Desktop Carousel

by Alan Wrigley


This application enables you to display a sequence of sprites in a continuous carousel in a multi-tasking window on the Desktop.

Before you can use the application, you must copy it onto a separate disc and decide which pictures will form the display. These should take the form of sprite files, of which the first sprite in each file will be displayed. The sprite files should be placed inside the Pics sub-directory of the !Carousel application directory, and should be named Pic01, Pic02, Pic03 and so on, in the order in which you want them to be displayed. There should be no other files inside the Pics directory other than those which form the display, and there should be no gaps in the numbering. The example sprites from the Landscapes CD can be used in the program; double-click on !Landscape to reach them.

The sprites may be created in any screen mode, since colour translation is performed before they are displayed. It should be possible to display new-format 16bpp and 32bpp sprites in the appropriate 32000 and 16 million colour modes if you have a new Acorn machine, but unfortunately these sprites cannot be displayed on existing machines since the old ColourTrans module does not recognise the new formats.

Running the application opens a window in the centre of the screen with the first sprite in the sequence displayed. The other sprites in the sequence are then shown in turn, with an initial time interval of 5 seconds (this can be altered, as described later). When the last picture has been displayed, the sequence wraps round again to the first. The window may be moved around as usual, and also re-sized. Although at first sight it may appear that the window cannot be made larger, since the scroll bars are fully extended, clicking on the window's Adjust size icon and holding the mouse button down will cause the sprite window to go blank and the scroll bars to shorten. You can now resize the window over the whole screen area. When you release the mouse button, the picture will be re-displayed at the new size.

Clicking Menu over the window opens a menu with one item, namely Controls. This allows you to open or close the control panel - the item is ticked when the panel is open. The control panel is in two sections. The upper section controls the time interval. To alter the interval, type a value in seconds into the writable icon and then either press Return or click on the OK icon.

The lower section of the control panel has 5 toolbox-style icons. From the left, these are the Full-screen tool, the Aspect tool, the Pause tool, the Back tool and the Next tool. Clicking on the Full-screen tool causes the carousel display to take over the entire screen. To return to the original windowed display, simply click on the mouse. The Aspect tool enables you to preserve the original aspect ratio of each sprite. If this is turned off (the default state), each sprite is always resized to fit the current window size exactly, regardless of the aspect ratio. If it is turned on, the original aspect ratio of the sprite is preserved. This means that if the x:y ratio of the window is greater than that of the sprite, the picture will not completely fill the window in the horizontal direction, while if it is less, the same will be true in the vertical direction. Clicking on the tool toggles the setting on or off.

Clicking on the Pause tool pauses the carousel at the currently displayed sprite. When Pause mode is on, the Back and Next tools can be used to display the previous or next sprite in the sequence respectively. When Pause mode is off, these twotools are inoperative.

Clicking on the main window's Close icon terminates the application.

 Copyright RISC User 1994