[Question] Destroying the window takes EXTREAMLY long time!

[CreeperIsASpy]

Question

setattr(page.window, "minimized", True)
setattr(page.window, "maximized", True)
page.window.destroy()

All these three expressions are EXTREMELY SLOW!
They take nearly 5 seconds to in the program below.

Btw, English is not my first language 😄.

Code sample

import flet as ft


def main(page: ft.Page):
    page.title = "性能测试"

    def close_app(e):
        page.window.destroy()

    page.add(ft.FilledButton("立即关闭", on_click=close_app))
    page.update()


ft.app(target=main)

Environment Information

PS D:\Programming\MGHClient> uv pip show flet
Name: flet
Version: 0.28.3
Location: D:\Programming\MGHClient\.venv\Lib\site-packages
Requires: httpx, oauthlib, repath
Required-by: flet-cli, flet-desktop, flet-web
PS D:\Programming\MGHClient> systeminfo

主机名:           ITX-03
OS 名称:          Microsoft Windows 11 专业工作站版
OS 版本:          10.0.22621 暂缺 Build 22621
OS 制造商:        Microsoft Corporation
OS 配置:          独立工作站
OS 构建类型:      Multiprocessor Free
注册的所有人:     Ext1nguisher
注册的组织:       暂缺
产品 ID:          00391-70000-00000-AA223
初始安装日期:     2025/8/17, 15:25:18
系统启动时间:     2025/8/27, 9:24:01
系统制造商:       Micro-Star International Co., Ltd.
系统型号:         MS-7D73
系统类型:         x64-based PC
处理器:           安装了 1 个处理器。
                  [01]: AMD64 Family 26 Model 68 Stepping 0 AuthenticAMD ~3800 Mhz
BIOS 版本:        American Megatrends International, LLC. 1.H0, 2025/3/12
Windows 目录:     C:\Windows
系统目录:         C:\Windows\system32
启动设备:         \Device\HarddiskVolume1
系统区域设置:     zh-cn;中文(中国)
输入法区域设置:   zh-cn;中文(中国)
时区:             (UTC+08:00) 北京，重庆，香港特别行政区，乌鲁木齐
物理内存总量:     48,233 MB
可用的物理内存:   37,784 MB
虚拟内存: 最大值: 51,305 MB
虚拟内存: 可用:   37,044 MB
虚拟内存: 使用中: 14,261 MB
页面文件位置:     C:\pagefile.sys
域:               WORKGROUP
登录服务器:       \\ITX-03
修补程序:         安装了 4 个修补程序。
                  [01]: KB5017026
                  [02]: KB5012170
                  [03]: KB5044285
                  [04]: KB5046247
网卡:             安装了 3 个 NIC。
                  [01]: Realtek Gaming 2.5GbE Family Controller
                      连接名:      以太网
                      启用 DHCP:   是
                      DHCP 服务器: 192.168.71.1
                      IP 地址
                        [01]: 192.168.71.16
                        [02]: fe80::3c2a:4daa:c78e:4cd4
                        [03]: 240e:b8f:bdc5:3100:55a:1bcf:51f1:3791
                        [04]: 240e:b8f:bdc5:3100:e103:7f00:3584:e65f
                  [02]: Bluetooth Device (Personal Area Network)
                      连接名:      蓝牙网络连接
                      状态:        媒体连接已中断
                  [03]: RZ616 Wi-Fi 6E 160MHz
                      连接名:      WLAN
                      状态:        媒体连接已中断
Hyper-V 要求:     虚拟机监视器模式扩展: 是
                  固件中已启用虚拟化: 是
                  二级地址转换: 是
                  数据执行保护可用: 是
PS D:\Programming\MGHClient> python --version
Python 3.11.2

------------------------------------------------------

• I have searched for answers to my question both in the issues and in previous discussions.

[CreeperIsASpy]

Major Update: I have captured a debug log that pinpoints the exact location of the delay!

I enabled debug logging (logging.basicConfig(level=logging.DEBUG)) and captured the following output when clicking the close button.

The Key Finding:
The delay occurs after the Python script receives the app_lifecycle_state_change: inactive event from fletd, and before the script proceeds to close the connection and shut down the thread pool. The hang happens right at the process cleanup stage.

Here is the relevant part of the log:

Details

DEBUG:asyncio:Using proactor: IocpProactor
INFO:flet:Assets path configured: D:\Programming\MGHClient\assets
DEBUG:flet:Creating new PubSubHub instance
DEBUG:flet:Creating new PubSubHub instance
INFO:flet:Starting up TCP server on localhost:58859
INFO:flet:Flet app has started...
INFO:flet:App URL: tcp://localhost:58859
INFO:flet_desktop:Starting Flet View app...
INFO:flet_desktop:Looking for Flet executable at: D:\Programming\MGHClient\.venv\Lib\site-packages\flet_desktop\app\flet\flet.exe
INFO:flet_desktop:Flet View found in: D:\Programming\MGHClient\.venv\Lib\site-packages\flet_desktop\app\flet\flet.exe
DEBUG:flet:Connected new TCP client
DEBUG:flet:_on_message: {"action":"registerWebClient","payload":{"pageName":"","pageRoute":"/","pageWidth":"1264.0","pageHeight":"681.0","windowWidth":"1280.0","windowHeight":"720.0","windowTop":"10.0","windowLeft":"10.0","isPWA":"false","isWeb":"false","isDebug":"false","platform":"windows","platformBrightness":"dark","media":"{\"padding\":{\"top\":0.0,\"right\":0.0,\"bottom\":0.0,\"left\":0.0},\"view_padding\":{\"top\":0.0,\"right\":0.0,\"bottom\":0.0,\"left\":0.0},\"view_insets\":{\"top\":0.0,\"right\":0.0,\"bottom\":0.0,\"left\":0.0}}","sessionId":""}}
DEBUG:flet:__send: {"action":"registerWebClient","payload":{"session":{"id":"","controls":{"page":{"i":"page","t":"page","p":"","c":[],"route":"/","width":"1264.0","height":"681.0","windowwidth":"1280.0","windowheight":"720.0","windowtop":"10.0","windowleft":"10.0","pwa":"false","web":"false","debug":"false","platform":"windows","platformBrightness":"dark","media":"{\"padding\":{\"top\":0.0,\"right\":0.0,\"bottom\":0.0,\"left\":0.0},\"view_padding\":{\"top\":0.0,\"right\":0.0,\"bottom\":0.0,\"left\":0.0},\"view_insets\":{\"top\":0.0,\"right\":0.0,\"bottom\":0.0,\"left\":0.0}}"}}},"error":"","appInactive":false}}
DEBUG:flet:_process_command: get ['page', 'route'] {}
DEBUG:flet:_process_command: get ['page', 'pwa'] {}
DEBUG:flet:_process_command: get ['page', 'web'] {}
DEBUG:flet:_process_command: get ['page', 'debug'] {}
DEBUG:flet:_process_command: get ['page', 'platform'] {}
DEBUG:flet:_process_command: get ['page', 'platformBrightness'] {}
DEBUG:flet:_process_command: get ['page', 'media'] {}
DEBUG:flet:_process_command: get ['page', 'width'] {}
DEBUG:flet:_process_command: get ['page', 'height'] {}
DEBUG:flet:_process_command: get ['page', 'windowWidth'] {}
DEBUG:flet:_process_command: get ['page', 'windowHeight'] {}
DEBUG:flet:_process_command: get ['page', 'windowTop'] {}
DEBUG:flet:_process_command: get ['page', 'windowLeft'] {}
DEBUG:flet:_process_command: get ['page', 'clientIP'] {}
DEBUG:flet:_process_command: get ['page', 'clientUserAgent'] {}
INFO:flet:App session started
DEBUG:flet:_process_command: set ['page'] {'title': '性能测试'}
DEBUG:flet:_process_command: add [] {'to': 'page', 'at': '0'}
DEBUG:flet:_process_command: add [] {'to': 'page', 'at': '1'}
DEBUG:flet:__send: {"action":"pageControlsBatch","payload":[{"action":"updateControlProps","payload":{"props":[{"i":"page","title":"\u6027\u80fd\u6d4b\u8bd5"}]}},{"action":"addPageControls","payload":{"controls":[{"t":"view","i":"_1","p":"page","c":["_2"],"at":"0"},{"t":"filledbutton","i":"_2","p":"_1","c":[],"style":"{\"padding\":{},\"side\":{},\"shape\":{},\"text_style\":{}}","text":"\u7acb\u5373\u5173\u95ed"}],"trimIDs":[]}},{"action":"addPageControls","payload":{"controls":[{"t":"offstage","i":"_3","p":"page","c":[],"at":"1"}],"trimIDs":[]}}]}
DEBUG:flet:sent to TCP: 604
DEBUG:flet:sent to TCP: 538
DEBUG:flet:_on_message: {"action":"pageEventFromWeb","payload":{"eventTarget":"_2","eventName":"click","eventData":null}}
DEBUG:flet:page.on_event_async: _2 click None
INFO:__main__:The button was pressed! This is a manual message!!!
DEBUG:flet:_process_command: set ['page'] {'windowdestroy': 'true'}
DEBUG:flet:__send: {"action":"pageControlsBatch","payload":[{"action":"updateControlProps","payload":{"props":[{"i":"page","windowdestroy":"true"}]}}]}
DEBUG:flet:sent to TCP: 136
DEBUG:flet:_on_message: {"action":"pageEventFromWeb","payload":{"eventTarget":"page","eventName":"app_lifecycle_state_change","eventData":"inactive"}}
DEBUG:flet:page.on_event_async: page app_lifecycle_state_change inactive
DEBUG:flet_desktop:Flet View process 17788
DEBUG:flet:Closing connection...
DEBUG:flet:Disconnecting all pages...
DEBUG:flet:page.on_event_async: page disconnect 
DEBUG:flet:Shutting down thread pool...

As you can see, the Python script sends the windowdestroy command, receives the inactive event back, and then hangs for 5-30 seconds before it continues to the final cleanup steps (Closing connection..., Shutting down thread pool...).

This confirms that the issue is not in sending the command, but in the final handshake or process termination step between the Python script and the fletd process on my specific Windows 11 environment.

[CreeperIsASpy]

okay, using page.window.close() instead of page.window.destroy() solved the problem 😄.