Keyboard storage can't fit keycodes that are large

[ocornut]

mattiasljungstrom says:
"I'm using SDL2, and when I input the key mappings from SDL2 for special keys they all have very large values. This also seems to brake the internal code of ImGui. I think it assumes all key code values are between 0-255?"

[mattiasljungstrom]

I've solved this issue in my code by using the SDL2 "scancodes" instead of the key codes. If anyone else is using SDL2 this is how I have it setup:

//
// setup SDL2 keymapping
//
io.KeyMap[ImGuiKey_Tab] = SDL_GetScancodeFromKey( SDLK_TAB );
io.KeyMap[ImGuiKey_LeftArrow] = SDL_GetScancodeFromKey( SDLK_LEFT );
io.KeyMap[ImGuiKey_RightArrow] = SDL_GetScancodeFromKey( SDLK_RIGHT );
io.KeyMap[ImGuiKey_UpArrow] = SDL_GetScancodeFromKey( SDLK_UP );
io.KeyMap[ImGuiKey_DownArrow] = SDL_GetScancodeFromKey( SDLK_DOWN );
io.KeyMap[ImGuiKey_Home] = SDL_GetScancodeFromKey( SDLK_HOME );
io.KeyMap[ImGuiKey_End] = SDL_GetScancodeFromKey( SDLK_END );
io.KeyMap[ImGuiKey_Delete] = SDL_GetScancodeFromKey( SDLK_DELETE );
io.KeyMap[ImGuiKey_Backspace] = SDL_GetScancodeFromKey( SDLK_BACKSPACE );
io.KeyMap[ImGuiKey_Enter] = SDL_GetScancodeFromKey( SDLK_RETURN );
io.KeyMap[ImGuiKey_Escape] = SDL_GetScancodeFromKey( SDLK_ESCAPE );
io.KeyMap[ImGuiKey_A] = SDLK_a;
io.KeyMap[ImGuiKey_C] = SDLK_c;
io.KeyMap[ImGuiKey_V] = SDLK_v;
io.KeyMap[ImGuiKey_X] = SDLK_x;
io.KeyMap[ImGuiKey_Y] = SDLK_y;
io.KeyMap[ImGuiKey_Z] = SDLK_z;

And then later I parse the events more or less like this (some code missing)

case SDL_KEYDOWN:
case SDL_KEYUP:
{
SDL_Scancode key = SDL_GetScancodeFromKey(_keycode);
if (key>=0 && key<512)
{
SDL_Keymod modstate = SDL_GetModState();

    ImGuiIO& io = ImGui::GetIO();

    if (bPressed)
    {
        io.KeysDown[key] = true;
    }
    else
    {
        io.KeysDown[key] = false;
    }
    io.KeyCtrl = (modstate & KMOD_CTRL) != 0;
    io.KeyShift = (modstate & KMOD_SHIFT) != 0;
}

}

//
case SDL_TEXTINPUT:
{
for (uint i=0; i<text.length(); i++)
{
uint32_t keycode = text[i];
if (keycode>=32 && keycode<=255)
{
//printable ASCII characters
ImGui::GetIO().AddInputCharacter( (char)keycode );
}
}
}

[ocornut]

I'll close this for now. The issue you reported is valid and still exist but until we find a library where key values cannot fit within 0..512 i don't think it is worth fixing.
(I don't have an idea for a fix that would be lightweight and not confusing for the most common user atm)

[ocornut]

At worse one can easily store the 17 keys that ImGui use in a contiguous array and just pass that to ImGui.

So instead of doing

io.KeyMap[ImGuiKey_Tab] = SDL_GetScancodeFromKey( SDLK_TAB );
io.KeyMap[ImGuiKey_LeftArrow] = SDL_GetScancodeFromKey( SDLK_LEFT );

and being unable to fill the KeyDown[] array you can do:

io.KeyMap[ImGuiKey_Tab] = ImGuiKey_Tab;
io.KeyMap[ImGuiKey_LeftArrow] = ImGuiKey_LeftArrow;

and fill the KeyDown[] array using ImGuiKey_* indices. The code would only be 2 lines longer to setup the keymap table with a for loop.