DirectX Backends

Relevant source files

• backends/imgui_impl_allegro5.h
• backends/imgui_impl_dx10.cpp
• backends/imgui_impl_dx10.h
• backends/imgui_impl_dx11.cpp
• backends/imgui_impl_dx11.h
• backends/imgui_impl_dx12.cpp
• backends/imgui_impl_dx12.h
• backends/imgui_impl_dx9.cpp
• backends/imgui_impl_dx9.h
• backends/imgui_impl_metal.h
• backends/imgui_impl_metal.mm
• backends/imgui_impl_opengl2.cpp
• backends/imgui_impl_opengl2.h
• backends/imgui_impl_opengl3.cpp
• backends/imgui_impl_opengl3.h
• backends/imgui_impl_opengl3_loader.h
• backends/imgui_impl_sdlgpu3.cpp
• backends/imgui_impl_sdlgpu3.h
• backends/imgui_impl_vulkan.cpp
• backends/imgui_impl_wgpu.cpp

This page documents the DirectX renderer backends for Dear ImGui, covering DirectX 9, 10, 11, and 12 implementations. These backends translate ImDrawData into DirectX graphics commands, handling vertex/index buffer management, shader setup, texture binding, and render state configuration.

For information about platform backends (Win32, etc.), see Platform Backends. For general backend architecture concepts, see Backend Architecture Overview. For other renderer backends (Vulkan, OpenGL, Metal), see Renderer Backends.

Overview

Dear ImGui provides four DirectX renderer backends, each targeting a specific DirectX API generation:

Backend	File	Primary Use Case	Complexity
DirectX 12	imgui_impl_dx12.cpp	Modern Windows applications, explicit GPU control	High
DirectX 11	imgui_impl_dx11.cpp	General Windows development, mature API	Medium
DirectX 10	imgui_impl_dx10.cpp	Legacy support, similar to DX11	Medium
DirectX 9	imgui_impl_dx9.cpp	Legacy applications, fixed-function pipeline	Low

All DirectX backends implement:

• ImGuiBackendFlags_RendererHasVtxOffset - Large mesh support (64k+ vertices)
• ImGuiBackendFlags_RendererHasTextures - Dynamic font atlas updates
• User texture binding via DirectX texture handles

Sources: backends/imgui_impl_dx12.cpp1-60 backends/imgui_impl_dx11.cpp1-43 backends/imgui_impl_dx10.cpp1-40 backends/imgui_impl_dx9.cpp1-42

Common Architecture Pattern

Backend Lifecycle

All DirectX backends follow a consistent initialization and rendering pattern:

Sources: backends/imgui_impl_dx12.cpp726-780 backends/imgui_impl_dx11.cpp384-429

Common Backend Data Structure

Each backend maintains state in a dedicated structure stored in io.BackendRendererUserData:

Sources: backends/imgui_impl_dx12.cpp92-120 backends/imgui_impl_dx11.cpp69-88 backends/imgui_impl_dx10.cpp67-85 backends/imgui_impl_dx9.cpp57-67

Vertex and Index Buffer Management

All backends dynamically resize vertex and index buffers as needed:

Sources: backends/imgui_impl_dx12.cpp226-267 backends/imgui_impl_dx11.cpp178-202

DirectX 12 Backend

Architecture and Initialization

DirectX 12 is the most complex backend due to its explicit resource management model. It requires descriptor heaps, command allocators, fences, and explicit synchronization.

Title: DX12 Backend Component Structure

The backend maintains separate pipeline states and root signatures for linear and nearest sampling modes, introduced to support different texture filtering requirements:

Title: DX12 Descriptor Allocation Flow

Sources: backends/imgui_impl_dx12.h33-54 backends/imgui_impl_dx12.cpp92-122

Root Signature and Pipeline State

DX12 uses two separate pipelines to support both linear and nearest texture sampling:

Title: DX12 Root Signature Layout

The root signature defines two parameters:

• Parameter 0: Root constants for the 4x4 projection matrix (16 float values)
• Parameter 1: Descriptor table with a single SRV for the texture

The static sampler is configured at root signature creation time, which is why the backend maintains two separate root signatures (pRootSignatureLinear and pRootSignatureNearest).

Sources: backends/imgui_impl_dx12.cpp587-642

Descriptor Management

DX12 requires CPU and GPU descriptor handles for texture access. The backend uses application-provided allocator callbacks:

The texture handle used as ImTextureID is actually the D3D12_GPU_DESCRIPTOR_HANDLE cast to ImTextureID:

Sources: backends/imgui_impl_dx12.cpp82-89 backends/imgui_impl_dx12.cpp369-462

Synchronization and Frame Resources

DX12 uses fences for GPU/CPU synchronization and maintains per-frame resources:

Sources: backends/imgui_impl_dx12.cpp129-136 backends/imgui_impl_dx12.cpp220-224

Render State Setup

DX12 render state configuration involves setting the pipeline, root signature, viewport, and vertex/index buffers:

Title: DX12 Render State Setup Sequence

The projection matrix is computed from draw_data->DisplayPos and draw_data->DisplaySize to create an orthographic projection that maps ImGui's coordinate space to normalized device coordinates:

float mvp[4][4] = {
    { 2.0f/(R-L),   0.0f,         0.0f,  0.0f },
    { 0.0f,         2.0f/(T-B),   0.0f,  0.0f },
    { 0.0f,         0.0f,         0.5f,  0.0f },
    { (R+L)/(L-R),  (T+B)/(B-T),  0.5f,  1.0f }
}

Sources: backends/imgui_impl_dx12.cpp164-213

Texture Upload Pipeline

DX12 texture uploads use a dedicated command allocator and list, with a reusable staging buffer:

Sources: backends/imgui_impl_dx12.cpp110-115 backends/imgui_impl_dx12.cpp369-550

DirectX 11 Backend

Architecture

DirectX 11 is simpler than DX12 due to its implicit resource management and immediate context model. The backend uses a single device context for all operations:

Title: DX11 Backend State Structure

Sources: backends/imgui_impl_dx11.cpp70-90

Shader Compilation

DX11 compiles HLSL shaders at runtime using D3DCompile(). The vertex shader transforms vertices using a constant buffer projection matrix:

Title: DX11 Shader and Input Layout

The input layout matches the ImDrawVert structure:

• POSITION: 2D position (8 bytes)
• TEXCOORD: UV coordinates (8 bytes)
• COLOR: RGBA color packed as 4 bytes

Sources: backends/imgui_impl_dx11.cpp332-476

Texture Management

DX11 uses ID3D11ShaderResourceView* directly as ImTextureID:

Texture updates use Map()/Unmap() for dynamic updates or UpdateSubresource() for initial creation:

Sources: backends/imgui_impl_dx11.cpp63-67 backends/imgui_impl_dx11.cpp241-330

Render Pipeline

DX11 render state setup involves mapping the constant buffer, configuring the input assembler, setting shaders, and configuring output merger states:

Title: DX11 Render State Configuration

The backend explicitly clears geometry, hull, domain, and compute shader stages to ensure no unexpected shaders are active. The blend state is configured for alpha blending with SrcAlpha and InvSrcAlpha factors.

Sources: backends/imgui_impl_dx11.cpp105-160

Sampler State Management

As of version 1.92, DX11 backend supports both linear and nearest texture sampling. The sampler state objects are created during device object initialization:

Title: DX11 Sampler State Configuration

The default sampler used during render is pTexSamplerLinear. Applications can change the sampler via the ImGui_ImplDX11_RenderState structure exposed in callbacks.

Sources: backends/imgui_impl_dx11.cpp478-522

DirectX 10 Backend

The DirectX 10 backend is architecturally similar to DirectX 11, providing compatibility with Windows Vista systems. It uses the ID3D10* interface family instead of ID3D11*.

Key Differences from DX11

Title: DX10 vs DX11 API Comparison

The main difference is that DX10 combines device and context into a single ID3D10Device interface, while DX11 separates them. The rendering logic and shader code are otherwise identical.

Title: DX10 Backend Structure

Sources: backends/imgui_impl_dx10.cpp68-87 backends/imgui_impl_dx10.cpp102-160

DirectX 9 Backend

Fixed-Function Pipeline

DirectX 9 uses the legacy fixed-function pipeline instead of programmable shaders. The backend configures the pipeline through render states, texture stage states, and transform matrices:

Title: DX9 Backend State Structure

Title: DX9 Fixed Function Pipeline Configuration

Sources: backends/imgui_impl_dx9.cpp58-67 backends/imgui_impl_dx9.cpp91-162

CUSTOMVERTEX Format and FVF

DX9 uses a Flexible Vertex Format (FVF) descriptor instead of an input layout. The vertex data must be converted from ImDrawVert to CUSTOMVERTEX:

Title: DX9 Vertex Format Conversion

The color conversion macro IMGUI_COL_TO_DX9_ARGB adapts to the build configuration:

When IMGUI_USE_BGRA_PACKED_COLOR is defined, Dear ImGui packs colors in BGRA order, which matches DX9's native D3DCOLOR format (ARGB in memory, BGRA in register order on little-endian systems).

Sources: backends/imgui_impl_dx9.cpp69-81 backends/imgui_impl_dx9.cpp211-233

State Block Management

DX9 uses state blocks to capture and restore the application's render state, ensuring ImGui rendering doesn't affect the application's state:

Title: DX9 State Block Save and Restore

The state block captures the entire Direct3D 9 state, including:

• All render states (blending, depth, culling, etc.)
• Texture stage states
• Sampler states
• Transform matrices
• Vertex declaration
• Texture assignments

After ImGui rendering completes, the state block is applied to restore the application's original state, then released.

Sources: backends/imgui_impl_dx9.cpp165-269

Texture Upload

DX9 texture creation and updates are simpler than modern APIs due to implicit resource management:

Title: DX9 Texture Creation and Update

The D3DPOOL_MANAGED flag allows the driver to manage texture memory automatically. The LockRect() call provides direct CPU access to texture memory. For RGBA format, each row is copied individually to handle potential stride differences.

Sources: backends/imgui_impl_dx9.cpp272-356

Comparison Table

Feature Support Matrix

Feature	DX12	DX11	DX10	DX9
Programmable Shaders	✓	✓	✓	✗ (fixed)
Explicit Synchronization	✓	✗	✗	✗
Descriptor Heaps	✓	✗	✗	✗
Command Lists	✓	✗	✗	✗
64k+ Vertices	✓	✓	✓	✓
Dynamic Textures	✓	✓	✓	✓
Render State Exposure	✓	✓	✓	✗
BGRA Packed Color	-	-	-	✓ (optimal)

Initialization API Comparison

Backend	Init Function	Key Parameters
DX12	ImGui_ImplDX12_Init(ImGui_ImplDX12_InitInfo*)	Device, CommandQueue, NumFramesInFlight, RTVFormat, Descriptor callbacks
DX11	ImGui_ImplDX11_Init(ID3D11Device*, ID3D11DeviceContext*)	Device, DeviceContext
DX10	ImGui_ImplDX10_Init(ID3D10Device*)	Device
DX9	ImGui_ImplDX9_Init(IDirect3DDevice9*)	Device

Sources: backends/imgui_impl_dx12.h51 backends/imgui_impl_dx11.h28 backends/imgui_impl_dx10.h28 backends/imgui_impl_dx9.h30

Texture Identifier Types

Sources: backends/imgui_impl_dx12.cpp338-341 backends/imgui_impl_dx11.cpp220-228 backends/imgui_impl_dx10.cpp220-228 backends/imgui_impl_dx9.cpp185-193

Migration Guidance

Choosing a Backend

DX11 to DX12 Migration Considerations

Key differences when migrating from DX11 to DX12:

1. Descriptor Management: Must provide allocator callbacks for SRV descriptors
2. Synchronization: Must manage fences and wait for GPU completion
3. Command Submission: Must provide ID3D12CommandQueue for texture uploads
4. Frame Resources: Must specify NumFramesInFlight and manage per-frame buffers
5. Initialization Structure: Use ImGui_ImplDX12_InitInfo instead of function parameters

Sources: backends/imgui_impl_dx12.cpp726-780 backends/imgui_impl_dx11.cpp384-403

Common Integration Patterns

All DirectX backends follow this integration pattern:

Sources: backends/imgui_impl_dx12.cpp207-348 backends/imgui_impl_dx11.cpp161-239