B boulabiar

Understanding and Modifying a Big C++ Project Fast (Linux / GCC + Clang)

A practical field guide. The goal is to go from "I just cloned this 500k-line monster" to "I can find the right code, understand it, and change it safely" as quickly as possible.

The core idea: don't read the code linearly — interrogate it. Use the build system, the compiler, indexers, debuggers, and tracing tools to make the program tell you about itself.

Rename constant namespaces from k-prefix to plural form

Current state

All LVGL constant namespaces use a k prefix:

obj.align(lv::kAlign::center);
obj.add_style(style, lv::kPart::main | lv::kState::pressed);
btn.on(lv::kEvent::clicked, handler);

Using systemd dbus

http://0pointer.net/blog/the-new-sd-bus-api-of-systemd.html

create an ellipse

busctl --user call org.inkscape /org/inkscape/document_0 org.inkscape.document ellipse iiii 0 0 20 40

get list of objects in layer1

busctl --user call org.inkscape /org/inkscape/document_0 org.inkscape.document get_children "s" layer1

Generic 1,2,3 Noise

float rand(float n){return fract(sin(n) * 43758.5453123);}

float noise(float p){
	float fl = floor(p);
  float fc = fract(p);
	return mix(rand(fl), rand(fl + 1.0), fc);
}

Keolis "open-data" : XML Realtime API

Les données retournées sont au format XML.

Document trouvé et modifié depuis Pastebin.

	<?php

	// Karen Bot by @levelsio
	//
	// ask Claude Code or Cursor to adapt it to your city
	// mine is for Lisbon in Portuguese but it should work with any city and any language!
	// save it as council.php and add a Nginx route /council on your server to use it
	// make sure to add /council?key= and set a key below to use it privately
	//
	// more info: https://x.com/levelsio/status/2009011216132526407?s=20

	fn arrange(&self, ui: &mut Ui, state: &mut DashboardState, repulsion_steps: usize, compaction_steps: usize) {
	if state.block_rect.is_empty() {
	return;
	}
	let original = state.block_rect.clone();
	let mut debug_copy = state.block_rect.clone();
	let rects = &mut state.block_rect;
	let keys: Vec<BlockKey> = rects.keys().collect();
	let keys = keys.iter().copied();

	// sources:
	// https://xcb.freedesktop.org/tutorial/events/
	// https://xcb.freedesktop.org/manual/group__XCB____API.html
	// https://github.com/wmutils/opt/blob/master/wew.c
	//
	// compile with:
	// gcc focus.c -lxcb

	#include <stdlib.h>
	#include <stdio.h>

	cmake_minimum_required(VERSION 3.5)
	set(CMAKE_CXX_STANDARD 11)
	project(demo LANGUAGES CXX)

	SET("OpenCV_DIR" "...../opencv4/opencv")
	find_package( OpenCV REQUIRED )
	MESSAGE(STATUS "Include dirs ${OpenCV_INCLUDE_DIRS}")
	MESSAGE(STATUS "LINK LIBRARIES ${OpenCV_LIBS}")

	find_package(al-runtime)

	# view the desktop into a window on Linux
	gst-launch-1.0 ximagesrc startx=1920 use-damage=0 \
	! video/x-raw,framerate=30/1 \
	! videoscale method=0 \
	! video/x-raw,width=1920,height=1080 \
	! ximagesink


	# view the desktop into a window on MacOS
	gst-launch-1.0 avfvideosrc capture-screen=true \