Improve performance for windowed rendering

src/windowed_context/plugin.rs

@@ -68,20 +68,30 @@ fn render_terminal_to_handle(
 ) {
     let width = softatui.backend().get_pixmap_width() as u32;
     let height = softatui.backend().get_pixmap_height() as u32;
-    let data = softatui.backend().get_pixmap_data_as_rgba();
 
     let image = images.get_mut(&my_handle.0).expect("Image not found");
-    *image = Image::new(
-        Extent3d {
+    if image.width() != width || image.height() != height {
+        image.resize(Extent3d {
             width,
             height,
             depth_or_array_layers: 1,
-        },
-        TextureDimension::D2,
-        data,
-        TextureFormat::Rgba8UnormSrgb,
-        RenderAssetUsages::RENDER_WORLD | RenderAssetUsages::MAIN_WORLD,
-    );
+        });
+        image.data = Some(softatui.backend().get_pixmap_data_as_rgba());
+    } else {
+        // efficient fast-path copy using chunks
+        let data_in = softatui.backend().get_pixmap_data();
+        let data_out = image.data.as_mut().expect("Image data missing");
+        let (pixels_in, _) = data_in.as_chunks::<3>();
+        let (pixels_out, _) = data_out.as_chunks_mut::<4>();
+        for i in 0..(width * height) as usize {
+            let px_out = &mut pixels_out[i];
+            let px_in = pixels_in[i];
+            px_out[0] = px_in[0];
+            px_out[1] = px_in[1];
+            px_out[2] = px_in[2];
+            // skip writing alpha as it is set to 255 by get_pixmap_data_as_rgba
+        }
+    }
 }
 
 /// System that reacts to window resize