Only draw when terminal state has changed

This is achieved by setting a `dirty` flag when the terminal receives
an event that causes visible state to change. The implementation is
pretty much crap because most methods know about the flag.

Figure out something better later.

1 files changed, 20 insertions, 16 deletions

diff --git a/src/main.rs b/src/main.rs
index 98daddf1..fd22b304 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -193,26 +193,30 @@ fn main() {
             gl::Clear(gl::COLOR_BUFFER_BIT);
         }
 
-        {
-            let _sampler = meter.sampler();
+        if terminal.dirty() {
+            {
+                let _sampler = meter.sampler();
 
-            renderer.with_api(&props, |mut api| {
-                // Draw the grid
-                api.render_grid(terminal.grid(), &mut glyph_cache);
+                renderer.with_api(&props, |mut api| {
+                    // Draw the grid
+                    api.render_grid(terminal.grid(), &mut glyph_cache);
 
-                // Also draw the cursor
-                api.render_cursor(terminal.cursor(), &mut glyph_cache);
-            })
-        }
+                    // Also draw the cursor
+                    api.render_cursor(terminal.cursor(), &mut glyph_cache);
+                })
+            }
 
-        // Draw render timer
-        let timing = format!("{:.3} usec", meter.average());
-        let color = Rgb { r: 0xd5, g: 0x4e, b: 0x53 };
-        renderer.with_api(&props, |mut api| {
-            api.render_string(&timing[..], &mut glyph_cache, &color);
-        });
+            // Draw render timer
+            let timing = format!("{:.3} usec", meter.average());
+            let color = Rgb { r: 0xd5, g: 0x4e, b: 0x53 };
+            renderer.with_api(&props, |mut api| {
+                api.render_string(&timing[..], &mut glyph_cache, &color);
+            });
+
+            terminal.clear_dirty();
 
-        window.swap_buffers().unwrap();
+            window.swap_buffers().unwrap();
+        }
     }
 
     // TODO handle child cleanup