MonkeGUI

Lightweight animated immediate-mode GUI framework for Unreal Engine canvas rendering. Inspired by Dear ImGui, built entirely on UCanvas with no external GUI dependencies.

For full API reference, see DOCUMENTATION.md

Discord: aactor

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Preview

Menu	Widgets

Color Picker	Tabs / Combo

Video Showcase

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Features

• Immediate-mode API — no retained widget tree
• Fully rendered via UCanvas — no external render dependencies
• Smooth animations on every widget (hover, press, open/close)
• Window dragging and resizing
• Collapsible windows
• Tabs, combo boxes, sliders, checkboxes, color picker, popups, search bar
• Custom styling via MonkeGUI::Style namespace
• UE4 / UE5 compatible

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Requirements

• Unreal Engine 4 or 5
• A valid UCanvas* (e.g. from PostRender)
• A 1×1 white UTexture* (used for all filled rect rendering)
• A UFont*
• C++

SDK note: MonkeGUI references FLinearColor, FVector2D, UCanvas, UTexture, and UFont from your UE SDK headers. Make sure these are available in your include path before including MonkeGUI.h.

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Quick Start

1. Initialize each frame

Call these at the top of your render function, before any widgets:

MonkeGUI::SetWhiteTexture(myWhiteTexture); // 1x1 white UTexture*
MonkeGUI::SetFont(myFont);                 // UFont*
MonkeGUI::SetupCanvas(Canvas, DeltaTime);  // resets state, updates mouse

2. Draw your UI

static FVector2D pos  = { 200.f, 150.f };
static FVector2D size = { 400.f, 300.f };

if (MonkeGUI::Begin("My Window", &pos, &size, true))
{
    static bool enabled = false;
    MonkeGUI::Checkbox("Enable Feature", &enabled);

    if (MonkeGUI::Button("Execute"))
    {
        // handle click
    }

    MonkeGUI::End();
}

3. Flush the draw queue

MonkeGUI::Render(); // always call last

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Widgets

Widget	Function
Text	MonkeGUI::Text(label)
Button	MonkeGUI::Button(label, width)
Checkbox	MonkeGUI::Checkbox(label, &bool)
Slider	MonkeGUI::SliderFloat(label, &float, min, max)
Combo	MonkeGUI::Combo(label, &index, items, count)
Color Picker	MonkeGUI::ColorPicker(label, &FLinearColor)
Separator	MonkeGUI::Separator()
Search Bar	MonkeGUI::SearchBar(label, buf, size)
Tabs	BeginTabs() / TabItem() / EndTabs()
Popup	OpenPopup(id) / BeginPopup(id, size) / EndPopup()

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Tabs Example

static int tab = 0;

MonkeGUI::BeginTabs();
MonkeGUI::TabItem("General",  0, &tab);
MonkeGUI::TabItem("Advanced", 1, &tab);
MonkeGUI::EndTabs();

if (tab == 0) { /* general widgets */ }
if (tab == 1) { /* advanced widgets */ }

Search Bar Example

static char search[128]{};
MonkeGUI::SearchBar("##search", search, sizeof(search));

for (int i = 0; i < count; i++)
    if (MonkeGUI::SearchMatches(names[i], search))
        MonkeGUI::Checkbox(names[i], &enabled[i]);

Popup Example

if (MonkeGUI::Button("Open Info"))
    MonkeGUI::OpenPopup("info");

if (MonkeGUI::BeginPopup("info", { 220.f, 100.f }))
{
    MonkeGUI::Text("Hello from a popup!");
    if (MonkeGUI::Button("Close", 80.f))
        MonkeGUI::OpenPopupId = -1;
    MonkeGUI::EndPopup();
}

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Styling

All style values are in MonkeGUI::Style and can be changed at any time:

MonkeGUI::Style::Accent    = MonkeGUI::SRGB(255, 100, 50, 220); // orange accent
MonkeGUI::Style::WindowBg  = MonkeGUI::SRGB(20, 20, 20, 240);
MonkeGUI::Style::RowH      = 20.f;

The window background and title bar colors can also be changed at runtime:

MonkeGUI::MenuBg  = someColor;
MonkeGUI::TitleBg = someColor;

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Optional: FPS Watermark

// Set once at init
MonkeGUI::SetFPSCallback([]() -> float {
    return 1.0f / myDeltaTime;
});

// Call each frame (before Render)
MonkeGUI::Watermark("My App v1.0");
// renders: "My App v1.0 | 144 FPS"

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Optional: Snow Effect

MonkeGUI::FX::SnowRender(DeltaTime, 0.85f); // call before Render()

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Known Limitations

• Windows only — mouse input uses GetAsyncKeyState and GetCursorPos.
• Single context — all state is global; multiple simultaneous GUI contexts are not supported.
• Draw queue cap — the post-render queue holds up to 2048 commands. Very complex layouts may silently drop commands.
• No scrolling — windows and combo boxes do not scroll; content that overflows is clipped.

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Design Goals

MonkeGUI was built to provide clean visuals and smooth animations with the simplest possible integration story — drop in one header, supply a canvas and a white texture, and start drawing.

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Credits

Inspired by Dear ImGui by Omar Cornut.

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License

MIT — see LICENSE.