dotnet/wpf · error · ArgumentException

SR.BadDistance

Error message

SR.BadDistance

What it means

DocumentSequenceTextPointer.CreatePointer throws ArgumentException (BadDistance) when the requested offset distance cannot be honored by scanning the text container. xGapAwareScan returns false when the distance overshoots the content or cannot be achieved respecting gaps between child pages, so the call fails rather than returning a pointer at an undefined position.

Solutions

  1. Clamp distance to the container's symbol count (e.g. via the symbol offsets of the start/end pointers) before calling.
  2. Use a smaller step size and iterate moves, checking position between steps.
  3. Catch ArgumentException and fall back to a CreatePointer() at the current position.

Example fix

// before
var p = docPointer.CreatePointer(bigDistance);
// after
var distance = Math.Min(bigDistance, Math.Abs(endOffset - currentOffset));
var p = docPointer.CreatePointer(distance);
Defensive patterns

Strategy: validation

Validate before calling

var max = Math.Abs(docPointer.TextContainerEndOffset - docPointer.Offset); distance = Math.Clamp(requested, -max, max);

Try / catch

try { p = pointer.CreatePointer(distance); } catch (ArgumentException) { p = pointer.CreatePointer(); /* stay at current position */ }

Prevention

When it happens

Trigger: Calling CreatePointer(distance) on a DocumentSequenceTextPointer with a distance larger than the remaining symbol count (or smaller than the available backward distance) in the sequence — the virtualized multi-page container cannot place a pointer that far away.

Common situations: Advancing a pointer by a fixed stride without checking remaining document length; distances computed from positions in a different text container; documents with gap (page-boundary) regions that make nominal distances unrecoverable.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/fa8cbe56ec9d41e4. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Documents/DocumentSequenceTextPointer.cs:785

        }

        /// <summary>
        /// <see cref="ITextPointer.CreatePointer(int,LogicalDirection)"/>
        /// </summary>
        public static ITextPointer CreatePointer(DocumentSequenceTextPointer thisTp, int distance, LogicalDirection gravity)
        {
            ValidationHelper.VerifyDirection(gravity, "gravity");

            // Special case for common case of distance == 0
            // to avoid calculating child container size, which
            // could be expansive especially in case where child
            // container requires virtualization.
            DocumentSequenceTextPointer newTp = new DocumentSequenceTextPointer(thisTp.ChildBlock, thisTp.ChildPointer.CreatePointer(gravity));
            if (distance != 0)
            {
                if (!xGapAwareScan(newTp, distance))
                {
                    throw new ArgumentException(SR.BadDistance, nameof(distance));
                }
            }
            return newTp;
        }

        #endregion TextPointer Methods

        //------------------------------------------------------
        //
        //  Public Properties
        //
        //------------------------------------------------------


        //------------------------------------------------------
        //
        //  Public Events
        //

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