feat(FeaturePanel): modernize UI with responsive layout, progress bar, and keyboard shortcuts

[AmlanDalai]

Summary

Comprehensive UI modernization of FeaturePanel.java, the main annotation/marking panel. Replaces the fragile null layout with proper Swing layout managers, adds training progress feedback, button tooltips, keyboard shortcuts, and fixes 4 string comparison bugs.

Addresses #60 (training state indicator), partially addresses #103 (== comparison bugs)

Changes

1. Responsive Layout (replaces null layout)

Replaced panel.setLayout(null) with a JSplitPane + BoxLayout hierarchy:

• Removed setResizable(false) — window is now fully resizable
• Removed all hardcoded setBounds() positioning
• Divider is draggable with one-touch expand buttons

2. Training Progress Bar (addresses #60)

Added JProgressBar that appears during training and shows completion:

• Shows animated "Training in progress..." during training
• Shows "Training complete!" for 2 seconds after finishing
• Graceful error handling with user-friendly dialog if training fails

3. Asynchronous Training (SwingWorker)

Wrapped featureManager.compute() in SwingWorker for both classification and segmentation modes:

• UI no longer freezes during training
• Progress bar updates on the EDT

4. Tooltips on All Buttons

Button	Tooltip
<<	Previous image (← key)
>>	Next image (→ key)
Train	Train the classifier (Ctrl+T)
Save	Save regions of interest (Ctrl+S)
Overlay	Toggle result overlay (Ctrl+O)
Masks	Show classification masks
Snap	Take a screenshot of the canvas

5. Keyboard Shortcuts

• ← / → — Navigate between images
• Ctrl+T — Train the classifier
• Ctrl+S — Save regions of interest
• Ctrl+O — Toggle result overlay

6. Bug Fixes (relates to #103)

Fixed 4 unsafe == string comparisons in doAction():

- if(event.getActionCommand()== "ColorButton"){
+ if("ColorButton".equals(event.getActionCommand())){

Applied the same fix to AddButton, UploadButton, and DownloadButton.

7. Code Cleanup

• Window title: "Marking" → "Active Segmentation - Feature Marking"
• Removed unused frameList variable
• Removed 18 lines of dead commented-out MouseWheelListener
• Removed duplicate frame.add(features) call

Screenshots

Before

After

Testing

• Verified all buttons function correctly
• Verified ROI add/delete operations work
• Verified image navigation via buttons and arrow keys
• Verified training progress bar appears and hides
• Verified window is resizable and split pane divider works
• Verified tooltips appear on hover