Merge PR #603 from NikitkaRa: Render: draw chart trendlines

# Conflicts:
#	crates/render/src/chart.rs

crates/model/src/chart.rs

@@ -487,6 +487,17 @@ impl Chart {
                 lo = lo.min(m);
             }
         }
+        if !percent {
+            for s in &ser {
+                if self.series_kind(s).stacked() {
+                    continue;
+                }
+                for y in s.trendline_ys(crate::trendline::series_is_scatter(self.series_kind(s))) {
+                    hi = hi.max(y);
+                    lo = lo.min(y);
+                }
+            }
+        }
         if percent {
             lo = lo.min(0.0);
             hi = hi.max(1.0);
@@ -579,6 +590,14 @@ impl Chart {
         if self.kind.percent() {
             return (0.0, 1.0);
         }
+        if !self.kind.stacked() {
+            for s in &self.series {
+                for y in s.trendline_ys(crate::trendline::series_is_scatter(self.series_kind(s))) {
+                    hi = hi.max(y);
+                    lo = lo.min(y);
+                }
+            }
+        }
         (self.y_min.unwrap_or(lo), self.y_max.unwrap_or(hi))
     }
 }
@@ -820,6 +839,17 @@ mod tests {
         assert_eq!(ticks, ["0", "0.025", "0.05", "0.075", "0.1", "0.125"]);
     }
 
+    #[test]
+    fn a_forecast_grows_the_value_axis() {
+        let mut c = Chart::sample(ChartType::Line);
+        c.series.truncate(1);
+        c.series[0].values = vec![Some(3.0), Some(5.0), Some(7.0), Some(9.0)];
+        let before = c.value_range().1;
+        c.series[0].trendlines.push(Trendline { forward: Some(1.0), ..Default::default() });
+        let after = c.value_range().1;
+        assert!(after > before && after >= 11.0 - 1e-6, "{before} {after}");
+    }
+
     #[test]
     fn axis_labels_use_the_format_and_language() {
         let mut c = Chart::sample(ChartType::Column);