Addin Usability Guidelines

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Throughout the OS and official add-ins, Casio maintains some amount of coherency regarding the user experience. This includes not just the appearance of the graphical interface, but also the way the user interacts with it and the way it responds. Whether the User Experience is effectively good or bad is a whole other subject, and add-ins can definitely try to improve on it. However, they should not provide a experience that's worse than that of the OS, and when improving, they should do so in ways that do not break user habits, namely in terms of how to navigate the interface, turn off the calculator, switch apps, etc.

Icon Guidelines

Read the original discussion topic on the Cemetech forum

Icons are a part of Prizm add-ins that are usually considered unimportant. They don't affect the add-in itself, but it's still a good idea to create a nice set of icons for any program. Users will see it even when they aren't running the program, and if the Main Menu is full of icons that don't adhere to a few guidelines, navigating the menu can be confusing.


The object that's the main focus of the icon shouldn't take up all of the 92x64 pixels that it has access to. It should generally be a bit smaller since the background and other elements also need a bit of space. The official icons from Casio are somewhat colorful, a bit 3D-looking, have shadows and are slightly translucent. You can follow the style of these if you want to, or create your own kind of icon. 2D sprites usually work fine if they aren't too similar to the backgrounds.

Example icons:



In all add-ins, two icons must be provided - the selected icon, and the unselected icon. The two icons should show the same objects with different backgrounds - not objects that are completely different from each other or the same objects with minor variations. There is one exception, though. When placing text in the icon (this should only be done in special cases, not for writing the name of the add-in!), the text in the unselected icon should be white with a black outline and the text in the selected icon should be black with a white outline. Run-Matrix and Equation are examples of this. The unselected icon needs to have a pure black background, and the selected icon needs to have this background:


If no custom icon has been made for your program, the background with nothing on top of it should be used for the selected icon. Never make the selected icon pure black!

Areas drawn by the OS

The Prizm OS is a bit unusual when it comes to icons, as it draws on top of certain areas. Those areas are marked in red here:


The square on the top right area of the icon will always be completely unseen, and anything important shouldn't be placed there. However, hiding defects or other odd things there is not recommended, since some users might use something other than the OS to view the icons. The larger area on the bottom is where the name of the add-in will be placed. The main focus of the icon shouldn't be under it, but the area won't be completely covered, so things that aren't very important can be placed there. For example, a small part of the ruler in the icons of Conversion and Geometry is placed there, and an unimportant part of one of the images in the Picture Plot icon is also placed there. The name of the add-in should never be included in the icon since the OS takes care of including it.

For projects in development

If you have an in-dev project and can't make an icon, there is salvation!

KermMartian made these icons for in-dev projects:





Key Usage

See Keyboard - Usability Guidelines.

Clock control

As discussed in an earlier thread, until recently most Prizms could safely overclock to around 95 MHz, but not all. More recently, the development of a tool called Ptune2 made overclocking to higher frequencies, in possibly more devices and in a eventually safer way, possible. Rather than make assumptions that can easily cause not just instability, but also an undesired increase of the power consumption and higher hardware wear-out, any modification to the system clocks should not be done without the user's permission or, at the bare minimum, knowledge.

The best way to handle overclocking is to simply not do it, by either optimizing the program, or reducing the amount of processing required. Drawing things to VRAM tends to be quite slow compared to computation, so optimizing the drawing in a program can offer significant speedups.

If the additional speed offered by overclocking is indeed important, to the point where the program will not work correctly without it, be sure to notify the user before doing anything and allow for backing out. There are some cases where this guideline could be safely ignored (such as an add-in designed specifically to allow the user to modify the clock settings), but in most cases the user should be notified before the program does anything that could negatively impact the calculator's stability (namely, overclocking).

In addition to keeping the user informed, an add-in that modifies the clock settings should also revert to the previous (stock or not) clock speed on exit by hooking the [MENU] key. Using SetQuitHandler to register a function that reverts the clock speed back to the default one will work fine in most cases.