Unclear how to hookup text input with SDL

[TimothyWrightSoftware]

Added this code:

    ImGuiIO& io = ImGui::GetIO();
    io.KeyMap[ImGuiKey_Tab] = SDLK_TAB;                 
    io.KeyMap[ImGuiKey_LeftArrow] = SDLK_LEFT;
    io.KeyMap[ImGuiKey_RightArrow] = SDLK_RIGHT;
    io.KeyMap[ImGuiKey_UpArrow] = SDLK_UP;
    io.KeyMap[ImGuiKey_DownArrow] = SDLK_DOWN;
    io.KeyMap[ImGuiKey_Home] = SDLK_HOME;
    io.KeyMap[ImGuiKey_End] = SDLK_END;
    io.KeyMap[ImGuiKey_Delete] = SDLK_DELETE;
    io.KeyMap[ImGuiKey_Backspace] = SDLK_BACKSPACE;
    io.KeyMap[ImGuiKey_Enter] = SDLK_KP_ENTER;
    io.KeyMap[ImGuiKey_Escape] = 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;

I get this assert:

Assertion failed: key_index >= 0 && key_index < ((int)(sizeof(g.IO.KeysDown)/sizeof(*g.IO.KeysDown))), file c:\game_dev\opengl_tests\gui_test\src\imgui.cpp, line 2850

Also, the application just crashes. Not really sure how to proceed.

[TimothyWrightSoftware]

On a side note, when I'm done with all this I'd be happy to give you a pull request with the example SDL code so other's crazy like me don't have to go through the extra pain.

[ocornut]

The values are used as indices into the KeyDown[] away which is arbitrary 512 long. Recent SDL uses value with bit 30 set so that'll fail to be used as an index.

Solution 1
Use the SDL_SCANCODE_* values.

Solution 2
Uses small indices, e.g you can set the mapping table like that:

    ImGuiIO& io = ImGui::GetIO();
    io.KeyMap[ImGuiKey_Tab] = ImGuiKey_Tab;                 
    io.KeyMap[ImGuiKey_LeftArrow] = ImGuiKey_LeftArrow;
    io.KeyMap[ImGuiKey_RightArrow] = ImGuiKey_RightArrow;
[...]

And then update the io.KeysDown[] array using those as indices.

Solution 3
I need to change the keyboard system anyway allow passing keyboard presses as events, but it likely won't be done soon.

There's already two PR for SDL.
More recent one
#233
Old one (was quite incomplete to start with)
#58

[TimothyWrightSoftware]

Well that example will be useful. SCANCODEs it is.

[ocornut]

Sorry I haven't merged an SDL example yet, I'm swamped.

[TimothyWrightSoftware]

No Problem. It's documented, so someone else can find this bug report and get there. It you didn't make such a good library you wouldn't have this problem. :-)