Changelog

The Border→SplitPanel→Border-host chain wasn't properly constraining

child content width. Rewrote as a Control subclass that directly

manages Pane1, Pane2, and the resize handle as visual/logical

children, with MeasureOverride and ArrangeOverride that measure each

child with its exact proportional width constraint and arrange at

exact rects. No intermediate containers to lose constraints.

The block type picker's InsertBlockType() switch statement had no

cases for columns_2, columns_3, or columns_2_wide_left. Selecting

any column layout from the "/" palette or Add Block button silently

did nothing.

Fix: add AddColumnsBlock relay command to NotesViewModel that

delegates to the existing CreateBlockFromTypeId() (which already

handles all three column variants). Wire the three column type IDs

in the picker's switch statement to call the new command.

ContentPresenter outside a ControlTemplate doesn't reliably present

Control content in Avalonia. Replaced with Border hosts that use

Child property directly.

Also fixed MeasureOverride: was returning availableSize which could

contain Infinity, causing the layout system to give zero size. Now

clamps infinite dimensions and measures each child with its

proportional share of space.

Cover image action buttons (Change/Reposition/Remove) were positioned

at top-right with Margin="0,44,12,0", placing them directly under the

ToolbarHoverZone (ZIndex=1, Height=120 when cover exists). The hover

zone captured all pointer events before they reached the buttons.

Fix: move buttons to bottom-right of the cover (VerticalAlignment=

Bottom, Margin="0,0,12,28") and set ZIndex=2 so they float above the

toolbar hover zone. Buttons now appear on cover hover and are fully

clickable.

Code-only Border subclass with a custom inner Panel that arranges

two content panes and a draggable resize handle using ratio-based

math. Avoids the star-column minimum width issues that plague

Grid-based split implementations.

Properties: Ratio (pane2 fraction), MinRatio, MaxRatio, HandleSize,

Pane1, Pane2. Fires RatioChanged event on drag release for

persistence. During drag, uses an internal _dragRatio for live

feedback without updating the bound property on every pixel.

Replaces the inline resize logic pattern found in Tasks and Data

plugins with a single reusable component.