sdl-ogc-keyboard

An on-screen keyboard (OSK) for Nintendo GameCube and Wii homebrew applications using libSDL. Features:

• Invoked using the usual SDL_StartTextInput() API
• Panning of application's window to ensure visibility of the input field
• Use own input field if the application didn't specify one
• Four selectable layout layers
• Vibration when hovering on keys
• Low memory impact: layout textures weight less than 64KB, UI is built using fillrect GX operations
• Wiimote support
• Customizable font

How to build

The key symbols on the OSK are drawn as textures, generated using the SDL_ttf library. While this generation could theoretically be done on the console itself, doing so freezes the application for several seconds, so we are instead following an approach where the textures are pre-generated on the host machine using the ogc-osk-tool found in the tools/ directory. Therefore, the first step in order to build sdl-ogc-keyboard is to build the tool on the host.

Build the ogc-osk-tool

Dependencies: The project uses the cmake build system, SDL 2.0 and SDL_ttf 2.0. They can all be installed on a Debian-based distribution using the following command:

apt install cmake libsdl2-dev libsdl2-ttf-dev

Build commands:

cmake -S. -Bhostbuild
cd hostbuild
make

The ogc-osk-tool will then be found in the hostbuild/tools/ directory.

Generate the layout data

Pick your favourite TTF font (the DejaVuSans.ttf in this repository is public domain) and run the generator tool:

# assuming you are still inside the `hostbuild` directory:
./tools/ogc-osk-tool ../example/DejaVuSans.ttf 24

(24 being the font size). Remember to copy the generated osk*.tex files to the directory where your application's data are: sdl-ogc-keyboard expects to find them in the current working directory.

Build sdl-ogc-keyboard

NOTE: the instructions below will only apply once this pull request will have been merged!

Dependencies: the devkitPro toolchain and the SDL2 package installable from the devkitPro repositories.

Build commands:

cmake -S. -Bbuild -DCMAKE_TOOLCHAIN_FILE="$DEVKITPRO/cmake/Wii.cmake
cd build
make

If building for the GameCube, replace Wii.cmake with Cube.cmake.

Using sdl-ogc-keyboard in your application

Enabling the OSK is a matter of changing a few lines only:

1. Include the header file:

   #include "ogc_keyboard.h"

2. Activate the module (this can be done even before calling SDL_Init()):

   SDL_OGC_RegisterVkPlugin(ogc_keyboard_get_plugin());

3. Call SDL_StartTextInput() when needed.

Example

The example/ directory contains a small program which shows how to use the OSK:

example.mp4

Configuring the layouts

Layouts can be configured by editing src/config.c.

Future plans

• Provide a way to embed the layout data in the application
• More flexible layout design (now it's hardcoded to 4 layouts, each with 5 rows)
• Read layouts from config files
• Play sounds as keys are pressed