Dimension-text formatting: primary, alternate, tolerance

[mme1950]

The measurement text can in AutoCAD be specified explicitly. In this case this text displayed as it is.

If no explicit text is specified the measurement text must be created using a set of properties defined by the DimensionStyle object associated with the Dimenison object. All properties can be overridden by Dimension object's ExtendedData.

The measurement text contains

• a primary part, essentially containing the measurement,
• optionally an alternate-unit part containing the measurement in a alternate scale or style,
• both parts can be enriched with a tolerance in various style.

The primary part and alternate part respectively can be formatted in various styles, specified by the enums defiened in ACadSharp:

• LinearUnitFormat for linear dimensions
• AngularUnitFormat for angular dimensions

To create a measurement text based on the effective DimensionStyle properties both the parts of the measurement text and the style must be considered.

[mme1950]

Concept

The DimensionSvg.CreateMeasurementText method creates the measurement text. Two implementations for linear dimensions and angular dimensions respectively.

Both implementation use a switch to distinguish the cases:

• Pure measurement value
• Measuement value with symmetric tolerance (MinusTolerance == PlusTolerance)
• Measuement value with plus/minus tolerance (MinusTolerance != PlusTolerance), stacked display
• Limits: +{Measurement+PlusTolerance}^-{Measurement-MinusTolerance}

For each LinearUnitFormat and AngularUnitFormat a formatter class is implemented.

For linear dimensions the measurement text is composed es primary and alternate part if specified. For both parts different formatters may be used.

The created measuement text is coded using AutoCAD "markup" as used for MTEXT entities.