Drawing a GUI¶

DttR provides built-in ImGui support for mod overlay menus, including debug windows, mod options, small tools, and overlays that do not need to be drawn through the game renderer.

Drawing UI in ImGui callbacks¶

Use these callbacks for ImGui widgets:

• DTTR_MODS_IMGUI_BEGIN: Add normal mod UI.
• DTTR_MODS_IMGUI_END: Add UI that should run near the end of the ImGui frame.

Most mods should use DTTR_MODS_IMGUI_BEGIN.

DTTR_MODS_IMGUI_BEGIN {
    igBegin("My Mod", NULL, 0);
    igText("Hello from my mod");
    igEnd();
}

Leaving the ImGui lifecycle to DttR¶

DttR owns the ImGui context, frame flow, SDL backend, and renderer backend. Submitting ImGui work outside a DttR ImGui callback can cause frame-order or backend-state bugs.

Calling these from a mod can break DttR's UI or another mod's UI:

• igCreateContext or igDestroyContext
• igNewFrame or igRender
• ImGui_ImplSDL3_* init or shutdown functions
• ImGui_ImplOpenGL3_* init or shutdown functions

Storing UI state in your mod¶

Store checkbox values, window visibility, and other UI state in mod-owned variables.

static bool show_window = true;

DTTR_MODS_IMGUI_BEGIN {
    if (!show_window) {
        return;
    }

    igBegin("My Mod", &show_window, 0);
    igText("Window state belongs to the mod");
    igEnd();
}

Storing pointers to short-lived ImGui data after the callback returns can create dangling-pointer bugs; copy any needed values instead.

Reading SDL events from callbacks¶

For SDL event callbacks, include SDL3/SDL.h and read the callback data directly.

Forwarding events to ImGui backend APIs from a mod can create duplicate or out-of-order ImGui event handling; read the callback data directly instead.