-color', effect);
			}
		}, this);
	}

	disable() {
		Main.wm.removeKeybinding(SHORTCUT);

		global.get_window_actors().forEach(function(actor) {
			actor.remove_effect_by_name('invert-color');
		}, this);

		this._settings = null;
	}
};