Use tracing crate for logging (#1192)

* egui_web: use tracing crate
* egui_glow: use tracing crate
* Log at the debug level
* egui_demo_app: enable tracing to log to stdout
* Use tracing in egui-winit
* Add opt-in tracing support to egui

CHANGELOG.md

@@ -15,6 +15,7 @@ NOTE: [`epaint`](epaint/CHANGELOG.md), [`eframe`](eframe/CHANGELOG.md), [`egui_w
   * Added `TextStyle::resolve`.
 * `Context::load_texture` to convert an image into a texture which can be displayed using e.g. `ui.image(texture, size)` ([#1110](https://github.com/emilk/egui/pull/1110)).
 * Added `Ui::add_visible` and `Ui::add_visible_ui`.
+* Opt-in dependency on `tracing` crate for logging warnings ([#1192](https://github.com/emilk/egui/pull/1192)).
 * Added `CollapsingHeader::icon` to override the default open/close icon using a custom function. ([1147](https://github.com/emilk/egui/pull/1147)).
 * Added `Plot::x_axis_formatter` and `Plot::y_axis_formatter` for custom axis labels ([#1130](https://github.com/emilk/egui/pull/1130)).
 * Added `ui.data()`, `ctx.data()`, `ctx.options()` and `ctx.tessellation_options()` ([#1175](https://github.com/emilk/egui/pull/1175)).

docs/index.html

@@ -122,17 +122,18 @@
         // We'll defer our execution until the wasm is ready to go.
         // Here we tell bindgen the path to the wasm file so it can start
         // initialization and return to us a promise when it's done.
+        console.debug("loading wasm…");
         wasm_bindgen("./egui_demo_app_bg.wasm")
             .then(on_wasm_loaded)
             .catch(on_wasm_error);
 
         function on_wasm_loaded() {
-            console.log("loaded wasm, starting egui app…");
+            console.debug("wasm loaded. starting egui app…");
 
             // This call installs a bunch of callbacks and then returns:
             wasm_bindgen.start("the_canvas_id");
 
-            console.log("egui app started.");
+            console.debug("egui app started.");
             document.getElementById("center_text").remove();
         }
 

eframe/CHANGELOG.md

@@ -11,6 +11,7 @@ NOTE: [`egui_web`](../egui_web/CHANGELOG.md), [`egui-winit`](../egui-winit/CHANG
 * Fix horizontal scrolling direction on Linux.
 * Added `App::on_exit_event` ([#1038](https://github.com/emilk/egui/pull/1038))
 * Shift-scroll will now result in horizontal scrolling on all platforms ([#1136](https://github.com/emilk/egui/pull/1136)).
+* Log using the `tracing` crate. Log to stdout by adding `tracing_subscriber::fmt::init();` to your `main` ([#1192](https://github.com/emilk/egui/pull/1192)).
 
 
 ## 0.16.0 - 2021-12-29

egui-winit/Cargo.toml

@@ -22,8 +22,9 @@ include = [
 all-features = true
 
 [dependencies]
-egui = { version = "0.16.0", path = "../egui", default-features = false, features = ["single_threaded"] }
+egui = { version = "0.16.0", path = "../egui", default-features = false, features = ["single_threaded", "tracing"] }
 instant = { version = "0.1", features = ["wasm-bindgen"] }
+tracing = "0.1"
 winit = "0.26.1"
 
 epi = { version = "0.16.0", path = "../epi", optional = true }

egui-winit/src/clipboard.rs

@@ -29,7 +29,7 @@ impl Clipboard {
             match clipboard.get_contents() {
                 Ok(contents) => Some(contents),
                 Err(err) => {
-                    eprintln!("Paste error: {}", err);
+                    tracing::error!("Paste error: {}", err);
                     None
                 }
             }
@@ -46,7 +46,7 @@ impl Clipboard {
         if let Some(clipboard) = &mut self.copypasta {
             use copypasta::ClipboardProvider as _;
             if let Err(err) = clipboard.set_contents(text) {
-                eprintln!("Copy/Cut error: {}", err);
+                tracing::error!("Copy/Cut error: {}", err);
             }
         }
 
@@ -62,7 +62,7 @@ fn init_copypasta() -> Option<copypasta::ClipboardContext> {
     match copypasta::ClipboardContext::new() {
         Ok(clipboard) => Some(clipboard),
         Err(err) => {
-            eprintln!("Failed to initialize clipboard: {}", err);
+            tracing::error!("Failed to initialize clipboard: {}", err);
             None
         }
     }

egui-winit/src/lib.rs

@@ -577,12 +577,12 @@ impl State {
 fn open_url_in_browser(_url: &str) {
     #[cfg(feature = "webbrowser")]
     if let Err(err) = webbrowser::open(_url) {
-        eprintln!("Failed to open url: {}", err);
+        tracing::warn!("Failed to open url: {}", err);
     }
 
     #[cfg(not(feature = "webbrowser"))]
     {
-        eprintln!("Cannot open url - feature \"links\" not enabled.");
+        tracing::warn!("Cannot open url - feature \"links\" not enabled.");
     }
 }
 

egui-winit/src/screen_reader.rs

@@ -15,11 +15,11 @@ impl Default for ScreenReader {
     fn default() -> Self {
         let tts = match tts::Tts::default() {
             Ok(screen_reader) => {
-                eprintln!("Initialized screen reader.");
+                tracing::debug!("Initialized screen reader.");
                 Some(screen_reader)
             }
             Err(err) => {
-                eprintln!("Failed to load screen reader: {}", err);
+                tracing::warn!("Failed to load screen reader: {}", err);
                 None
             }
         };
@@ -38,10 +38,10 @@ impl ScreenReader {
             return;
         }
         if let Some(tts) = &mut self.tts {
-            eprintln!("Speaking: {:?}", text);
+            tracing::debug!("Speaking: {:?}", text);
             let interrupt = true;
             if let Err(err) = tts.speak(text, interrupt) {
-                eprintln!("Failed to read: {}", err);
+                tracing::warn!("Failed to read: {}", err);
             }
         }
     }

egui/Cargo.toml

@@ -28,15 +28,22 @@ epaint = { version = "0.16.0", path = "../epaint", default-features = false }
 
 ahash = "0.7"
 nohash-hasher = "0.2"
+
+# Optional:
 ron = { version = "0.7", optional = true }
 serde = { version = "1", features = ["derive", "rc"], optional = true }
+# egui doesn't log much, but when it does, it uses `tracing`
+tracing = { version = "0.1", optional = true }
 
 [features]
 default = ["default_fonts", "single_threaded"]
 
 # add compatibility with https://crates.io/crates/cint
 cint = ["epaint/cint"]
 
+# implement bytemuck on most types.
+convert_bytemuck = ["epaint/convert_bytemuck"]
+
 # If set, egui will use `include_bytes!` to bundle some fonts.
 # If you plan on specifying your own fonts you may disable this feature.
 default_fonts = ["epaint/default_fonts"]
@@ -55,9 +62,6 @@ persistence = ["serde", "epaint/serialize", "ron"]
 # implement serde on most types.
 serialize = ["serde", "epaint/serialize"]
 
-# implement bytemuck on most types.
-convert_bytemuck = ["epaint/convert_bytemuck"]
-
 # multi_threaded is only needed if you plan to use the same egui::Context
 # from multiple threads. It comes with a minor performance impact.
 single_threaded = ["epaint/single_threaded"]

egui/src/util/id_type_map.rs

@@ -275,11 +275,12 @@ impl Element {
 fn from_ron_str<T: serde::de::DeserializeOwned>(ron: &str) -> Option<T> {
     match ron::from_str::<T>(ron) {
         Ok(value) => Some(value),
-        Err(err) => {
-            eprintln!(
+        Err(_err) => {
+            #[cfg(feature = "tracing")]
+            tracing::warn!(
                 "egui: Failed to deserialize {} from memory: {}, ron error: {:?}",
                 std::any::type_name::<T>(),
-                err,
+                _err,
                 ron
             );
             None

egui_demo_app/Cargo.toml

@@ -17,6 +17,7 @@ eframe = { version = "0.16.0", path = "../eframe" }
 # eframe = { version = "0.16.0", path = "../eframe", default-features = false, features = ["default_fonts", "egui_glium"] }
 
 egui_demo_lib = { version = "0.16.0", path = "../egui_demo_lib", features = ["extra_debug_asserts"] }
+tracing-subscriber = "0.3"
 
 [features]
 default = ["persistence"]

egui_demo_app/src/main.rs

@@ -7,6 +7,9 @@
 
 // When compiling natively:
 fn main() {
+    // Log to stdout (if you run with `RUST_LOG=debug`).
+    tracing_subscriber::fmt::init();
+
     let app = egui_demo_lib::WrapApp::default();
     let options = eframe::NativeOptions {
         // Let's show off that we support transparent windows

egui_glow/Cargo.toml

@@ -32,6 +32,7 @@ epi = { version = "0.16.0", path = "../epi", optional = true }
 bytemuck = "1.7"
 glow = "0.11"
 memoffset = "0.6"
+tracing = "0.1"
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 egui-winit = { version = "0.16.0", path = "../egui-winit", default-features = false, features = ["epi"], optional = true }

egui_glow/src/epi_backend.rs

@@ -60,8 +60,7 @@ pub fn run(app: Box<dyn epi::App>, native_options: &epi::NativeOptions) -> ! {
     )));
 
     let mut painter = crate::Painter::new(&gl, None, "")
-        .map_err(|error| eprintln!("some OpenGL error occurred {}\n", error))
-        .unwrap();
+        .unwrap_or_else(|error| panic!("some OpenGL error occurred {}\n", error));
     let mut integration = egui_winit::epi::EpiIntegration::new(
         "egui_glow",
         painter.max_texture_side(),

egui_glow/src/lib.rs

@@ -124,10 +124,7 @@ impl EguiGlow {
     pub fn new(window: &winit::window::Window, gl: &glow::Context) -> Self {
         let painter = crate::Painter::new(gl, None, "")
             .map_err(|error| {
-                crate::misc_util::glow_print_error(format!(
-                    "error occurred in initializing painter:\n{}",
-                    error
-                ));
+                tracing::error!("error occurred in initializing painter:\n{}", error);
             })
             .unwrap();