Fix conversion progress updates when navigating between modules

Previously, when a conversion was started and the user navigated away from
the Convert module and returned, the progress stats would freeze (though the
progress bar would continue animating). This was caused by the conversion
goroutine updating stale widget references.

Changes:
- Decoupled conversion state from UI widgets
- Conversion goroutine now only updates appState (convertBusy, convertStatus)
- Added 200ms UI refresh ticker in buildConvertView to update widgets from state
- Removed all direct widget manipulation from background conversion process

This ensures conversion progress stats remain accurate and update correctly
regardless of module navigation, supporting the persistent video context
design where conversions continue running while users work in other modules.

main.go

@@ -993,6 +993,65 @@ func buildConvertView(state *appState, src *videoSource) fyne.CanvasObject {
 	// Wrap mainArea in a scroll container to prevent content from forcing window resize
 	scrollableMain := container.NewScroll(mainArea)
 
+	// Start a UI refresh ticker to update widgets from state while conversion is active
+	// This ensures progress updates even when navigating between modules
+	go func() {
+		ticker := time.NewTicker(200 * time.Millisecond)
+		defer ticker.Stop()
+
+		// Track the previous busy state to detect transitions
+		wasBusy := state.convertBusy
+
+		for {
+			select {
+			case <-ticker.C:
+				isBusy := state.convertBusy
+
+				// Update UI on the main thread
+				fyne.CurrentApp().Driver().DoFromGoroutine(func() {
+					// Update status label from state
+					if isBusy {
+						statusLabel.SetText(state.convertStatus)
+					} else if wasBusy {
+						// Just finished - update one last time
+						statusLabel.SetText(state.convertStatus)
+					}
+
+					// Update button states
+					if isBusy {
+						convertBtn.Disable()
+						cancelBtn.Enable()
+						activity.Show()
+						if !activity.Running() {
+							activity.Start()
+						}
+					} else {
+						if src != nil {
+							convertBtn.Enable()
+						} else {
+							convertBtn.Disable()
+						}
+						cancelBtn.Disable()
+						activity.Stop()
+						activity.Hide()
+					}
+				}, false)
+
+				// If conversion finished, stop the ticker after one final update
+				if wasBusy && !isBusy {
+					return
+				}
+				wasBusy = isBusy
+
+			case <-time.After(30 * time.Second):
+				// Safety timeout - if no conversion after 30s, stop ticker
+				if !state.convertBusy {
+					return
+				}
+			}
+		}
+	}()
+
 	return container.NewBorder(
 		backBar,
 		container.NewVBox(widget.NewSeparator(), actionBar),
@@ -2123,13 +2182,8 @@ func (s *appState) cancelConvert(cancelBtn, btn *widget.Button, spinner *widget.
 	if s.convertCancel == nil {
 		return
 	}
-	if cancelBtn != nil {
-		cancelBtn.Disable()
-	}
 	s.convertStatus = "Cancelling…"
-	if status != nil {
+	// Widget states will be updated by the UI refresh ticker
-		status.SetText(s.convertStatus)
-	}
 	s.convertCancel()
 }
 
@@ -2137,9 +2191,8 @@ func (s *appState) startConvert(status *widget.Label, btn, cancelBtn *widget.But
 	setStatus := func(msg string) {
 		s.convertStatus = msg
 		logging.Debug(logging.CatFFMPEG, "convert status: %s", msg)
-		if status != nil {
+		// Note: Don't update widgets here - they may be stale if user navigated away
-			status.SetText(msg)
+		// The UI will refresh from state.convertStatus via a ticker
-		}
 	}
 	if s.source == nil {
 		dialog.ShowInformation("Convert", "Load a video first.", s.window)
@@ -2316,16 +2369,7 @@ func (s *appState) startConvert(status *widget.Label, btn, cancelBtn *widget.But
 	logging.Debug(logging.CatFFMPEG, "convert command: ffmpeg %s", strings.Join(args, " "))
 	s.convertBusy = true
 	setStatus("Preparing conversion…")
-	if btn != nil {
+	// Widget states will be updated by the UI refresh ticker
-		btn.Disable()
-	}
-	if spinner != nil {
-		spinner.Show()
-		spinner.Start()
-	}
-	if cancelBtn != nil {
-		cancelBtn.Enable()
-	}
 
 	ctx, cancel := context.WithCancel(context.Background())
 	s.convertCancel = cancel
@@ -2344,16 +2388,6 @@ func (s *appState) startConvert(status *widget.Label, btn, cancelBtn *widget.But
 				dialog.ShowError(fmt.Errorf("convert failed: %w", err), s.window)
 				s.convertBusy = false
 				setStatus("Failed")
-				if btn != nil {
-					btn.Enable()
-				}
-				if cancelBtn != nil {
-					cancelBtn.Disable()
-				}
-				if spinner != nil {
-					spinner.Stop()
-					spinner.Hide()
-				}
 			}, false)
 			s.convertCancel = nil
 			return
@@ -2418,16 +2452,6 @@ func (s *appState) startConvert(status *widget.Label, btn, cancelBtn *widget.But
 				dialog.ShowError(fmt.Errorf("convert failed: %w", err), s.window)
 				s.convertBusy = false
 				setStatus("Failed")
-				if btn != nil {
-					btn.Enable()
-				}
-				if cancelBtn != nil {
-					cancelBtn.Disable()
-				}
-				if spinner != nil {
-					spinner.Stop()
-					spinner.Hide()
-				}
 			}, false)
 			s.convertCancel = nil
 			return
@@ -2441,16 +2465,6 @@ func (s *appState) startConvert(status *widget.Label, btn, cancelBtn *widget.But
 				fyne.CurrentApp().Driver().DoFromGoroutine(func() {
 					s.convertBusy = false
 					setStatus("Cancelled")
-					if btn != nil {
-						btn.Enable()
-					}
-					if cancelBtn != nil {
-						cancelBtn.Disable()
-					}
-					if spinner != nil {
-						spinner.Stop()
-						spinner.Hide()
-					}
 				}, false)
 				s.convertCancel = nil
 				return
@@ -2460,16 +2474,6 @@ func (s *appState) startConvert(status *widget.Label, btn, cancelBtn *widget.But
 				dialog.ShowError(fmt.Errorf("convert failed: %w", err), s.window)
 				s.convertBusy = false
 				setStatus("Failed")
-				if btn != nil {
-					btn.Enable()
-				}
-				if cancelBtn != nil {
-					cancelBtn.Disable()
-				}
-				if spinner != nil {
-					spinner.Stop()
-					spinner.Hide()
-				}
 			}, false)
 			s.convertCancel = nil
 			return
@@ -2483,16 +2487,6 @@ func (s *appState) startConvert(status *widget.Label, btn, cancelBtn *widget.But
 				dialog.ShowError(fmt.Errorf("conversion output is invalid: %w", probeErr), s.window)
 				s.convertBusy = false
 				setStatus("Failed")
-				if btn != nil {
-					btn.Enable()
-				}
-				if cancelBtn != nil {
-					cancelBtn.Disable()
-				}
-				if spinner != nil {
-					spinner.Stop()
-					spinner.Hide()
-				}
 			}, false)
 			s.convertCancel = nil
 			return
@@ -2502,16 +2496,6 @@ func (s *appState) startConvert(status *widget.Label, btn, cancelBtn *widget.But
 			dialog.ShowInformation("Convert", fmt.Sprintf("Saved %s", outPath), s.window)
 			s.convertBusy = false
 			setStatus("Done")
-			if btn != nil {
-				btn.Enable()
-			}
-			if cancelBtn != nil {
-				cancelBtn.Disable()
-			}
-			if spinner != nil {
-				spinner.Stop()
-				spinner.Hide()
-			}
 		}, false)
 		s.convertCancel = nil
 	}()