Refactor cell selection out of renderer

The terminal now has a `renderable_cells()` function that returns a
`RenderableCellIter` iterator. This allows reuse of the cell selection
code by multiple renderers, makes it testable, and makes it
independently optimizable.

The render API now takes an `Iterator<Item=IndexedCell>` to support both
the new renderable cells iterator and the `render_string()` method which
generates its own iterator.

The `vim_large_window_scoll` ref test was added here because it provides
a nice large and busy grid to benchmark the cell selection with.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/meter.rs b/src/meter.rs
index b73c1004..b4bab5ff 100644
--- a/src/meter.rs
+++ b/src/meter.rs
@@ -33,7 +33,7 @@
 
 use std::time::{Instant, Duration};
 
-const NUM_SAMPLES: usize = 60;
+const NUM_SAMPLES: usize = 10;
 
 /// The meter
 pub struct Meter {