Backends: Vulkan: Rework support for custom function/symbol loader (#3759, #3227), add ImGui_ImplVulkan_LoadFunctions (amend 6001c54)

Making it a separate function allows to use/test this with our examples or any code using the VulkanH helper called before ImGui_ImplVulkan_Init()

backends/imgui_impl_vulkan.cpp

@@ -22,6 +22,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2021-01-27: Vulkan: Added support for custom function load and IMGUI_IMPL_VULKAN_NO_PROTOTYPES by using ImGui_ImplVulkan_LoadFunctions().
 //  2020-11-11: Vulkan: Added support for specifying which subpass to reference during VkPipeline creation.
 //  2020-09-07: Vulkan: Added VkPipeline parameter to ImGui_ImplVulkan_RenderDrawData (default to one passed to ImGui_ImplVulkan_Init).
 //  2020-05-04: Vulkan: Fixed crash if initial frame has no vertices.
@@ -51,72 +52,6 @@
 #include "imgui_impl_vulkan.h"
 #include <stdio.h>
 
-#ifdef IMGUI_IMPL_VULKAN_NO_PROTOTYPES
-#define IMGUI_VULKAN_FUNCTIONS_DEF(func) static PFN_##func func;
-#define IMGUI_VULKAN_FUNCTIONS_MAP(IMGUI_VULKAN_FUNCTIONS_MAP_MACRO) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkAllocateCommandBuffers) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkAllocateDescriptorSets) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkAllocateMemory) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkBindBufferMemory) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkBindImageMemory) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCmdBindDescriptorSets) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCmdBindIndexBuffer) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCmdBindPipeline) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCmdBindVertexBuffers) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCmdCopyBufferToImage) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCmdDrawIndexed) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCmdPipelineBarrier) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCmdPushConstants) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCmdSetScissor) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCmdSetViewport) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCreateBuffer) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCreateCommandPool) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCreateDescriptorSetLayout) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCreateFence) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCreateFramebuffer) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCreateGraphicsPipelines) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCreateImage) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCreateImageView) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCreatePipelineLayout) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCreateRenderPass) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCreateSampler) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCreateSemaphore) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCreateShaderModule) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkCreateSwapchainKHR) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkDestroyBuffer) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkDestroyCommandPool) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkDestroyDescriptorSetLayout) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkDestroyFence) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkDestroyFramebuffer) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkDestroyImage) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkDestroyImageView) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkDestroyPipeline) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkDestroyPipelineLayout) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkDestroyRenderPass) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkDestroySampler) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkDestroySemaphore) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkDestroyShaderModule) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkDestroySurfaceKHR) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkDestroySwapchainKHR) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkDeviceWaitIdle) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkFlushMappedMemoryRanges) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkFreeCommandBuffers) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkFreeMemory) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkGetBufferMemoryRequirements) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkGetImageMemoryRequirements) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkGetPhysicalDeviceMemoryProperties) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkGetPhysicalDeviceSurfaceCapabilitiesKHR) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkGetPhysicalDeviceSurfaceFormatsKHR) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkGetPhysicalDeviceSurfacePresentModesKHR) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkGetSwapchainImagesKHR) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkMapMemory) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkUnmapMemory) \
-    IMGUI_VULKAN_FUNCTIONS_MAP_MACRO(vkUpdateDescriptorSets)
-
-IMGUI_VULKAN_FUNCTIONS_MAP(IMGUI_VULKAN_FUNCTIONS_DEF)
-#undef IMGUI_VULKAN_FUNCTIONS_DEF
-#endif
-
 // Reusable buffers used for rendering 1 current in-flight frame, for ImGui_ImplVulkan_RenderDrawData()
 // [Please zero-clear before use!]
 struct ImGui_ImplVulkanH_FrameRenderBuffers
@@ -150,6 +85,11 @@ static VkPipeline               g_Pipeline = VK_NULL_HANDLE;
 static uint32_t                 g_Subpass = 0;
 static VkShaderModule           g_ShaderModuleVert;
 static VkShaderModule           g_ShaderModuleFrag;
+#ifdef VK_NO_PROTOTYPES
+static bool                     g_FunctionsLoaded = false;
+#else
+static bool                     g_FunctionsLoaded = true;
+#endif
 
 // Font data
 static VkSampler                g_FontSampler = VK_NULL_HANDLE;
@@ -172,6 +112,75 @@ void ImGui_ImplVulkanH_DestroyWindowRenderBuffers(VkDevice device, ImGui_ImplVul
 void ImGui_ImplVulkanH_CreateWindowSwapChain(VkPhysicalDevice physical_device, VkDevice device, ImGui_ImplVulkanH_Window* wd, const VkAllocationCallbacks* allocator, int w, int h, uint32_t min_image_count);
 void ImGui_ImplVulkanH_CreateWindowCommandBuffers(VkPhysicalDevice physical_device, VkDevice device, ImGui_ImplVulkanH_Window* wd, uint32_t queue_family, const VkAllocationCallbacks* allocator);
 
+// Vulkan prototypes for use with custom loaders
+// (see description of IMGUI_IMPL_VULKAN_NO_PROTOTYPES in imgui_impl_vulkan.h
+#ifdef VK_NO_PROTOTYPES
+#define IMGUI_VULKAN_FUNC_MAP(IMGUI_VULKAN_FUNC_MAP_MACRO) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkAllocateCommandBuffers) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkAllocateDescriptorSets) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkAllocateMemory) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkBindBufferMemory) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkBindImageMemory) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdBindDescriptorSets) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdBindIndexBuffer) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdBindPipeline) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdBindVertexBuffers) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdCopyBufferToImage) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdDrawIndexed) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdPipelineBarrier) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdPushConstants) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdSetScissor) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCmdSetViewport) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCreateBuffer) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCreateCommandPool) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCreateDescriptorSetLayout) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCreateFence) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCreateFramebuffer) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCreateGraphicsPipelines) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCreateImage) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCreateImageView) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCreatePipelineLayout) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCreateRenderPass) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCreateSampler) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCreateSemaphore) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCreateShaderModule) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkCreateSwapchainKHR) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkDestroyBuffer) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkDestroyCommandPool) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkDestroyDescriptorSetLayout) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkDestroyFence) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkDestroyFramebuffer) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkDestroyImage) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkDestroyImageView) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkDestroyPipeline) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkDestroyPipelineLayout) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkDestroyRenderPass) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkDestroySampler) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkDestroySemaphore) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkDestroyShaderModule) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkDestroySurfaceKHR) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkDestroySwapchainKHR) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkDeviceWaitIdle) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkFlushMappedMemoryRanges) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkFreeCommandBuffers) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkFreeMemory) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkGetBufferMemoryRequirements) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkGetImageMemoryRequirements) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkGetPhysicalDeviceMemoryProperties) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkGetPhysicalDeviceSurfaceCapabilitiesKHR) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkGetPhysicalDeviceSurfaceFormatsKHR) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkGetPhysicalDeviceSurfacePresentModesKHR) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkGetSwapchainImagesKHR) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkMapMemory) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkUnmapMemory) \
+    IMGUI_VULKAN_FUNC_MAP_MACRO(vkUpdateDescriptorSets)
+
+// Define function pointers
+#define IMGUI_VULKAN_FUNC_DEF(func) static PFN_##func func;
+IMGUI_VULKAN_FUNC_MAP(IMGUI_VULKAN_FUNC_DEF)
+#undef IMGUI_VULKAN_FUNC_DEF
+#endif // VK_NO_PROTOTYPES
+
 //-----------------------------------------------------------------------------
 // SHADERS
 //-----------------------------------------------------------------------------
@@ -951,19 +960,30 @@ void    ImGui_ImplVulkan_DestroyDeviceObjects()
     if (g_Pipeline)             { vkDestroyPipeline(v->Device, g_Pipeline, v->Allocator); g_Pipeline = VK_NULL_HANDLE; }
 }
 
+bool    ImGui_ImplVulkan_LoadFunctions(PFN_vkVoidFunction(*loader_func)(const char* function_name, void* user_data), void* user_data)
+{
+    // Load function pointers
+    // You can use the default Vulkan loader using:
+    //      ImGui_ImplVulkan_LoadFunctions([](const char* function_name, void*) { return vkGetInstanceProcAddr(your_vk_isntance, function_name); });
+    // But this would be equivalent to not setting VK_NO_PROTOTYPES.
+#ifdef VK_NO_PROTOTYPES
+#define IMGUI_VULKAN_FUNC_LOAD(func) \
+    func = reinterpret_cast<decltype(func)>(loader_func(#func, user_data)); \
+    if (func == NULL)   \
+        return false;
+    IMGUI_VULKAN_FUNC_MAP(IMGUI_VULKAN_FUNC_LOAD)
+#undef IMGUI_VULKAN_FUNC_LOAD
+#else
+    IM_UNUSED(loader_func);
+    IM_UNUSED(user_data);
+#endif
+    g_FunctionsLoaded = true;
+    return true;
+}
+
 bool    ImGui_ImplVulkan_Init(ImGui_ImplVulkan_InitInfo* info, VkRenderPass render_pass)
 {
-
+    IM_ASSERT(g_FunctionsLoaded && "Need to call ImGui_ImplVulkan_LoadFunctions() if IMGUI_IMPL_VULKAN_NO_PROTOTYPES or VK_NO_PROTOTYPES are set!");
-#ifdef IMGUI_IMPL_VULKAN_NO_PROTOTYPES
-    IM_ASSERT(info->GetVulkanProcAddressFn != NULL);
-#define IMGUI_VULKAN_FUNCTIONS_LOAD(func) \
-    func = reinterpret_cast<decltype(func)>(info->GetVulkanProcAddressFn(info->user_data, #func)); \
-    if(NULL == func) { \
-        return false; \
-    }
-    IMGUI_VULKAN_FUNCTIONS_MAP(IMGUI_VULKAN_FUNCTIONS_LOAD)
-#undef IMGUI_VULKAN_FUNCTIONS_LOAD
-#endif
 
     // Setup backend capabilities flags
     ImGuiIO& io = ImGui::GetIO();
@@ -1029,6 +1049,7 @@ void ImGui_ImplVulkan_SetMinImageCount(uint32_t min_image_count)
 
 VkSurfaceFormatKHR ImGui_ImplVulkanH_SelectSurfaceFormat(VkPhysicalDevice physical_device, VkSurfaceKHR surface, const VkFormat* request_formats, int request_formats_count, VkColorSpaceKHR request_color_space)
 {
+    IM_ASSERT(g_FunctionsLoaded && "Need to call ImGui_ImplVulkan_LoadFunctions() if IMGUI_IMPL_VULKAN_NO_PROTOTYPES or VK_NO_PROTOTYPES are set!");
     IM_ASSERT(request_formats != NULL);
     IM_ASSERT(request_formats_count > 0);
 
@@ -1073,6 +1094,7 @@ VkSurfaceFormatKHR ImGui_ImplVulkanH_SelectSurfaceFormat(VkPhysicalDevice physic
 
 VkPresentModeKHR ImGui_ImplVulkanH_SelectPresentMode(VkPhysicalDevice physical_device, VkSurfaceKHR surface, const VkPresentModeKHR* request_modes, int request_modes_count)
 {
+    IM_ASSERT(g_FunctionsLoaded && "Need to call ImGui_ImplVulkan_LoadFunctions() if IMGUI_IMPL_VULKAN_NO_PROTOTYPES or VK_NO_PROTOTYPES are set!");
     IM_ASSERT(request_modes != NULL);
     IM_ASSERT(request_modes_count > 0);
 
@@ -1323,6 +1345,7 @@ void ImGui_ImplVulkanH_CreateWindowSwapChain(VkPhysicalDevice physical_device, V
 // Create or resize window
 void ImGui_ImplVulkanH_CreateOrResizeWindow(VkInstance instance, VkPhysicalDevice physical_device, VkDevice device, ImGui_ImplVulkanH_Window* wd, uint32_t queue_family, const VkAllocationCallbacks* allocator, int width, int height, uint32_t min_image_count)
 {
+    IM_ASSERT(g_FunctionsLoaded && "Need to call ImGui_ImplVulkan_LoadFunctions() if IMGUI_IMPL_VULKAN_NO_PROTOTYPES or VK_NO_PROTOTYPES are set!");
     (void)instance;
     ImGui_ImplVulkanH_CreateWindowSwapChain(physical_device, device, wd, allocator, width, height, min_image_count);
     ImGui_ImplVulkanH_CreateWindowCommandBuffers(physical_device, device, wd, queue_family, allocator);

backends/imgui_impl_vulkan.h

@@ -23,15 +23,21 @@
 #pragma once
 #include "imgui.h"      // IMGUI_IMPL_API
 
-// In order to be able to use a customized Vulkan loader instead of the default one, you can uncomment the
+// [Configuration] in order to use a custom Vulkan function loader:
-// underlying definition in here (not in your code) or define it as a compilation flag in your build system.
+// (1) You'll need to disable default Vulkan function prototypes.
-// After enabling this, the user has to provide 'GetVulkanProcAddressFn' (and 'user_data' if it was needed) in
+//     We provide a '#define IMGUI_IMPL_VULKAN_NO_PROTOTYPES' convenience configuration flag.
-// the 'ImGui_ImplVulkan_InitInfo' so the implementation can resolve function addresses with that.
+//     In order to make sure this is visible from the imgui_impl_vulkan.cpp compilation unit:
-// If you have no idea what it is, leave it alone!
+//     - Add '#define IMGUI_IMPL_VULKAN_NO_PROTOTYPES' in your imconfig.h file
+//     - Or as a compilation flag in your build system
+//     - Or uncomment here (not recommended because you'd be modifying imgui sources!)
+//     - Do not simply add it in a .cpp file!
+// (2) Call ImGui_ImplVulkan_LoadFunctions() before ImGui_ImplVulkan_Init() with your custom function.
+// If you have no idea what this is, leave it alone!
 //#define IMGUI_IMPL_VULKAN_NO_PROTOTYPES
 
-#ifdef IMGUI_IMPL_VULKAN_NO_PROTOTYPES
+// Vulkan includes
-#define VK_NO_PROTOTYPES 1
+#if defined(IMGUI_IMPL_VULKAN_NO_PROTOTYPES) && !defined(VK_NO_PROTOTYPES)
+#define VK_NO_PROTOTYPES
 #endif
 #include <vulkan/vulkan.h>
 
@@ -39,27 +45,19 @@
 // [Please zero-clear before use!]
 struct ImGui_ImplVulkan_InitInfo
 {
-    VkInstance                     Instance;
+    VkInstance                      Instance;
-    VkPhysicalDevice               PhysicalDevice;
+    VkPhysicalDevice                PhysicalDevice;
-    VkDevice                       Device;
+    VkDevice                        Device;
-    uint32_t                       QueueFamily;
+    uint32_t                        QueueFamily;
-    VkQueue                        Queue;
+    VkQueue                         Queue;
-    VkPipelineCache                PipelineCache;
+    VkPipelineCache                 PipelineCache;
-    VkDescriptorPool               DescriptorPool;
+    VkDescriptorPool                DescriptorPool;
-    uint32_t                       Subpass;
+    uint32_t                        Subpass;
-    uint32_t                       MinImageCount;          // >= 2
+    uint32_t                        MinImageCount;          // >= 2
-    uint32_t                       ImageCount;             // >= MinImageCount
+    uint32_t                        ImageCount;             // >= MinImageCount
-    VkSampleCountFlagBits          MSAASamples;            // >= VK_SAMPLE_COUNT_1_BIT
+    VkSampleCountFlagBits           MSAASamples;            // >= VK_SAMPLE_COUNT_1_BIT
-    const VkAllocationCallbacks*   Allocator;
+    const VkAllocationCallbacks*    Allocator;
-    void                         (*CheckVkResultFn)(VkResult err);
+    void                            (*CheckVkResultFn)(VkResult err);
-#ifdef IMGUI_IMPL_VULKAN_NO_PROTOTYPES
-    // This function pointer is needed when the default Vulkan loader is disabled(not applicable).
-    // For more information look at comments before '#define IMGUI_IMPL_VULKAN_NO_PROTOTYPES' 
-    PFN_vkVoidFunction           (*GetVulkanProcAddressFn)(void *user_data, const char* pName);
-    // This pointer is going to be fed to the 'GetVulkanProcAddressFn', you can use it for
-    // accessing contex/object that is maybe needed for the function call.
-    void *user_data;
-#endif
 };
 
 // Called by user code
@@ -71,6 +69,9 @@ IMGUI_IMPL_API bool     ImGui_ImplVulkan_CreateFontsTexture(VkCommandBuffer comm
 IMGUI_IMPL_API void     ImGui_ImplVulkan_DestroyFontUploadObjects();
 IMGUI_IMPL_API void     ImGui_ImplVulkan_SetMinImageCount(uint32_t min_image_count); // To override MinImageCount after initialization (e.g. if swap chain is recreated)
 
+// Optional: load Vulkan functions with a custom function loader
+// This is only useful with IMGUI_IMPL_VULKAN_NO_PROTOTYPES / VK_NO_PROTOTYPES
+IMGUI_IMPL_API bool     ImGui_ImplVulkan_LoadFunctions(PFN_vkVoidFunction(*loader_func)(const char* function_name, void* user_data), void* user_data = NULL);
 
 //-------------------------------------------------------------------------
 // Internal / Miscellaneous Vulkan Helpers

docs/CHANGELOG.txt

@@ -55,6 +55,8 @@ Other Changes:
   Would lead to a buffer read overflow.
 - Backends: Win32: Dynamically loading XInput DLL instead of linking with it, facilite compiling with
   old WindowSDK versions or running on Windows 7. (#3646, #3645, #3248, #2716) [@Demonese]
+- Backends: Vulkan: Add support for custom Vulkan function loader and VK_NO_PROTOTYPES. (#3759, #3227) [@Hossein-Noroozpour]
+  User needs to call ImGui_ImplVulkan_LoadFunctions() with their custom loader prior to other functions.
 - Backends: Metal: Fixed texture storage mode when building on Mac Catalyst. (#3748) [@Belinsky-L-V]
 - Backends: OSX: Fixed mouse position not being reported when mouse buttons other than left one are down. (#3762) [@rokups]