| 29 | | This is the most important part of the RFC. It describes the problem domain in detail. Focusing on this will allow reviewers to fully understand why the proposed change is being made, and potentially suggest different/better ways of accomplishing the desired results. The more time we spend on understanding the problem, the better our solution will be. |
| | 29 | === Multi-Variate Theming === |
| | 30 | In the new symbolization we have symbol definitions which define parameters, and symbol instances which define overrides - constant values or expressions - for these parameters. For !MapGuide 1.3 we will be introducing new expression functions which can be used to specify themes. Multi-variate theming is achieved by using these new expression functions in parameter overrides. No schema change is needed to support the new expression functions - expressions are just strings and the parameter overrides are string properties. Multi-variate theming does add some complexity when it comes to legend labels, and this is where additional information in the schema is needed. |
| | 31 | |
| | 32 | The current layer definition schema defines a legend label per style rule. Today when we create a theme we generate multiple style rules, and the legend label for each rule is set appropriately. The new multi-variate theming approach, however, uses expression and not rules to define the theme. With the current schema this means only one legend label is available for all the themes, and this is inadequate. The proposed schema change is to therefore include additional theme information to the parameter override elements. |
| | 33 | |
| | 34 | For this release it will be sufficient to add two pieces of information: a theme description and a theme category format. Any parameter override whose value is set to a theming expression would also set these properties. The legend generation code can then use this information to generate appropriate labels for each theme / theme category. The theme description is a string that would be displayed the same as it's entered. The theme category format is a string which includes a mix of formatting codes and text, and these can appear in any order. Three codes will be supported: <min>, <max>, and <value>. The <min> and <max> codes are used with themes where each category corresponds to a range of values. This applies to themes that use Equal, Standard Deviation, Quantile, or Jenks distributions. Some example category format strings: |
| | 35 | |
| | 36 | * "<min> to <max> miles per hour" |
| | 37 | * "Parcel value: <min> - <max> Euros" |
| | 38 | * "<min> <= Population < <max>" |
| | 39 | |
| | 40 | The <value> code is used with themes that assign a single value to each category, so for themes that use Individual Values distributions. Some additional example format strings: |
| | 41 | |
| | 42 | * "Zip code: <value>" |
| | 43 | * "Zone <value>" |
| | 44 | |
| | 45 | |
| | 46 | === Rendering Passes === |
| | 47 | |
| | 48 | |
| | 49 | |
| | 50 | === Angle Offset Relative to Feature Geometry === |
| | 51 | |
| | 52 | |
| | 53 | |
