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// Dear ImGui: standalone example application for Emscripten, using GLFW + WebGPU
// (Emscripten is a C++-to-javascript compiler, used to publish executables for the web. See
// If you are new to Dear ImGui, read documentation from the docs/ folder + read the top of imgui.cpp.
// Read online:
#include "imgui.h"
#include "imgui_impl_glfw.h"
#include "imgui_impl_wgpu.h"
#include <stdio.h>
#include <emscripten.h>
#include <emscripten/html5.h>
#include <emscripten/html5_webgpu.h>
#include <GLFW/glfw3.h>
#include <webgpu/webgpu.h>
#include <webgpu/webgpu_cpp.h>
// Global WebGPU required states
static WGPUDevice wgpu_device = NULL;
static WGPUSurface wgpu_surface = NULL;
static WGPUSwapChain wgpu_swap_chain = NULL;
static int wgpu_swap_chain_width = 0;
static int wgpu_swap_chain_height = 0;
// States tracked across render frames
static bool show_demo_window = true;
static bool show_another_window = false;
static ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);
// Forward declarations
static bool init_wgpu();
static void main_loop(void* window);
static void print_glfw_error(int error, const char* description);
static void print_wgpu_error(WGPUErrorType error_type, const char* message, void*);
int main(int, char**)
if (!glfwInit())
return 1;
// Make sure GLFW does not initialize any graphics context.
// This needs to be done explicitly later
GLFWwindow* window = glfwCreateWindow(1280, 720, "Dear ImGui GLFW+WebGPU example", NULL, NULL);
if (!window)
return 1;
// Initialize the WebGPU environment
if (!init_wgpu())
if (window)
return 1;
// Setup Dear ImGui context
ImGuiIO& io = ImGui::GetIO(); (void)io;
//io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard; // Enable Keyboard Controls
//io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad; // Enable Gamepad Controls
// For an Emscripten build we are disabling file-system access, so let's not attempt to do a fopen() of the imgui.ini file.
// You may manually call LoadIniSettingsFromMemory() to load settings from your own storage.
io.IniFilename = NULL;
// Setup Dear ImGui style
// Setup Platform/Renderer backends
ImGui_ImplGlfw_InitForOther(window, true);
ImGui_ImplWGPU_Init(wgpu_device, 3, WGPUTextureFormat_RGBA8Unorm);
// Load Fonts
// - If no fonts are loaded, dear imgui will use the default font. You can also load multiple fonts and use ImGui::PushFont()/PopFont() to select them.
// - AddFontFromFileTTF() will return the ImFont* so you can store it if you need to select the font among multiple.
// - If the file cannot be loaded, the function will return NULL. Please handle those errors in your application (e.g. use an assertion, or display an error and quit).
// - The fonts will be rasterized at a given size (w/ oversampling) and stored into a texture when calling ImFontAtlas::Build()/GetTexDataAsXXXX(), which ImGui_ImplXXXX_NewFrame below will call.
// - Read 'docs/' for more instructions and details.
// - Remember that in C/C++ if you want to include a backslash \ in a string literal you need to write a double backslash \\ !
// - Emscripten allows preloading a file or folder to be accessible at runtime. See Makefile for details.
io.Fonts->AddFontFromFileTTF("fonts/Roboto-Medium.ttf", 16.0f);
//io.Fonts->AddFontFromFileTTF("fonts/Cousine-Regular.ttf", 15.0f);
//io.Fonts->AddFontFromFileTTF("fonts/DroidSans.ttf", 16.0f);
//io.Fonts->AddFontFromFileTTF("fonts/ProggyTiny.ttf", 10.0f);
//ImFont* font = io.Fonts->AddFontFromFileTTF("fonts/ArialUni.ttf", 18.0f, NULL, io.Fonts->GetGlyphRangesJapanese());
//IM_ASSERT(font != NULL);
// This function will directly return and exit the main function.
// Make sure that no required objects get cleaned up.
// This way we can use the browsers 'requestAnimationFrame' to control the rendering.
emscripten_set_main_loop_arg(main_loop, window, 0, false);
return 0;
static bool init_wgpu()
wgpu_device = emscripten_webgpu_get_device();
if (!wgpu_device)
return false;
wgpuDeviceSetUncapturedErrorCallback(wgpu_device, print_wgpu_error, NULL);
// Use C++ wrapper due to misbehavior in Emscripten.
// Some offset computation for wgpuInstanceCreateSurface in JavaScript
// seem to be inline with struct alignments in the C++ structure
wgpu::SurfaceDescriptorFromCanvasHTMLSelector html_surface_desc = {};
html_surface_desc.selector = "#canvas";
wgpu::SurfaceDescriptor surface_desc = {};
surface_desc.nextInChain = &html_surface_desc;
// Use 'null' instance
wgpu::Instance instance = {};
wgpu_surface = instance.CreateSurface(&surface_desc).Release();
return true;
static void main_loop(void* window)
int width, height;
glfwGetFramebufferSize((GLFWwindow*) window, &width, &height);
// React to changes in screen size
if (width != wgpu_swap_chain_width && height != wgpu_swap_chain_height)
if (wgpu_swap_chain)
wgpu_swap_chain_width = width;
wgpu_swap_chain_height = height;
WGPUSwapChainDescriptor swap_chain_desc = {};
swap_chain_desc.usage = WGPUTextureUsage_RenderAttachment;
swap_chain_desc.format = WGPUTextureFormat_RGBA8Unorm;
swap_chain_desc.width = width;
swap_chain_desc.height = height;
swap_chain_desc.presentMode = WGPUPresentMode_Fifo;
wgpu_swap_chain = wgpuDeviceCreateSwapChain(wgpu_device, wgpu_surface, &swap_chain_desc);
// Start the Dear ImGui frame
// 1. Show the big demo window (Most of the sample code is in ImGui::ShowDemoWindow()! You can browse its code to learn more about Dear ImGui!).
if (show_demo_window)
// 2. Show a simple window that we create ourselves. We use a Begin/End pair to created a named window.
static float f = 0.0f;
static int counter = 0;
ImGui::Begin("Hello, world!"); // Create a window called "Hello, world!" and append into it.
ImGui::Text("This is some useful text."); // Display some text (you can use a format strings too)
ImGui::Checkbox("Demo Window", &show_demo_window); // Edit bools storing our window open/close state
ImGui::Checkbox("Another Window", &show_another_window);
ImGui::SliderFloat("float", &f, 0.0f, 1.0f); // Edit 1 float using a slider from 0.0f to 1.0f
ImGui::ColorEdit3("clear color", (float*)&clear_color); // Edit 3 floats representing a color
if (ImGui::Button("Button")) // Buttons return true when clicked (most widgets return true when edited/activated)
ImGui::Text("counter = %d", counter);
ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / ImGui::GetIO().Framerate, ImGui::GetIO().Framerate);
// 3. Show another simple window.
if (show_another_window)
ImGui::Begin("Another Window", &show_another_window); // Pass a pointer to our bool variable (the window will have a closing button that will clear the bool when clicked)
ImGui::Text("Hello from another window!");
if (ImGui::Button("Close Me"))
show_another_window = false;
// Rendering
WGPURenderPassColorAttachment color_attachments = {};
color_attachments.loadOp = WGPULoadOp_Clear;
color_attachments.storeOp = WGPUStoreOp_Store;
color_attachments.clearValue = { clear_color.x * clear_color.w, clear_color.y * clear_color.w, clear_color.z * clear_color.w, clear_color.w };
color_attachments.view = wgpuSwapChainGetCurrentTextureView(wgpu_swap_chain);
WGPURenderPassDescriptor render_pass_desc = {};
render_pass_desc.colorAttachmentCount = 1;
render_pass_desc.colorAttachments = &color_attachments;
render_pass_desc.depthStencilAttachment = NULL;
WGPUCommandEncoderDescriptor enc_desc = {};
WGPUCommandEncoder encoder = wgpuDeviceCreateCommandEncoder(wgpu_device, &enc_desc);
WGPURenderPassEncoder pass = wgpuCommandEncoderBeginRenderPass(encoder, &render_pass_desc);
ImGui_ImplWGPU_RenderDrawData(ImGui::GetDrawData(), pass);
WGPUCommandBufferDescriptor cmd_buffer_desc = {};
WGPUCommandBuffer cmd_buffer = wgpuCommandEncoderFinish(encoder, &cmd_buffer_desc);
WGPUQueue queue = wgpuDeviceGetQueue(wgpu_device);
wgpuQueueSubmit(queue, 1, &cmd_buffer);
static void print_glfw_error(int error, const char* description)
printf("Glfw Error %d: %s\n", error, description);
static void print_wgpu_error(WGPUErrorType error_type, const char* message, void*)
const char* error_type_lbl = "";
switch (error_type)
case WGPUErrorType_Validation: error_type_lbl = "Validation"; break;
case WGPUErrorType_OutOfMemory: error_type_lbl = "Out of memory"; break;
case WGPUErrorType_Unknown: error_type_lbl = "Unknown"; break;
case WGPUErrorType_DeviceLost: error_type_lbl = "Device lost"; break;
default: error_type_lbl = "Unknown";
printf("%s error: %s\n", error_type_lbl, message);