TerrainStrokeCommand

Remarks

[docs/plan/31 § D11], and the record it wraps is the kernel's. TerrainStroke holds the layer, the union of the rectangles the stroke touched, and that rectangle's deltas before and after; this is the thing that puts it on CommandStack and tells the terrain what to recomposite either way.

⚠ Merging is off, deliberately and not by omission. Two strokes are two undos — which is what an artist means by "undo that" and what every paint application does. What does merge is inside the stroke: a drag is one TerrainStroke being extended rather than four hundred commands, so by the time one of these exists the merging has already happened.

⚠ Built at pointer-up, from a stroke that has already been applied. Every command in the editor records this way — see EditMeshCommand.Moved — because a drag applies as it goes and the command is what makes the finished state undoable rather than what performs it. So Do is a redo the first time it is not called, which is why the constructor takes the captured after-image rather than reapplying the brush.

Fields and properties (5)

• public string Name

  What this is called in the undo history, as a person would say it.

• public TerrainRect Rect

  Which samples the stroke touched.

• public TerrainEditLayer Layer

  Which layer it wrote.

• public int RecordedSamples

  How many samples the record holds, before and after together.

• public long Bytes

  How many bytes it occupies.

Methods (4)

• public TerrainStrokeCommand(Terrain terrain, TerrainStroke stroke, string name, Action<TerrainRect>? changed = null)

  Records an applied stroke.

• public void Do(EditorContext context)

  Applies the change.

• public void Undo(EditorContext context)

  Puts back exactly what Do changed.

• public bool TryMergeWith(IEditorCommand previous, out IEditorCommand? merged)

Used by (1)

• TerrainEditVixen.Editor.Terrain