platform: smart_leds: move StrideSampler into mappings module

src/mappings.rs

@@ -1,6 +1,8 @@
+use crate::buffers::Pixbuf;
 use crate::geometry::*;
 
 use crate::lib8::interpolate::scale8;
+use crate::render::PixelView;
 
 use core::cmp::{max, min};
 use core::fmt::{Formatter, Debug};
@@ -301,3 +303,29 @@ impl<'a> CoordinateView<'a> for StrideView<'a> {
         None
     }
 }
+
+pub struct StrideSampler<'a, P: Pixbuf> {
+    pixbuf: &'a mut P,
+    selection: StrideView<'a>
+}
+
+impl<'a, P: Pixbuf> StrideSampler<'a, P> {
+    pub fn new(pixbuf: &'a mut P, selection: StrideView<'a>) -> Self {
+        StrideSampler {
+            pixbuf,
+            selection
+        }
+    }
+}
+
+impl<'a, P: Pixbuf> PixelView for StrideSampler<'a, P> {
+    type Pixel = P::Pixel;
+    fn next(&mut self) -> Option<(Coordinates<Virtual>, &mut Self::Pixel)> {
+        if let Some((virt, coords)) = self.selection.next() {
+            let idx = self.selection.map.strides[coords.x as usize].pixel_idx_for_offset(coords.y);
+            Some((virt, &mut self.pixbuf[idx]))
+        } else {
+            None
+        }
+    }
+}