Fix date pickers not showing date when initially rendered in a hidden container

CHANGELOG.md

@@ -2,6 +2,12 @@
 All notable changes to `dash` will be documented in this file.
 This project adheres to [Semantic Versioning](https://semver.org/).
 
+## [UNRELEASED]
+
+## Fixed
+- [#3629](https://github.com/plotly/dash/pull/3629) Fix date pickers not showing date when initially rendered in a hidden container.
+
+
 ## [4.0.0] - 2026-02-03
 
 ## Added

components/dash-core-components/src/fragments/DatePickerRange.tsx

@@ -20,6 +20,7 @@ import {
     strAsDate,
 } from '../utils/calendar/helpers';
 import {captureCSSForPortal} from '../utils/calendar/cssVariables';
+import ResizeDetector from '../utils/ResizeDetector';
 import '../components/css/datepickers.css';
 
 const DatePickerRange = ({
@@ -104,6 +105,8 @@ const DatePickerRange = ({
     const containerRef = useRef<HTMLDivElement>(null);
     const startInputRef = useRef<HTMLInputElement | null>(null);
     const endInputRef = useRef<HTMLInputElement | null>(null);
+    const startAutosizeRef = useRef<any>(null);
+    const endAutosizeRef = useRef<any>(null);
     const calendarRef = useRef<CalendarHandle>(null);
     const hasPortal = with_portal || with_full_screen_portal;
 
@@ -128,6 +131,19 @@ const DatePickerRange = ({
         setEndInputValue(formatDate(internalEndDate, display_format));
     }, [internalEndDate, display_format]);
 
+    const handleResize = useCallback(() => {
+        startAutosizeRef.current?.updateInputWidth?.();
+        endAutosizeRef.current?.updateInputWidth?.();
+    }, []);
+
+    useEffect(() => {
+        startAutosizeRef.current?.updateInputWidth?.();
+    }, [startInputValue]);
+
+    useEffect(() => {
+        endAutosizeRef.current?.updateInputWidth?.();
+    }, [endInputValue]);
+
     useEffect(() => {
         // Controls when setProps is called. Basically, whenever internal state
         // diverges from props (i.e., user interaction)
@@ -313,6 +329,10 @@ const DatePickerRange = ({
     );
 
     return (
+        <ResizeDetector
+            onResize={handleResize}
+            targets={[containerRef]}
+        >
         <div className="dash-datepicker" ref={containerRef}>
             <Popover.Root
                 open={!disabled && isCalendarOpen}
@@ -335,6 +355,7 @@ const DatePickerRange = ({
                         }}
                     >
                         <AutosizeInput
+                            ref={startAutosizeRef}
                             inputRef={node => {
                                 startInputRef.current = node;
                             }}
@@ -356,6 +377,7 @@ const DatePickerRange = ({
                         />
                         <ArrowIcon className="dash-datepicker-range-arrow" />
                         <AutosizeInput
+                            ref={endAutosizeRef}
                             inputRef={node => {
                                 endInputRef.current = node;
                             }}
@@ -458,6 +480,7 @@ const DatePickerRange = ({
                 </Popover.Portal>
             </Popover.Root>
         </div>
+        </ResizeDetector>
     );
 };
 

components/dash-core-components/src/fragments/DatePickerSingle.tsx

@@ -14,6 +14,7 @@ import {
     strAsDate,
 } from '../utils/calendar/helpers';
 import {captureCSSForPortal} from '../utils/calendar/cssVariables';
+import ResizeDetector from '../utils/ResizeDetector';
 import '../components/css/datepickers.css';
 
 const DatePickerSingle = ({
@@ -63,6 +64,7 @@ const DatePickerSingle = ({
 
     const containerRef = useRef<HTMLDivElement>(null);
     const inputRef = useRef<HTMLInputElement | null>(null);
+    const autosizeRef = useRef<any>(null);
     const calendarRef = useRef<CalendarHandle>(null);
     const hasPortal = with_portal || with_full_screen_portal;
 
@@ -87,6 +89,15 @@ const DatePickerSingle = ({
         }
     }, [internalDate]);
 
+    const handleResize = useCallback(() => {
+        autosizeRef.current?.updateInputWidth?.();
+    }, []);
+
+
+    useEffect(() => {
+        autosizeRef.current?.updateInputWidth?.();
+    }, [inputValue]);
+
     const parseUserInput = useCallback(
         (focusCalendar = false) => {
             if (inputValue === '') {
@@ -157,6 +168,7 @@ const DatePickerSingle = ({
     }
 
     return (
+        <ResizeDetector onResize={handleResize} targets={[containerRef]}>
         <div className="dash-datepicker" ref={containerRef}>
             <Popover.Root
                 open={!disabled && isCalendarOpen}
@@ -179,6 +191,7 @@ const DatePickerSingle = ({
                         }}
                     >
                         <AutosizeInput
+                            ref={autosizeRef}
                             inputRef={node => {
                                 inputRef.current = node;
                             }}
@@ -274,6 +287,7 @@ const DatePickerSingle = ({
                 </Popover.Portal>
             </Popover.Root>
         </div>
+        </ResizeDetector>
     );
 };
 

components/dash-core-components/tests/integration/calendar/test_date_picker_single.py

@@ -676,3 +676,43 @@ def display_date(date):
     ), "Input should display 2021-06-23"
 
     assert dash_dcc.get_logs() == []
+
+
+def test_dtps031_resize_detector(dash_dcc):
+    """Test that DatePickerSingle displays date if initially rendered in hidden container"""
+    app = Dash(__name__)
+    app.layout = html.Div(
+        [
+            html.Button("Unhide", id="update-btn"),
+            html.Div(
+                id="hidden",
+                style={"display": "none"},
+                children=dcc.DatePickerSingle(date="2026-02-24", id="dps"),
+            ),
+        ]
+    )
+
+    @app.callback(
+        Output("hidden", "style"),
+        Input("update-btn", "n_clicks"),
+        prevent_initial_call=True,
+    )
+    def update_date(n_clicks):
+        return {}
+
+    dash_dcc.start_server(app)
+
+    input_element = dash_dcc.find_element(".dash-datepicker-input")
+    initial_style = input_element.get_attribute("style")
+    assert "width: 2px;" in initial_style
+
+    # Click button to unhide
+    btn = dash_dcc.find_element("#update-btn")
+    btn.click()
+    time.sleep(0.5)
+
+    updated_style = input_element.get_attribute("style")
+
+    assert "width: 77px;" in updated_style
+
+    assert dash_dcc.get_logs() == []