Application gadgets by type
This section list application gadgets and their functions.
Each of the Amiga's application gadgets has a particular use and limitation. This section gives an overview of each type. Each type of gadget can be recognized by its appearance. Do not make gadgets that look like these standard gadgets but act differently.
Action Gadget
Action gadgets (often referred to as buttons) are graphic rectangles usually containing a few words. Clicking on an action gadget should perform the activity named on the action gadget.
Fig. 5.5: An action gadget.
Labels
Make the label descriptive. "OK" and "Cancel" may not always be the best choice. Use friendly, less technical terms (ie. "Stop", rather than "Abort").
The user shouldn't have to read an entire body of text before deciding which action gadget to press. Instead, a carefully selected label should tell the user what the gadget does in one to three words.
Triggering the Action
The action should be triggered on the release of the mouse's select button - not the downpress. This gives the user a chance to "roll off" the gadget before activating it.
More Choices
When an action gadget brings up another window or requester, the label should end in an ellipsis (three periods).
Fig. 5.6: A gadget which brings up another window or requester should have a label ending in an ellipsis.
Use of Cancel
An action gadget labelled "Cancel" should only be used if it actually allows the user to back out, leaving the application exactly as it was before the requester appeared. For example, "Cancel" is not appropriate for a gadget on a requester that is displayed while printing is occurring. "Stop" would be a better label.
Gadget Placement
The positive choice, or continuation of the requested action, should be displayed on the lower left side of [the] requester/window, while the negative choice or discontinuation of the action should be displayed on the lower right.
Fig. 5.7: The positive choice should be placed in the lower left, while the negative choice should go in the lower right corner.
Keystroke Activation
If an action gadget is activated through a keystroke, the gadget should appear to be pressed in on the downpress of the key. On release of the key, the gadget should appear to come back out.
Check Box
A check box is a small square that toggles from being blank to having a check mark in it. Check boxes are appropriate whenever you need to present an option that may be turned off or on.
Fig. 5.8: Check box gadget.
Keystroke Activation
If activated through a keystroke, the state of the check mark should toggle within the box.
Scroll Gadget
Scroll gadgets are used to adjust the position of a view. By themselves, scroll gadgets are used to adjust a large display area within a window's view, such as a text file that won't all fit within one window's view. Scroll gadgets are also a component of a scrolling list gadget (see next section).
Fig. 5.9: A scroll gadget.
A scroll gadget is comprised of the scroll bar, scroll box and scroll arrows.
Any window that displays only a portion of the file's entire contents should have scroll gadgets. If your application allows the editing of files that are wider than the window, it would be good to have a horizontal scroll gadget as well.
Moving Through in Steps
The display area should be updated immediately as the scroll bar is dragged.
When the user clicks in the scroll box (the rectangle containing the scroll bar) but not directly on the scroll bar, the display should move in viewfuls. For instance, if the user clicks in the scroll box above the scroll bar, the user's view of the list should move up so that the line which was first is now at the bottom of the view. The inverse applies where the user clicks below the scroll bar. This lets the user walk through the list in steps without missing anything on the list. Leaving one line from the previous view assures the user that he hasn't missed anything.
Scrolling List
A scrolling list features a view box showing textual names of files or objects accompanied by a scroll gadget to the right of the view box. If the list is longer than can be accommodated by the view box, the user can move through the list using the scroll gadget.
A scrolling list should be used whenever you need to present the user with a variable list of objects. Probably the most common example is found in the requester presented when a user chooses to open or save a file.
Fig. 5.10: A scrolling list.
Custom Scrolling Gadgets
On the Amiga, only one of the items in the system-supplied scrolling list may be selected at a time. Using custom code, it is possible to create a scrolling list gadget that supports multiple selection. If implemented, that gadget should still follow the multiple selection guidelines for text covered in Chapter 2.
Keystroke Activation
The scrolling list gadget reacts differently to shifted and unshifted keystrokes. An unshifted keystroke should cause the list to scroll forwards through the choices. A shifted keystroke should cause the list to scroll backwards through the choices.
Note: Using the Shift key in tandem with another key should never be the only way to do things since it is usually a choice that is not immediately apparent to the user. In the above case, it is backed up by the mouse.
Radio Buttons
Radio buttons are a group of mutually exclusive gadgets - one and no more than one is always selected. Use this when the user must choose one option from a short list of possibilities.
Fig. 5.11: Radio buttons.
Radio buttons are similar to cycle gadgets in functionality. Each has its beneefits and drawbacks. See later for a discussion on this subject.
Keystroke Activation
Radio buttons react differently to shifted and unshifted keystrokes. An unshifted keystroke should cause the highlighted button to cycle in one direction. A shifted keystroke should cause the highlighted button to cycle in the opposite direction.
Cycle Gadget
Like radio buttons, cycle gadgets allow the user to choose one option from several but only the selected option is visible.
Fig. 5.12: A cycle gadget.
Cycle gadgets should be used to set attributes, not trigger actions. Never use a cycle gadget for an on/off choice - use a check box instead.
Keystroke Activation
The cycle gadget reacts differently to shifted and unshifted keystrokes. An unshifted keystroke should cause the gadget to cycle forwards through the choices. A shifted keystroke should cause the gadget to cycle backwards through the choices.
Cycle Gadgets vs. Radio Buttons vs. Scrolling Lists
If the user needs to choose one option from a choice of three or more, cycle gadgets, radio buttons and scrolling lists are viable options. Which one you choose to implement depends on your application, your preference and common sense. Consider the following points:
A cycle gadget presents a cleaner interface. The selected choice is quickly evident and the unwanted choices are hidden away. Theoretically it's also able to handle a larger number of choices, although users will probably have trouble remembering a really large number of choices. Large numbers of choices may work well in a cycle gadget if they are ordered choices, such as the months of the year.
In general though, options with more than about a dozen choices should use a scrolling list.
Radio buttons present a clear choice to the user - the possible choices are always visible. Radio buttons work well with a small number of options. They are probably also slightly more intuitive than cycle gadgets.
Colour Selection Gadget
The colour selection gadget (sometimes referred to as the palette gadget) allows the user to pick a colour from a set palette.
Fig. 5.13: A colour selection gadget.
Keystroke Activation
The colour selection gadget reacts differently to shifted and unshifted keystrokes. An unshifted keystroke should cause the gadget to cycle forwards through the choices. A shifted keystroke should cause the gadget to cycle backwards through the choices.
Slider
Sliders are used to choose a value in a given range. Usually, this value represents a level or an intensity such as volume or colour.
Fig. 5.14: Slider gadgets.
Sliders look similar to scrollers without arrows, but when the user clicks in the slider box above or below the slider bart, the slider value should change in single increments rather than entire views.
Keystroke Activation
The slider reaacts differently to shifted and unshifted keystrokes. An unshifted keystroke should cause the horizontal bar in the slider to move up. A shifted keystroke should cause the horizontal bar to move down. When the horizontal bar reaches either the top or bottom it should change directions automatically. Don't tie the direction solely to a shifted keystroke.
Text Gadget
Text gadgets (sometimes referred to as string gadgets) are rectangular boxes used to accept keyboard input for alphanumeric fields.
Fig. 5.15: A text gadget.
Activating Text Gadgets
When a window or requester appears containing a text gadget, have the gadget immediately activated and ready for keyboard input if:
- there are no gadgets on the requester that can be activated by the keyboard;
- the window or requester appeared in direct response to user activity (ie. it is not asynchronous).
If the window or requester has other gadgets that can be activated from the keyboard, the user should also be able to activate the text gadget from the keyboard. In this case, it should not be activated by default.
The user should not have to select the text gadget with the mouse before typing an entry (if he chose an action that directly called that requester up). If may seem like a small delay to go from keyboard to mouse to keyboard, but all breaks in the flow of your program should be minimized.
Ordering of Text Gadgets
When a window contains a series of text gadgets, activate the gadget in the far upper left region of the window first (depending on the scanning direction of the local language).
Moving Through Fields
Let the user move through fields with the Tab key. When the user presses Tab, activate the next text or number gadget in the series. When the user reaches the end of the series and presses Tab, the cursor should return to the first entry gadget. This function is supported by Intuition.
Shift-Tab should activate the previous gadget in the series.
Display Box
A display box is a rectangle that shows non-editable textual or numeric information.
Display boxes look similar to text gadgets, but since they are read-only, they appear recessed. This follows the 3-D conventions given in Chapter 2.
Fig. 5.16: A display gadget.
Icon Drop Box
Icon drop boxes are used for manipulation of icons. If a user drags an icon to an icon drop box, the image of the icon is copied into the box. Depending on the function assigned to that icon drop box, the icon imagery may then be redrawn or used to represent other files.
Fig. 5.17: An icon drop box.
Custom Gadgets
Sometimes a system-supported control does not provide the exact function you need. In that case, you may choose to create a custom gadget.
If a custom gadget is an extension to an existing gadget type, then you should try to emulate the features of the existing gadget.
For example, a custom multi-line text gadget should support the same keyboard functions that the standard single-line text gadget does. Right-Amiga-X should erase the text and Right-Amiga-Q should undo changes. Refer to Chapter 10 for more information on the keyboard conventions used in text gadgets.
All custom gadgets should support a minimum of three images: normal, selected and disabled. The gadget images must be usable on a monochrome screen.
Custom Icons
Custom icons are application-specific gadgets that can be moved and manipulated. The note object in a music package is one example.
Take care when using custom icons alongside action gadgets that have graphical labels. Since it is not clear which symbols trigger an action when clicked and which symbols move when clicked, users could be triggering unwanted actions. If you use both in the same application, be sure the user can tell at a glance which is which. Grouping them spatially is one possible solution. Colour cues may provide a solution. Boxing them may be a third solution.