fix(DockView): restore a re-shown group's size only when collapsed to its minimum

[zhaijunlei955]

#Issues
close #1052

Follow-up to #1047, which restored a re-opened group's width unconditionally and never restored height. In a left/right + nested (top/bottom) layout, re-showing a previously-closed group could then misbehave:

Problem

• The opposite side goes blank: re-showing a group re-applied its stale saved width and shrank it; the freed space went to a sibling region that had no visible groups, so that whole side rendered blank (no content, though still draggable/operable).
• Or the sibling gets squeezed to ~100px when the stale saved width was larger than the group's current width.
• Vertical groups stuck at ~100px: groups in a top/bottom split came back at the minimum because height was never restored at all.

Fix

Restore a saved dimension (width and height) only when the group is actually collapsed to its minimum (offset <= group.minimum + 2); if the layout already gave it a real size, keep it.

.dv-view is an unstyled absolute wrapper, so its offset size equals the splitview size exactly — at collapse that is the group's minimum, making the check reliable.

Known limitation

Deleting both groups of one side in sequence then re-adding them can still squeeze one (the later-deleted group captured the full size while alone). Inherent to storing absolute sizes at delete time; a proportional / redistribute-on-re-add fix is deferred.

Summary by Sourcery

Adjust DockView group size restoration when re-showing previously closed groups to avoid layout issues in nested grid splits.

Bug Fixes:

• Restore both width and height of re-shown groups only when they were previously collapsed to their minimum size, preventing sibling regions from being squeezed or rendered blank.
• Ensure pending size state is cleared after a conditional size restore so future visibility changes do not replay stale dimensions.

Enhancements:

• Add conditional logic for initial width and height when reusing empty grid groups based on current container size and group minimums.

[bb-auto]

Thanks for your PR, @zhaijunlei955. Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Adjusts how DockView restores panel group sizes when re-showing a previously deleted group, restoring saved width/height only when the placeholder group is actually collapsed to its minimum size and clearing pending sizes after use.

Sequence diagram for restoring DockView group size on re-show

sequenceDiagram
    participant DockView as dockview
    participant Group as group
    participant Panel as panel
    participant Parent as group_parent_element

    DockView->>Group: addPanelWidthGroupId(dockview, panel, index)
    Note over Group,Panel: reusedEmptyGroup && group.api.location.type === grid
    Group->>Parent: read offsetWidth, offsetHeight
    Group->>Panel: read params.currentPosition (cp.width, cp.height)
    alt [parent collapsed to minimum]
        Group->>DockView: set initialWidth = cp.width (if width > offsetWidth && offsetWidth <= minimumWidth + 2)
        Group->>DockView: set initialHeight = cp.height (if height > offsetHeight && offsetHeight <= minimumHeight + 2)
    else [parent has real size]
        Group->>DockView: leave initialWidth, initialHeight undefined
    end
    DockView->>Group: addPanel({ initialWidth, initialHeight, ... })
    Group->>Group: reRenderActionStates(group)
    Group->>Group: group.api._pendingSize = undefined (if initialWidth > 0 || initialHeight > 0)

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Flow diagram for conditional restoration of DockView group width/height

flowchart TD
    A[reusedEmptyGroup && location.type === grid && parentElement exists] --> B[get cp.width, cp.height]
    B --> C[get parent offsetWidth, offsetHeight]
    C --> D{offsetWidth <= minimumWidth + 2\nand cp.width > offsetWidth}
    D -->|yes| E[initialWidth = cp.width]
    D -->|no| F[initialWidth undefined]
    C --> G{offsetHeight <= minimumHeight + 2\nand cp.height > offsetHeight}
    G -->|yes| H[initialHeight = cp.height]
    G -->|no| I[initialHeight undefined]
    E --> J[call dockview.addPanel with initialWidth/initialHeight]
    F --> J
    H --> J
    I --> J
    J --> K{initialWidth > 0 or initialHeight > 0}
    K -->|yes| L[group.api._pendingSize = undefined]
    K -->|no| M[leave _pendingSize unchanged]

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File-Level Changes

Change	Details	Files
Restore saved width and height for reused grid groups only when the placeholder is collapsed to its minimum size, and clear pending sizes after the restore.	Replace single restoreWidth calculation with logic that conditionally sets initialWidth and initialHeight based on the parent element’s offset size and the group’s minimum size thresholds. Use both initialWidth and initialHeight when adding a panel to a reused empty group, instead of restoring width unconditionally. Update the post-restore cleanup to clear group.api._pendingSize when either width or height was restored, so stale sizes are not replayed later.	src/components/BootstrapBlazor.DockView/wwwroot/js/dockview-group.js

Possibly linked issues

• #fix(DockView): PR implements a key correctness fix for DockView group reinsert/visibility, restoring size only for collapsed groups.
• fix(DockView): correctness fixes for group delete/re-insert, float and dock-back #1048: PR changes conditional size restoration for re-shown groups, fixing the left/right panel width misbehavior reported.

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[sourcery-ai]

Hey - I've left some high level feedback:

• The + 2 tolerance when comparing offsetWidth/offsetHeight to minimumWidth/Height is a bit opaque; consider extracting this into a named constant or helper to document the rationale and keep the magic number in one place.
• The reusedEmptyGroup && group.api.location.type === 'grid' guard is now used in two places; consider centralizing the grid-specific reuse logic into a small helper to avoid duplicating conditions and keep behavior changes localized.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The `+ 2` tolerance when comparing `offsetWidth/offsetHeight` to `minimumWidth/Height` is a bit opaque; consider extracting this into a named constant or helper to document the rationale and keep the magic number in one place.
- The `reusedEmptyGroup && group.api.location.type === 'grid'` guard is now used in two places; consider centralizing the grid-specific reuse logic into a small helper to avoid duplicating conditions and keep behavior changes localized.

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