add helper methods for creating a window

src/containers/bitmap.rs

@@ -1,6 +1,6 @@
 use crate::{
     DataRef, DisplayBitVec, Grid, GridMut, Payload, ValueGrid, Window,
-    PIXEL_HEIGHT, PIXEL_WIDTH,
+    WindowMut, PIXEL_HEIGHT, PIXEL_WIDTH,
 };
 use ::bitvec::{order::Msb0, prelude::BitSlice, slice::IterMut};
 use inherent::inherent;
@@ -176,6 +176,32 @@ impl Bitmap {
             row: 0,
         }
     }
+
+    /// Creates a window into the bitmap.
+    ///
+    /// Returns None in case the window does not fit.
+    pub fn window(
+        &self,
+        x: usize,
+        y: usize,
+        width: usize,
+        height: usize,
+    ) -> Option<Window<bool, Self>> {
+        Window::new(self, x, y, width, height)
+    }
+
+    /// Creates a mutable window into the bitmap.
+    ///
+    /// Returns None in case the window does not fit.
+    pub fn window_mut(
+        &mut self,
+        x: usize,
+        y: usize,
+        width: usize,
+        height: usize,
+    ) -> Option<WindowMut<bool, Self>> {
+        WindowMut::new(self, x, y, width, height)
+    }
 }
 
 #[inherent]

src/containers/value_grid.rs

@@ -1,4 +1,4 @@
-use crate::{DataRef, Grid, GridMut, Window};
+use crate::{DataRef, Grid, GridMut, Window, WindowMut};
 use inherent::inherent;
 use std::fmt::Debug;
 use std::slice::{Iter, IterMut};
@@ -310,6 +310,32 @@ impl<T: Value> ValueGrid<T> {
             row: 0,
         }
     }
+
+    /// Creates a window into the grid.
+    ///
+    /// Returns None in case the window does not fit.
+    pub fn window(
+        &self,
+        x: usize,
+        y: usize,
+        width: usize,
+        height: usize,
+    ) -> Option<Window<T, Self>> {
+        Window::new(self, x, y, width, height)
+    }
+
+    /// Creates a mutable window into the grid.
+    ///
+    /// Returns None in case the window does not fit.
+    pub fn window_mut(
+        &mut self,
+        x: usize,
+        y: usize,
+        width: usize,
+        height: usize,
+    ) -> Option<WindowMut<T, Self>> {
+        WindowMut::new(self, x, y, width, height)
+    }
 }
 
 /// Errors that can occur when loading a grid

src/containers/window.rs

@@ -105,7 +105,7 @@ mod tests {
         let mut bitmap = Bitmap::new(8, 4).unwrap();
 
         // non-byte-aligned views work
-        let mut view = WindowMut::new(&mut bitmap, 3, 1, 4, 2).unwrap();
+        let mut view = bitmap.window_mut(3, 1, 4, 2).unwrap();
         view.fill(true);
 
         assert_eq!(bitmap.data_ref(), &[0, 30, 30, 0]);
@@ -113,7 +113,7 @@ mod tests {
         assert_eq!(bitmap.set_optional(99, 99, false), false);
 
         // full size view works
-        _ = Window::new(&mut bitmap, 0, 0, 8, 4).unwrap();
+        bitmap.window(0, 0, 8, 4).unwrap();
 
         // zero size view does not work
         assert!(Window::new(&mut bitmap, 1, 2, 3, 0).is_none());
@@ -130,12 +130,13 @@ mod tests {
         let mut grid = CharGrid::new(3, 4);
         grid.fill(' ');
 
-        let mut view = WindowMut::new(&mut grid, 1, 1, 1, 2).unwrap();
+        let mut view = WindowMut::new(&mut grid, 1, 1, 1, 3).unwrap();
         view.fill('#');
+        view.set(0,0, '!');
 
         assert_eq!(
             grid.data_ref(),
-            &[' ', ' ', ' ', ' ', '#', ' ', ' ', '#', ' ', ' ', ' ', ' ']
+            &[' ', ' ', ' ', ' ', '!', ' ', ' ', '#', ' ', ' ', '#', ' ']
         );
 
         // full size view works