femtovg: clamping sim - add a stop at 1.0 on a gradient (slint-ui#7909)

* femtovg: clamping sim - add a stop at 1.0  on a gradient to match the last stop set if last stop is not at 1.0
linear and radial adjusted

* [autofix.ci] apply automated fixes

* add conditional for last stop for femtovg gradients

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

Author: szecket

internal/renderers/femtovg/itemrenderer.rs

@@ -1559,8 +1559,18 @@ impl<'a, R: femtovg::Renderer + TextureImporter> GLItemRenderer<'a, R> {
                     [path_width, path_height].into(),
                 );
 
-                let stops =
-                    gradient.stops().map(|stop| (stop.position, to_femtovg_color(&stop.color)));
+                let mut stops: Vec<_> = gradient
+                    .stops()
+                    .map(|stop| (stop.position, to_femtovg_color(&stop.color)))
+                    .collect();
+
+                // Add an extra stop at 1.0 with the same color as the last stop
+                if let Some(last_stop) = stops.last().cloned() {
+                    if last_stop.0 != 1.0 {
+                        stops.push((1.0, last_stop.1));
+                    }
+                }
+
                 femtovg::Paint::linear_gradient_stops(start.x, start.y, end.x, end.y, stops)
             }
             Brush::RadialGradient(gradient) => {
@@ -1569,8 +1579,18 @@ impl<'a, R: femtovg::Renderer + TextureImporter> GLItemRenderer<'a, R> {
                 let path_width = path_bounds.width();
                 let path_height = path_bounds.height();
 
-                let stops =
-                    gradient.stops().map(|stop| (stop.position, to_femtovg_color(&stop.color)));
+                let mut stops: Vec<_> = gradient
+                    .stops()
+                    .map(|stop| (stop.position, to_femtovg_color(&stop.color)))
+                    .collect();
+
+                // Add an extra stop at 1.0 with the same color as the last stop
+                if let Some(last_stop) = stops.last().cloned() {
+                    if last_stop.0 != 1.0 {
+                        stops.push((1.0, last_stop.1));
+                    }
+                }
+
                 femtovg::Paint::radial_gradient_stops(
                     path_width / 2.,
                     path_height / 2.,