add app_root_dir helper function. integrate with all examples

examples/audio_playback/src/main.rs

@@ -58,11 +58,11 @@ fn main() -> Result<()> {
 	let mut volume = 1.0;
 
 	let sounds = [
-		load_and_convert_wav(Path::new("./assets/pickup-coin.wav"), system.res.audio.spec())?,
+		load_and_convert_wav(system.app_root_dir.join("./assets/pickup-coin.wav").as_path(), system.res.audio.spec())?,
-		load_and_convert_wav(Path::new("./assets/powerup.wav"), system.res.audio.spec())?,
+		load_and_convert_wav(system.app_root_dir.join("./assets/powerup.wav").as_path(), system.res.audio.spec())?,
-		load_and_convert_wav(Path::new("./assets/explosion.wav"), system.res.audio.spec())?,
+		load_and_convert_wav(system.app_root_dir.join("./assets/explosion.wav").as_path(), system.res.audio.spec())?,
-		load_and_convert_wav(Path::new("./assets/jump.wav"), system.res.audio.spec())?,
+		load_and_convert_wav(system.app_root_dir.join("./assets/jump.wav").as_path(), system.res.audio.spec())?,
-		load_and_convert_wav(Path::new("./assets/laser-shoot.wav"), system.res.audio.spec())?,
+		load_and_convert_wav(system.app_root_dir.join("./assets/laser-shoot.wav").as_path(), system.res.audio.spec())?,
 	];
 
 	let mut statuses = [AudioChannelStatus { size: 0, position: 0, playing: false }; NUM_CHANNELS];

examples/balls/src/main.rs

@@ -1,5 +1,3 @@
-use std::path::Path;
-
 use anyhow::Result;
 
 use ggdt::prelude::*;
@@ -26,7 +24,8 @@ fn main() -> Result<()> {
 
 	let font = BitmaskFont::new_vga_font()?;
 
-	let (balls_bmp, balls_palette) = IndexedBitmap::load_pcx_file(Path::new("./assets/balls.pcx"))?;
+	let (balls_bmp, balls_palette) =
+		IndexedBitmap::load_pcx_file(system.app_root_dir.join("./assets/balls.pcx").as_path())?;
 	system.res.palette = balls_palette.clone();
 
 	let mut sprites = Vec::<IndexedBitmap>::new();

examples/balls_v2/src/states.rs

@@ -25,7 +25,8 @@ impl Game {
 	pub fn new(mut system: System<DosLike>) -> Result<Self> {
 		let font = BitmaskFont::new_vga_font()?;
 
-		let (balls_bmp, balls_palette) = IndexedBitmap::load_pcx_file(Path::new("./assets/balls.pcx"))?;
+		let (balls_bmp, balls_palette) =
+			IndexedBitmap::load_pcx_file(system.app_root_dir.join("./assets/balls.pcx").as_path())?;
 		system.res.palette = balls_palette.clone();
 
 		let mut sprites = Vec::new();

examples/imgui_integration/src/context.rs

@@ -1,5 +1,4 @@
 use std::collections::HashMap;
-use std::path::Path;
 use std::rc::Rc;
 
 use anyhow::Result;
@@ -91,17 +90,20 @@ impl AppContext<Standard> for GameContext {
 
 impl GameContext {
 	pub fn new(system: System<Standard>) -> Result<Self> {
-		let palette = load_palette(Path::new("./assets/db16.pal"))?;
+		let palette = load_palette(system.app_root_dir.join("./assets/db16.pal").as_path())?;
 
-		let font = load_font(Path::new("./assets/dp.fnt"))?;
+		let font = load_font(system.app_root_dir.join("./assets/dp.fnt").as_path())?;
-		let small_font = load_font(Path::new("./assets/small.fnt"))?;
+		let small_font = load_font(system.app_root_dir.join("./assets/small.fnt").as_path())?;
 
-		let tiles = Rc::new(load_bitmap_atlas_autogrid(Path::new("./assets/tiles.pcx"))?);
+		let tiles = Rc::new(load_bitmap_atlas_autogrid(system.app_root_dir.join("./assets/tiles.pcx").as_path())?);
-		let green_slime = Rc::new(load_bitmap_atlas_autogrid(Path::new("./assets/green_slime.pcx"))?);
+		let green_slime =
-		let blue_slime = Rc::new(load_bitmap_atlas_autogrid(Path::new("./assets/blue_slime.pcx"))?);
+			Rc::new(load_bitmap_atlas_autogrid(system.app_root_dir.join("./assets/green_slime.pcx").as_path())?);
-		let orange_slime = Rc::new(load_bitmap_atlas_autogrid(Path::new("./assets/orange_slime.pcx"))?);
+		let blue_slime =
+			Rc::new(load_bitmap_atlas_autogrid(system.app_root_dir.join("./assets/blue_slime.pcx").as_path())?);
+		let orange_slime =
+			Rc::new(load_bitmap_atlas_autogrid(system.app_root_dir.join("./assets/orange_slime.pcx").as_path())?);
 
-		let tilemap = TileMap::load_from(Path::new("./assets/arena.map.json"))?;
+		let tilemap = TileMap::load_from(system.app_root_dir.join("./assets/arena.map.json").as_path())?;
 
 		let entities = Entities::new();
 		let component_systems = ComponentSystems::new();

examples/slimed/src/main.rs

@@ -1,7 +1,6 @@
 extern crate core;
 
 use std::collections::HashMap;
-use std::path::Path;
 use std::rc::Rc;
 
 use anyhow::{Context, Result};
@@ -108,30 +107,36 @@ impl AppContext<DosLike> for Game {
 
 impl Game {
 	pub fn new(mut system: System<DosLike>) -> Result<Self> {
-		let palette = load_palette(Path::new("./assets/db16.pal"))?;
+		let palette = load_palette(system.app_root_dir.join("./assets/db16.pal").as_path())?;
 		system.res.palette = palette.clone();
 
-		let font = load_font(Path::new("./assets/dp.fnt"))?;
+		let font = load_font(system.app_root_dir.join("./assets/dp.fnt").as_path())?;
 
-		let tiles = Rc::new(load_bitmap_atlas_autogrid(Path::new("./assets/tiles.pcx"))?);
+		let tiles = Rc::new(load_bitmap_atlas_autogrid(system.app_root_dir.join("./assets/tiles.pcx").as_path())?);
-		let hero_male = Rc::new(load_bitmap_atlas_autogrid(Path::new("./assets/hero_male.pcx"))?);
+		let hero_male =
-		let hero_female = Rc::new(load_bitmap_atlas_autogrid(Path::new("./assets/hero_female.pcx"))?);
+			Rc::new(load_bitmap_atlas_autogrid(system.app_root_dir.join("./assets/hero_male.pcx").as_path())?);
-		let green_slime = Rc::new(load_bitmap_atlas_autogrid(Path::new("./assets/green_slime.pcx"))?);
+		let hero_female =
-		let blue_slime = Rc::new(load_bitmap_atlas_autogrid(Path::new("./assets/blue_slime.pcx"))?);
+			Rc::new(load_bitmap_atlas_autogrid(system.app_root_dir.join("./assets/hero_female.pcx").as_path())?);
-		let orange_slime = Rc::new(load_bitmap_atlas_autogrid(Path::new("./assets/orange_slime.pcx"))?);
+		let green_slime =
-		let fist = Rc::new(load_bitmap_atlas_autogrid(Path::new("./assets/fist.pcx"))?);
+			Rc::new(load_bitmap_atlas_autogrid(system.app_root_dir.join("./assets/green_slime.pcx").as_path())?);
-		let sword = Rc::new(load_bitmap_atlas_autogrid(Path::new("./assets/sword.pcx"))?);
+		let blue_slime =
-		let particles = Rc::new(load_bitmap_atlas_autogrid(Path::new("./assets/particles.pcx"))?);
+			Rc::new(load_bitmap_atlas_autogrid(system.app_root_dir.join("./assets/blue_slime.pcx").as_path())?);
-		let items = Rc::new(load_bitmap_atlas_autogrid(Path::new("./assets/items.pcx"))?);
+		let orange_slime =
+			Rc::new(load_bitmap_atlas_autogrid(system.app_root_dir.join("./assets/orange_slime.pcx").as_path())?);
+		let fist = Rc::new(load_bitmap_atlas_autogrid(system.app_root_dir.join("./assets/fist.pcx").as_path())?);
+		let sword = Rc::new(load_bitmap_atlas_autogrid(system.app_root_dir.join("./assets/sword.pcx").as_path())?);
+		let particles =
+			Rc::new(load_bitmap_atlas_autogrid(system.app_root_dir.join("./assets/particles.pcx").as_path())?);
+		let items = Rc::new(load_bitmap_atlas_autogrid(system.app_root_dir.join("./assets/items.pcx").as_path())?);
 
-		let mut ui = load_bitmap_atlas(Path::new("./assets/ui.pcx"))?;
+		let mut ui = load_bitmap_atlas(system.app_root_dir.join("./assets/ui.pcx").as_path())?;
 		ui.add(Rect::new(0, 0, 16, 16))?;
 		ui.add(Rect::new(16, 0, 16, 16))?;
 		for i in 0..8 {
 			ui.add(Rect::new(i * 8, 16, 8, 8))?;
 		}
 
-		let tilemap = TileMap::load_from(Path::new("./assets/title_screen.map.json"))?;
+		let tilemap = TileMap::load_from(system.app_root_dir.join("./assets/title_screen.map.json").as_path())?;
 
 		let entities = Entities::new();
 		let component_systems = ComponentSystems::new();

examples/slimed/src/states.rs

@@ -1,5 +1,3 @@
-use std::path::Path;
-
 use ggdt::prelude::*;
 
 use crate::entities::*;
@@ -88,7 +86,13 @@ impl AppState<Game> for MainMenuState {
 	fn state_change(&mut self, new_state: State, old_state: State, context: &mut Game) {
 		match new_state {
 			State::Pending | State::Resume => {
-				init_everything(context, Path::new("./assets/title_screen.map.json"), 0.2, 1.0, 32);
+				init_everything(
+					context,
+					context.core.system.app_root_dir.join("./assets/title_screen.map.json").as_path(),
+					0.2,
+					1.0,
+					32,
+				);
 			}
 			State::TransitionIn => {
 				self.fade = 0.0;
@@ -219,7 +223,13 @@ impl AppState<Game> for GamePlayState {
 	fn state_change(&mut self, new_state: State, old_state: State, context: &mut Game) {
 		match new_state {
 			State::Pending => {
-				init_everything(context, Path::new("./assets/arena.map.json"), 0.5, 2.0, 100);
+				init_everything(
+					context,
+					context.core.system.app_root_dir.join("./assets/arena.map.json").as_path(),
+					0.5,
+					2.0,
+					100,
+				);
 				spawn_player_randomly(&mut context.core);
 			}
 			State::TransitionIn => {

ggdt/src/system/mod.rs

@@ -1,6 +1,7 @@
 use thiserror::Error;
 
 use crate::audio::AudioError;
+use crate::utils::app_root_dir;
 
 mod event;
 mod framebuffer;
@@ -51,6 +52,9 @@ pub enum SystemError {
 
 	#[error("SystemResources error: {0}")]
 	SystemResourcesError(#[from] SystemResourcesError),
+
+	#[error("System I/O error")]
+	IOError(#[from] std::io::Error),
 }
 
 /// Builder for configuring and constructing an instance of [`System`].
@@ -195,6 +199,8 @@ impl SystemBuilder {
 
 		let event_pump = SystemEventPump::from(sdl_event_pump);
 
+		let app_root_dir = app_root_dir()?;
+
 		Ok(System {
 			sdl_context,
 			sdl_audio_subsystem,
@@ -202,6 +208,7 @@ impl SystemBuilder {
 			sdl_timer_subsystem,
 			res: system_resources,
 			event_pump,
+			app_root_dir,
 			vsync: self.vsync,
 			target_framerate: self.target_framerate,
 			target_framerate_delta: None,
@@ -231,6 +238,8 @@ where
 	pub res: SystemResType,
 
 	pub event_pump: SystemEventPump,
+
+	pub app_root_dir: std::path::PathBuf,
 }
 
 impl<SystemResType> std::fmt::Debug for System<SystemResType>

ggdt/src/utils/io.rs

@@ -1,5 +1,8 @@
 use byteorder::{ReadBytesExt, WriteBytesExt};
-use std::io::{Error, SeekFrom};
+use std::{
+	io::{Error, SeekFrom},
+	path::PathBuf,
+};
 
 /// Provides a convenience method for determining the total size of a stream. This is provided
 /// as a temporary alternative to [std::io::Seek::stream_len] which is currently marked unstable.
@@ -34,3 +37,28 @@ pub trait WriteType {
 
 	fn write<T: WriteBytesExt>(&self, writer: &mut T) -> Result<(), Self::ErrorType>;
 }
+
+/// Returns the application root directory (the directory that the application executable is
+/// located in).
+///
+/// First tries to automatically detect this from the `CARGO_MANIFEST_DIR` environment variable,
+/// if present, to catch scenarios where the application is running from a Cargo workspace as a
+/// sub-project/binary within that workspace. In such a case, the application root directory is
+/// the same as that sub-project/binary's `Cargo.toml`.
+///
+/// If `CARGO_MANIFEST_DIR` is not present, then an attempt is made to determine the application
+/// root directory from the running executable's location.
+///
+/// If this fails for some reason, then this returns the current working directory.
+pub fn app_root_dir() -> Result<PathBuf, Error> {
+	if let Some(manifest_path) = std::env::var_os("CARGO_MANIFEST_DIR") {
+		return Ok(PathBuf::from(manifest_path));
+	}
+
+	let mut exe_path = std::env::current_exe()?.canonicalize()?;
+	if exe_path.pop() {
+		return Ok(exe_path);
+	}
+
+	std::env::current_dir()
+}