Allow loading new DEM after one has already been loaded

src/app/dem_renderer/mod.rs

@@ -11,7 +11,7 @@ use {
 };
 
 pub struct DemRenderer {
-    source: Rc<Dem>,
+    pub source: Rc<Dem>,
     pipeline: wgpu::RenderPipeline,
     bind_group: wgpu::BindGroup,
     vertex_buffer: wgpu::Buffer,

src/app/mod.rs

@@ -158,8 +158,12 @@ impl MvuApp<Model> for App {
     async fn view(&mut self, model: Rc<Model>) -> Result<(), Box<dyn std::error::Error>> {
         if let Some(context) = &mut self.context {
             context.frame_timer.mark_frame_start();
-            if context.scene_data.is_none() {
             if let Some(dem) = &model.dem {
+                if context
+                    .scene_data
+                    .as_ref()
+                    .is_none_or(|scene_data| scene_data.source.id != dem.id)
+                {
                     context.scene_data = Some(DemRenderer::new(
                         dem.clone(),
                         &context.device,

src/app/raster/dem.rs

@@ -1,4 +1,5 @@
 use crate::mvu::File;
+use std::sync::atomic::{AtomicU32, Ordering};
 
 #[derive(Clone)]
 pub struct Dem {
@@ -11,6 +12,7 @@ pub struct Dem {
     pub z_min: f32,
     pub z_max: f32,
     pub grid: Vec<u16>,
+    pub id: Id,
 }
 
 impl std::fmt::Debug for Dem {
@@ -46,6 +48,18 @@ pub struct DemBvhLayer {
     pub data: Vec<u16>,
 }
 
+#[derive(Clone, Eq, PartialEq)]
+pub struct Id(u32);
+
+impl Id {
+    fn get_next() -> Self {
+        NEXT_ID.fetch_add(1, Ordering::SeqCst);
+        Self(NEXT_ID.load(Ordering::SeqCst))
+    }
+}
+
+static NEXT_ID: AtomicU32 = AtomicU32::new(0);
+
 /// Find the smallest number that's larger then the input and that is also one
 /// less than a power of two.
 fn round_bound(v: u32) -> u32 {
@@ -198,6 +212,7 @@ impl Dem {
                     z_min,
                     z_max,
                     grid,
+                    id: Id::get_next(),
                 }
             }
             _ => {
@@ -283,6 +298,7 @@ mod tests {
                     z_min: z1.min(z2),
                     z_max: z1.max(z2),
                     grid,
+                    id: Id::get_next()
                 },
             )
             .boxed()