Backends: DirectX11: added ImGuiBackendFlags_RendererHasTextures support.

# Conflicts:
#	backends/imgui_impl_dx11.cpp

backends/imgui_impl_dx11.cpp

@@ -2,8 +2,9 @@
 // This needs to be used along with a Platform Backend (e.g. Win32)
 
 // Implemented features:
-//  [X] Renderer: User texture binding. Use 'ID3D11ShaderResourceView*' as ImTextureID. Read the FAQ about ImTextureID!
+//  [X] Renderer: User texture binding. Use 'ID3D11ShaderResourceView*' as texture identifier. Read the FAQ about ImTextureID/ImTextureRef!
 //  [X] Renderer: Large meshes support (64k+ vertices) even with 16-bit indices (ImGuiBackendFlags_RendererHasVtxOffset).
+//  [X] Renderer: Texture updates support for dynamic font atlas (ImGuiBackendFlags_RendererHasTextures).
 //  [X] Renderer: Expose selected render state for draw callbacks to use. Access in '(ImGui_ImplXXXX_RenderState*)GetPlatformIO().Renderer_RenderState'.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
@@ -16,6 +17,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2025-06-11: DirectX11: Added support for ImGuiBackendFlags_RendererHasTextures, for dynamic font atlas.
 //  2025-05-07: DirectX11: Honor draw_data->FramebufferScale to allow for custom backends and experiment using it (consistently with other renderer backends, even though in normal condition it is not set under Windows).
 //  2025-01-06: DirectX11: Expose VertexConstantBuffer in ImGui_ImplDX11_RenderState. Reset projection matrix in ImDrawCallback_ResetRenderState handler.
 //  2024-10-07: DirectX11: Changed default texture sampler to Clamp instead of Repeat/Wrap.
@@ -51,6 +53,12 @@
 #endif
 
 // DirectX11 data
+struct ImGui_ImplDX11_Texture
+{
+    ID3D11Texture2D*            pTexture;
+    ID3D11ShaderResourceView*   pTextureView;
+};
+
 struct ImGui_ImplDX11_Data
 {
     ID3D11Device*               pd3dDevice;
@@ -63,7 +71,6 @@ struct ImGui_ImplDX11_Data
     ID3D11Buffer*               pVertexConstantBuffer;
     ID3D11PixelShader*          pPixelShader;
     ID3D11SamplerState*         pFontSampler;
-    ID3D11ShaderResourceView*   pFontTextureView;
     ID3D11RasterizerState*      pRasterizerState;
     ID3D11BlendState*           pBlendState;
     ID3D11DepthStencilState*    pDepthStencilState;
@@ -153,6 +160,13 @@ void ImGui_ImplDX11_RenderDrawData(ImDrawData* draw_data)
     ImGui_ImplDX11_Data* bd = ImGui_ImplDX11_GetBackendData();
     ID3D11DeviceContext* device = bd->pd3dDeviceContext;
 
+    // Catch up with texture updates. Most of the times, the list will have 1 element with an OK status, aka nothing to do.
+    // (This almost always points to ImGui::GetPlatformIO().Textures[] but is part of ImDrawData to allow overriding or disabling texture updates).
+    if (draw_data->Textures != nullptr)
+        for (ImTextureData* tex : *draw_data->Textures)
+            if (tex->Status != ImTextureStatus_OK)
+                ImGui_ImplDX11_UpdateTexture(tex);
+
     // Create and grow vertex/index buffers if needed
     if (!bd->pVB || bd->VertexBufferSize < draw_data->TotalVtxCount)
     {
@@ -320,21 +334,39 @@ void ImGui_ImplDX11_RenderDrawData(ImDrawData* draw_data)
     device->IASetInputLayout(old.InputLayout); if (old.InputLayout) old.InputLayout->Release();
 }
 
-static void ImGui_ImplDX11_CreateFontsTexture()
+static void ImGui_ImplDX11_DestroyTexture(ImTextureData* tex)
 {
-    // Build texture atlas
-    ImGuiIO& io = ImGui::GetIO();
-    ImGui_ImplDX11_Data* bd = ImGui_ImplDX11_GetBackendData();
-    unsigned char* pixels;
-    int width, height;
-    io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);
+    ImGui_ImplDX11_Texture* backend_tex = (ImGui_ImplDX11_Texture*)tex->BackendUserData;
+    if (backend_tex == nullptr)
+        return;
+    IM_ASSERT(backend_tex->pTextureView == (ID3D11ShaderResourceView*)(intptr_t)tex->TexID);
+    backend_tex->pTextureView->Release();
+    backend_tex->pTexture->Release();
+    IM_DELETE(backend_tex);
+
+    // Clear identifiers and mark as destroyed (in order to allow e.g. calling InvalidateDeviceObjects while running)
+    tex->SetTexID(ImTextureID_Invalid);
+    tex->SetStatus(ImTextureStatus_Destroyed);
+    tex->BackendUserData = nullptr;
+}
 
-    // Upload texture to graphics system
+void ImGui_ImplDX11_UpdateTexture(ImTextureData* tex)
+{
+    ImGui_ImplDX11_Data* bd = ImGui_ImplDX11_GetBackendData();
+    if (tex->Status == ImTextureStatus_WantCreate)
     {
+        // Create and upload new texture to graphics system
+        //IMGUI_DEBUG_LOG("UpdateTexture #%03d: WantCreate %dx%d\n", tex->UniqueID, tex->Width, tex->Height);
+        IM_ASSERT(tex->TexID == ImTextureID_Invalid && tex->BackendUserData == nullptr);
+        IM_ASSERT(tex->Format == ImTextureFormat_RGBA32);
+        unsigned int* pixels = (unsigned int*)tex->GetPixels();
+        ImGui_ImplDX11_Texture* backend_tex = IM_NEW(ImGui_ImplDX11_Texture)();
+
+        // Create texture
         D3D11_TEXTURE2D_DESC desc;
         ZeroMemory(&desc, sizeof(desc));
-        desc.Width = width;
-        desc.Height = height;
+        desc.Width = (UINT)tex->Width;
+        desc.Height = (UINT)tex->Height;
         desc.MipLevels = 1;
         desc.ArraySize = 1;
         desc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
@@ -342,14 +374,12 @@ static void ImGui_ImplDX11_CreateFontsTexture()
         desc.Usage = D3D11_USAGE_DEFAULT;
         desc.BindFlags = D3D11_BIND_SHADER_RESOURCE;
         desc.CPUAccessFlags = 0;
-
-        ID3D11Texture2D* pTexture = nullptr;
         D3D11_SUBRESOURCE_DATA subResource;
         subResource.pSysMem = pixels;
         subResource.SysMemPitch = desc.Width * 4;
         subResource.SysMemSlicePitch = 0;
-        bd->pd3dDevice->CreateTexture2D(&desc, &subResource, &pTexture);
-        IM_ASSERT(pTexture != nullptr);
+        bd->pd3dDevice->CreateTexture2D(&desc, &subResource, &backend_tex->pTexture);
+        IM_ASSERT(backend_tex->pTexture != nullptr && "Backend failed to create texture!");
 
         // Create texture view
         D3D11_SHADER_RESOURCE_VIEW_DESC srvDesc;
@@ -358,23 +388,29 @@ static void ImGui_ImplDX11_CreateFontsTexture()
         srvDesc.ViewDimension = D3D11_SRV_DIMENSION_TEXTURE2D;
         srvDesc.Texture2D.MipLevels = desc.MipLevels;
         srvDesc.Texture2D.MostDetailedMip = 0;
-        bd->pd3dDevice->CreateShaderResourceView(pTexture, &srvDesc, &bd->pFontTextureView);
-        pTexture->Release();
-    }
+        bd->pd3dDevice->CreateShaderResourceView(backend_tex->pTexture, &srvDesc, &backend_tex->pTextureView);
+        IM_ASSERT(backend_tex->pTextureView != nullptr && "Backend failed to create texture!");
 
-    // Store our identifier
-    io.Fonts->SetTexID((ImTextureID)bd->pFontTextureView);
-}
-
-static void ImGui_ImplDX11_DestroyFontsTexture()
-{
-    ImGui_ImplDX11_Data* bd = ImGui_ImplDX11_GetBackendData();
-    if (bd->pFontTextureView)
+        // Store identifiers
+        tex->SetTexID((ImTextureID)(intptr_t)backend_tex->pTextureView);
+        tex->SetStatus(ImTextureStatus_OK);
+        tex->BackendUserData = backend_tex;
+    }
+    else if (tex->Status == ImTextureStatus_WantUpdates)
     {
-        bd->pFontTextureView->Release();
-        bd->pFontTextureView = nullptr;
-        ImGui::GetIO().Fonts->SetTexID(0); // We copied data->pFontTextureView to io.Fonts->TexID so let's clear that as well.
+        // Update selected blocks. We only ever write to textures regions which have never been used before!
+        // This backend choose to use tex->Updates[] but you can use tex->UpdateRect to upload a single region.
+        ImGui_ImplDX11_Texture* backend_tex = (ImGui_ImplDX11_Texture*)tex->BackendUserData;
+        IM_ASSERT(backend_tex->pTextureView == (ID3D11ShaderResourceView*)(intptr_t)tex->TexID);
+        for (ImTextureRect& r : tex->Updates)
+        {
+            D3D11_BOX box = { (UINT)r.x, (UINT)r.y, (UINT)0, (UINT)(r.x + r.w), (UINT)(r.y + r .h), (UINT)1 };
+            bd->pd3dDeviceContext->UpdateSubresource(backend_tex->pTexture, 0, &box, tex->GetPixelsAt(r.x, r.y), (UINT)tex->GetPitch(), 0);
+        }
+        tex->SetStatus(ImTextureStatus_OK);
     }
+    if (tex->Status == ImTextureStatus_WantDestroy && tex->UnusedFrames > 0)
+        ImGui_ImplDX11_DestroyTexture(tex);
 }
 
 bool    ImGui_ImplDX11_CreateDeviceObjects()
@@ -382,8 +418,7 @@ bool    ImGui_ImplDX11_CreateDeviceObjects()
     ImGui_ImplDX11_Data* bd = ImGui_ImplDX11_GetBackendData();
     if (!bd->pd3dDevice)
         return false;
-    if (bd->pFontSampler)
-        ImGui_ImplDX11_InvalidateDeviceObjects();
+    ImGui_ImplDX11_InvalidateDeviceObjects();
 
     // By using D3DCompile() from <d3dcompiler.h> / d3dcompiler.lib, we introduce a dependency to a given version of d3dcompiler_XX.dll (see D3DCOMPILER_DLL_A)
     // If you would like to use this DX11 sample code but remove this dependency you can:
@@ -542,8 +577,6 @@ bool    ImGui_ImplDX11_CreateDeviceObjects()
         bd->pd3dDevice->CreateSamplerState(&desc, &bd->pFontSampler);
     }
 
-    ImGui_ImplDX11_CreateFontsTexture();
-
     return true;
 }
 
@@ -553,7 +586,10 @@ void    ImGui_ImplDX11_InvalidateDeviceObjects()
     if (!bd->pd3dDevice)
         return;
 
-    ImGui_ImplDX11_DestroyFontsTexture();
+    // Destroy all textures
+    for (ImTextureData* tex : ImGui::GetPlatformIO().Textures)
+        if (tex->RefCount == 1)
+            ImGui_ImplDX11_DestroyTexture(tex);
 
     if (bd->pFontSampler)           { bd->pFontSampler->Release(); bd->pFontSampler = nullptr; }
     if (bd->pIB)                    { bd->pIB->Release(); bd->pIB = nullptr; }
@@ -578,6 +614,10 @@ bool    ImGui_ImplDX11_Init(ID3D11Device* device, ID3D11DeviceContext* device_co
     io.BackendRendererUserData = (void*)bd;
     io.BackendRendererName = "imgui_impl_dx11";
     io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset;  // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.
+    io.BackendFlags |= ImGuiBackendFlags_RendererHasTextures;   // We can honor ImGuiPlatformIO::Textures[] requests during render.
+
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    platform_io.Renderer_TextureMaxWidth = platform_io.Renderer_TextureMaxHeight = D3D11_REQ_TEXTURE2D_U_OR_V_DIMENSION;
 
     // Get factory from device
     IDXGIDevice* pDXGIDevice = nullptr;
@@ -612,7 +652,7 @@ void ImGui_ImplDX11_Shutdown()
     if (bd->pd3dDeviceContext)    { bd->pd3dDeviceContext->Release(); }
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
-    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
+    io.BackendFlags &= ~(ImGuiBackendFlags_RendererHasVtxOffset | ImGuiBackendFlags_RendererHasTextures);
     IM_DELETE(bd);
 }
 
@@ -621,7 +661,7 @@ void ImGui_ImplDX11_NewFrame()
     ImGui_ImplDX11_Data* bd = ImGui_ImplDX11_GetBackendData();
     IM_ASSERT(bd != nullptr && "Context or backend not initialized! Did you call ImGui_ImplDX11_Init()?");
 
-    if (!bd->pFontSampler)
+    if (!bd->pVertexShader)
         ImGui_ImplDX11_CreateDeviceObjects();
 }
 

backends/imgui_impl_dx11.h

@@ -2,8 +2,9 @@
 // This needs to be used along with a Platform Backend (e.g. Win32)
 
 // Implemented features:
-//  [X] Renderer: User texture binding. Use 'ID3D11ShaderResourceView*' as ImTextureID. Read the FAQ about ImTextureID!
+//  [X] Renderer: User texture binding. Use 'ID3D11ShaderResourceView*' as texture identifier. Read the FAQ about ImTextureID/ImTextureRef!
 //  [X] Renderer: Large meshes support (64k+ vertices) even with 16-bit indices (ImGuiBackendFlags_RendererHasVtxOffset).
+//  [X] Renderer: Texture updates support for dynamic font atlas (ImGuiBackendFlags_RendererHasTextures).
 //  [X] Renderer: Expose selected render state for draw callbacks to use. Access in '(ImGui_ImplXXXX_RenderState*)GetPlatformIO().Renderer_RenderState'.
 
 // You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
@@ -33,6 +34,9 @@ IMGUI_IMPL_API void     ImGui_ImplDX11_RenderDrawData(ImDrawData* draw_data);
 IMGUI_IMPL_API bool     ImGui_ImplDX11_CreateDeviceObjects();
 IMGUI_IMPL_API void     ImGui_ImplDX11_InvalidateDeviceObjects();
 
+// (Advanced) Use e.g. if you need to precisely control the timing of texture updates (e.g. for staged rendering), by setting ImDrawData::Textures = NULL to handle this manually.
+IMGUI_IMPL_API void     ImGui_ImplDX11_UpdateTexture(ImTextureData* tex);
+
 // [BETA] Selected render state data shared with callbacks.
 // This is temporarily stored in GetPlatformIO().Renderer_RenderState during the ImGui_ImplDX11_RenderDrawData() call.
 // (Please open an issue if you feel you need access to more data)