render: add api for setting the rectangle on a surface

src/buffers.rs

@@ -59,6 +59,10 @@ impl Surface for BoundSurface<Rc<RefCell<ShaderBinding>>> {
     fn clear_shader(&mut self) {
         self.binding.borrow_mut().shader = None;
     }
+    
+    fn set_rect(&mut self, rect: &Rectangle<u8, Virtual>) {
+        self.binding.borrow_mut().rect = rect.clone();
+    }
 }
 
 #[cfg(feature="threads")]
@@ -132,8 +136,9 @@ impl<S: Surface + Default> SurfacePool<S> {
 }
 
 impl<S: Surface + Default> Surfaces<S> for SurfacePool<S> {
-    fn new_surface(&mut self, _area: &Rectangle<u8, Virtual>) -> Result<S, io::Error> {
-        let surface = S::default();
+    fn new_surface(&mut self, area: &Rectangle<u8, Virtual>) -> Result<S, io::Error> {
+        let mut surface = S::default();
+        surface.set_rect(area);
         self.surfaces.push(surface.clone());
         return Ok(surface);
     }

src/render.rs

@@ -22,6 +22,7 @@ pub trait Surface: Default + Clone + Debug {
     fn clear_shader(&mut self);
 
     fn rect(&self) -> Rectangle<u8, Virtual>;
+    fn set_rect(&mut self, rect: &Rectangle<u8, Virtual>);
 }
 
 pub trait Framed {