Add an example to test small window sizes

Author: DJMcNab

.github/example-run/expanding_window.ron

@@ -0,0 +1,3 @@
+(
+    exit_after: Some(410)
+)

Cargo.toml

@@ -615,6 +615,10 @@ path = "examples/window/transparent_window.rs"
 name = "window_settings"
 path = "examples/window/window_settings.rs"
 
+[[example]]
+name = "expanding_window"
+path = "examples/window/expanding_window.rs"
+
 # Android
 [[example]]
 crate-type = ["cdylib"]

examples/README.md

@@ -307,6 +307,7 @@ Example | File | Description
 `scale_factor_override` | [`window/scale_factor_override.rs`](./window/scale_factor_override.rs) | Illustrates how to customize the default window settings
 `transparent_window` | [`window/transparent_window.rs`](./window/transparent_window.rs) | Illustrates making the window transparent and hiding the window decoration
 `window_settings` | [`window/window_settings.rs`](./window/window_settings.rs) | Demonstrates customizing default window settings
+`expanding_window` | [`window/expanding_window.rs`](./window/expanding_window.rs) | Demonstrates changing window settings at runtime. Also used to validate that `bevy` can handle arbitrarily small windows
 
 # Platform-Specific Examples
 

examples/window/expanding_window.rs

@@ -0,0 +1,56 @@
+use bevy::prelude::*;
+
+fn main() {
+    App::new()
+        .insert_resource(WindowDescriptor {
+            width: 200.,
+            height: 200.,
+            scale_factor_override: Some(1.),
+            ..Default::default()
+        })
+        .add_plugins(DefaultPlugins)
+        .insert_resource(Phase::ContractingY)
+        .add_system(change_window_size)
+        .run();
+}
+
+enum Phase {
+    ContractingY,
+    ContractingX,
+    ExpandingY,
+    ExpandingX,
+}
+
+use Phase::*;
+
+fn change_window_size(mut windows: ResMut<Windows>, mut phase: ResMut<Phase>) {
+    let primary = windows.get_primary_mut().unwrap();
+    let height = primary.height();
+    let width = primary.width();
+    match *phase {
+        Phase::ContractingY => {
+            if height <= 0.5 {
+                *phase = ContractingX;
+            }
+            primary.set_resolution(width, (height - 4.).max(0.0))
+        }
+        Phase::ContractingX => {
+            if width <= 0.5 {
+                *phase = ExpandingY;
+            }
+            primary.set_resolution((width - 4.).max(0.0), height)
+        }
+        Phase::ExpandingY => {
+            if height >= 200. {
+                *phase = ExpandingX;
+            }
+            primary.set_resolution(width, height + 4.)
+        }
+        Phase::ExpandingX => {
+            if width >= 200. {
+                *phase = ContractingY;
+            }
+            primary.set_resolution(width + 4., height)
+        }
+    }
+}