From 08fc32cdc6eff18ff2db6d9c30cfa9c1a91f2bee Mon Sep 17 00:00:00 2001
From: Aitor Moreno <asakon28@gmail.com>
Date: Tue, 25 Mar 2025 16:39:45 +0100
Subject: [PATCH] :tada: Cache extra tiles

---
 render-wasm/src/render.rs       | 17 +++++++----------
 render-wasm/src/render/tiles.rs |  8 ++++++++
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/render-wasm/src/render.rs b/render-wasm/src/render.rs
index ca0068177..0a1f77573 100644
--- a/render-wasm/src/render.rs
+++ b/render-wasm/src/render.rs
@@ -28,6 +28,8 @@ pub use blend::BlendMode;
 pub use fonts::*;
 pub use images::*;
 
+// This is the extra are used for tile rendering.
+const VIEWPORT_INTEREST_AREA_THRESHOLD: i32 = 1;
 const MAX_BLOCKING_TIME_MS: i32 = 32;
 const NODE_BATCH_THRESHOLD: i32 = 10;
 
@@ -449,17 +451,12 @@ impl RenderState {
             },
         );
 
-        let (sx, sy, ex, ey) = tiles::get_tiles_for_viewbox(self.viewbox);
+        // TODO: Maybe we should calculate the interest area based on the actual viewport. See how.
+        let (sx, sy, ex, ey) = tiles::get_tiles_for_viewbox_with_interest(
+            self.viewbox,
+            VIEWPORT_INTEREST_AREA_THRESHOLD,
+        );
         debug::render_debug_tiles_for_viewbox(self, sx, sy, ex, ey);
-        /*
-        // TODO: Instead of rendering only the visible area
-        // we could apply an offset to the viewbox to render
-        // more tiles.
-        sx - interest_delta
-        sy - interest_delta
-        ex + interest_delta
-        ey + interest_delta
-        */
         let tile_center = ((ex - sx) / 2, (ey - sy) / 2);
         self.pending_tiles = vec![];
         self.surfaces.cache_clear_visited();
diff --git a/render-wasm/src/render/tiles.rs b/render-wasm/src/render/tiles.rs
index 0062e6ba3..4cf401045 100644
--- a/render-wasm/src/render/tiles.rs
+++ b/render-wasm/src/render/tiles.rs
@@ -33,6 +33,14 @@ pub fn get_tiles_for_viewbox(viewbox: Viewbox) -> (i32, i32, i32, i32) {
     get_tiles_for_rect(viewbox.area, tile_size)
 }
 
+pub fn get_tiles_for_viewbox_with_interest(
+    viewbox: Viewbox,
+    interest: i32,
+) -> (i32, i32, i32, i32) {
+    let (sx, sy, ex, ey) = get_tiles_for_viewbox(viewbox);
+    (sx - interest, sy - interest, ex + interest, ey + interest)
+}
+
 pub fn get_tile_pos(viewbox: Viewbox, (x, y): Tile) -> (f32, f32) {
     (
         x as f32 * get_tile_size(viewbox),