feat: Implement a cancel button on the loading overlay to allow users to stop data fetching.

server.R

@@ -488,6 +488,9 @@ server <- function(input, output, session) {
 
     reset_fetch <- function(msg = NULL) {
         fetch_stage(0)
+        # Invalidate token to kill pending async tasks
+        fetch_current_token(as.numeric(Sys.time()))
+
         loading_status(FALSE)
         if (!is.null(msg)) loading_diagnostics(msg)
         tmp <- fetch_temp_file()
@@ -498,6 +501,11 @@ server <- function(input, output, session) {
         session$sendCustomMessage("unfreezeUI", list())
     }
 
+    # Handle Cancel from Freeze Window
+    observeEvent(input$cancel_loading, {
+        reset_fetch("Cancelled by user")
+    })
+
     # Stage 1: Initialization
     observe({
         req(window_debounced()$id, window_debounced()$start, window_debounced()$end)

ui.R

@@ -28,6 +28,7 @@ ui <- page_navbar(
         justify-content: center;
       }
       .frozen-overlay-content {
+        position: relative;
         background: white;
         width: 400px;
         min-height: 200px;
@@ -50,6 +51,20 @@ ui <- page_navbar(
         font-size: 1.1rem;
         color: #333;
       }
+      .frozen-overlay-close {
+        position: absolute;
+        top: 10px;
+        right: 15px;
+        border: none;
+        background: none;
+        font-size: 1.5rem;
+        color: #666;
+        cursor: pointer;
+        line-height: 1;
+      }
+      .frozen-overlay-close:hover {
+        color: #000;
+      }
       /* Disable pointer events on sidebar when frozen */
       body.ui-frozen .bslib-sidebar-layout > .sidebar {
         pointer-events: none;
@@ -127,6 +142,11 @@ ui <- page_navbar(
         $(document).on('hidden.bs.modal', '.modal', function () {
           Shiny.setInputValue('modal_closed', new Date().getTime(), {priority: 'event'});
         });
+
+        // Handle freeze window close
+        $(document).on('click', '.frozen-overlay-close', function () {
+          Shiny.setInputValue('cancel_loading', new Date().getTime(), {priority: 'event'});
+        });
       });
 
       function toggleFullScreen() {
@@ -159,6 +179,7 @@ ui <- page_navbar(
       class = "frozen-overlay",
       div(
         class = "frozen-overlay-content",
+        tags$button(class = "frozen-overlay-close", "×", title = "Cancel loading"),
         div(class = "spinner-border text-primary", role = "status"),
         p(class = "frozen-overlay-message", "Loading data...")
       )