SNTUI: Fix inconsistent handling of UI states

Author: tferr

src/main/java/sc/fiji/snt/SNT.java

@@ -1040,24 +1040,25 @@ protected synchronized void saveFill() {
 		fillerSet.clear();
 		pathAndFillManager.getLoadedFills().clear();
 		fillerThreadPool = null;
-		changeUIState(SNTUI.WAITING_TO_START_PATH);
+        changeUIState(tracingHalted ? SNTUI.TRACING_PAUSED : SNTUI.WAITING_TO_START_PATH);
 		if (getUI() != null)
 			getUI().getFillManager().changeState(FillManagerUI.State.READY);
 	}
 
 	protected synchronized void discardFill() {
 		if (fillerSet.isEmpty()) {
 			SNTUtils.log("No Fill(s) to discard...");
+            return;
 		}
 		for (FillerThread filler : fillerSet) {
 			removeThreadToDraw(filler);
 		}
 		fillerSet.clear();
 		pathAndFillManager.getLoadedFills().clear();
 		fillerThreadPool = null;
-		changeUIState(SNTUI.WAITING_TO_START_PATH);
-		if (getUI() != null)
-			getUI().getFillManager().changeState(FillManagerUI.State.READY);
+        changeUIState(tracingHalted ? SNTUI.TRACING_PAUSED : SNTUI.WAITING_TO_START_PATH);
+        if (getUI() != null)
+            getUI().getFillManager().changeState(FillManagerUI.State.READY);
 	}
 
 	protected synchronized void stopFilling() {

src/main/java/sc/fiji/snt/SNTUI.java

@@ -915,7 +915,8 @@ private void updateRebuildCanvasButton() {
 	private interface UIState {
 		void enter();
 		int getStateId();
-	}
+        default void exit() {}
+    }
 
 	// State registry
 	private final Map<Integer, UIState> states = new HashMap<>();
@@ -950,9 +951,15 @@ private void initializeStates() {
 	 */
 	public void changeState(final int newState) {
 		if (newState == currentState || plugin == null) return; // plugin may be null when exiting
+
+        // Call exit() on current state
+        UIState oldState = states.get(currentState);
+        if (oldState != null) oldState.exit();
+
 		currentState = newState;
 
 		SwingUtilities.invokeLater(() -> {
+            if (currentState != newState) return; // Verify state hasn't changed since we queued this
 			UIState state = states.get(newState);
 			if (state != null) {
 				state.enter();
@@ -1087,11 +1094,37 @@ public int getStateId() {
 	}
 
 	private class RunningCmdState implements UIState {
+        private static final String[] BRAILLE = {"⠋", "⠙", "⠹", "⠸", "⠼", "⠴", "⠦", "⠧", "⠇", "⠏"};
+        private static final String[] SPINNER_FRAMES;
+        static {
+            SPINNER_FRAMES = new String[BRAILLE.length];
+            for (int i = 0; i < BRAILLE.length; i++) {
+                SPINNER_FRAMES[i] = "<html><strong>Running Command... <span style='font-size:1.1em'>"
+                        + BRAILLE[i] + " " + BRAILLE[i] + " " + BRAILLE[i] + "</span></strong></html>";
+            }
+        }
+        Timer runningAnimationTimer;
+        private int spinnerIndex = 0;
+
 		@Override
 		public void enter() {
 			updateStatusText("Running Command...");
 			disableEverything();
-		}
+            spinnerIndex = 0;
+            runningAnimationTimer = new Timer(150, e -> {
+                spinnerIndex = (spinnerIndex + 1) % SPINNER_FRAMES.length;
+                statusText.setText(SPINNER_FRAMES[spinnerIndex]);
+            });
+            runningAnimationTimer.start();
+		}
+
+        @Override
+        public void exit() {
+            if (runningAnimationTimer != null) {
+                runningAnimationTimer.stop();
+                runningAnimationTimer = null;
+            }
+        }
 
 		@Override
 		public int getStateId() {
@@ -4284,7 +4317,7 @@ protected void abortCurrentOperation() {// FIXME: MOVE TO SNT?
             }
         }
 		if (activeWorker != null && !activeWorker.isDone()) activeWorker.kill();
-		changeState(WAITING_TO_START_PATH);
+        changeState(plugin.tracingHalted ? TRACING_PAUSED : WAITING_TO_START_PATH);
 	}
 
 	protected void launchSigmaPaletteAround(final int x, final int y) {

src/main/java/sc/fiji/snt/gui/DemoRunner.java

@@ -448,8 +448,11 @@ private void error(final Throwable ex) {
 	}
 
 	private void exit() {
-		ui.changeState(priorUIState);
-		ui.showStatus(null, true);
+        if (priorUIState == SNTUI.TRACING_PAUSED && ui.getState() != SNTUI.TRACING_PAUSED) {
+            return; // Don't restore TRACING_PAUSED if we're no longer in that state
+        }
+        ui.changeState(priorUIState);
+        ui.showStatus(null, true);
 	}
 
 	public Demo getChoice() {

src/main/java/sc/fiji/snt/gui/GuiUtils.java

@@ -434,20 +434,6 @@ public int getNextMatch(final String prefix, final int startIndex, final Positio
 		});
 		list.setSelectedIndex(defIdx);
 		list.ensureIndexIsVisible(defIdx);
-		list.setCellRenderer(new DefaultListCellRenderer() {
-
-			private static final long serialVersionUID = -810009340376431810L;
-
-			@Override
-			public Component getListCellRendererComponent(JList<?> list, Object value, int index, boolean isSelected,
-					boolean cellHasFocus) {
-				final Component c = super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);
-				if (isSelected)
-					c.setFont(c.getFont().deriveFont(Font.BOLD));
-				return c;
-			}
-		} );
-
 		ta.setText(descriptions[defIdx]);
 		ta.setCaretPosition(0);
 		ta.setBackground(list.getBackground());