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, 3 insertions, 1 deletions

diff --git a/src/main.rs b/src/main.rs
index fbf1eaca..aaa20953 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -361,8 +361,10 @@ impl Display {
 
                 let size_info = terminal.size_info().clone();
                 self.renderer.with_api(&size_info, |mut api| {
+                    api.clear();
+
                     // Draw the grid
-                    api.render_grid(&terminal.render_grid(), glyph_cache);
+                    api.render_grid(terminal.renderable_cells(), glyph_cache);
                 });
             }