Show pen thickness indicator with fade-out on mouse wheel scroll

[Copilot]

Displays the current brush thickness value in the top-right corner when adjusting via mouse wheel during drawing mode. Indicator appears instantly and fades out after 1.5s of inactivity.

Changes

OverlayWindow.xaml

• Added ThicknessIndicatorBorder with cyberpunk styling (neon pink border, glow effect)
• Positioned top-right, initially hidden, non-interactive

OverlayWindow.xaml.cs

• DispatcherTimer triggers fade-out after 1.5s display duration
• ShowThicknessIndicator() - updates text, resets timer, shows immediately
• ThicknessIndicatorTimer_Tick() - starts 300ms fade-out animation
• HideThicknessIndicator() - immediate hide on drawing disable
• Timer cleanup on window close

Behavior

• Wheel scroll → show "X px" instantly
• Subsequent scrolls reset the timer
• Fades out smoothly after idle period
• Hidden when exiting drawing mode

Original prompt

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This section details on the original issue you should resolve

<issue_title>Feature Request: Show current pen thickness value when scrolling mouse wheel (with fade-out)</issue_title>
<issue_description># Feature Request: Show current pen thickness value when scrolling mouse wheel (with fade-out)

Summary

When the user adjusts line thickness with the mouse wheel while the overlay is active, briefly display the current thickness value (e.g. “18 px”) in the top-right corner, then fade it out after ~1–2 seconds.

Proposed Behavior

• While overlay is active:
  • Every mouse-wheel tick → update thickness as usual
  • Show current thickness as large, readable text in the top-right corner (e.g. “24 px”)
  • Text appears instantly on first wheel movement
  • Text fades out smoothly after 1.5 seconds of no further wheel activity
  • If user scrolls again before fade completes → reset timer and update value
• Style suggestions:
  • Match current cyber punk theme for color and font ect.

Use Cases

• Immediate feedback so users know exactly how thick/thin their stroke is
• Prevents “guess and check” when trying to match a specific size and having to deactivate and going to look at the settings.
• Feels polished and professional (used by Epic Pen, Paint, Krita, etc.)

Optional Polish

• Include unit toggle in future settings (px ↔ mm)
• Show a tiny preview circle next to the number (visual representation of current thickness)
• Make position and fade duration configurable later

Tiny feature, huge perceived quality boost.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Feature Request: Show current pen thickness value when scrolling mouse wheel (with fade-out) #12

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