🐞 Bug Report：Deepin 25 xdg-desktop-portal FileChooser D-Bus Timeout

标题（Title）

Deepin 25: xdg-desktop-portal-dde claims default backend but does not provide FileChooser, causing D-Bus timeout and application freeze

（如果需要中文）：

Deepin 25 中 xdg-desktop-portal-dde 占用默认后端但未实现 FileChooser，导致文件对话框 D-Bus 超时与应用卡死

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系统信息（System Information）

• OS：Deepin 25
• Repository：beige / crimson
• Desktop Environment：DDE
• Architecture：amd64
• Session Type：Wayland / X11（如实填写）

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相关软件版本（Package Versions）

xdg-desktop-portal        1.20.3+ds-1
xdg-desktop-portal-dde    1.1.1
xdg-desktop-portal-gtk    1.10.0-3

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问题描述（Description）

On Deepin 25, xdg-desktop-portal-dde is selected as the default portal backend by xdg-desktop-portal.
However, the DDE portal backend does not implement the org.freedesktop.impl.portal.FileChooser interface.

As a result:

• org.freedesktop.impl.portal.FileChooser is never registered on the user D-Bus
• Any application invoking the FileChooser portal blocks on D-Bus until timeout
• Affected applications appear frozen when opening file dialogs

This affects GTK, Qt, Electron, Flatpak, and sandboxed applications.

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复现步骤（Steps to Reproduce）

1. Install Deepin 25 with default desktop (DDE)
2. Ensure the following packages are installed:

sudo apt install xdg-desktop-portal xdg-desktop-portal-dde xdg-desktop-portal-gtk

3. Log into DDE session
4. Run:

busctl --user tree org.freedesktop.impl.portal.FileChooser

实际结果（Actual Result）

• Command blocks and eventually times out:

Failed to introspect object / of service org.freedesktop.impl.portal.FileChooser: Connection timed out

• Applications freeze when opening file chooser dialogs

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期望结果（Expected Result）

• org.freedesktop.impl.portal.FileChooser should be provided by at least one backend
• File chooser dialogs should open instantly

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日志信息（Logs）

xdg-desktop-portal journal

Choosing gtk.portal for org.freedesktop.impl.portal.Lockdown as a last-resort fallback
Choosing gtk.portal for org.freedesktop.impl.portal.AppChooser as a last-resort fallback
Choosing gtk.portal for org.freedesktop.impl.portal.Print as a last-resort fallback

Indicates missing backend implementation for FileChooser

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根因分析（Root Cause Analysis）

• xdg-desktop-portal-dde is selected as the default portal backend
• The DDE backend does not implement FileChooser
• xdg-desktop-portal does not fall back to xdg-desktop-portal-gtk for FileChooser
• This results in a deadlock / timeout on D-Bus

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临时解决方案（Workaround）

Force GTK portal backend by creating:

~/.config/xdg-desktop-portal/config

[preferred]
default=gtk

Then restart user services:

systemctl --user restart xdg-desktop-portal xdg-desktop-portal-gtk

After this workaround, org.freedesktop.impl.portal.FileChooser is correctly registered and works as expected.

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建议修复方案（Suggested Fix）

One of the following:

1. Implement FileChooser in xdg-desktop-portal-dde
2. Do not advertise DDE backend as default unless it provides FileChooser
3. Automatically fall back to xdg-desktop-portal-gtk for missing interfaces

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影响范围（Impact）

• File dialogs fail or block across many applications
• Severe usability regression
• Affects default Deepin 25 installations

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附加信息（Additional Information）

This issue is reproducible on a clean Deepin 25 installation and does not require third-party software.