apexcharts_flutter

Hovering a dense chart re-painted the entire chart: shouldRepaint returned
true on any hit change, so each pointer move re-laid-out the grid labels
(~2N TextPainter.layout) and rebuilt the series spline.

• Move crosshair/markers + drag-select rectangle into a separate top
  _OverlayPainter; the base _ApexChartPainter no longer depends on hit or
  selection, so a hover repaints only the lightweight overlay.
• Cache laid-out TextPainters in TextDrawer (keyed by text + style) so the
  repeated layout cost during mount/pan/zoom animations is paid once per
  unique label instead of every frame.

Ports unchanged; verified via existing golden + smoke suites.

• Performance: hovering a dense chart no longer repaints the whole chart. The crosshair, active markers and drag-select rectangle now live in their own overlay layer, so a pointer move repaints only that cheap layer instead of re-laying-out the grid labels and rebuilding the series spline every frame.
• Performance: axis/legend/data-label text layout is now cached (keyed by text + style), so the repeated TextPainter.layout() cost during mount/pan/zoom animations is paid once per unique label rather than every frame.

• Fix a freeze on repeated zoom for charts with zoom.autoScaleYaxis (e.g. the area-datetime demo): getGCD/mod now match ApexCharts' precision-capped scaling (p = 7), so FP-dirty axis ranges no longer make niceScale stall for seconds. Worst case dropped from ~35s to <2ms per call.
• Add chart screenshots (README gallery + pub.dev screenshots carousel).
• Example gallery: the interactive area-datetime zoom/pan demo is now a card on the main page instead of a separate route.

Initial release — a native Flutter/Dart port of ApexCharts v4.7.0 (the last MIT release), rendered on CustomPainter/Canvas with zero runtime dependencies (no WebView, no JS engine). Runs on every Flutter platform: Android, iOS, web, Windows, macOS and Linux.

Chart types (13)

• Line, area (straight / smooth / stepline), with markers and gradient fills
• Bar — grouped, stacked, and horizontal
• Pie and donut
• Scatter and bubble
• Range bar / timeline (Gantt)
• Candlestick / OHLC
• Radar (spider)
• Radial bar / gauge
• Heatmap
• Treemap (squarified layout)

Interactivity

• Tooltips on every chart type (shared and intersect modes), including heatmap, treemap and radar
• Crosshair and active markers
• Drag- and wheel-zoom with a toolbar, smooth path-morph transitions
• Y-axis that eases (no discrete jumps) while panning when autoScaleYaxis is on
• Mount/entrance animations

Axes & scales

• Category, datetime and numeric x-axes
• Linear and logarithmic y-axes, "nice" tick selection
• Value formatters and axis titles

Method

Every visual/numeric decision is traced to the upstream ApexCharts v4.7.0 source and verified against the real library rendered headless with Puppeteer (golden-image diffing). See NOTICE for the exact upstream tag and commit.