[Feature] Add GUI zoom functionality with scalable interface

[tensquaresoftware]

Feature Request: GUI Zoom Functionality

Overview

Implement a zoom feature to allow users to scale the entire plugin interface, improving accessibility and adapting to different screen sizes and resolutions.

Proposed Implementation

1. Zoom Control Location

• Add a zoom ComboBox in the HeaderPanel
• Position it in a logical location (e.g., top-right corner near other global controls)
• Use existing ComboBox widget for consistency with current UI design

2. Zoom Levels

Standard zoom levels to implement:

• 50% (very small)
• 75% (small)
• 90% (slightly reduced)
• 100% (default) - current size
• 110% (slightly enlarged)
• 125% (medium)
• 150% (large)
• 200% (very large)
• 300% (extra large)
• 400% (maximum)

3. Technical Approach

Using JUCE AffineTransform:

// Apply zoom transform to main component (scale from selected zoom level)
auto transform = juce::AffineTransform::scale(zoomLevelScale);
mainComponent.setTransform(transform);

Key considerations:

• Apply transform to the root GUI component (likely MainComponent)
• Adjust component bounds to accommodate scaled size
• Ensure the plugin window resizes appropriately
• Cache images may need invalidation on zoom change

4. Persistence

• Store zoom preference in plugin state (APVTS or separate settings)
• Restore zoom level when plugin is reopened
• Consider per-instance vs global preference

5. HiDPI/Retina Considerations

• Ensure zoom works correctly with existing HiDPI support
• Zoom level (scale) should multiply with display scale factor
• Test on different display configurations (1x, 2x, 3x scaling)

6. Performance Optimization

• Invalidate widget caches when zoom changes
• Trigger full repaint after zoom application
• Consider debouncing if zoom can be changed rapidly

7. Edge Cases to Handle

• Minimum window size constraints
• Maximum window size (especially at 400%)
• Host window resizing behavior
• DAW-specific constraints (some hosts limit plugin window sizes)

UI/UX Considerations

1. Visual Feedback:

   • Show current zoom percentage in ComboBox
   • Possibly add keyboard shortcuts (Cmd/Ctrl +/- for zoom in/out)

2. Smooth Transitions:

   • Consider animating zoom changes (optional, may be overkill)
   • Ensure no visual glitches during scaling

3. Accessibility:

   • This feature particularly helps users with vision impairments
   • Larger zoom levels should maintain readability and usability

Testing Checklist

• Test all zoom levels on macOS (Retina and non-Retina)
• Test all zoom levels on Windows (different DPI settings)
• Verify zoom persistence across plugin instances
• Test in multiple DAWs (Logic Pro, Ableton Live, Reaper)
• Verify no performance degradation at extreme zoom levels
• Check that all widgets remain functional when scaled
• Test edge cases (very small/large window sizes)

Implementation Priority

Medium Priority - Nice-to-have feature that improves accessibility and user experience, but not critical for core functionality.

Related Considerations

• This feature will work well with the current image caching system
• May need to adjust cache invalidation logic in widgets
• Consider adding a "Reset to Default" option (100%)
• Could add a tooltip explaining the zoom feature

Alternative Approaches

If AffineTransform causes issues:

• Use Component::setScaleFactor() (JUCE 7+)
• Manually scale all widget dimensions (not recommended, too complex)
• Use OpenGL scaling (not applicable since we removed OpenGL)

Notes

• Current GUI is 1920x1080, so 400% zoom would require significant screen real estate
• Consider warning users if zoomed size exceeds screen dimensions
• Some DAWs may override or constrain plugin window sizes

[tensquaresoftware]

Progress update (Clean Code refactoring, v0.0.61-alpha):

Done:

• Zoom levels source of truth: PluginIDs::Settings::ZoomLevels (k50…k400, kDefault=k100, kMin=k50, kMax=k400)
• Display names: PluginDisplayNames::ChoiceLists::ZoomLevels ("50%" … "200%" — extend for 250%, 300%, 400% if needed)
• getZoomLevel(int zoomLevelId) for factor conversion
• Zoom ComboBox in HeaderPanel wired to these constants (no magic numbers)

Not yet done:

• Apply AffineTransform (or equivalent) to scale the GUI
• Persistence (APVTS/settings)
• HiDPI considerations, performance, edge cases

Leaving issue open until scaling and persistence are implemented.