4 Dialog Editor

The Object, Relationship, Role, Port and Graph Tools allow you to open a Dialog Editor to modify the layout of the dialog used to edit the properties of an instance of that type. To edit the dialog layout:

As a result a dialog editor opens (as in Figure 4–1), showing the layout and contents of a dialog for the type. In other words, it shows the appearance of the dialog that the modeling tool user uses when creating or editing an instance of this type.

Each widget in the dialog is determined by the data type and widget type of its property type (a string is a single line field, text is a text box, collection is a list box etc.). The labels are the local names of the properties in this type.

The font used for displaying text in dialog component widgets can be changed by selecting the component and choosing Font... from its pop-up menu. This opens a list of platform-independent text styles to pick from, e.g. code or pixelFixed are good choices for a fixed width font for editing program code. Choose the desired style and accept the selection by pressing OK.

The location of any field or label can be changed by selecting the item and dragging it to the desired location with the mouse (as in Figure 4–1). You can also use the cursor keys to move the element, Shift + cursor keys to move just its bottom or right edge, and Ctrl + cursor keys to move just its top or left edge.

Several items can be selected for moving as one unit by keeping the shift button down while selecting the items from the window, or by dragging to select an area enclosing them. When dragging the selection, it is possible to constrain the movement to happen only either vertically or horizontally by holding shift as you begin the drag: the axis along which movement is restricted is taken from the direction in which you first move the selection.

If the location of dialog components is changed you usually must also set resizing information for dialog components. This is needed to specify how individual property fields, labels and buttons are resized when the whole dialog is resized. For this purpose MetaEdit+ offers the Position Settings Tool for each dialog component (as in Figure 4–2). To open a Position Settings Tool, select a component and either select Position... from the component’s pop-up menu or press Esc-L.

The Position Settings Tool has a Proportion column and an Offset column for each edge of a component: Left, Top, Right and Bottom. For components whose width and height is calculated automatically, i.e. text labels, fields show the origin’s X and Y co-ordinates, and the position of the origin point within the component: normally 0 and 0, for the top left corner, but could be 1 and 1 to make the bottom right corner the origin.

The proportion value for a dialog component’s edge controls how much that side moves relative to the size of the property dialog window. Values can be between 0 and 1, where 0 is the left or top of the window and 1 is the right or bottom of the window. Thus setting it to 0 causes the dialog component’s side to remain a fixed distance from the top or left side of the dialog, and setting it to 0.5 will make the side remain a fixed distance from the middle of the dialog.

Offset sets the desired distance to offset the component’s side from the value given by the proportion. It may be positive or negative. For example, a left proportion value of 0.5 and offset value 50 means that the dialog element is located 50 pixels right of the middle of the window. Thus the pixel position of the side is equal to the window’s extent in that direction (width or height) multiplied by the proportion value, plus the offset value.

The most common use for the Position Settings Tool is for customized dialogs where you want dialog components to expand or shrink with the window. This is done by setting the component’s right proportion to be different from its left proportion, and/or by setting its bottom proportion to be different from the top proportion. The latter is useful for dialog elements like list and text fields which can use the additional height when the dialog is resized vertically: input fields and other single-line fields normally have the same proportion value for top and bottom sides.

By default, MetaEdit+ creates dialogs where all fields have a left proportion of 0 and a right proportion of 1: thus resizing a dialog horizontally makes each field grow to fill the extra width. Similarly, top and bottom proportions of fields higher than a single line are set to different values. Thus resizing a dialog vertically makes each field with more than a single line grow to fill the extra height; the extra height is shared equally among these fields. Each label is given the same top proportion as that of its field, so it moves with that field. Finally, the buttons are always centered at the bottom of the dialog.

To layout dialog components to resize with the window as you wish, you should first get the layout right for a given size of the window:

Now that you have the layout right in this size, you can set the proportion values for the components so that they will move and resize appropriately when the window is resized:

The resulting setting is shown immediately in the dialog, and you can test it by resizing the dialog window: the component should behave as expected, but other components that have not yet been set will not move. You may continue in this way to select and position other dialog elements.

Sometimes several components need to be aligned or distributed relative to each other. These operations can be performed by selecting first the components and then the appropriate commands from the pop-up menu.

To align a group of widgets, select them keeping the shift key pressed and select Align... from the pop-up menu. In the Align dialog (see Figure 4–3) select the On Vertical Line option to align widgets in a column. To align widgets side by side, select On Horizontal Line. Select First Selection to align widgets with the first widget that was selected. Select Merged Box to align the widgets on a line halfway between the most extreme positions within the group of widgets. To align the edges of the widgets select either Left Edges, or Right Edges, or Centers.

After making modifications it is often necessary to equalize spaces between a group of widgets. This can be done by selecting Distribute... from the pop-up menu. In the distribute dialog (Figure 4–4), select Left To Right for widgets that are to be evenly spaced horizontally. Select Top to Bottom for an even vertical spacing. The type of spacing can be set either as Equal Spacing Between Centers or Edges, which distribute all elements between the outermost two, or as Constant Spacing Between Edges. If you choose constant spacing, you have to specify the constant, the number of pixels between each pair of widgets. The widgets are then spaced using that constant, starting from the top or leftmost widget.

Series of widgets can be forced to adopt the same width, height or both by choosing Equalize... from the pop-up menu. The size can be equalized using the first of the selected objects as the size for others, or then you can set the minimum or maximum of the sizes to be used for all. If you want the size to be a certain number of pixels, that can be set in the Constant box.

When a user opens a property dialog for an instance, the cursor is initially in a certain field (by default, the first property of that type). By pressing Tab, the user can advance through all the fields, and finally to the OK, Cancel and Info... buttons. This tab order of the fields can be set by keeping the shift key pressed and selecting the widgets, in the order in which the tabbing should advance the focus, and selecting Tab Order from the pop-up menu.

By default each dialog has a fixed size in which it opens in modeling tools. This size is determined automatically after ordering the property fields and related labels below each other.

If the opening size of the default dialog is not suitable you may change it by simply resizing the window with the mouse, and closing it, accepting changes. You may also set the minimum and maximum sizes for the property dialog, by scaling the window to the required size and then selecting either Set Minimum Size or Set Maximum Size. Normally, the minimum size is set to be the smallest size at which all components are visible, and components with more than one line of text are showing roughly two lines. The maximum size is not normally set. After setting minimum or maximum sizes, remember to return the window to an appropriate default size before saving your changes.

If the window’s height is such that it would not fit on the current display, the system automatically turns on the vertical scroll bar. If the scroll bar is not needed it can be turned off by selecting Toggle Vertical Scroll Bar from the pop-up menu.

In some cases you might also want to use horizontal scroll bar: for example to hide some rarely needed design information and to make the size of property dialogs smaller. To turn it on or off, select Toggle Horizontal Scroll Bar from the window’s pop-up menu.

In some circumstances, for example when using subclasses of existing types, there may be a need to delete a field from the dialog. The field can be deleted by selecting the field and pressing the delete button from keyboard. Note that the users can not give values for a property whose input field has been removed, but the property is still stored, with its current value (or default empty value for new objects).

The most recently deleted selection can be added back into the window with Alt+V or Ctrl+J. This allows even multiple selections to be cut and pasted between dialog editors. Be aware however that property entry fields are specific to a given type. They can only be copied for a given property in a given non-property type if they are defined in the same type (this type or a common supertype), and that property in that type does not change between the cut and paste. Labels and buttons can be cut from any dialog editor, and pasted into any other dialog editor, regardless of which type the dialog represents.

Cutting and pasting dialog elements is most useful when building a custom dialog that extends an existing custom dialog with new properties. This can happen when sub-typing an existing type and adding a new property, or adding a new property to an existing type.

Care should be taken in this procedure, especially in making sure that the cut property fields are defined in the same type. If incorrect property fields are present in a dialog, that dialog will not be able to open, preventing editing and creation of instances of that type. In this case, you should rebuild the default dialog for the type.

Abstract and read-only properties affect the visibility and behavior of the property dialog widgets. If a custom property dialog has read-only widgets (i.e. whose property slots were read-only at the time the dialog was created), they will be maintained as read-only even if those property slots no longer are. On the other hand, editable widgets that have become read-only will be opened read-only. Similarly, if a custom property dialog has visible widgets whose slots are now marked as hidden, those widgets will be hidden (their labels still remain visible even if the values are hidden).

The new window specification can be saved by closing the window and answering yes to the dialog that asks whether or not the changes should be saved.