Backends: Vulkan: added a way to specify custom vertex/fragment shaders. (#8585, #8271)

backends/imgui_impl_vulkan.cpp

@@ -27,6 +27,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2025-09-26: Vulkan: Added a way to customize shaders by filling ImGui_ImplVulkan_InitInfo::CustomShaderVertCreateInfo/CustomShaderFragCreateInfo. (#8585)
 //  2025-09-18: Call platform_io.ClearRendererHandlers() on shutdown.
 //  2025-09-04: Vulkan: Added ImGui_ImplVulkan_CreateMainPipeline(). (#8110, #8111)
 //  2025-07-27: Vulkan: Fixed texture update corruption introduced on 2025-06-11. (#8801, #8755, #8840)
@@ -887,24 +888,26 @@ void ImGui_ImplVulkan_UpdateTexture(ImTextureData* tex)
 
 static void ImGui_ImplVulkan_CreateShaderModules(VkDevice device, const VkAllocationCallbacks* allocator)
 {
-    // Create the shader modules
     ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
+    ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
     if (bd->ShaderModuleVert == VK_NULL_HANDLE)
     {
-        VkShaderModuleCreateInfo vert_info = {};
-        vert_info.sType = VK_STRUCTURE_TYPE_SHADER_MODULE_CREATE_INFO;
-        vert_info.codeSize = sizeof(__glsl_shader_vert_spv);
-        vert_info.pCode = (uint32_t*)__glsl_shader_vert_spv;
-        VkResult err = vkCreateShaderModule(device, &vert_info, allocator, &bd->ShaderModuleVert);
+        VkShaderModuleCreateInfo default_vert_info = {};
+        default_vert_info.sType = VK_STRUCTURE_TYPE_SHADER_MODULE_CREATE_INFO;
+        default_vert_info.codeSize = sizeof(__glsl_shader_vert_spv);
+        default_vert_info.pCode = (uint32_t*)__glsl_shader_vert_spv;
+        VkShaderModuleCreateInfo* p_vert_info = (v->CustomShaderVertCreateInfo.sType == VK_STRUCTURE_TYPE_SHADER_MODULE_CREATE_INFO) ? &v->CustomShaderVertCreateInfo : &default_vert_info;
+        VkResult err = vkCreateShaderModule(device, p_vert_info, allocator, &bd->ShaderModuleVert);
         check_vk_result(err);
     }
     if (bd->ShaderModuleFrag == VK_NULL_HANDLE)
     {
-        VkShaderModuleCreateInfo frag_info = {};
-        frag_info.sType = VK_STRUCTURE_TYPE_SHADER_MODULE_CREATE_INFO;
-        frag_info.codeSize = sizeof(__glsl_shader_frag_spv);
-        frag_info.pCode = (uint32_t*)__glsl_shader_frag_spv;
-        VkResult err = vkCreateShaderModule(device, &frag_info, allocator, &bd->ShaderModuleFrag);
+        VkShaderModuleCreateInfo default_frag_info = {};
+        default_frag_info.sType = VK_STRUCTURE_TYPE_SHADER_MODULE_CREATE_INFO;
+        default_frag_info.codeSize = sizeof(__glsl_shader_frag_spv);
+        default_frag_info.pCode = (uint32_t*)__glsl_shader_frag_spv;
+        VkShaderModuleCreateInfo* p_frag_info = (v->CustomShaderFragCreateInfo.sType == VK_STRUCTURE_TYPE_SHADER_MODULE_CREATE_INFO) ? &v->CustomShaderFragCreateInfo : &default_frag_info;
+        VkResult err = vkCreateShaderModule(device, p_frag_info, allocator, &bd->ShaderModuleFrag);
         check_vk_result(err);
     }
 }

backends/imgui_impl_vulkan.h

@@ -102,7 +102,13 @@ struct ImGui_ImplVulkan_InitInfo
     // (Optional) Allocation, Debugging
     const VkAllocationCallbacks*    Allocator;
     void                            (*CheckVkResultFn)(VkResult err);
-    VkDeviceSize                    MinAllocationSize;              // Minimum allocation size. Set to 1024*1024 to satisfy zealous best practices validation layer and waste a little memory.
+    VkDeviceSize                    MinAllocationSize;          // Minimum allocation size. Set to 1024*1024 to satisfy zealous best practices validation layer and waste a little memory.
+
+    // (Optional) Customize default vertex/fragment shaders.
+    // - if .sType == VK_STRUCTURE_TYPE_SHADER_MODULE_CREATE_INFO we use specified structs, otherwise we use defaults.
+    // - Shader inputs/outputs need to match ours. Code/data pointed to by the structure needs to survive for whole during of backend usage.
+    VkShaderModuleCreateInfo        CustomShaderVertCreateInfo;
+    VkShaderModuleCreateInfo        CustomShaderFragCreateInfo;
 };
 
 // Follow "Getting Started" link and check examples/ folder to learn about using backends!

docs/CHANGELOG.txt

@@ -64,6 +64,8 @@ Other Changes:
   - Better perf on X11 as querying global position requires a round trip to X11 server.
 - Backends: Win32: minor optimization not submitting gamepad io again if
   XInput's dwPacketNumber has not changed. (#8556) [@MidTerm-CN]
+- Backends: Vulkan: added a way to specify custom shaders by filling init fields
+  CustomShaderVertCreateInfo and CustomShaderFragCreateInfo. (#8585, #8271) [@johan0A]
 - Examples: SDL2+DirectX11: Try WARP software driver if hardware driver is
   not available. (#5924, #5562)
 - Examples: SDL3+DirectX11: Added SDL3+DirectX11 example. (#8956, #8957) [@tomaz82]