Example with a progress bar while loading

CHANGES.md

@@ -2,6 +2,7 @@
 
 ## Work In Progress
 - Addition and subtraction of Tranforms supported to help with easing function calculations
+- Added an example with loading progress bar
 
 ## v0.4.0-alpha0.3
 - Update `golem` to `v0.1.1` to fix non-power-of-2 textures

examples/06_loading_screen.rs

@@ -0,0 +1,81 @@
+// Example 6: draw a progress bar while loading the application
+//
+// This (pretends to) load some data when starting and in between each step (eg. each texture or
+// model or whatever), it updates a progress bar.
+//
+// Alternatively, one could also do loading in a background thread or threads and do only the
+// redrawing in the main one, to separate it.
+use std::thread::sleep;
+use std::time::Duration;
+
+use quicksilver::{
+    geom::{Rectangle, Vector},
+    graphics::{Color, Graphics},
+    lifecycle::{run, EventStream, Settings, Window},
+    Result,
+};
+
+fn main() {
+    run(
+        Settings {
+            size: Vector::new(800.0, 600.0).into(),
+            title: "Square Example",
+            ..Settings::default()
+        },
+        app,
+    )
+}
+
+const STEPS: usize = 10;
+
+fn load_something() {
+    /*
+     * Here would be some actual loading of something, like textures.
+     * In this example we simply call sleep as a placeholder.
+     *
+     * TODO: Something better than sleep here would be nice.
+     * Also, there's a problem with sleeps:
+     * https://github.com/ryanisaacg/quicksilver/issues/580
+     */
+    sleep(Duration::from_secs(1));
+}
+
+fn draw_loader(window: &Window, gfx: &mut Graphics, progress: usize, total: usize) -> Result<()> {
+    gfx.clear(Color::BLACK);
+    gfx.fill_rect(
+        &Rectangle::new(Vector::new(50.0, 500.0), Vector::new(700.0, 25.0)),
+        Color::YELLOW,
+    );
+
+    let width = 700.0 * progress as f32 / total as f32;
+    gfx.fill_rect(
+        &Rectangle::new(Vector::new(50.0, 500.0), Vector::new(width, 25.0)),
+        Color::BLUE,
+    );
+
+    /*
+     * In real game, this might be a good place to make the loading screen nicer, possibly by
+     * adding an image. We stick with just the progress bar in the example for simplicity.
+     */
+
+    gfx.present(&window)?;
+
+    Ok(())
+}
+
+async fn app(window: Window, mut gfx: Graphics, mut events: EventStream) -> Result<()> {
+    for i in 0..STEPS {
+        draw_loader(&window, &mut gfx, i, STEPS)?;
+        load_something();
+    }
+
+    // Now we have everything loaded. The rest is not interesting for this example, so it just
+    // fills the whole window with green.
+
+    gfx.clear(Color::GREEN);
+    gfx.present(&window)?;
+
+    loop {
+        while let Some(_) = events.next_event().await {}
+    }
+}