Backends: Vulkan: added ImGuiBackendFlags_RendererHasTextures support.

# Conflicts:
#	backends/imgui_impl_vulkan.cpp

backends/imgui_impl_vulkan.cpp

@@ -2,8 +2,9 @@
 // This needs to be used along with a Platform Backend (e.g. GLFW, SDL, Win32, custom..)
 
 // Implemented features:
-//  [!] Renderer: User texture binding. Use 'VkDescriptorSet' as ImTextureID. Call ImGui_ImplVulkan_AddTexture() to register one. Read the FAQ about ImTextureID! See https://github.com/ocornut/imgui/pull/914 for discussions.
+//  [!] Renderer: User texture binding. Use 'VkDescriptorSet' as texture identifier. Call ImGui_ImplVulkan_AddTexture() to register one. Read the FAQ about ImTextureID/ImTextureRef + https://github.com/ocornut/imgui/pull/914 for discussions.
 //  [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'.
 
 // The aim of imgui_impl_vulkan.h/.cpp is to be usable in your engine without any modification.
@@ -26,7 +27,8 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
-//  2025-05-07- Vulkan: Fixed validation errors during window detach in multi-viewport mode. (#8600, #8176)
+//  2025-06-11: Vulkan: Added support for ImGuiBackendFlags_RendererHasTextures, for dynamic font atlas. Removed ImGui_ImplVulkan_CreateFontsTexture() and ImGui_ImplVulkan_DestroyFontsTexture().
+//  2025-05-07: Vulkan: Fixed validation errors during window detach in multi-viewport mode. (#8600, #8176)
 //  2025-05-07: Vulkan: Load dynamic rendering functions using vkGetDeviceProcAddr() + try both non-KHR and KHR versions. (#8600, #8326, #8365)
 //  2025-04-07: Vulkan: Deep-copy ImGui_ImplVulkan_InitInfo::PipelineRenderingCreateInfo's pColorAttachmentFormats buffer when set, in order to reduce common user-error of specifying a pointer to data that gets out of scope. (#8282)
 //  2025-02-14: *BREAKING CHANGE*: Added uint32_t api_version to ImGui_ImplVulkan_LoadFunctions().
@@ -251,7 +253,6 @@ struct ImGui_ImplVulkan_Data
     VkDescriptorPool            DescriptorPool;
 
     // Texture management
-    ImGui_ImplVulkan_Texture    FontTexture;
     VkSampler                   TexSampler;
     VkCommandPool               TexCommandPool;
     VkCommandBuffer             TexCommandBuffer;
@@ -502,6 +503,13 @@ void ImGui_ImplVulkan_RenderDrawData(ImDrawData* draw_data, VkCommandBuffer comm
     if (fb_width <= 0 || fb_height <= 0)
         return;
 
+    // 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_ImplVulkan_UpdateTexture(tex);
+
     ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
     ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
     if (pipeline == VK_NULL_HANDLE)
@@ -638,64 +646,50 @@ void ImGui_ImplVulkan_RenderDrawData(ImDrawData* draw_data, VkCommandBuffer comm
     vkCmdSetScissor(command_buffer, 0, 1, &scissor);
 }
 
-bool ImGui_ImplVulkan_CreateFontsTexture()
+static void ImGui_ImplVulkan_DestroyTexture(ImTextureData* tex)
 {
-    ImGuiIO& io = ImGui::GetIO();
+    ImGui_ImplVulkan_Texture* backend_tex = (ImGui_ImplVulkan_Texture*)tex->BackendUserData;
+    if (backend_tex == nullptr)
+        return;
+    IM_ASSERT(backend_tex->DescriptorSet == (VkDescriptorSet)tex->TexID);
+    ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
+    ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
+    ImGui_ImplVulkan_RemoveTexture(backend_tex->DescriptorSet);
+    vkDestroyImageView(v->Device, backend_tex->ImageView, v->Allocator);
+    vkDestroyImage(v->Device, backend_tex->Image, v->Allocator);
+    vkFreeMemory(v->Device, backend_tex->Memory, v->Allocator);
+    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;
+}
+
+void ImGui_ImplVulkan_UpdateTexture(ImTextureData* tex)
+{
+    if (tex->Status == ImTextureStatus_OK)
+        return;
     ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
     ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
     VkResult err;
 
-    // Destroy existing texture (if any)
+    if (tex->Status == ImTextureStatus_WantCreate)
-    if (bd->FontTexture.DescriptorSet)
     {
-        vkQueueWaitIdle(v->Queue);
+        // Create and upload new texture to graphics system
-        ImGui_ImplVulkan_DestroyFontsTexture();
+        //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);
-    // Create command pool/buffer
+        ImGui_ImplVulkan_Texture* backend_tex = IM_NEW(ImGui_ImplVulkan_Texture)();
-    if (bd->TexCommandPool == VK_NULL_HANDLE)
-    {
-        VkCommandPoolCreateInfo info = {};
-        info.sType = VK_STRUCTURE_TYPE_COMMAND_POOL_CREATE_INFO;
-        info.flags = 0;
-        info.queueFamilyIndex = v->QueueFamily;
-        vkCreateCommandPool(v->Device, &info, v->Allocator, &bd->TexCommandPool);
-    }
-    if (bd->TexCommandBuffer == VK_NULL_HANDLE)
-    {
-        VkCommandBufferAllocateInfo info = {};
-        info.sType = VK_STRUCTURE_TYPE_COMMAND_BUFFER_ALLOCATE_INFO;
-        info.commandPool = bd->TexCommandPool;
-        info.commandBufferCount = 1;
-        err = vkAllocateCommandBuffers(v->Device, &info, &bd->TexCommandBuffer);
-        check_vk_result(err);
-    }
-
-    // Start command buffer
-    {
-        err = vkResetCommandPool(v->Device, bd->TexCommandPool, 0);
-        check_vk_result(err);
-        VkCommandBufferBeginInfo begin_info = {};
-        begin_info.sType = VK_STRUCTURE_TYPE_COMMAND_BUFFER_BEGIN_INFO;
-        begin_info.flags |= VK_COMMAND_BUFFER_USAGE_ONE_TIME_SUBMIT_BIT;
-        err = vkBeginCommandBuffer(bd->TexCommandBuffer, &begin_info);
-        check_vk_result(err);
-    }
-
-    unsigned char* pixels;
-    int width, height;
-    io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);
-    size_t upload_size = width * height * 4 * sizeof(char);
 
         // Create the Image:
-    ImGui_ImplVulkan_Texture* backend_tex = &bd->FontTexture;
         {
             VkImageCreateInfo info = {};
             info.sType = VK_STRUCTURE_TYPE_IMAGE_CREATE_INFO;
             info.imageType = VK_IMAGE_TYPE_2D;
             info.format = VK_FORMAT_R8G8B8A8_UNORM;
-        info.extent.width = width;
+            info.extent.width = tex->Width;
-        info.extent.height = height;
+            info.extent.height = tex->Height;
             info.extent.depth = 1;
             info.mipLevels = 1;
             info.arrayLayers = 1;
@@ -732,12 +726,32 @@ bool ImGui_ImplVulkan_CreateFontsTexture()
             check_vk_result(err);
         }
 
-    // Create the Descriptor Set:
+        // Create the Descriptor Set
         backend_tex->DescriptorSet = ImGui_ImplVulkan_AddTexture(bd->TexSampler, backend_tex->ImageView, VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL);
 
+        // Store identifiers
+        tex->SetTexID((ImTextureID)backend_tex->DescriptorSet);
+        tex->BackendUserData = backend_tex;
+    }
+
+    if (tex->Status == ImTextureStatus_WantCreate || tex->Status == ImTextureStatus_WantUpdates)
+    {
+        ImGui_ImplVulkan_Texture* backend_tex = (ImGui_ImplVulkan_Texture*)tex->BackendUserData;
+
+        // Update full texture or selected blocks. We only ever write to textures regions which have never been used before!
+        // This backend choose to use tex->UpdateRect but you can use tex->Updates[] to upload individual regions.
+        // We could use the smaller rect on _WantCreate but using the full rect allows us to clear the texture.
+        const int upload_x = (tex->Status == ImTextureStatus_WantCreate) ? 0 : tex->UpdateRect.x;
+        const int upload_y = (tex->Status == ImTextureStatus_WantCreate) ? 0 : tex->UpdateRect.y;
+        const int upload_w = (tex->Status == ImTextureStatus_WantCreate) ? tex->Width : tex->UpdateRect.w;
+        const int upload_h = (tex->Status == ImTextureStatus_WantCreate) ? tex->Height : tex->UpdateRect.h;
+
         // Create the Upload Buffer:
         VkDeviceMemory upload_buffer_memory;
+
         VkBuffer upload_buffer;
+        VkDeviceSize upload_pitch = upload_w * tex->BytesPerPixel;
+        VkDeviceSize upload_size = upload_h * upload_pitch;
         {
             VkBufferCreateInfo buffer_info = {};
             buffer_info.sType = VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO;
@@ -764,7 +778,8 @@ bool ImGui_ImplVulkan_CreateFontsTexture()
             char* map = nullptr;
             err = vkMapMemory(v->Device, upload_buffer_memory, 0, upload_size, 0, (void**)(&map));
             check_vk_result(err);
-        memcpy(map, pixels, upload_size);
+            for (int y = 0; y < upload_h; y++)
+                memcpy(map + upload_pitch * y, tex->GetPixelsAt(upload_x, upload_y + y), (size_t)upload_pitch);
             VkMappedMemoryRange range[1] = {};
             range[0].sType = VK_STRUCTURE_TYPE_MAPPED_MEMORY_RANGE;
             range[0].memory = upload_buffer_memory;
@@ -774,6 +789,17 @@ bool ImGui_ImplVulkan_CreateFontsTexture()
             vkUnmapMemory(v->Device, upload_buffer_memory);
         }
 
+        // Start command buffer
+        {
+            err = vkResetCommandPool(v->Device, bd->TexCommandPool, 0);
+            check_vk_result(err);
+            VkCommandBufferBeginInfo begin_info = {};
+            begin_info.sType = VK_STRUCTURE_TYPE_COMMAND_BUFFER_BEGIN_INFO;
+            begin_info.flags |= VK_COMMAND_BUFFER_USAGE_ONE_TIME_SUBMIT_BIT;
+            err = vkBeginCommandBuffer(bd->TexCommandBuffer, &begin_info);
+            check_vk_result(err);
+        }
+
         // Copy to Image:
         {
             VkImageMemoryBarrier copy_barrier[1] = {};
@@ -792,9 +818,11 @@ bool ImGui_ImplVulkan_CreateFontsTexture()
             VkBufferImageCopy region = {};
             region.imageSubresource.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
             region.imageSubresource.layerCount = 1;
-        region.imageExtent.width = width;
+            region.imageExtent.width = upload_w;
-        region.imageExtent.height = height;
+            region.imageExtent.height = upload_h;
             region.imageExtent.depth = 1;
+            region.imageOffset.x = upload_x;
+            region.imageOffset.y = upload_y;
             vkCmdCopyBufferToImage(bd->TexCommandBuffer, upload_buffer, backend_tex->Image, VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL, 1, &region);
 
             VkImageMemoryBarrier use_barrier[1] = {};
@@ -812,10 +840,8 @@ bool ImGui_ImplVulkan_CreateFontsTexture()
             vkCmdPipelineBarrier(bd->TexCommandBuffer, VK_PIPELINE_STAGE_TRANSFER_BIT, VK_PIPELINE_STAGE_FRAGMENT_SHADER_BIT, 0, 0, nullptr, 0, nullptr, 1, use_barrier);
         }
 
-    // Store our identifier
-    io.Fonts->SetTexID((ImTextureID)backend_tex->DescriptorSet);
-
         // End command buffer
+        {
             VkSubmitInfo end_info = {};
             end_info.sType = VK_STRUCTURE_TYPE_SUBMIT_INFO;
             end_info.commandBufferCount = 1;
@@ -824,34 +850,18 @@ bool ImGui_ImplVulkan_CreateFontsTexture()
             check_vk_result(err);
             err = vkQueueSubmit(v->Queue, 1, &end_info, VK_NULL_HANDLE);
             check_vk_result(err);
+        }
 
-    err = vkQueueWaitIdle(v->Queue);
+        err = vkQueueWaitIdle(v->Queue); // FIXME-OPT: Suboptimal!
         check_vk_result(err);
-
         vkDestroyBuffer(v->Device, upload_buffer, v->Allocator);
         vkFreeMemory(v->Device, upload_buffer_memory, v->Allocator);
 
-    return true;
+        tex->SetStatus(ImTextureStatus_OK);
     }
 
-// You probably never need to call this, as it is called by ImGui_ImplVulkan_CreateFontsTexture() and ImGui_ImplVulkan_Shutdown().
+    if (tex->Status == ImTextureStatus_WantDestroy && tex->UnusedFrames >= (int)bd->VulkanInitInfo.ImageCount)
-void ImGui_ImplVulkan_DestroyFontsTexture()
+        ImGui_ImplVulkan_DestroyTexture(tex);
-{
-    ImGuiIO& io = ImGui::GetIO();
-    ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
-    ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
-
-    ImGui_ImplVulkan_Texture* backend_tex = &bd->FontTexture;
-
-    if (backend_tex->DescriptorSet)
-    {
-        ImGui_ImplVulkan_RemoveTexture(backend_tex->DescriptorSet);
-        backend_tex->DescriptorSet = VK_NULL_HANDLE;
-        io.Fonts->SetTexID(0);
-    }
-    if (backend_tex->ImageView) { vkDestroyImageView(v->Device, backend_tex->ImageView, v->Allocator); backend_tex->ImageView = VK_NULL_HANDLE; }
-    if (backend_tex->Image)     { vkDestroyImage(v->Device, backend_tex->Image, v->Allocator); backend_tex->Image = VK_NULL_HANDLE; }
-    if (backend_tex->Memory)    { vkFreeMemory(v->Device, backend_tex->Memory, v->Allocator); backend_tex->Memory = VK_NULL_HANDLE; }
 }
 
 static void ImGui_ImplVulkan_CreateShaderModules(VkDevice device, const VkAllocationCallbacks* allocator)
@@ -1066,6 +1076,26 @@ bool ImGui_ImplVulkan_CreateDeviceObjects()
 
     ImGui_ImplVulkan_CreatePipeline(v->Device, v->Allocator, v->PipelineCache, v->RenderPass, v->MSAASamples, &bd->Pipeline, v->Subpass);
 
+    // Create command pool/buffer for texture upload
+    if (!bd->TexCommandPool)
+    {
+        VkCommandPoolCreateInfo info = {};
+        info.sType = VK_STRUCTURE_TYPE_COMMAND_POOL_CREATE_INFO;
+        info.flags = 0;
+        info.queueFamilyIndex = v->QueueFamily;
+        err = vkCreateCommandPool(v->Device, &info, v->Allocator, &bd->TexCommandPool);
+        check_vk_result(err);
+    }
+    if (!bd->TexCommandBuffer)
+    {
+        VkCommandBufferAllocateInfo info = {};
+        info.sType = VK_STRUCTURE_TYPE_COMMAND_BUFFER_ALLOCATE_INFO;
+        info.commandPool = bd->TexCommandPool;
+        info.commandBufferCount = 1;
+        err = vkAllocateCommandBuffers(v->Device, &info, &bd->TexCommandBuffer);
+        check_vk_result(err);
+    }
+
     return true;
 }
 
@@ -1074,7 +1104,11 @@ void    ImGui_ImplVulkan_DestroyDeviceObjects()
     ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
     ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
     ImGui_ImplVulkan_DestroyWindowRenderBuffers(v->Device, &bd->MainWindowRenderBuffers, v->Allocator);
-    ImGui_ImplVulkan_DestroyFontsTexture();
+
+    // Destroy all textures
+    for (ImTextureData* tex : ImGui::GetPlatformIO().Textures)
+        if (tex->RefCount == 1)
+            ImGui_ImplVulkan_DestroyTexture(tex);
 
     if (bd->TexCommandBuffer)     { vkFreeCommandBuffers(v->Device, bd->TexCommandPool, 1, &bd->TexCommandBuffer); bd->TexCommandBuffer = VK_NULL_HANDLE; }
     if (bd->TexCommandPool)       { vkDestroyCommandPool(v->Device, bd->TexCommandPool, v->Allocator); bd->TexCommandPool = VK_NULL_HANDLE; }
@@ -1175,6 +1209,7 @@ bool    ImGui_ImplVulkan_Init(ImGui_ImplVulkan_InitInfo* info)
     io.BackendRendererUserData = (void*)bd;
     io.BackendRendererName = "imgui_impl_vulkan";
     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.
 
     IM_ASSERT(info->Instance != VK_NULL_HANDLE);
     IM_ASSERT(info->PhysicalDevice != VK_NULL_HANDLE);
@@ -1219,7 +1254,7 @@ void ImGui_ImplVulkan_Shutdown()
 
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
-    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
+    io.BackendFlags &= ~(ImGuiBackendFlags_RendererHasVtxOffset | ImGuiBackendFlags_RendererHasTextures);
     IM_DELETE(bd);
 }
 
@@ -1227,9 +1262,7 @@ void ImGui_ImplVulkan_NewFrame()
 {
     ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
     IM_ASSERT(bd != nullptr && "Context or backend not initialized! Did you call ImGui_ImplVulkan_Init()?");
-
+    IM_UNUSED(bd);
-    if (!bd->FontTexture.DescriptorSet)
-        ImGui_ImplVulkan_CreateFontsTexture();
 }
 
 void ImGui_ImplVulkan_SetMinImageCount(uint32_t min_image_count)

backends/imgui_impl_vulkan.h

@@ -2,8 +2,9 @@
 // This needs to be used along with a Platform Backend (e.g. GLFW, SDL, Win32, custom..)
 
 // Implemented features:
-//  [!] Renderer: User texture binding. Use 'VkDescriptorSet' as ImTextureID. Call ImGui_ImplVulkan_AddTexture() to register one. Read the FAQ about ImTextureID! See https://github.com/ocornut/imgui/pull/914 for discussions.
+//  [!] Renderer: User texture binding. Use 'VkDescriptorSet' as texture identifier. Call ImGui_ImplVulkan_AddTexture() to register one. Read the FAQ about ImTextureID/ImTextureRef + https://github.com/ocornut/imgui/pull/914 for discussions.
 //  [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'.
 
 // The aim of imgui_impl_vulkan.h/.cpp is to be usable in your engine without any modification.
@@ -61,9 +62,8 @@
 #define IMGUI_IMPL_VULKAN_HAS_DYNAMIC_RENDERING
 #endif
 
-// Current version of the backend use 1 descriptor for the font atlas + as many as additional calls done to ImGui_ImplVulkan_AddTexture().
+// Backend uses a small number of descriptors per font atlas + as many as additional calls done to ImGui_ImplVulkan_AddTexture().
-// It is expected that as early as Q1 2025 the backend will use a few more descriptors. Use this value + number of desired calls to ImGui_ImplVulkan_AddTexture().
+#define IMGUI_IMPL_VULKAN_MINIMUM_IMAGE_SAMPLER_POOL_SIZE   (8)     // Minimum per atlas
-#define IMGUI_IMPL_VULKAN_MINIMUM_IMAGE_SAMPLER_POOL_SIZE   (1)     // Minimum per atlas
 
 // Initialization data, for ImGui_ImplVulkan_Init()
 // [Please zero-clear before use!]
@@ -112,10 +112,11 @@ IMGUI_IMPL_API bool             ImGui_ImplVulkan_Init(ImGui_ImplVulkan_InitInfo*
 IMGUI_IMPL_API void             ImGui_ImplVulkan_Shutdown();
 IMGUI_IMPL_API void             ImGui_ImplVulkan_NewFrame();
 IMGUI_IMPL_API void             ImGui_ImplVulkan_RenderDrawData(ImDrawData* draw_data, VkCommandBuffer command_buffer, VkPipeline pipeline = VK_NULL_HANDLE);
-IMGUI_IMPL_API bool             ImGui_ImplVulkan_CreateFontsTexture();
-IMGUI_IMPL_API void             ImGui_ImplVulkan_DestroyFontsTexture();
 IMGUI_IMPL_API void             ImGui_ImplVulkan_SetMinImageCount(uint32_t min_image_count); // To override MinImageCount after initialization (e.g. if swap chain is recreated)
 
+// (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_ImplVulkan_UpdateTexture(ImTextureData* tex);
+
 // Register a texture (VkDescriptorSet == ImTextureID)
 // FIXME: This is experimental in the sense that we are unsure how to best design/tackle this problem
 // Please post to https://github.com/ocornut/imgui/pull/914 if you have suggestions.