feat: a repaired invalid span is shaded faintly, not solidly

src/plot/plot.cpp

@@ -344,7 +344,7 @@ void Plot::set_y_axis_origin_from_range(u32 axis, bool on) {
 
 void Plot::set_x_note(std::string text) { x_note_ = std::move(text); }
 
-void Plot::set_invalid_spans(std::span<const std::pair<f64, f64>> spans) {
+void Plot::set_invalid_spans(std::span<const InvalidSpan> spans) {
   invalid_spans_.assign(spans.begin(), spans.end());
 }
 
@@ -1378,9 +1378,9 @@ void Plot::build_invalid_spans() {
   // the band is most needed for. One device pixel is the floor.
   const f32 min_w = std::max(1.0f, style_.device(1.0f));
 
-  for (const std::pair<f64, f64>& span : invalid_spans_) {
-    const f64 a = std::min(span.first, span.second);
-    const f64 b = std::max(span.first, span.second);
+  for (const InvalidSpan& span : invalid_spans_) {
+    const f64 a = std::min(span.x0, span.x1);
+    const f64 b = std::max(span.x0, span.x1);
     if (!std::isfinite(a) || !std::isfinite(b)) continue;
     const f32 lo = static_cast<f32>(tx.to_screen_x(a));
     const f32 hi = static_cast<f32>(tx.to_screen_x(b));
@@ -1394,7 +1394,7 @@ void Plot::build_invalid_spans() {
     // Widening a band at the right edge would run it over the axis line, so the floor is taken
     // out of the left instead: the span's own edge is kept wherever there is room for it.
     const f32 x = std::clamp(first, axes.x, axes.right() - w);
-    layout_.invalid_spans.push_back(Rect{x, axes.y, w, axes.h});
+    layout_.invalid_spans.push_back(InvalidSpanLayout{Rect{x, axes.y, w, axes.h}, span.repaired});
   }
 }