🔧 Skip slow operations on fast render

frontend/src/app/render_wasm/api.cljs

@@ -883,6 +883,9 @@
 
 (defn set-view-box
   [prev-zoom zoom vbox]
+  ;; Enable fast mode at the start of pan/zoom interaction
+  ;; This will be disabled when render-finish fires (after debounce delay)
+  (h/call wasm/internal-module "_set_view_start")
   (h/call wasm/internal-module "_set_view" zoom (- (:x vbox)) (- (:y vbox)))
 
   (if (mth/close? prev-zoom zoom)

render-wasm/src/main.rs

@@ -235,9 +235,20 @@ pub extern "C" fn set_view(zoom: f32, x: f32, y: f32) {
     });
 }
 
+/// Called at the start of pan/zoom interaction to enable fast rendering mode.
+/// In fast mode, expensive operations like shadows are skipped for better performance.
+#[no_mangle]
+pub extern "C" fn set_view_start() {
+    with_state_mut!(state, {
+        state.render_state.options.set_fast_mode(true);
+    });
+}
+
 #[no_mangle]
 pub extern "C" fn set_view_end() {
     with_state_mut!(state, {
+        // Disable fast mode when interaction ends
+        state.render_state.options.set_fast_mode(false);
         // We can have renders in progress
         state.render_state.cancel_animation_frame();
         if state.render_state.options.is_profile_rebuild_tiles() {

render-wasm/src/options.rs

@@ -1,2 +1,3 @@
 pub const DEBUG_VISIBLE: u32 = 0x01;
 pub const PROFILE_REBUILD_TILES: u32 = 0x02;
+pub const FAST_MODE: u32 = 0x04;

render-wasm/src/render.rs

@@ -1479,8 +1479,11 @@ impl RenderState {
                     .surfaces
                     .get_render_context_translation(self.render_area, scale);
 
+                // Skip expensive drop shadow rendering in fast mode (during pan/zoom)
+                let skip_shadows = self.options.is_fast_mode();
+
                 // For text shapes, render drop shadow using text rendering logic
-                if !matches!(element.shape_type, Type::Text(_)) {
+                if !skip_shadows && !matches!(element.shape_type, Type::Text(_)) {
                     // Shadow rendering technique: Two-pass approach for proper opacity handling
                     //
                     // The shadow rendering uses a two-pass technique to ensure that overlapping

render-wasm/src/render/options.rs

@@ -15,6 +15,20 @@ impl RenderOptions {
         self.flags & options::PROFILE_REBUILD_TILES == options::PROFILE_REBUILD_TILES
     }
 
+    /// Fast mode is enabled during interactive pan/zoom operations.
+    /// When active, expensive operations like shadows are skipped for better performance.
+    pub fn is_fast_mode(&self) -> bool {
+        self.flags & options::FAST_MODE == options::FAST_MODE
+    }
+
+    pub fn set_fast_mode(&mut self, enabled: bool) {
+        if enabled {
+            self.flags |= options::FAST_MODE;
+        } else {
+            self.flags &= !options::FAST_MODE;
+        }
+    }
+
     pub fn dpr(&self) -> f32 {
         self.dpr.unwrap_or(1.0)
     }