feat: render a HSpan in segmented axis (#50)

Author: 0xb-s

egui_plot/src/lib.rs

@@ -55,7 +55,7 @@ use emath::Float as _;
 use axis::AxisWidget;
 use items::{horizontal_line, rulers_color, vertical_line};
 use legend::LegendWidget;
-
+use egui::pos2;
 type LabelFormatterFn<'a> = dyn Fn(&str, &PlotPoint) -> String + 'a;
 pub type LabelFormatter<'a> = Option<Box<LabelFormatterFn<'a>>>;
 
@@ -1454,6 +1454,18 @@ impl<'a> Plot<'a> {
 
         let (plot_cursors, mut hovered_plot_item) = prepared.ui(ui, &response);
 
+        if let Some(gaps) = mem.transform.segment_x_gap_screen_ranges() {
+            let frame = mem.transform.frame();
+            let gap_color = ui.visuals().extreme_bg_color;
+            for (left, right) in gaps {
+                let gap_rect =
+                    Rect::from_min_max(pos2(left, frame.top()), pos2(right, frame.bottom()));
+                ui.painter()
+                    .with_clip_rect(*frame)
+                    .add(egui::Shape::rect_filled(gap_rect, 0.0, gap_color));
+            }
+        }
+
         // Click/Context menu -> events
         if response.clicked() {
             events.push(PlotEvent::Activate {

egui_plot/src/transform.rs

@@ -660,7 +660,7 @@ impl PlotTransform {
             let total_len: f64 = bx
                 .segments
                 .iter()
-                .map(|seg| seg.len().max(f64::EPSILON)) // avoid 0
+                .map(|seg| seg.len().max(f64::EPSILON)) 
                 .sum();
 
             let total_gap_px: f32 = if n >= 2 {
@@ -681,6 +681,26 @@ impl PlotTransform {
             self.segment_x_offset = 0.0;
         }
     }
+    pub fn segment_x_gap_screen_ranges(&self) -> Option<Vec<(f32, f32)>> {
+        let bx = self.segment_xaxis()?;
+        let mut out = Vec::new();
+
+        let mut cursor_px = self.frame.left() + self.segment_x_offset;
+
+        for (i, seg) in bx.segments.iter().enumerate() {
+            let seg_px = (seg.len() as f32) * self.pixels_per_x;
+            cursor_px += seg_px;
+
+            if i + 1 < bx.segments.len() {
+                let gap_left = cursor_px;
+                let gap_right = cursor_px + bx.gap_px;
+                out.push((gap_left, gap_right));
+                cursor_px += bx.gap_px;
+            }
+        }
+
+        Some(out)
+    }
 
     #[inline]
     pub fn segment_x_offset(&self) -> f32 {