我正在尝试使用所有 3 个库或诸如此类的东西,但我对示例代码感到很困惑,而且我不能完全遵循文档。这是代码,并在下面解释了我的困惑:
#include <iostream>
#include <string>
#include <SDL2/SDL.h>
#include <GL/glew.h>
#include <imgui/imgui.h>
#include <imgui/imgui_stdlib.h>
#include <imgui/imgui_impl_sdl.h>
#include <imgui/imgui_impl_opengl3.h>
// Main code
int main(int argc, char* argv[])
{
if (SDL_Init(SDL_INIT_VIDEO) != 0)
{
std::cout << SDL_GetError() << std::endl;
return -1;
}
// GL 3.0 + GLSL 130
const char* glsl_version = "#version 130";
SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, 0);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
// Create window with graphics context
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
SDL_WindowFlags window_flags = (SDL_WindowFlags)(SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI);
SDL_Window* window = SDL_CreateWindow("Dear ImGui SDL2+OpenGL3 example", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 1280, 720, window_flags);
SDL_GLContext gl_context = SDL_GL_CreateContext(window);
SDL_GL_MakeCurrent(window, gl_context);
SDL_GL_SetSwapInterval(0); // Disable vsync
if (glewInit() != GLEW_OK) {
std::cout << "Error initializing glew\n";
}
IMGUI_CHECKVERSION();
ImGui::CreateContext();
ImGuiIO& io = ImGui::GetIO();
io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard; // Enable Keyboard Controls
//io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad; // Enable Gamepad Controls
// Setup Dear ImGui style
ImGui::StyleColorsDark();
//ImGui::StyleColorsClassic();
// Setup Platform/Renderer backends
ImGui_ImplSDL2_InitForOpenGL(window, gl_context);
ImGui_ImplOpenGL3_Init(glsl_version);
ImFont* font = io.Fonts->AddFontFromFileTTF("C:\\Windows\\Fonts\\Arial.ttf", 30.0f);
ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);
// Main loop
bool running = false;
SDL_Event event;
while (!running)
{
while (SDL_PollEvent(&event))
{
ImGui_ImplSDL2_ProcessEvent(&event);
if (event.type == SDL_QUIT)
running = true;
if (event.type == SDL_WINDOWEVENT && event.window.event == SDL_WINDOWEVENT_CLOSE && event.window.windowID == SDL_GetWindowID(window))
running = true;
}
// Start the Dear ImGui frame
ImGui_ImplOpenGL3_NewFrame();
ImGui_ImplSDL2_NewFrame(window);
ImGui::NewFrame();
{
static std::string buf = "";
ImGui::PushFont(font);
ImGui::Begin("Window");
ImGui::InputText("Hello", &buf);
//std::cout << io.Fonts->Fonts.size() << std::endl;
ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / ImGui::GetIO().Framerate, ImGui::GetIO().Framerate);
ImGui::End();
ImGui::PopFont();
}
// Rendering
glViewport(0, 0, (int)io.DisplaySize.x, (int)io.DisplaySize.y);
glClearColor(clear_color.x, clear_color.y, clear_color.z, clear_color.w);
glClear(GL_COLOR_BUFFER_BIT);
ImGui::Render();
ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
SDL_GL_SwapWindow(window);
}
// Cleanup
ImGui_ImplOpenGL3_Shutdown();
ImGui_ImplSDL2_Shutdown();
ImGui::DestroyContext();
SDL_GL_DeleteContext(gl_context);
SDL_DestroyWindow(window);
SDL_Quit();
return 0;
}
我在这里有一些困惑,首先SDL_Renderer
是代码中没有任何地方。我注意到显示绘制颜色由 OpenGL 处理,但渲染是通过glClear(GL_COLOR_BUFFER_BIT);
(我认为)调用的。不过,我不确定,我如何才能真正调用任何 SDL2 函数,例如SDL_RenderFillRect()
没有 SDL_Renderer ?我最好的提示是这一行:
ImGui::Render();
ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
SDL_GL_SwapWindow(window);
它的 SDL_GL_SwapWindow() 在哪里,但我相信这也为 OpenGL 渲染?我不太确定所有撕裂中的哪条线实际上做了什么。我的意思是我本来以为ImGui::Render()
会渲染所有 ImGui 的东西,但是有一个ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
然后我不确定SDL_GL_SwapWindow
关系如何,因为我已经调用了glClear()
. 此外,为什么ImGui::EndFrame()
在一帧末尾的示例代码中调用但未调用一个函数,然后ImGui::NewFrame()
每个循环都有一个函数,并且对于ImGui_ImplOpenGL3_NewFrame();
ImGui_ImplSDL2_NewFrame(window);
有人可以解释其中一些非常令人困惑的事情。