fix: prevent crash in SurfaceListModel::data when accessing childItem…

[zorowk]

fix: surface guard against null container in SurfaceListModel::data

SurfaceListModel::data() may be queried before a SurfaceWrapper
is fully attached to a workspace container.

After application startup, ShellHandler::matchOrCreateXdgWrapper()
and ShellHandler::matchOrCreateXwaylandWrapper() add wrappers into
the workspace. At this stage, Workspace::addSurface() is called
with surface->container() still unset, which is expected and
asserted by:

Q_ASSERT(surface && !surface->container());

However, QML may access SurfaceListModel and request
Qt::InitialSortOrderRole before the container is initialized.
This leads to a null pointer dereference when accessing
container->childItems().

Fix this by explicitly checking for a null container in
SurfaceListModel::data() and returning an invalid QVariant
until the surface is fully initialized.

This prevents crashes during early QML evaluation while keeping
the existing initialization order unchanged.

issue: #659
comment: #659 (comment)

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: zorowk

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[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Adds defensive null checks in SurfaceListModel::data for the InitialSortOrderRole to avoid dereferencing incompletely initialized QQuickItem instances, and falls back to INT_MAX as the sort order for surfaces whose parent/container is not yet ready.

Class diagram for updated SurfaceListModel::data null-check behavior

classDiagram
    class SurfaceListModel {
        +data(index QModelIndex, role int) QVariant
        +surfaces() QList~Surface*~
    }

    class Surface {
        +parentItem() QQuickItem*
        +container() QQuickItem*
    }

    class QQuickItem {
        +childItems() QList~QQuickItem*~
    }

    class QModelIndex
    class QVariant

    SurfaceListModel --> Surface : uses
    Surface --> QQuickItem : parentItem
    Surface --> QQuickItem : container
    QQuickItem --> QQuickItem : childItems
    SurfaceListModel --> QModelIndex : parameter
    SurfaceListModel --> QVariant : return type

Loading

File-Level Changes

Change	Details	Files
Harden SurfaceListModel::data against partially initialized surfaces when computing InitialSortOrderRole, falling back to a max-int sort order for unparented/uncontained items.	Guard access to surface->parentItem() and return INT_MAX when the parent item is null. Guard access to surface->container() and return INT_MAX when the container is null. Keep using container->childItems().indexOf(surface) to derive the sort index, asserting the index is non-negative for valid cases.	src/surface/surfacecontainer.cpp

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[sourcery-ai]

Hey - I've left some high level feedback:

• Instead of returning the magic value INT_MAX in multiple places, consider defining a named constant (e.g. kUnreadySurfaceSortOrder) or using std::numeric_limits::max() to improve readability and type safety.
• Given that container->childItems().indexOf(surface) can theoretically return -1 even after your null checks, it may be safer to replace the Q_ASSERT with a conditional that also falls back to the default sort order rather than crashing in release builds.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Instead of returning the magic value INT_MAX in multiple places, consider defining a named constant (e.g. kUnreadySurfaceSortOrder) or using std::numeric_limits<int>::max() to improve readability and type safety.
- Given that container->childItems().indexOf(surface) can theoretically return -1 even after your null checks, it may be safer to replace the Q_ASSERT with a conditional that also falls back to the default sort order rather than crashing in release builds.

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[zorowk]

打开应用之后 ShellHandler::matchOrCreateXdgWrapper 和ShellHandler::matchOrCreateXwaylandWrapper 会添加wrapper到workspace中

void Workspace::addSurface(SurfaceWrapper *surface, int workspaceId)
{
Q_ASSERT(surface && !surface->container() && surface->workspaceId() == -1);

此时的surface->container 还未初始化是空指针

后续qml读取了surfacelistmodel中的数据导致崩溃

[Copilot]

Pull request overview

This PR addresses a crash in SurfaceListModel::data that occurs when accessing childItems() on surfaces that have not yet been fully initialized in the scene graph. The fix adds a null check for the container before dereferencing it.

Key Changes:

• Added null check for surface->container() in the data method to prevent dereferencing null containers
• Returns an empty QVariant() when container is null as a fallback

[wineee]

#671 可能是同一个问题

[zorowk]

#671 可能是同一个问题

确实可以 如果将workspace model添加surface调整到container初始化后