imgui/examples/opengl3_example/main.cpp

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// ImGui - standalone example application for OpenGL 3, using programmable pipeline
#ifdef _MSC_VER
#pragma warning (disable: 4996) // 'This function or variable may be unsafe': strcpy, strdup, sprintf, vsnprintf, sscanf, fopen
#endif
#include "../../imgui.h"
#define STB_IMAGE_IMPLEMENTATION
#include "../shared/stb_image.h" // stb_image.h for PNG loading
// Glfw/Glew
#define GLEW_STATIC
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT))
static GLFWwindow* window;
static GLuint fontTex;
static bool mousePressed[2] = { false, false };
static ImVec2 mousePosScale(1.0f, 1.0f);
// Shader variables
static int shader_handle, vert_handle, frag_handle;
static int texture_location, ortho_location;
static int position_location, uv_location, colour_location;
static size_t vbo_max_size = 20000;
static unsigned int vbo_handle, vao_handle;
// This is the main rendering function that you have to implement and provide to ImGui (via setting up 'RenderDrawListsFn' in the ImGuiIO structure)
// If text or lines are blurry when integrating ImGui in your engine:
// - try adjusting ImGui::GetIO().PixelCenterOffset to 0.0f or 0.5f
// - in your Render function, try translating your projection matrix by (0.5f,0.5f) or (0.375f,0.375f)
static void ImImpl_RenderDrawLists(ImDrawList** const cmd_lists, int cmd_lists_count)
{
if (cmd_lists_count == 0)
return;
// Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled
glEnable(GL_BLEND);
glBlendEquation(GL_FUNC_ADD);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glDisable(GL_CULL_FACE);
glDisable(GL_DEPTH_TEST);
glEnable(GL_SCISSOR_TEST);
// Setup texture
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, fontTex);
// Setup orthographic projection matrix
const float width = ImGui::GetIO().DisplaySize.x;
const float height = ImGui::GetIO().DisplaySize.y;
const float ortho_projection[4][4] =
{
{ 2.0f/width, 0.0f, 0.0f, 0.0f },
{ 0.0f, 2.0f/-height, 0.0f, 0.0f },
{ 0.0f, 0.0f, -1.0f, 0.0f },
{ -1.0f, 1.0f, 0.0f, 1.0f },
};
glUseProgram(shader_handle);
glUniform1i(texture_location, 0);
glUniformMatrix4fv(ortho_location, 1, GL_FALSE, &ortho_projection[0][0]);
// Grow our buffer according to what we need
size_t total_vtx_count = 0;
for (int n = 0; n < cmd_lists_count; n++)
total_vtx_count += cmd_lists[n]->vtx_buffer.size();
glBindBuffer(GL_ARRAY_BUFFER, vbo_handle);
size_t neededBufferSize = total_vtx_count * sizeof(ImDrawVert);
if (neededBufferSize > vbo_max_size)
{
vbo_max_size = neededBufferSize + 5000; // Grow buffer
glBufferData(GL_ARRAY_BUFFER, neededBufferSize, NULL, GL_STREAM_DRAW);
}
// Copy and convert all vertices into a single contiguous buffer
unsigned char* buffer_data = (unsigned char*)glMapBuffer(GL_ARRAY_BUFFER, GL_WRITE_ONLY);
if (!buffer_data)
return;
for (int n = 0; n < cmd_lists_count; n++)
{
const ImDrawList* cmd_list = cmd_lists[n];
memcpy(buffer_data, &cmd_list->vtx_buffer[0], cmd_list->vtx_buffer.size() * sizeof(ImDrawVert));
buffer_data += cmd_list->vtx_buffer.size() * sizeof(ImDrawVert);
}
glUnmapBuffer(GL_ARRAY_BUFFER);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(vao_handle);
int cmd_offset = 0;
for (int n = 0; n < cmd_lists_count; n++)
{
const ImDrawList* cmd_list = cmd_lists[n];
int vtx_offset = cmd_offset;
const ImDrawCmd* pcmd_end = cmd_list->commands.end();
for (const ImDrawCmd* pcmd = cmd_list->commands.begin(); pcmd != pcmd_end; pcmd++)
{
glScissor((int)pcmd->clip_rect.x, (int)(height - pcmd->clip_rect.w), (int)(pcmd->clip_rect.z - pcmd->clip_rect.x), (int)(pcmd->clip_rect.w - pcmd->clip_rect.y));
glDrawArrays(GL_TRIANGLES, vtx_offset, pcmd->vtx_count);
vtx_offset += pcmd->vtx_count;
}
cmd_offset = vtx_offset;
}
// Restore modified state
glBindVertexArray(0);
glUseProgram(0);
glDisable(GL_SCISSOR_TEST);
glBindTexture(GL_TEXTURE_2D, 0);
}
static const char* ImImpl_GetClipboardTextFn()
{
return glfwGetClipboardString(window);
}
static void ImImpl_SetClipboardTextFn(const char* text)
{
glfwSetClipboardString(window, text);
}
// GLFW callbacks to get events
static void glfw_error_callback(int error, const char* description)
{
fputs(description, stderr);
}
static void glfw_mouse_button_callback(GLFWwindow* window, int button, int action, int mods)
{
if (action == GLFW_PRESS && button >= 0 && button < 2)
mousePressed[button] = true;
}
static void glfw_scroll_callback(GLFWwindow* window, double xoffset, double yoffset)
{
ImGuiIO& io = ImGui::GetIO();
io.MouseWheel += (float)yoffset; // Use fractional mouse wheel, 1.0 unit 5 lines.
}
static void glfw_key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
ImGuiIO& io = ImGui::GetIO();
if (action == GLFW_PRESS)
io.KeysDown[key] = true;
if (action == GLFW_RELEASE)
io.KeysDown[key] = false;
io.KeyCtrl = (mods & GLFW_MOD_CONTROL) != 0;
io.KeyShift = (mods & GLFW_MOD_SHIFT) != 0;
}
static void glfw_char_callback(GLFWwindow* window, unsigned int c)
{
if (c > 0 && c < 0x10000)
ImGui::GetIO().AddInputCharacter((unsigned short)c);
}
// OpenGL code based on http://open.gl tutorials
void InitGL()
{
glfwSetErrorCallback(glfw_error_callback);
if (!glfwInit())
exit(1);
glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
window = glfwCreateWindow(1280, 720, "ImGui OpenGL example", NULL, NULL);
glfwMakeContextCurrent(window);
glfwSetKeyCallback(window, glfw_key_callback);
glfwSetMouseButtonCallback(window, glfw_mouse_button_callback);
glfwSetScrollCallback(window, glfw_scroll_callback);
glfwSetCharCallback(window, glfw_char_callback);
glewExperimental = GL_TRUE;
GLenum err = glewInit();
if (GLEW_OK != err)
fprintf(stderr, "Error: %s\n", glewGetErrorString(err));
const GLchar *vertex_shader =
"#version 330\n"
"uniform mat4 ortho;\n"
"in vec2 Position;\n"
"in vec2 UV;\n"
"in vec4 Colour;\n"
"out vec2 Frag_UV;\n"
"out vec4 Frag_Colour;\n"
"void main()\n"
"{\n"
" Frag_UV = UV;\n"
" Frag_Colour = Colour;\n"
" gl_Position = ortho*vec4(Position.xy,0,1);\n"
"}\n";
const GLchar* fragment_shader =
"#version 330\n"
"uniform sampler2D Texture;\n"
"in vec2 Frag_UV;\n"
"in vec4 Frag_Colour;\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
" FragColor = Frag_Colour * texture( Texture, Frag_UV.st);\n"
"}\n";
shader_handle = glCreateProgram();
vert_handle = glCreateShader(GL_VERTEX_SHADER);
frag_handle = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(vert_handle, 1, &vertex_shader, 0);
glShaderSource(frag_handle, 1, &fragment_shader, 0);
glCompileShader(vert_handle);
glCompileShader(frag_handle);
glAttachShader(shader_handle, vert_handle);
glAttachShader(shader_handle, frag_handle);
glLinkProgram(shader_handle);
texture_location = glGetUniformLocation(shader_handle, "Texture");
ortho_location = glGetUniformLocation(shader_handle, "ortho");
position_location = glGetAttribLocation(shader_handle, "Position");
uv_location = glGetAttribLocation(shader_handle, "UV");
colour_location = glGetAttribLocation(shader_handle, "Colour");
glGenBuffers(1, &vbo_handle);
glBindBuffer(GL_ARRAY_BUFFER, vbo_handle);
glBufferData(GL_ARRAY_BUFFER, vbo_max_size, NULL, GL_DYNAMIC_DRAW);
glGenVertexArrays(1, &vao_handle);
glBindVertexArray(vao_handle);
glBindBuffer(GL_ARRAY_BUFFER, vbo_handle);
glEnableVertexAttribArray(position_location);
glEnableVertexAttribArray(uv_location);
glEnableVertexAttribArray(colour_location);
glVertexAttribPointer(position_location, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, pos));
glVertexAttribPointer(uv_location, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, uv));
glVertexAttribPointer(colour_location, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, col));
glBindVertexArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
}
void InitImGui()
{
int w, h;
int display_w, display_h;
glfwGetWindowSize(window, &w, &h);
glfwGetFramebufferSize(window, &display_w, &display_h);
mousePosScale.x = (float)display_w / w; // Some screens e.g. Retina display have framebuffer size != from window size, and mouse inputs are given in window/screen coordinates.
mousePosScale.y = (float)display_h / h;
ImGuiIO& io = ImGui::GetIO();
io.DisplaySize = ImVec2((float)display_w, (float)display_h); // Display size, in pixels. For clamping windows positions.
io.DeltaTime = 1.0f / 60.0f; // Time elapsed since last frame, in seconds (in this sample app we'll override this every frame because our timestep is variable)
io.PixelCenterOffset = 0.5f; // Align OpenGL texels
io.KeyMap[ImGuiKey_Tab] = GLFW_KEY_TAB; // Keyboard mapping. ImGui will use those indices to peek into the io.KeyDown[] array.
io.KeyMap[ImGuiKey_LeftArrow] = GLFW_KEY_LEFT;
io.KeyMap[ImGuiKey_RightArrow] = GLFW_KEY_RIGHT;
io.KeyMap[ImGuiKey_UpArrow] = GLFW_KEY_UP;
io.KeyMap[ImGuiKey_DownArrow] = GLFW_KEY_DOWN;
io.KeyMap[ImGuiKey_Home] = GLFW_KEY_HOME;
io.KeyMap[ImGuiKey_End] = GLFW_KEY_END;
io.KeyMap[ImGuiKey_Delete] = GLFW_KEY_DELETE;
io.KeyMap[ImGuiKey_Backspace] = GLFW_KEY_BACKSPACE;
io.KeyMap[ImGuiKey_Enter] = GLFW_KEY_ENTER;
io.KeyMap[ImGuiKey_Escape] = GLFW_KEY_ESCAPE;
io.KeyMap[ImGuiKey_A] = GLFW_KEY_A;
io.KeyMap[ImGuiKey_C] = GLFW_KEY_C;
io.KeyMap[ImGuiKey_V] = GLFW_KEY_V;
io.KeyMap[ImGuiKey_X] = GLFW_KEY_X;
io.KeyMap[ImGuiKey_Y] = GLFW_KEY_Y;
io.KeyMap[ImGuiKey_Z] = GLFW_KEY_Z;
io.RenderDrawListsFn = ImImpl_RenderDrawLists;
io.SetClipboardTextFn = ImImpl_SetClipboardTextFn;
io.GetClipboardTextFn = ImImpl_GetClipboardTextFn;
// Load font texture
glGenTextures(1, &fontTex);
glBindTexture(GL_TEXTURE_2D, fontTex);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
const void* png_data;
unsigned int png_size;
ImGui::GetDefaultFontData(NULL, NULL, &png_data, &png_size);
int tex_x, tex_y, tex_comp;
void* tex_data = stbi_load_from_memory((const unsigned char*)png_data, (int)png_size, &tex_x, &tex_y, &tex_comp, 0);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, tex_x, tex_y, 0, GL_RGBA, GL_UNSIGNED_BYTE, tex_data);
stbi_image_free(tex_data);
}
void UpdateImGui()
{
ImGuiIO& io = ImGui::GetIO();
// Setup timestep
static double time = 0.0f;
const double current_time = glfwGetTime();
io.DeltaTime = (float)(current_time - time);
time = current_time;
// Setup inputs
// (we already got mouse wheel, keyboard keys & characters from glfw callbacks polled in glfwPollEvents())
double mouse_x, mouse_y;
glfwGetCursorPos(window, &mouse_x, &mouse_y);
io.MousePos = ImVec2((float)mouse_x * mousePosScale.x, (float)mouse_y * mousePosScale.y); // Mouse position, in pixels (set to -1,-1 if no mouse / on another screen, etc.)
io.MouseDown[0] = mousePressed[0] || glfwGetMouseButton(window, GLFW_MOUSE_BUTTON_LEFT) != 0; // If a mouse press event came, always pass it as "mouse held this frame", so we don't miss click-release events that are shorter than 1 frame.
io.MouseDown[1] = mousePressed[1] || glfwGetMouseButton(window, GLFW_MOUSE_BUTTON_RIGHT) != 0;
// Start the frame
ImGui::NewFrame();
}
// Application code
int main(int argc, char** argv)
{
InitGL();
InitImGui();
while (!glfwWindowShouldClose(window))
{
ImGuiIO& io = ImGui::GetIO();
io.MouseWheel = 0;
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mousePressed[0] = mousePressed[1] = false;
glfwPollEvents();
UpdateImGui();
static bool show_test_window = true;
static bool show_another_window = false;
// 1. Show a simple window
// Tip: if we don't call ImGui::Begin()/ImGui::End() the widgets appears in a window automatically called "Debug"
{
static float f;
ImGui::Text("Hello, world!");
ImGui::SliderFloat("float", &f, 0.0f, 1.0f);
show_test_window ^= ImGui::Button("Test Window");
show_another_window ^= ImGui::Button("Another Window");
// Calculate and show frame rate
static float ms_per_frame[120] = { 0 };
static int ms_per_frame_idx = 0;
static float ms_per_frame_accum = 0.0f;
ms_per_frame_accum -= ms_per_frame[ms_per_frame_idx];
ms_per_frame[ms_per_frame_idx] = ImGui::GetIO().DeltaTime * 1000.0f;
ms_per_frame_accum += ms_per_frame[ms_per_frame_idx];
ms_per_frame_idx = (ms_per_frame_idx + 1) % 120;
const float ms_per_frame_avg = ms_per_frame_accum / 120;
ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", ms_per_frame_avg, 1000.0f / ms_per_frame_avg);
}
// 2. Show another simple window, this time using an explicit Begin/End pair
if (show_another_window)
{
ImGui::Begin("Another Window", &show_another_window, ImVec2(200,100));
ImGui::Text("Hello");
ImGui::End();
}
// 3. Show the ImGui test window. Most of the sample code is in ImGui::ShowTestWindow()
if (show_test_window)
{
ImGui::SetNewWindowDefaultPos(ImVec2(650, 20)); // Normally user code doesn't need/want to call this, because positions are saved in .ini file. Here we just want to make the demo initial state a bit more friendly!
ImGui::ShowTestWindow(&show_test_window);
}
// Rendering
glViewport(0, 0, (int)io.DisplaySize.x, (int)io.DisplaySize.y);
glClearColor(0.8f, 0.6f, 0.6f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
ImGui::Render();
glfwSwapBuffers(window);
}
// Cleanup
if (vao_handle) glDeleteVertexArrays(1, &vao_handle);
if (vbo_handle) glDeleteBuffers(1, &vbo_handle);
glDetachShader(shader_handle, vert_handle);
glDetachShader(shader_handle, frag_handle);
glDeleteShader(vert_handle);
glDeleteShader(frag_handle);
glDeleteProgram(shader_handle);
ImGui::Shutdown();
glfwTerminate();
return 0;
}