add diagnostic examples

Cargo.toml

@@ -109,6 +109,14 @@ path = "examples/app/headless.rs"
 name = "plugin"
 path = "examples/app/plugin.rs"
 
+[[example]]
+name = "custom_diagnostic"
+path = "examples/diagnostics/custom_diagnostic.rs"
+
+[[example]]
+name = "print_diagnostics"
+path = "examples/diagnostics/print_diagnostics.rs"
+
 [[example]]
 name = "event"
 path = "examples/ecs/event.rs"

crates/bevy_diagnostic/src/print_diagnostics_plugin.rs

@@ -73,7 +73,7 @@ impl PrintDiagnosticsPlugin {
         if state.elapsed >= state.wait_seconds {
             state.elapsed = 0.0;
             println!("Diagnostics:");
-            println!("{}", "-".repeat(50));
+            println!("{}", "-".repeat(60));
             if let Some(ref filter) = state.filter {
                 for diagnostic in filter.iter().map(|id| diagnostics.get(*id).unwrap()) {
                     Self::print_diagnostic(diagnostic);
@@ -95,7 +95,7 @@ impl PrintDiagnosticsPlugin {
         if state.elapsed >= state.wait_seconds {
             state.elapsed = 0.0;
             println!("Diagnostics (Debug):");
-            println!("{}", "-".repeat(30));
+            println!("{}", "-".repeat(60));
             if let Some(ref filter) = state.filter {
                 for diagnostic in filter.iter().map(|id| diagnostics.get(*id).unwrap()) {
                     println!("{:#?}\n", diagnostic);

examples/diagnostics/custom_diagnostic.rs

@@ -0,0 +1,33 @@
+use bevy::{
+    diagnostic::{Diagnostic, DiagnosticId, Diagnostics, PrintDiagnosticsPlugin},
+    prelude::*,
+};
+
+fn main() {
+    App::build()
+        .add_default_plugins()
+        // The "print diagnostics" plugin is optional. It just visualizes our diagnostics in the console
+        .add_plugin(PrintDiagnosticsPlugin::default())
+        .add_startup_system(setup_diagnostic_system.system())
+        .add_system(my_system.system())
+        .run();
+}
+
+// All diagnostics should have a unique DiagnosticId. for each new diagnostic, generate a new random number
+pub const SYSTEM_ITERATION_COUNT: DiagnosticId =
+    DiagnosticId::from_u128(337040787172757619024841343456040760896);
+
+fn setup_diagnostic_system(mut diagnostics: ResourceMut<Diagnostics>) {
+    // Diagnostics must be initialized before measurements can be added.
+    // In general it's a good idea to set them up in a "startup system".
+    diagnostics.add(Diagnostic::new(
+        SYSTEM_ITERATION_COUNT,
+        "system_iteration_count",
+        10,
+    ));
+}
+
+fn my_system(mut diagnostics: ResourceMut<Diagnostics>) {
+    // Add a measurement of 10.0 for our diagnostic each time this system runs
+    diagnostics.add_measurement(SYSTEM_ITERATION_COUNT, 10.0);
+}

examples/diagnostics/print_diagnostics.rs

@@ -0,0 +1,12 @@
+use bevy::{
+    diagnostic::{FrameTimeDiagnosticsPlugin, PrintDiagnosticsPlugin},
+    prelude::*,
+};
+
+fn main() {
+    App::build()
+        .add_default_plugins()
+        .add_plugin(FrameTimeDiagnosticsPlugin::default())
+        .add_plugin(PrintDiagnosticsPlugin::default())
+        .run();
+}