Slider: warn if max < min and swap the values (#1882)

CHANGELOG.md

@@ -52,6 +52,7 @@ You can find its changes [documented below](#070---2021-01-01).
 - x11: Implement primary_clipboard ([#1867] by [@psychon])
 - x11: Set WM_CLASS property ([#1868] by [@psychon])
 - Expose `RawWindowHandle` for `WindowHandle` under the `raw-win-handle` feature ([#1828] by [@djeedai])
+- `Slider` widget now warns if max < min and swaps the values ([#1882] by [@Maan2003])
 
 ### Changed
 
@@ -765,6 +766,7 @@ Last release without a changelog :(
 [#1868]: https://github.com/linebender/druid/pull/1868
 [#1873]: https://github.com/linebender/druid/pull/1873
 [#1876]: https://github.com/linebender/druid/pull/1876
+[#1882]: https://github.com/linebender/druid/pull/1882
 
 [Unreleased]: https://github.com/linebender/druid/compare/v0.7.0...master
 [0.7.0]: https://github.com/linebender/druid/compare/v0.6.0...v0.7.0

druid/src/widget/slider.rs

@@ -17,7 +17,7 @@
 use crate::kurbo::{Circle, Shape};
 use crate::widget::prelude::*;
 use crate::{theme, LinearGradient, Point, Rect, UnitPoint};
-use tracing::{instrument, trace};
+use tracing::{instrument, trace, warn};
 
 const TRACK_THICKNESS: f64 = 4.0;
 const BORDER_WIDTH: f64 = 2.0;
@@ -56,6 +56,17 @@ impl Slider {
         self.max = max;
         self
     }
+
+    /// check self.min <= self.max, if not swaps the values.
+    fn check_range(&mut self) {
+        if self.max < self.min {
+            warn!(
+                "min({}) should be less than max({}), swaping the values",
+                self.min, self.max
+            );
+            std::mem::swap(&mut self.max, &mut self.min);
+        }
+    }
 }
 
 impl Slider {
@@ -125,8 +136,11 @@ impl Widget<f64> for Slider {
 
     #[instrument(name = "Slider", level = "trace", skip(self, ctx, event, _data, _env))]
     fn lifecycle(&mut self, ctx: &mut LifeCycleCtx, event: &LifeCycle, _data: &f64, _env: &Env) {
-        if let LifeCycle::DisabledChanged(_) = event {
-            ctx.request_paint();
+        match event {
+            // checked in LifeCycle::WidgetAdded because logging may not be setup in with_range
+            LifeCycle::WidgetAdded => self.check_range(),
+            LifeCycle::DisabledChanged(_) => ctx.request_paint(),
+            _ => (),
         }
     }