Vulkan: Use GPU device address for ImTextureID in descriptor heap mode

janagor · Jun 9, 2026 · Jul 23, 2026 · Aug 5, 2026 · Aug 5, 2026 · Aug 5, 2026
commit c33ea3ccb68e4313e36765fce67860dfd029681b
diff --git a/backends/imgui_impl_vulkan.cpp b/backends/imgui_impl_vulkan.cpp
@@ -244,6 +244,17 @@ static PFN_vkCmdEndRenderingKHR     ImGuiImplVulkanFuncs_vkCmdEndRenderingKHR;
 #ifdef IMGUI_IMPL_VULKAN_HAS_DESCRIPTOR_HEAP
 // VK_EXT_descriptor_heap (not exported by most Vulkan loaders; resolve like dynamic rendering)
 static PFN_vkCmdPushDataEXT         ImGuiImplVulkanFuncs_vkCmdPushDataEXT = nullptr;
+
+// Convert GPU descriptor handle (device address) back to a heap index for PushData.
+static uint32_t ImGui_ImplVulkan_DescriptorHeapIndexFromTexID(const ImGui_ImplVulkan_DescriptorHeapInfo* info, ImTextureID tex_id)
+{
+    IM_ASSERT(tex_id != ImTextureID_Invalid);
+    IM_ASSERT(info->ResourceHeapAddress != 0 && info->ImageDescriptorSize != 0);
+    const VkDeviceAddress addr = (VkDeviceAddress)(ImU64)tex_id;
+    IM_ASSERT(addr >= info->ResourceHeapAddress);
+    IM_ASSERT(((addr - info->ResourceHeapAddress) % info->ImageDescriptorSize) == 0);
+    return (uint32_t)((addr - info->ResourceHeapAddress) / info->ImageDescriptorSize);
+}
 #endif
 
 // Reusable buffers used for rendering 1 current in-flight frame, for ImGui_ImplVulkan_RenderDrawData()
@@ -273,7 +284,7 @@ struct ImGui_ImplVulkan_Texture
     VkImage                     Image;
     VkImageView                 ImageView;
     VkDescriptorSet             DescriptorSet;
-    uint32_t                    DescriptorHeapIndex;
+    uint64_t                    DescriptorHeapGpuHandle; // Device address into resource heap (== ImTextureID in heap mode)
 
     ImGui_ImplVulkan_Texture() { memset((void*)this, 0, sizeof(*this)); }
 };
@@ -823,11 +834,8 @@ void ImGui_ImplVulkan_RenderDrawData(ImDrawData* draw_data, VkCommandBuffer comm
 #ifdef IMGUI_IMPL_VULKAN_HAS_DESCRIPTOR_HEAP
                     if (v->DescriptorHeapInfo)
                     {
-                        // Heap-mode TexIDs are tagged (index | 0x80000000). Use ImU64 for bit ops (ImTextureID may be redefined; default is ImU64).
-                        // Push a uint32_t index (not &image_id) so size=4 is endian-safe.
-                        const ImU64 tex_id_u64 = (ImU64)image_id;
-                        IM_ASSERT((tex_id_u64 & 0x80000000ull) != 0 && "ImTextureID is not a descriptor-heap index (do not use ImGui_ImplVulkan_AddTexture when DescriptorHeapInfo is set; use DescriptorHeapInfo::RegisterImage and tag with 0x80000000)");
-                        uint32_t heap_index = (uint32_t)(tex_id_u64 & 0x7FFFFFFFull);
+                        // ImTextureID is a GPU descriptor device address.
+                        uint32_t heap_index = ImGui_ImplVulkan_DescriptorHeapIndexFromTexID(v->DescriptorHeapInfo, image_id);
                         VkPushDataInfoEXT push{};
                         push.sType = VK_STRUCTURE_TYPE_PUSH_DATA_INFO_EXT;
                         push.data.address = &heap_index;
@@ -867,15 +875,18 @@ static void ImGui_ImplVulkan_DestroyTexture(ImTextureData* tex)
 {
     if (ImGui_ImplVulkan_Texture* backend_tex = (ImGui_ImplVulkan_Texture*)tex->BackendUserData)
     {
-        IM_ASSERT(backend_tex->DescriptorSet == (VkDescriptorSet)tex->TexID ||
-                  backend_tex->DescriptorHeapIndex == (uint32_t)((ImU64)tex->TexID & 0x7FFFFFFFull));
+        IM_ASSERT(backend_tex->DescriptorSet == (VkDescriptorSet)tex->TexID
+#ifdef IMGUI_IMPL_VULKAN_HAS_DESCRIPTOR_HEAP
+                  || backend_tex->DescriptorHeapGpuHandle == (uint64_t)(ImU64)tex->TexID
+#endif
+        );
         ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
         ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
         if (backend_tex->DescriptorSet != VK_NULL_HANDLE)
             ImGui_ImplVulkan_RemoveTexture(backend_tex->DescriptorSet);
 #ifdef IMGUI_IMPL_VULKAN_HAS_DESCRIPTOR_HEAP
         else if (v->DescriptorHeapInfo)
-            v->DescriptorHeapInfo->UnRegisterImage(v->DescriptorHeapInfo->UserContext, backend_tex->DescriptorHeapIndex);
+            v->DescriptorHeapInfo->UnRegisterImage(v->DescriptorHeapInfo->UserContext, backend_tex->DescriptorHeapGpuHandle);
 #endif
         if (backend_tex->ImageView != VK_NULL_HANDLE)
             vkDestroyImageView(v->Device, backend_tex->ImageView, v->Allocator);
@@ -947,10 +958,10 @@ void ImGui_ImplVulkan_UpdateTexture(ImTextureData* tex)
 #ifdef IMGUI_IMPL_VULKAN_HAS_DESCRIPTOR_HEAP
         if (v->DescriptorHeapInfo)
         {
-            backend_tex->DescriptorHeapIndex =
+            backend_tex->DescriptorHeapGpuHandle =
                 v->DescriptorHeapInfo->RegisterImage(v->DescriptorHeapInfo->UserContext, &info);
-            // Store identifiers (ImU64 cast so tagging works if ImTextureID is customized)
-            tex->SetTexID((ImTextureID)(ImU64)(backend_tex->DescriptorHeapIndex | 0x80000000u));
+            IM_ASSERT(backend_tex->DescriptorHeapGpuHandle != 0 && "RegisterImage must return a non-zero device address");
+            tex->SetTexID((ImTextureID)backend_tex->DescriptorHeapGpuHandle);
         }
         else
 #endif
@@ -1602,6 +1613,10 @@ bool    ImGui_ImplVulkan_Init(ImGui_ImplVulkan_InitInfo* info)
         ImGuiImplVulkanFuncs_vkCmdPushDataEXT = reinterpret_cast<PFN_vkCmdPushDataEXT>(vkGetDeviceProcAddr(info->Device, "vkCmdPushDataEXT"));
 #endif
         IM_ASSERT(ImGuiImplVulkanFuncs_vkCmdPushDataEXT != nullptr && "vkCmdPushDataEXT not available (enable VK_EXT_descriptor_heap)");
+        IM_ASSERT(sizeof(ImTextureID) >= sizeof(VkDeviceAddress) && "Descriptor heap mode needs 64-bit ImTextureID");
+        IM_ASSERT(info->DescriptorHeapInfo->ResourceHeapAddress != 0 && info->DescriptorHeapInfo->ImageDescriptorSize != 0);
+        IM_ASSERT(info->DescriptorHeapInfo->RegisterImage != nullptr && info->DescriptorHeapInfo->UnRegisterImage != nullptr);
+        IM_ASSERT(info->DescriptorHeapInfo->RegisterSampler != nullptr && info->DescriptorHeapInfo->UnRegisterSampler != nullptr);
     }
 #endif
 
@@ -1696,7 +1711,7 @@ VkDescriptorSet ImGui_ImplVulkan_AddTexture(VkImageView image_view, VkImageLayou
     ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
     ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
 #ifdef IMGUI_IMPL_VULKAN_HAS_DESCRIPTOR_HEAP
-    IM_ASSERT(v->DescriptorHeapInfo == nullptr && "ImGui_ImplVulkan_AddTexture() is unavailable when using DescriptorHeapInfo; use DescriptorHeapInfo::RegisterImage and set ImTextureID to (index | 0x80000000)");
+    IM_ASSERT(v->DescriptorHeapInfo == nullptr && "ImGui_ImplVulkan_AddTexture() is unavailable when using DescriptorHeapInfo; use DescriptorHeapInfo::RegisterImage");
 #endif
     VkDescriptorPool pool = bd->DescriptorPool ? bd->DescriptorPool : v->DescriptorPool;
 

diff --git a/backends/imgui_impl_vulkan.h b/backends/imgui_impl_vulkan.h
@@ -97,13 +97,22 @@ struct ImGui_ImplVulkan_PipelineInfo
 };
 
 #ifdef IMGUI_IMPL_VULKAN_HAS_DESCRIPTOR_HEAP
+// App owns heap slots. ImTextureID is the descriptor's device address in the resource heap (like D3D12_GPU_DESCRIPTOR_HANDLE.ptr).
+// Backend converts to a heap index for vkCmdPushDataEXT via (tex_id - ResourceHeapAddress) / ImageDescriptorSize.
+// Requires a 64-bit ImTextureID (Dear ImGui default since 1.91.4). Do not redefine ImTextureID to a 32-bit type.
 struct ImGui_ImplVulkan_DescriptorHeapInfo
 {
-    uint32_t (*RegisterSampler)(void *, const VkSamplerCreateInfo *);
-    void (*UnRegisterSampler)(void *, uint32_t);
-    uint32_t (*RegisterImage)(void *, const VkImageViewCreateInfo *);
-    void (*UnRegisterImage)(void *, uint32_t);
-    void *UserContext;
+    VkDeviceAddress ResourceHeapAddress;    // Bound resource heap base (vkGetBufferDeviceAddress of heap buffer)
+    VkDeviceSize    ImageDescriptorSize;    // imageDescriptorSize from VkPhysicalDeviceDescriptorHeapPropertiesEXT
+
+    // RegisterImage returns GPU descriptor handle (device address / VkDeviceAddress). UnRegisterImage takes that same handle.
+    // Returned value is stored as ImTextureID; needs sizeof(ImTextureID) >= 8.
+    uint64_t (*RegisterImage)(void*, const VkImageViewCreateInfo*);
+    void     (*UnRegisterImage)(void*, uint64_t);
+    // Samplers are not ImTextureIDs; indices are fine (including 0).
+    uint32_t (*RegisterSampler)(void*, const VkSamplerCreateInfo*);
+    void     (*UnRegisterSampler)(void*, uint32_t);
+    void*    UserContext;
 };
 #endif
 
@@ -117,9 +126,10 @@ struct ImGui_ImplVulkan_DescriptorHeapInfo
 //   - When using dynamic rendering, set UseDynamicRendering=true + fill PipelineInfoMain.PipelineRenderingCreateInfo structure.
 // - About descriptor heap (requires VK_EXT_descriptor_heap in your Vulkan headers → IMGUI_IMPL_VULKAN_HAS_DESCRIPTOR_HEAP):
 //   - When using descriptor heaps, set DescriptorHeapInfo and leave DescriptorPool / DescriptorPoolSize unset.
-//   - Like DX12's SrvDescriptorAllocFn/FreeFn: the application owns heap allocation via Register*/UnRegister* callbacks.
-//   - ImGui_ImplVulkan_AddTexture()/RemoveTexture() are unavailable in this mode (pool path only).
-//   - User textures: call RegisterImage yourself and use ImTextureID = (heap_index | 0x80000000); free with UnRegisterImage.
+//   - The application owns heap slots via Register*/UnRegister* callbacks.
+//   - ImTextureID is the GPU descriptor device address returned by RegisterImage.
+//     Requires a 64-bit ImTextureID.
+//   - ImGui_ImplVulkan_AddTexture()/RemoveTexture() are pool-path only.
 struct ImGui_ImplVulkan_InitInfo
 {
     uint32_t                        ApiVersion;                 // Fill with API version of Instance, e.g. VK_API_VERSION_1_3 or your value of VkApplicationInfo::apiVersion. May be lower than header version (VK_HEADER_VERSION_COMPLETE)
@@ -158,7 +168,7 @@ struct ImGui_ImplVulkan_InitInfo
 
 #ifdef IMGUI_IMPL_VULKAN_HAS_DESCRIPTOR_HEAP
     // (Optional) If set, use VK_EXT_descriptor_heap (app-owned Register*/UnRegister* callbacks; see comment above).
-    // ImTextureID must be (RegisterImage() index | 0x80000000). ImGui_ImplVulkan_AddTexture() is unavailable in this mode.
+    // ImTextureID = RegisterImage(...) device address. ImGui_ImplVulkan_AddTexture() is unavailable in this mode.
     const ImGui_ImplVulkan_DescriptorHeapInfo *DescriptorHeapInfo;
 #endif
 };
@@ -180,7 +190,7 @@ IMGUI_IMPL_API void             ImGui_ImplVulkan_UpdateTexture(ImTextureData* te
 
 // Register a texture (VkDescriptorSet for a VK_DESCRIPTOR_TYPE_SAMPLED_IMAGE == ImTextureID)
 // - Pool path only. Not available when InitInfo::DescriptorHeapInfo is set (asserts).
-// - Heap mode: use DescriptorHeapInfo::RegisterImage / UnRegisterImage and ImTextureID = (heap_index | 0x80000000).
+// - Heap mode: ImTextureID = DescriptorHeapInfo::RegisterImage(...) device address; free with UnRegisterImage.
 IMGUI_IMPL_API VkDescriptorSet  ImGui_ImplVulkan_AddTexture(VkImageView image_view, VkImageLayout image_layout);
 IMGUI_IMPL_API void             ImGui_ImplVulkan_RemoveTexture(VkDescriptorSet descriptor_set);
 

diff --git a/examples/example_glfw_vulkan/main.cpp b/examples/example_glfw_vulkan/main.cpp
@@ -146,8 +146,8 @@ struct ExampleDescriptorHeapAllocator
         BindInfo.reservedRangeSize = reserved_range;
 
         FreeIndices.reserve(capacity);
-        for (int n = capacity; n > 0; n--)
-            FreeIndices.push_back(n - 1);
+        for (int n = capacity - 1; n >= 0; n--)
+            FreeIndices.push_back(n);
     }
     void Destroy(VkDevice device, const VkAllocationCallbacks* allocator)
     {
@@ -170,6 +170,16 @@ struct ExampleDescriptorHeapAllocator
     {
         FreeIndices.push_back(idx);
     }
+    VkDeviceAddress GpuHandleFromIndex(int idx) const
+    {
+        return BindInfo.heapRange.address + (VkDeviceAddress)idx * (VkDeviceAddress)Stride;
+    }
+    int IndexFromGpuHandle(VkDeviceAddress gpu_handle) const
+    {
+        IM_ASSERT(gpu_handle >= BindInfo.heapRange.address);
+        IM_ASSERT(((gpu_handle - BindInfo.heapRange.address) % Stride) == 0);
+        return (int)((gpu_handle - BindInfo.heapRange.address) / Stride);
+    }
     VkHostAddressRangeEXT DescriptorAddress(int idx) const
     {
         return VkHostAddressRangeEXT{ (char*)Mapped + (VkDeviceSize)idx * Stride, Stride };
@@ -417,8 +427,12 @@ static void SetupVulkan(ImVector<const char*> instance_extensions, bool require_
             descriptor_heap_properties.minSamplerHeapReservedRange, APP_SAMPLER_HEAP_SIZE, g_Allocator);
 
         // Allocating descriptors is up to the application, so we provide callbacks (same idea as DX12 SrvDescriptorAllocFn/FreeFn).
+        // ImTextureID = GPU descriptor device address (like D3D12_GPU_DESCRIPTOR_HANDLE.ptr); slot 0 is usable.
+        g_DescriptorHeapInfo = {};
+        g_DescriptorHeapInfo.ResourceHeapAddress = g_ResourceHeapAlloc.BindInfo.heapRange.address;
+        g_DescriptorHeapInfo.ImageDescriptorSize = g_ResourceHeapAlloc.Stride;
         g_DescriptorHeapInfo.UserContext = nullptr;
-        g_DescriptorHeapInfo.RegisterImage = [](void*, const VkImageViewCreateInfo* ci) -> uint32_t {
+        g_DescriptorHeapInfo.RegisterImage = [](void*, const VkImageViewCreateInfo* ci) -> uint64_t {
             int idx = g_ResourceHeapAlloc.Alloc();
             VkImageDescriptorInfoEXT image = {};
             image.sType = VK_STRUCTURE_TYPE_IMAGE_DESCRIPTOR_INFO_EXT;
@@ -430,9 +444,11 @@ static void SetupVulkan(ImVector<const char*> instance_extensions, bool require_
             resource.data.pImage = &image;
             VkHostAddressRangeEXT addr = g_ResourceHeapAlloc.DescriptorAddress(idx);
             check_vk_result(g_DescHeapFns.vkWriteResourceDescriptorsEXT(g_Device, 1, &resource, &addr));
-            return (uint32_t)idx;
+            return (uint64_t)g_ResourceHeapAlloc.GpuHandleFromIndex(idx);
+        };
+        g_DescriptorHeapInfo.UnRegisterImage = [](void*, uint64_t gpu_handle) {
+            g_ResourceHeapAlloc.Free(g_ResourceHeapAlloc.IndexFromGpuHandle((VkDeviceAddress)gpu_handle));
         };
-        g_DescriptorHeapInfo.UnRegisterImage = [](void*, uint32_t idx) { g_ResourceHeapAlloc.Free((int)idx); };
         g_DescriptorHeapInfo.RegisterSampler = [](void*, const VkSamplerCreateInfo* ci) -> uint32_t {
             int idx = g_SamplerHeapAlloc.Alloc();
             VkHostAddressRangeEXT addr = g_SamplerHeapAlloc.DescriptorAddress(idx);