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Kalideoscope Zone - articles
Introducing the GuideLayout, Part I
16-May-2005 Part I: Introducing the GuideLayout By default when visually assembling a XUI page absolute positioning of components is used. Simply speaking this means that each component must have a specified X, Y location and a width and size dimension. The dimensions are all in pixels and do not vary with the size of the application window or the page container. For a localized application or for one that does not employ a fixed window size this can be a painful limitation. Java's built-in layout managers are useful but tend to be either limited in functionality or difficult to programme correctly. Support for layout managers is also limited and may even add to the complexity. Traditionally graphical designers have used desktop publishing tools such as Quark and PageMaker to layout documents. These DTP applications have for a long time supported the notion of guides and in version 2.0 of XUI we try to emulate some of these solutions. XUI's NetBeans plug-in has for some time supported visual layout tools called guides to help explicitly align components. In version 2.0 we are introducing runtime support for this layout mechanism with the new GuideLayout layout manager. Guides are simply lines drawn on the page at design time to assist layout. Components can snap to the guide position when dragged around a page at design time and in this way guides allow components to be aligned with respect to one another and with respect to the page instead of just the parent container. Visually the behaviour is obvious and from a programming perspective the guides are also easy to use with the component's layout constraints being automatically maintained. All the page designer need do is choose the GuideLayout for the container. Grids and Guides In the page designer the page being edited can be shown within a grid and with layout guides. The designer shows rulers to the top and left of the page, set out in pixel units. The designer allows components to optionally snap to the grid. The selection of this option and the granularity of the grid can be configured within the page designer. In the top left hand corner or the designer is a button, that when pressed toggles the display mode. When in the configuration mode the rulers are shown with a red tint and the guides are numbered.
Figure 1 - Using guides in the Kalideoscope editor
Once in the configuration mode you may right click anywhere on the page to get a context menu giving some options to control the layout. Once configuration has been completed just click the button in the top left to return to the page editing mode. The grid and guide options that can be configured in this way include:
Listing 1 - Grid and guide options
Adding guides Guides can be configured on a page by page basis or on an application wide basis (as master guides) to help enforce layout rules across pages. In the page designer adding guides is carried out by:
To remove a guide simply enter the guide editing mode and drag a guide back to the ruler. Individual guides can then be configured by right clicking on them and choosing the Guide Options... menu option. This option allows control over how the guide is positioned at runtime. Guides can be positioned relative to one another or relative to the size at which the page is displayed so as to give a controlled final layout. The coordinates system used for the guide can also be expressed in relative terms of the page size instead of the absolute pixel size used at design time. The guide ID shown in the dialog is used to reference the guide by the constraint specified for each component on the panel controlled by the guide layout manager.
Figure 2 - The guide option chooser
Several more options are available for configuration of the guides:
Listing 2 - Guide options
The area of guide sensitivity, that is the area within which a component will snap to the guide when moved can be highlighted (as illustrated above) by choosing the Show snap zone context menu option. The context menu is display by right clicking on a guide in edit mode. To enter the guide's edit mode toggle the button to the top left of the page at the vertex of the two rulers. In this mode the rulers are shown with a red background. Some of the guide options are context sensitive and depend on the guide on which the mouse is clicked. The options are described below: Snapping to guides As a component or set of components is dragged about within the page designer the edges of the components will automatically snap to the guide whenever within range. Guides will tend to cause a component to resize as a component is dragged but once a component goes out of range it will snap back to its original size. Setting up Columns While in the configuration mode you can choose to setup columns and rows to assist layout. The GuideChooser dialog appears when this option is chosen. You can use this dialog to quickly setup regularly spaced columns and rows. Once the guides have been added you may reposition the guides to best suit your layout needs.
Figure 3 - The guide settings
An example guide layout To illustrate the use of the guide layout let's look at a sample form. The form is made up of two columns of labels and edits. Therefore a four column guide layout is created so that we can specify the spacing between the labels and edits and also teh spacing between the columns, just as is shown above. The leftmost guide in each column and the last guide (vertical guides 0, 3 and 7) are scaled guides so that each holds its position relative to the page. The next guide is a relative guide specifying a fixed width for the label. Following this another relative guide with a fixed with of 10 pixels is used to specify the spacing between label and edit. The edit field is then left to use the remaining space between the fixed guides and the scaled guides.
Figure 4 - The running application
The XML code for the complete form layout is shown below.
Listing 3 - Guide Layout
The constraints for each component specify the guide ID for the left, top, right and bottom edges. If the component is not bound to a guide then the ID can be specified as -1 and the x, y, w or h dimesions will be used to size and position the component as needed. In the above XML example all the edges are bound to guides so the explicit dimensions are redundant and could be omitted. To see the guide layout in action we then resize the form. In the resized form each column still occupies half of the page although the relative size of the edit fields has increased.
Figure 5 - The resized application
Other layout tools And if the guides aren't enough to help you layout the components the editor also provides a set of alignment tools for making components match width, height, alignment or spacing. The editor also provides hints to assist layout as the components are moved or sized. The hints are shown briefly while moving or select components and connect edges of components that have matching coordinates. The components will by default snap to the coordinates of other components to self align. When JSE 6 is released we will add support for matching of the component baselines and user interface spacing, kind of like NetBeans's project Matisse.
Figure 6 - Spacing components in the editor
Using the GuideLayout outside of XUI The GuideLayout can be used outside of XUI with a little work. However before the final release of XUI 2.0 we expect to have enhanced the API sufficient to make such use more convenient. The current API can be found . Part II of this article describes use of the GuideLayout outside of XUI. Further Enhancements In future versions we also hope to extend the GuideLayout to include support for features such as alignment of baselines, autosizing columns (fit to say the maximum width of a column of labels) and some more advanced arrangements of the guides. comments If you were logged in you could rate this article or add a comment. |
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