Add feature flag to enable all log levels in examples (#98)

- Adds extra troubleshooting documentation to the README

README.md

@@ -36,6 +36,27 @@ requests a low power (aka integrated) GPU by default. If the examples are not wo
 
 You should also try to keep your graphics drivers up-to-date, especially if you have an old Intel integrated GPU. Keep in mind that some drivers and GPUs are EOL and will not be supported.
 
+### Logging
+
+You may want to use the `RUST_LOG` environment variable (see [`env_logger`](https://docs.rs/env_logger) for full documentation) to gain additional insight while troubleshooting the examples. `RUST_LOG=trace` will spew all logs to `stderr` on debug builds:
+
+```
+$ RUST_LOG=trace cargo run --package minimal-winit
+```
+
+And also on release builds when default features are disabled:
+
+```
+$ cd examples/minimal-winit
+$ RUST_LOG=trace cargo run --release --no-default-features
+```
+
+Alternatively, nightly Cargo allows using the `--no-default-features` flag directly from the top-level directory in combination with the unstable `-Zpackage-features` flag:
+
+```
+$ RUST_LOG=trace cargo run --release --package minimal-winit -Zpackage-features --no-default-features
+```
+
 ## Comparison with `minifb`
 
 The [`minifb`](https://crates.io/crates/minifb) crate shares some similarities with `pixels`; it also allows rapid prototyping of 2D games and emulators. But it requires the use of its own window/GUI management, event loop, and input handling. One of the disadvantages with the `minifb` approach is the lack of hardware acceleration (except on macOS, which uses Metal but is not configurable). An advantage is that it relies on fewer dependencies.

examples/conway/Cargo.toml

@@ -5,12 +5,16 @@ authors = ["Jay Oster <jay@kodewerx.org>"]
 edition = "2018"
 publish = false
 
+[features]
+optimize = ["log/release_max_level_warn"]
+default = ["optimize"]
+
 [dependencies]
 byteorder = "1.3.4"
 env_logger = "0.7.1"
 getrandom = "0.1.14"
 line_drawing = "0.8.0"
-log = { version = "0.4.8", features = [ "release_max_level_warn" ] }
+log = "0.4.8"
 pixels = { path = "../.." }
 randomize = "3.0.1"
 winit = "0.22.0"

examples/invaders/Cargo.toml

@@ -5,12 +5,16 @@ authors = ["Jay Oster <jay@kodewerx.org>"]
 edition = "2018"
 publish = false
 
+[features]
+optimize = ["log/release_max_level_warn"]
+default = ["optimize"]
+
 [dependencies]
 byteorder = "1.3.4"
 env_logger = "0.7.1"
 getrandom = "0.1.14"
 gilrs = "0.7.4"
-log = { version = "0.4.8", features = [ "release_max_level_warn" ] }
+log = "0.4.8"
 pixels = { path = "../.." }
 randomize = "3.0.1"
 simple-invaders = { path = "simple-invaders" }

examples/minimal-sdl2/Cargo.toml

@@ -5,8 +5,12 @@ authors = ["Jay Oster <jay@kodewerx.org>"]
 edition = "2018"
 publish = false
 
+[features]
+optimize = ["log/release_max_level_warn"]
+default = ["optimize"]
+
 [dependencies]
-beryllium = { version = "0.2.1", features = [ "extern_crate_raw_window_handle" ] }
+beryllium = { version = "0.2.1", features = ["extern_crate_raw_window_handle"] }
 env_logger = "0.7.1"
-log = { version = "0.4.8", features = [ "release_max_level_warn" ] }
+log = "0.4.8"
 pixels = { path = "../.." }

examples/minimal-winit/Cargo.toml

@@ -5,9 +5,13 @@ authors = ["Jay Oster <jay@kodewerx.org>"]
 edition = "2018"
 publish = false
 
+[features]
+optimize = ["log/release_max_level_warn"]
+default = ["optimize"]
+
 [dependencies]
 env_logger = "0.7.1"
-log = { version = "0.4.8", features = [ "release_max_level_warn" ] }
+log = "0.4.8"
 pixels = { path = "../.." }
 winit = "0.22.0"
 winit_input_helper = "0.6.0"