From 29fcdc5a4277e79799db9ecde0319e00918abb25 Mon Sep 17 00:00:00 2001 From: Marcus Ottosson Date: Wed, 20 Apr 2016 17:48:43 +0100 Subject: [PATCH] Created Getting Started (markdown) --- Getting-Started.md | 279 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 279 insertions(+) create mode 100644 Getting-Started.md diff --git a/Getting-Started.md b/Getting-Started.md new file mode 100644 index 0000000..5d40de1 --- /dev/null +++ b/Getting-Started.md @@ -0,0 +1,279 @@ +This article will guide you through getting up and running with as many assumptions about your system as possible. + +You are: + +- On Linux +- Using C++11 +- Using OpenGL 3.3 or above, core profile +- Using clang 3.4 or above +- Using glfw 3.0 or above + +
+
+
+ +### Layout + +This is the layout of your code. + +``` +| Directory | Description +|---------------------|---------------------------------- +| myproject/ | +| build/ | Output goes here +| include/ | Any include files you may eventually have +| src/ | +| main.cpp | Your single source file +| build.sh | Your build script +``` + +
+
+
+ +### Build + +Here is how your code will be built. + +```bash +$ cd myproject +$ ./build.sh +``` + +**build.sh** + +```bash +#!/usr/bin/env bash + +mkdir -p build && \ +pushd build && \ +clang++ \ + -o main \ + ../ext/imgui/imgui.cpp \ + ../ext/imgui/imgui_draw.cpp \ + ../src/main.cpp \ + -Wall \ + -g `# Generate complete debug info` \ + -std=c++11 \ + -I ../include \ + -I ../ext/glfw/include \ + -I ../ext/imgui \ + -L ../lib \ + -lglfw3 \ + -lGL \ + -lGLU \ + -lX11 \ + -lXxf86vm \ + -lXrandr \ + -lpthread \ + -lXi \ + -lXinerama \ + -lXcursor && \ +popd || exit 1 +``` + +
+
+
+ +### Source + +Here is the source. + +**main.cpp** + +```cpp +// dear imgui minimal example. + +#include +#include "GLFW/glfw3.h" +#include "imgui.h" + +void setup(GLFWwindow* window); +void renderer(ImDrawData* draw_data); + +int main(void) +{ + if (!glfwInit()) + { + exit(EXIT_FAILURE); + } + + static GLFWwindow* window { + glfwCreateWindow(320, 240, "Simple example", NULL, NULL) + }; + + if (!window) + { + glfwTerminate(); + exit(EXIT_FAILURE); + } + + glfwMakeContextCurrent(window); + + // Close window on pressing ESC + glfwSetKeyCallback(window, [](GLFWwindow* window, int key, int scancode, int action, int mods) { + if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS) + glfwSetWindowShouldClose(window, GL_TRUE); + }); + + setup(window); + + glClearColor(0.1f, 0.1f, 0.1f, 1.0f); + while (!glfwWindowShouldClose(window)) + { + glClear(GL_COLOR_BUFFER_BIT); + + glfwPollEvents(); + + // Use ImGui functions between here and Render() + ImGui::NewFrame(); + + // This creates a window + ImGui::Begin("Window Title Here"); + ImGui::Text("Hello, world!"); + ImGui::End(); + + // ImGui functions end here + ImGui::Render(); + + glfwSwapBuffers(window); + } + + glfwDestroyWindow(window); + glfwTerminate(); + + exit(EXIT_SUCCESS); +} + +/*! /brief Initialise the ImGuiIO struct. + * + * The ImGuiIO struct is the main configuration and + * I/O between your application and ImGui. + */ +void setup(GLFWwindow* window) +{ + unsigned char* pixels; + int width, + height, + display_width, + display_height; + GLuint g_FontTexture; + + ImGuiIO& io { ImGui::GetIO() }; + + io.Fonts->GetTexDataAsAlpha8(&pixels, &width, &height); + + // Upload texture to graphics system + GLint last_texture; + glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture); + glGenTextures(1, &g_FontTexture); + glBindTexture(GL_TEXTURE_2D, g_FontTexture); + glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); + glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); + glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, width, height, 0, GL_ALPHA, GL_UNSIGNED_BYTE, pixels); + + // Get display size + glfwGetWindowSize(window, &width, &height); + glfwGetFramebufferSize(window, &display_width, &display_height); + + io.DisplaySize = ImVec2((float)width, (float)height); + io.RenderDrawListsFn = renderer; + io.Fonts->TexID = (void *)(intptr_t)g_FontTexture; + + // Restore state + glBindTexture(GL_TEXTURE_2D, last_texture); +} + +/*! /brief Boilerplate function for OpenGL 2.0 rendering. + * + * This function isn't written by us, but is mandatory + * boilerplate from the library. It can be copy/pasted + * into your projects, but should really be part of the + * library itself? + */ +void renderer(ImDrawData* draw_data) +{ + ImGuiIO& io { ImGui::GetIO() }; + int fb_width { (int)(io.DisplaySize.x * io.DisplayFramebufferScale.x) }; + int fb_height { (int)(io.DisplaySize.y * io.DisplayFramebufferScale.y) }; + + draw_data->ScaleClipRects(io.DisplayFramebufferScale); + + GLint last_texture; glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture); + GLint last_viewport[4]; glGetIntegerv(GL_VIEWPORT, last_viewport); + glPushAttrib(GL_ENABLE_BIT | GL_COLOR_BUFFER_BIT | GL_TRANSFORM_BIT); + glEnable(GL_BLEND); + glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); + glDisable(GL_CULL_FACE); + glDisable(GL_DEPTH_TEST); + glEnable(GL_SCISSOR_TEST); + glEnableClientState(GL_VERTEX_ARRAY); + glEnableClientState(GL_TEXTURE_COORD_ARRAY); + glEnableClientState(GL_COLOR_ARRAY); + glEnable(GL_TEXTURE_2D); + + // Setup viewport, orthographic projection matrix + glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height); + glMatrixMode(GL_PROJECTION); + glPushMatrix(); + glLoadIdentity(); + glOrtho(0.0f, io.DisplaySize.x, io.DisplaySize.y, 0.0f, -1.0f, +1.0f); + glMatrixMode(GL_MODELVIEW); + glPushMatrix(); + glLoadIdentity(); + + // Render command lists + #define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT)) + for (int n = 0; n < draw_data->CmdListsCount; n++) + { + const ImDrawList* cmd_list = draw_data->CmdLists[n]; + const unsigned char* vtx_buffer = (const unsigned char*)&cmd_list->VtxBuffer.front(); + const ImDrawIdx* idx_buffer = &cmd_list->IdxBuffer.front(); + glVertexPointer(2, GL_FLOAT, sizeof(ImDrawVert), (void*)(vtx_buffer + OFFSETOF(ImDrawVert, pos))); + glTexCoordPointer(2, GL_FLOAT, sizeof(ImDrawVert), (void*)(vtx_buffer + OFFSETOF(ImDrawVert, uv))); + glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(ImDrawVert), (void*)(vtx_buffer + OFFSETOF(ImDrawVert, col))); + + for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.size(); cmd_i++) + { + const ImDrawCmd* pcmd = &cmd_list->CmdBuffer[cmd_i]; + if (pcmd->UserCallback) + { + pcmd->UserCallback(cmd_list, pcmd); + } + else + { + glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->TextureId); + glScissor((int)pcmd->ClipRect.x, (int)(fb_height - pcmd->ClipRect.w), (int)(pcmd->ClipRect.z - pcmd->ClipRect.x), (int)(pcmd->ClipRect.w - pcmd->ClipRect.y)); + glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, idx_buffer); + } + idx_buffer += pcmd->ElemCount; + } + } + #undef OFFSETOF + + // Restore modified state + glDisableClientState(GL_COLOR_ARRAY); + glDisableClientState(GL_TEXTURE_COORD_ARRAY); + glDisableClientState(GL_VERTEX_ARRAY); + glBindTexture(GL_TEXTURE_2D, last_texture); + glMatrixMode(GL_MODELVIEW); + glPopMatrix(); + glMatrixMode(GL_PROJECTION); + glPopMatrix(); + glPopAttrib(); + glViewport(last_viewport[0], last_viewport[1], (GLsizei)last_viewport[2], (GLsizei)last_viewport[3]); +} +``` + +
+
+
+ +#### TODO + +Here are some ideas for how to shorten this example substantially. + +- Remove lines that aren't absolutely critical +- Remove `renderer()` - Seems unnecessary and better included with ImGui? +- Remove need to manually upload texture to GPU in `setup()`, can/should be included in ImGui? \ No newline at end of file