imgui/examples/directx10_example/imgui_impl_dx10.cpp

// ImGui Win32 + DirectX10 binding
// In this binding, ImTextureID is used to store a 'ID3D10ShaderResourceView*' texture identifier. Read the FAQ about ImTextureID in imgui.cpp.

// You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
// If you use this binding you'll need to call 4 functions: ImGui_ImplXXXX_Init(), ImGui_ImplXXXX_NewFrame(), ImGui::Render() and ImGui_ImplXXXX_Shutdown().
// If you are new to ImGui, see examples/README.txt and documentation at the top of imgui.cpp.
// https://github.com/ocornut/imgui

#include "imgui.h"
#include "imgui_impl_dx10.h"

// DirectX
#include <d3d10_1.h>
#include <d3d10.h>
#include <d3dcompiler.h>
#define DIRECTINPUT_VERSION 0x0800
#include <dinput.h>

// Data
static INT64                    g_Time = 0;
static INT64                    g_TicksPerSecond = 0;

static HWND                     g_hWnd = 0;
static ID3D10Device*            g_pd3dDevice = NULL;
static ID3D10Buffer*            g_pVB = NULL;
static ID3D10Buffer*            g_pIB = NULL;
static ID3D10Blob *             g_pVertexShaderBlob = NULL;
static ID3D10VertexShader*      g_pVertexShader = NULL;
static ID3D10InputLayout*       g_pInputLayout = NULL;
static ID3D10Buffer*            g_pVertexConstantBuffer = NULL;
static ID3D10Blob *             g_pPixelShaderBlob = NULL;
static ID3D10PixelShader*       g_pPixelShader = NULL;
static ID3D10SamplerState*      g_pFontSampler = NULL;
static ID3D10ShaderResourceView*g_pFontTextureView = NULL;
static ID3D10RasterizerState*   g_pRasterizerState = NULL;
static ID3D10BlendState*        g_pBlendState = NULL;
static int                      g_VertexBufferSize = 5000, g_IndexBufferSize = 10000;

struct VERTEX_CONSTANT_BUFFER
{
    float        mvp[4][4];
};

// This is the main rendering function that you have to implement and provide to ImGui (via setting up 'RenderDrawListsFn' in the ImGuiIO structure)
// If text or lines are blurry when integrating ImGui in your engine:
// - in your Render function, try translating your projection matrix by (0.5f,0.5f) or (0.375f,0.375f)
void ImGui_ImplDX10_RenderDrawLists(ImDrawData* draw_data)
{
    // Create and grow vertex/index buffers if needed
    if (!g_pVB || g_VertexBufferSize < draw_data->TotalVtxCount)
    {
        if (g_pVB) { g_pVB->Release(); g_pVB = NULL; }
        g_VertexBufferSize = draw_data->TotalVtxCount + 5000;
        D3D10_BUFFER_DESC desc;
        memset(&desc, 0, sizeof(D3D10_BUFFER_DESC));
        desc.Usage = D3D10_USAGE_DYNAMIC;
        desc.ByteWidth = g_VertexBufferSize * sizeof(ImDrawVert);
        desc.BindFlags = D3D10_BIND_VERTEX_BUFFER;
        desc.CPUAccessFlags = D3D10_CPU_ACCESS_WRITE;
        desc.MiscFlags = 0;
        if (g_pd3dDevice->CreateBuffer(&desc, NULL, &g_pVB) < 0)
            return;
    }

    if (!g_pIB || g_IndexBufferSize < draw_data->TotalIdxCount)
    {
        if (g_pIB) { g_pIB->Release(); g_pIB = NULL; }
        g_IndexBufferSize = draw_data->TotalIdxCount + 10000;
        D3D10_BUFFER_DESC bufferDesc;
        memset(&bufferDesc, 0, sizeof(D3D10_BUFFER_DESC));
        bufferDesc.Usage = D3D10_USAGE_DYNAMIC;
        bufferDesc.ByteWidth = g_IndexBufferSize * sizeof(ImDrawIdx);
        bufferDesc.BindFlags = D3D10_BIND_INDEX_BUFFER;
        bufferDesc.CPUAccessFlags = D3D10_CPU_ACCESS_WRITE;
        if (g_pd3dDevice->CreateBuffer(&bufferDesc, NULL, &g_pIB) < 0)
            return;
    }

    // Copy and convert all vertices into a single contiguous buffer
    ImDrawVert* vtx_dst = NULL;
    ImDrawIdx* idx_dst = NULL;
    g_pVB->Map(D3D10_MAP_WRITE_DISCARD, 0, (void**)&vtx_dst);
    g_pIB->Map(D3D10_MAP_WRITE_DISCARD, 0, (void**)&idx_dst);

    for (int n = 0; n < draw_data->CmdListsCount; n++)
    {
        const ImDrawList* cmd_list = draw_data->CmdLists[n];
        memcpy(vtx_dst, &cmd_list->VtxBuffer[0], cmd_list->VtxBuffer.size() * sizeof(ImDrawVert));
        memcpy(idx_dst, &cmd_list->IdxBuffer[0], cmd_list->IdxBuffer.size() * sizeof(ImDrawIdx));
        vtx_dst += cmd_list->VtxBuffer.size();
        idx_dst += cmd_list->IdxBuffer.size();
    }
    g_pVB->Unmap();
    g_pIB->Unmap();

    // Setup orthographic projection matrix into our constant buffer
    {
        void* mappedResource;
        if (g_pVertexConstantBuffer->Map(D3D10_MAP_WRITE_DISCARD, 0, &mappedResource) != S_OK)
            return;

        VERTEX_CONSTANT_BUFFER* pConstantBuffer = (VERTEX_CONSTANT_BUFFER*)mappedResource;
        const float L = 0.0f;
        const float R = ImGui::GetIO().DisplaySize.x;
        const float B = ImGui::GetIO().DisplaySize.y;
        const float T = 0.0f;
        const 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 },
        };
        memcpy(&pConstantBuffer->mvp, mvp, sizeof(mvp));
        g_pVertexConstantBuffer->Unmap();
    }

    // Setup viewport
    {
        D3D10_VIEWPORT vp;
        memset(&vp, 0, sizeof(D3D10_VIEWPORT));
        vp.Width = (UINT)ImGui::GetIO().DisplaySize.x;
        vp.Height = (UINT)ImGui::GetIO().DisplaySize.y;
        vp.MinDepth = 0.0f;
        vp.MaxDepth = 1.0f;
        vp.TopLeftX = 0;
        vp.TopLeftY = 0;
        g_pd3dDevice->RSSetViewports(1, &vp);
    }

    // Bind shader and vertex buffers
    unsigned int stride = sizeof(ImDrawVert);
    unsigned int offset = 0;
    g_pd3dDevice->IASetInputLayout(g_pInputLayout);
    g_pd3dDevice->IASetVertexBuffers(0, 1, &g_pVB, &stride, &offset);
    g_pd3dDevice->IASetIndexBuffer(g_pIB, sizeof(ImDrawIdx) == 2 ? DXGI_FORMAT_R16_UINT : DXGI_FORMAT_R32_UINT, 0);
    g_pd3dDevice->IASetPrimitiveTopology(D3D10_PRIMITIVE_TOPOLOGY_TRIANGLELIST);
    g_pd3dDevice->VSSetShader(g_pVertexShader);
    g_pd3dDevice->VSSetConstantBuffers(0, 1, &g_pVertexConstantBuffer);
    g_pd3dDevice->PSSetShader(g_pPixelShader);
    g_pd3dDevice->PSSetSamplers(0, 1, &g_pFontSampler);

    // Setup render state
    const float blendFactor[4] = { 0.f, 0.f, 0.f, 0.f };
    g_pd3dDevice->OMSetBlendState(g_pBlendState, blendFactor, 0xffffffff);
    g_pd3dDevice->RSSetState(g_pRasterizerState);

    // Render command lists
    int vtx_offset = 0;
    int idx_offset = 0;
    for (int n = 0; n < draw_data->CmdListsCount; n++)
    {
        const ImDrawList* cmd_list = draw_data->CmdLists[n];
        for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.size(); cmd_i++)
        {
            const ImDrawCmd* pcmd = &cmd_list->CmdBuffer[cmd_i];
            if (pcmd->UserCallback)
            {
                pcmd->UserCallback(cmd_list, pcmd);
            }
            else
            {
                const D3D10_RECT r = { (LONG)pcmd->ClipRect.x, (LONG)pcmd->ClipRect.y, (LONG)pcmd->ClipRect.z, (LONG)pcmd->ClipRect.w };
                g_pd3dDevice->PSSetShaderResources(0, 1, (ID3D10ShaderResourceView**)&pcmd->TextureId);
                g_pd3dDevice->RSSetScissorRects(1, &r);
                g_pd3dDevice->DrawIndexed(pcmd->ElemCount, idx_offset, vtx_offset);
            }
            idx_offset += pcmd->ElemCount;
        }
        vtx_offset += cmd_list->VtxBuffer.size();
    }

    // Restore modified state
    g_pd3dDevice->IASetInputLayout(NULL);
    g_pd3dDevice->PSSetShader(NULL);
    g_pd3dDevice->VSSetShader(NULL);
}

IMGUI_API LRESULT ImGui_ImplDX10_WndProcHandler(HWND, UINT msg, WPARAM wParam, LPARAM lParam)
{
    ImGuiIO& io = ImGui::GetIO();
    switch (msg)
    {
    case WM_LBUTTONDOWN:
        io.MouseDown[0] = true;
        return true;
    case WM_LBUTTONUP:
        io.MouseDown[0] = false;
        return true;
    case WM_RBUTTONDOWN:
        io.MouseDown[1] = true;
        return true;
    case WM_RBUTTONUP:
        io.MouseDown[1] = false;
        return true;
    case WM_MBUTTONDOWN:
        io.MouseDown[2] = true;
        return true;
    case WM_MBUTTONUP:
        io.MouseDown[2] = false;
        return true;
    case WM_MOUSEWHEEL:
        io.MouseWheel += GET_WHEEL_DELTA_WPARAM(wParam) > 0 ? +1.0f : -1.0f;
        return true;
    case WM_MOUSEMOVE:
        io.MousePos.x = (signed short)(lParam);
        io.MousePos.y = (signed short)(lParam >> 16);
        return true;
    case WM_KEYDOWN:
        if (wParam < 256)
            io.KeysDown[wParam] = 1;
        return true;
    case WM_KEYUP:
        if (wParam < 256)
            io.KeysDown[wParam] = 0;
        return true;
    case WM_CHAR:
        // You can also use ToAscii()+GetKeyboardState() to retrieve characters.
        if (wParam > 0 && wParam < 0x10000)
            io.AddInputCharacter((unsigned short)wParam);
        return true;
    }
    return 0;
}

static void ImGui_ImplDX10_CreateFontsTexture()
{
    ImGuiIO& io = ImGui::GetIO();

    // Build
    unsigned char* pixels;
    int width, height;
    io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);

    // Create DX10 texture
    {
        D3D10_TEXTURE2D_DESC texDesc;
        ZeroMemory(&texDesc, sizeof(texDesc));
        texDesc.Width = width;
        texDesc.Height = height;
        texDesc.MipLevels = 1;
        texDesc.ArraySize = 1;
        texDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
        texDesc.SampleDesc.Count = 1;
        texDesc.Usage = D3D10_USAGE_DEFAULT;
        texDesc.BindFlags = D3D10_BIND_SHADER_RESOURCE;
        texDesc.CPUAccessFlags = 0;

        ID3D10Texture2D *pTexture = NULL;
        D3D10_SUBRESOURCE_DATA subResource;
        subResource.pSysMem = pixels;
        subResource.SysMemPitch = texDesc.Width * 4;
        subResource.SysMemSlicePitch = 0;
        g_pd3dDevice->CreateTexture2D(&texDesc, &subResource, &pTexture);

        // Create texture view
        D3D10_SHADER_RESOURCE_VIEW_DESC srvDesc;
        ZeroMemory(&srvDesc, sizeof(srvDesc));
        srvDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
        srvDesc.ViewDimension = D3D10_SRV_DIMENSION_TEXTURE2D;
        srvDesc.Texture2D.MipLevels = texDesc.MipLevels;
        srvDesc.Texture2D.MostDetailedMip = 0;
        g_pd3dDevice->CreateShaderResourceView(pTexture, &srvDesc, &g_pFontTextureView);
        pTexture->Release();
    }

    // Store our identifier
    io.Fonts->TexID = (void *)g_pFontTextureView;

    // Create texture sampler
    {
        D3D10_SAMPLER_DESC samplerDesc;
        ZeroMemory(&samplerDesc, sizeof(samplerDesc));
        samplerDesc.Filter = D3D10_FILTER_MIN_MAG_MIP_LINEAR;
        samplerDesc.AddressU = D3D10_TEXTURE_ADDRESS_WRAP;
        samplerDesc.AddressV = D3D10_TEXTURE_ADDRESS_WRAP;
        samplerDesc.AddressW = D3D10_TEXTURE_ADDRESS_WRAP;
        samplerDesc.MipLODBias = 0.f;
        samplerDesc.ComparisonFunc = D3D10_COMPARISON_ALWAYS;
        samplerDesc.MinLOD = 0.f;
        samplerDesc.MaxLOD = 0.f;
        g_pd3dDevice->CreateSamplerState(&samplerDesc, &g_pFontSampler);
    }

    // Cleanup (don't clear the input data if you want to append new fonts later)
    io.Fonts->ClearInputData();
    io.Fonts->ClearTexData();
}

bool    ImGui_ImplDX10_CreateDeviceObjects()
{
    if (!g_pd3dDevice)
        return false;
    if (g_pFontSampler)
        ImGui_ImplDX10_InvalidateDeviceObjects();

    // Create the vertex shader
    {
        static const char* vertexShader =
            "cbuffer vertexBuffer : register(b0) \
            {\
            float4x4 ProjectionMatrix; \
            };\
            struct VS_INPUT\
            {\
            float2 pos : POSITION;\
            float4 col : COLOR0;\
            float2 uv  : TEXCOORD0;\
            };\
            \
            struct PS_INPUT\
            {\
            float4 pos : SV_POSITION;\
            float4 col : COLOR0;\
            float2 uv  : TEXCOORD0;\
            };\
            \
            PS_INPUT main(VS_INPUT input)\
            {\
            PS_INPUT output;\
            output.pos = mul( ProjectionMatrix, float4(input.pos.xy, 0.f, 1.f));\
            output.col = input.col;\
            output.uv  = input.uv;\
            return output;\
            }";

        D3DCompile(vertexShader, strlen(vertexShader), NULL, NULL, NULL, "main", "vs_4_0", 0, 0, &g_pVertexShaderBlob, NULL);
        if (g_pVertexShaderBlob == NULL) // NB: Pass ID3D10Blob* pErrorBlob to D3DCompile() to get error showing in (const char*)pErrorBlob->GetBufferPointer(). Make sure to Release() the blob!
            return false;
        if (g_pd3dDevice->CreateVertexShader((DWORD*)g_pVertexShaderBlob->GetBufferPointer(), g_pVertexShaderBlob->GetBufferSize(), &g_pVertexShader) != S_OK)
            return false;

        // Create the input layout
        D3D10_INPUT_ELEMENT_DESC localLayout[] = {
            { "POSITION", 0, DXGI_FORMAT_R32G32_FLOAT,   0, (size_t)(&((ImDrawVert*)0)->pos), D3D10_INPUT_PER_VERTEX_DATA, 0 },
            { "TEXCOORD", 0, DXGI_FORMAT_R32G32_FLOAT,   0, (size_t)(&((ImDrawVert*)0)->uv),  D3D10_INPUT_PER_VERTEX_DATA, 0 },
            { "COLOR",    0, DXGI_FORMAT_R8G8B8A8_UNORM, 0, (size_t)(&((ImDrawVert*)0)->col), D3D10_INPUT_PER_VERTEX_DATA, 0 },
        };

        if (g_pd3dDevice->CreateInputLayout(localLayout, 3, g_pVertexShaderBlob->GetBufferPointer(), g_pVertexShaderBlob->GetBufferSize(), &g_pInputLayout) != S_OK)
            return false;

        // Create the constant buffer
        {
            D3D10_BUFFER_DESC cbDesc;
            cbDesc.ByteWidth = sizeof(VERTEX_CONSTANT_BUFFER);
            cbDesc.Usage = D3D10_USAGE_DYNAMIC;
            cbDesc.BindFlags = D3D10_BIND_CONSTANT_BUFFER;
            cbDesc.CPUAccessFlags = D3D10_CPU_ACCESS_WRITE;
            cbDesc.MiscFlags = 0;
            g_pd3dDevice->CreateBuffer(&cbDesc, NULL, &g_pVertexConstantBuffer);
        }
    }

    // Create the pixel shader
    {
        static const char* pixelShader =
            "struct PS_INPUT\
            {\
            float4 pos : SV_POSITION;\
            float4 col : COLOR0;\
            float2 uv  : TEXCOORD0;\
            };\
            sampler sampler0;\
            Texture2D texture0;\
            \
            float4 main(PS_INPUT input) : SV_Target\
            {\
            float4 out_col = input.col * texture0.Sample(sampler0, input.uv); \
            return out_col; \
            }";

        D3DCompile(pixelShader, strlen(pixelShader), NULL, NULL, NULL, "main", "ps_4_0", 0, 0, &g_pPixelShaderBlob, NULL);
        if (g_pPixelShaderBlob == NULL)  // NB: Pass ID3D10Blob* pErrorBlob to D3DCompile() to get error showing in (const char*)pErrorBlob->GetBufferPointer(). Make sure to Release() the blob!
            return false;
        if (g_pd3dDevice->CreatePixelShader((DWORD*)g_pPixelShaderBlob->GetBufferPointer(), g_pPixelShaderBlob->GetBufferSize(), &g_pPixelShader) != S_OK)
            return false;
    }

    // Create the blending setup
    {
        D3D10_BLEND_DESC desc;
        ZeroMemory(&desc, sizeof(desc));
        desc.AlphaToCoverageEnable = false;
        desc.BlendEnable[0] = true;
        desc.SrcBlend = D3D10_BLEND_SRC_ALPHA;
        desc.DestBlend = D3D10_BLEND_INV_SRC_ALPHA;
        desc.BlendOp = D3D10_BLEND_OP_ADD;
        desc.SrcBlendAlpha = D3D10_BLEND_INV_SRC_ALPHA;
        desc.DestBlendAlpha = D3D10_BLEND_ZERO;
        desc.BlendOpAlpha = D3D10_BLEND_OP_ADD;
        desc.RenderTargetWriteMask[0] = D3D10_COLOR_WRITE_ENABLE_ALL;
        g_pd3dDevice->CreateBlendState(&desc, &g_pBlendState);
    }

    // Create the rasterizer state
    {
        D3D10_RASTERIZER_DESC desc;
        ZeroMemory(&desc, sizeof(desc));
        desc.FillMode = D3D10_FILL_SOLID;
        desc.CullMode = D3D10_CULL_NONE;
        desc.ScissorEnable = true;
        desc.DepthClipEnable = true;
        g_pd3dDevice->CreateRasterizerState(&desc, &g_pRasterizerState);
    }

    ImGui_ImplDX10_CreateFontsTexture();

    return true;
}

void    ImGui_ImplDX10_InvalidateDeviceObjects()
{
    if (!g_pd3dDevice)
        return;

    if (g_pFontSampler) { g_pFontSampler->Release(); g_pFontSampler = NULL; }
    if (g_pFontTextureView) { g_pFontTextureView->Release(); g_pFontTextureView = NULL; ImGui::GetIO().Fonts->TexID = 0; }
    if (g_pIB) { g_pIB->Release(); g_pIB = NULL; }
    if (g_pVB) { g_pVB->Release(); g_pVB = NULL; }

    if (g_pBlendState) { g_pBlendState->Release(); g_pBlendState = NULL; }
    if (g_pRasterizerState) { g_pRasterizerState->Release(); g_pRasterizerState = NULL; }
    if (g_pPixelShader) { g_pPixelShader->Release(); g_pPixelShader = NULL; }
    if (g_pPixelShaderBlob) { g_pPixelShaderBlob->Release(); g_pPixelShaderBlob = NULL; }
    if (g_pVertexConstantBuffer) { g_pVertexConstantBuffer->Release(); g_pVertexConstantBuffer = NULL; }
    if (g_pInputLayout) { g_pInputLayout->Release(); g_pInputLayout = NULL; }
    if (g_pVertexShader) { g_pVertexShader->Release(); g_pVertexShader = NULL; }
    if (g_pVertexShaderBlob) { g_pVertexShaderBlob->Release(); g_pVertexShaderBlob = NULL; }
}

bool    ImGui_ImplDX10_Init(void* hwnd, ID3D10Device* device)
{
    g_hWnd = (HWND)hwnd;
    g_pd3dDevice = device;

    if (!QueryPerformanceFrequency((LARGE_INTEGER *)&g_TicksPerSecond))
        return false;
    if (!QueryPerformanceCounter((LARGE_INTEGER *)&g_Time))
        return false;

    ImGuiIO& io = ImGui::GetIO();
    io.KeyMap[ImGuiKey_Tab] = VK_TAB;                       // Keyboard mapping. ImGui will use those indices to peek into the io.KeyDown[] array that we will update during the application lifetime.
    io.KeyMap[ImGuiKey_LeftArrow] = VK_LEFT;
    io.KeyMap[ImGuiKey_RightArrow] = VK_RIGHT;
    io.KeyMap[ImGuiKey_UpArrow] = VK_UP;
    io.KeyMap[ImGuiKey_DownArrow] = VK_DOWN;
    io.KeyMap[ImGuiKey_PageUp] = VK_PRIOR;
    io.KeyMap[ImGuiKey_PageDown] = VK_NEXT;
    io.KeyMap[ImGuiKey_Home] = VK_HOME;
    io.KeyMap[ImGuiKey_End] = VK_END;
    io.KeyMap[ImGuiKey_Delete] = VK_DELETE;
    io.KeyMap[ImGuiKey_Backspace] = VK_BACK;
    io.KeyMap[ImGuiKey_Enter] = VK_RETURN;
    io.KeyMap[ImGuiKey_Escape] = VK_ESCAPE;
    io.KeyMap[ImGuiKey_A] = 'A';
    io.KeyMap[ImGuiKey_C] = 'C';
    io.KeyMap[ImGuiKey_V] = 'V';
    io.KeyMap[ImGuiKey_X] = 'X';
    io.KeyMap[ImGuiKey_Y] = 'Y';
    io.KeyMap[ImGuiKey_Z] = 'Z';

    io.RenderDrawListsFn = ImGui_ImplDX10_RenderDrawLists;  // Alternatively you can set this to NULL and call ImGui::GetDrawData() after ImGui::Render() to get the same ImDrawData pointer.
    io.ImeWindowHandle = g_hWnd;

    return true;
}

void ImGui_ImplDX10_Shutdown()
{
    ImGui_ImplDX10_InvalidateDeviceObjects();
    ImGui::Shutdown();
    g_pd3dDevice = NULL;
    g_hWnd = (HWND)0;
}

void ImGui_ImplDX10_NewFrame()
{
    if (!g_pFontSampler)
        ImGui_ImplDX10_CreateDeviceObjects();

    ImGuiIO& io = ImGui::GetIO();

    // Setup display size (every frame to accommodate for window resizing)
    RECT rect;
    GetClientRect(g_hWnd, &rect);
    io.DisplaySize = ImVec2((float)(rect.right - rect.left), (float)(rect.bottom - rect.top));

    // Setup time step
    INT64 current_time;
    QueryPerformanceCounter((LARGE_INTEGER *)&current_time);
    io.DeltaTime = (float)(current_time - g_Time) / g_TicksPerSecond;
    g_Time = current_time;

    // Read keyboard modifiers inputs
    io.KeyCtrl = (GetKeyState(VK_CONTROL) & 0x8000) != 0;
    io.KeyShift = (GetKeyState(VK_SHIFT) & 0x8000) != 0;
    io.KeyAlt = (GetKeyState(VK_MENU) & 0x8000) != 0;
    io.KeySuper = false;
    // io.KeysDown : filled by WM_KEYDOWN/WM_KEYUP events
    // io.MousePos : filled by WM_MOUSEMOVE events
    // io.MouseDown : filled by WM_*BUTTON* events
    // io.MouseWheel : filled by WM_MOUSEWHEEL events

    // Hide OS mouse cursor if ImGui is drawing it
    SetCursor(io.MouseDrawCursor ? NULL : LoadCursor(NULL, IDC_ARROW));

    // Start the frame
    ImGui::NewFrame();
}