Large STEP imports: no more multi-minute hang, shared STEP text, cancel and progress (#925)

crates/ui-egui/src/file_load.rs

@@ -474,6 +474,8 @@ pub fn show(app: &mut SolveApp, ctx: &egui::Context) {
     };
     let phase = r.phase.load(Ordering::Relaxed);
     let (done, total) = r.progress.features();
+    // Long work inside one feature (a large STEP file) has progress of its own.
+    let work = r.progress.work().filter(|(_, d, t)| phase == 0 && d < t);
     let screen = ctx.content_rect();
     // Leave the title bar to the window. The resize edges are a foreground layer above this.
     let cover = egui::Rect::from_min_max(egui::pos2(screen.left(), screen.top() + crate::toolbar::APP_BAR_HEIGHT), screen.max);
@@ -538,16 +540,22 @@ pub fn show(app: &mut SolveApp, ctx: &egui::Context) {
                 ui.label(if cancelled {
                     "Waiting for the previous operation to stop...".to_string()
                 } else {
-                    match phase {
-                        1 => "Preparing the view...".into(),
-                        2 => "Preparing the thumbnail...".into(),
+                    match (phase, work) {
+                        (_, Some(("reading", d, t))) => format!("Reading the file... {}%", d * 100 / t.max(1)),
+                        (_, Some((_, d, t))) => format!("Converting solid {} of {t}", d + 1),
+                        (1, _) => "Preparing the view...".into(),
+                        (2, _) => "Preparing the thumbnail...".into(),
                         _ if total > 0 => format!("Rebuilding feature {} of {total}", (done + 1).min(total)),
                         _ => "Reading the file...".into(),
                     }
                 });
             });
             // Always there, so the card keeps its height as the phases change.
-            let fraction = if cancelled || total == 0 {
+            let fraction = if cancelled {
+                0.0
+            } else if let Some((_, d, t)) = work {
+                d as f32 / t.max(1) as f32
+            } else if total == 0 {
                 0.0
             } else if phase == 0 {
                 done as f32 / total as f32