From a948e49e51cb4e751480730bb47f7853aecbb810 Mon Sep 17 00:00:00 2001
From: Alejandro Alonso <alejandroalonsofernandez@gmail.com>
Date: Tue, 30 Dec 2025 09:25:29 +0100
Subject: [PATCH] :bug: Fix using cache on first zoom after pan

---
 render-wasm/src/main.rs            |  8 ++++++++
 render-wasm/src/render.rs          | 11 +++++++++++
 render-wasm/src/render/surfaces.rs |  4 ++++
 render-wasm/src/state.rs           |  4 ++++
 4 files changed, 27 insertions(+)

diff --git a/render-wasm/src/main.rs b/render-wasm/src/main.rs
index c519e27b6a..9d4ff41617 100644
--- a/render-wasm/src/main.rs
+++ b/render-wasm/src/main.rs
@@ -275,6 +275,14 @@ pub extern "C" fn set_view_end() {
             }
             performance::end_measure!("set_view_end::rebuild_tiles");
             performance::end_timed_log!("rebuild_tiles", _rebuild_start);
+        } else {
+            // During pan, we only clear the tile index without
+            // invalidating cached textures, which is more efficient.
+            let _clear_start = performance::begin_timed_log!("clear_tile_index");
+            performance::begin_measure!("set_view_end::clear_tile_index");
+            state.clear_tile_index();
+            performance::end_measure!("set_view_end::clear_tile_index");
+            performance::end_timed_log!("clear_tile_index", _clear_start);
         }
         performance::end_measure!("set_view_end");
         performance::end_timed_log!("set_view_end", _end_start);
diff --git a/render-wasm/src/render.rs b/render-wasm/src/render.rs
index e74e59d516..a0763e6d40 100644
--- a/render-wasm/src/render.rs
+++ b/render-wasm/src/render.rs
@@ -1962,6 +1962,17 @@ impl RenderState {
         performance::end_measure!("rebuild_tiles_shallow");
     }
 
+    /// Clears the tile index without invalidating cached tile textures.
+    /// This is useful when tile positions don't change (e.g., during pan operations)
+    /// but the tile index needs to be synchronized. The cached tile textures remain
+    /// valid since they don't depend on the current view position, only on zoom level.
+    /// This is much more efficient than clearing the entire cache surface.
+    pub fn clear_tile_index(&mut self) {
+        performance::begin_measure!("clear_tile_index");
+        self.surfaces.clear_tiles();
+        performance::end_measure!("clear_tile_index");
+    }
+
     pub fn rebuild_tiles_from(&mut self, tree: ShapesPoolRef, base_id: Option<&Uuid>) {
         performance::begin_measure!("rebuild_tiles");
 
diff --git a/render-wasm/src/render/surfaces.rs b/render-wasm/src/render/surfaces.rs
index 845410a577..fe0edbb455 100644
--- a/render-wasm/src/render/surfaces.rs
+++ b/render-wasm/src/render/surfaces.rs
@@ -108,6 +108,10 @@ impl Surfaces {
         }
     }
 
+    pub fn clear_tiles(&mut self) {
+        self.tiles.clear();
+    }
+
     pub fn resize(&mut self, gpu_state: &mut GpuState, new_width: i32, new_height: i32) {
         self.reset_from_target(gpu_state.create_target_surface(new_width, new_height));
     }
diff --git a/render-wasm/src/state.rs b/render-wasm/src/state.rs
index 5e48cea05e..40b272007c 100644
--- a/render-wasm/src/state.rs
+++ b/render-wasm/src/state.rs
@@ -197,6 +197,10 @@ impl<'a> State<'a> {
         self.render_state.rebuild_tiles_shallow(&self.shapes);
     }
 
+    pub fn clear_tile_index(&mut self) {
+        self.render_state.clear_tile_index();
+    }
+
     pub fn rebuild_tiles(&mut self) {
         self.render_state.rebuild_tiles_from(&self.shapes, None);
     }