Configuration pane and editors

The Configuration pane has 4 typical layouts for displaying properties to be configured using the Simple editor:

• Key properties. Displayed whenever a step is selected from the flowchart, or the root navigational link is clicked. This layout presents all the properties that are typically required to configure a step.

• Single property. Displayed whenever you select a single property (for example, the Camera step's ExposureDelay property) from the Quick Access pane or Properties pane. Either select or enter the value for the single property in the dropdown list that appears.

• Group properties. Displayed whenever you select a property that has several properties directly associated with it (for example, the EdgeLocator step's SearchRegion property). Select an associated property from the list that appears and enter its value in the dropdown list.

• Condition properties. Displayed when you select a Condition step, or when you are setting a condition in another step. This layout allows you to select (link to) an input or output property of a step in your project, and compare it to a user-defined value. In addition, you are asked to select a comparison operator and enter a value with which to compare a selected property. If your condition requires 2 links, switch to the Advanced editor.

  

If the value that you assign to a property is invalid, an exclamation point inside a red circle appears next to the property in the Configuration pane. For more details, read the error message that appears in the Errors pane. The information presented should help you locate and fix the error.

If a step input is bound to an operator view input element, a icon will be displayed next to it. See the Binding subsection of the Configuring input elements section in Chapter 50: Customizing the operator view for more information.

When the Link editor is accessed, the Configuration pane displays a tree structure that allows you to set the selected property to the value of a specific input, output, variable, or platform configuration setting already in your project. Typical use of the Link editor includes constructing conditions or linking an output to a value in the Operator View Layout tab.

To use the Link editor, perform the following:

1. Click on the In, Out, or Variables button beside the tree structure. This changes the list of items from properties that are set (inputs) to results that return a value (outputs) or variables (or vice versa).

   If the size of the pane is too small to see all 3 buttons (the In, Out, and Variables buttons), a little triangle appears to the right of the visible buttons; clicking the triangle displays the missing ones.

   

2. Click on the plus sign next to a step to display its related properties. When selecting an output property, you can filter out categories of properties using the Filter button just above the In button.

3. Double-click on the property to which you want to link. The text box above the tree structure will change to show the name of the step and the property to which you have linked.

   

The Advanced editor is used to build expressions. For information on building expressions, refer to Chapter 26: Building Expressions and Appendix A: Expression syntax.

You can access the Advanced editor from the Configuration pane by double-clicking on any text box, or pressing the F8 key.

To add to an expression, do any of the following:

• Select properties, functions, and operators from a category.

• Drag and drop links into the expression window.

• Type directly into the text box.

When you access the Advanced editor, the Configuration pane displays the following categories from which to build an expression:

Some of these categories also contain keywords. For example, the ARRAY category contains the ItemCount keyword (to denote the number of elements in the source array).

The Advanced editor has several uses. It can be used to build input expressions using results from other steps (for example, to set the location of a test region based on the average of 2 previously determined points). An expression calculating the average of 2 X-coordinates is shown below.

An expression can also be used to verify if a result falls within a given range. For example, in the following expression with 3 links, logic operations are used to check if a point of intersection, calculated in the Metrology step, lies inside the image.

In the Advanced editor, you can also quickly extract a particular result element, of all occurrences, by selecting the required menu item from the Advanced editor context menu, as shown in the following example.

When you select a function from the list of available functions in a group, the Advanced editor displays all possible variations of the function and a short description. For more information, click on the question mark button or press F1 to go to the reference document that gives more explanations and usage examples.

If there is an error in the expression, an error message appears above the expression in the Advanced editor of the Configuration pane and in the Errors pane. The information presented should help you locate and fix the error.

To simplify working with complex expressions, the expression is syntax color-coded. When you click on a function with parameters, all of the text belonging to that function is highlighted to help check for mismatched parentheses.

Also, note that, to improve readability of long expressions (such as the one below):

you can insert breaks using the Shift+Enter key combination:

If you link to an output that does not exist at the moment the link is evaluated in a deployed project, a runtime error will be generated. This will cause the project to stop running. For example, linking to the result of the second occurrence of a pattern match will fail if only one occurrence is found.

There are 2 ways to protect your project from failing on an invalid link:

• The first way is to add a condition step to verify that the expected number of results were found, and only execute other steps that depend on the results if the condition is true.

• The second way is to use the CHECKVALID or ISVALID functions. These functions determine if a link points to a valid result at the time of execution. When you create a link in the Advanced editor, you can double-click on the item to which it should link, in the tree structure view. However, it is recommended that you right-click on the item, and select Insert with ISVALID or Insert with CHECKVALID.

  CHECKVALID can be particularly useful in a Store step that creates messages (for example, for log files). CHECKVALID returns the value of the linked item if the link is valid, or a specified replacement value if the link is not valid. For example, if a CodeReader step fails to read a bar code, CHECKVALID returns "FAILED"; if the read is successful, CHECKVALID returns the decoded string.

  CHECKVALID (CodeReader.DecodedString, "FAILED")
  

For more information about runtime error handling, see the Deploying and running your project section in Chapter 2: Building a project.

The Advanced editor can be used in the Operator View Layout tab to format and display results.