bc63ea7629
- Remove find_library(LIB_GLEW ...) from 'resources.cmake' - Use the variable FLTK_GLEW_DIR to "find" a user supplied GLEW library for OpenGL3 example programs (examples/OpenGL3*.cxx). Both static and shared libs (DLLs) are supported, but the static library is preferred to avoid DLL dependencies. - Define preprocessor macro 'GLEW_STATIC' by CMake compile definitions if and only if the static glew library (glew32s) was found and linked. The previous code defined 'GLEW_STATIC' unconditionally in the source code which led to undefined references if a shared lib (DLL) was used.
266 lines
8.8 KiB
C++
266 lines
8.8 KiB
C++
//
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// Tiny OpenGL v3 demo program for the Fast Light Tool Kit (FLTK).
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//
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// Copyright 1998-2024 by Bill Spitzak and others.
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//
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// This library is free software. Distribution and use rights are outlined in
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// the file "COPYING" which should have been included with this file. If this
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// file is missing or damaged, see the license at:
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//
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// https://www.fltk.org/COPYING.php
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//
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// Please see the following page on how to report bugs and issues:
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//
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// https://www.fltk.org/bugs.php
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//
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#include <stdarg.h>
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#include <FL/Fl.H>
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#include <FL/platform.H>
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#include <FL/Fl_Window.H>
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#include <FL/Fl_Gl_Window.H>
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#include <FL/Fl_Light_Button.H>
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#include <FL/Fl_Text_Display.H>
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#include <FL/Fl_Text_Buffer.H>
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#if defined(__APPLE__)
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# include <OpenGL/gl3.h> // defines OpenGL 3.0+ functions
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#else
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// Note: GLEW_STATIC is defined by CMake if the static lib is linked
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# include <GL/glew.h>
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#endif
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#include <FL/gl.h> // for gl_texture_reset()
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void add_output(const char *format, ...);
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class SimpleGL3Window : public Fl_Gl_Window {
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GLuint shaderProgram;
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GLuint vertexArrayObject;
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GLuint vertexBuffer;
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GLint positionUniform;
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GLint colourAttribute;
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GLint positionAttribute;
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int gl_version_major;
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public:
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SimpleGL3Window(int x, int y, int w, int h) : Fl_Gl_Window(x, y, w, h) {
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mode(FL_RGB8 | FL_DOUBLE | FL_OPENGL3);
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shaderProgram = 0;
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gl_version_major = 0;
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}
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void draw(void) FL_OVERRIDE {
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if (gl_version_major >= 3 && !shaderProgram) {
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GLuint vs;
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GLuint fs;
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int Mslv, mslv; // major and minor version numbers of the shading language
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sscanf((char*)glGetString(GL_SHADING_LANGUAGE_VERSION), "%d.%d", &Mslv, &mslv);
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add_output("Shading Language Version=%d.%d\n",Mslv, mslv);
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const char *vss_format="#version %d%d\n\
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uniform vec2 p;\
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in vec4 position;\
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in vec4 colour;\
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out vec4 colourV;\
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void main (void)\
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{\
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colourV = colour;\
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gl_Position = vec4(p, 0.0, 0.0) + position;\
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}";
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char vss_string[300]; const char *vss = vss_string;
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snprintf(vss_string, 300, vss_format, Mslv, mslv);
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const char *fss_format="#version %d%d\n\
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in vec4 colourV;\
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out vec4 fragColour;\
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void main(void)\
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{\
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fragColour = colourV;\
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}";
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char fss_string[200]; const char *fss = fss_string;
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snprintf(fss_string, 200, fss_format, Mslv, mslv);
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GLint err; GLchar CLOG[1000]; GLsizei length;
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vs = glCreateShader(GL_VERTEX_SHADER);
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glShaderSource(vs, 1, &vss, NULL);
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glCompileShader(vs);
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glGetShaderiv(vs, GL_COMPILE_STATUS, &err);
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if (err != GL_TRUE) {
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glGetShaderInfoLog(vs, sizeof(CLOG), &length, CLOG);
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add_output("vs ShaderInfoLog=%s\n",CLOG);
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}
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fs = glCreateShader(GL_FRAGMENT_SHADER);
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glShaderSource(fs, 1, &fss, NULL);
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glCompileShader(fs);
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glGetShaderiv(fs, GL_COMPILE_STATUS, &err);
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if (err != GL_TRUE) {
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glGetShaderInfoLog(fs, sizeof(CLOG), &length, CLOG);
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add_output("fs ShaderInfoLog=%s\n",CLOG);
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}
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// Attach the shaders
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shaderProgram = glCreateProgram();
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glAttachShader(shaderProgram, vs);
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glAttachShader(shaderProgram, fs);
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glBindFragDataLocation(shaderProgram, 0, "fragColour");
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glLinkProgram(shaderProgram);
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glGetProgramiv(shaderProgram, GL_LINK_STATUS, &err);
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if (err != GL_TRUE) {
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glGetProgramInfoLog(shaderProgram, sizeof(CLOG), &length, CLOG);
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add_output("link log=%s\n", CLOG);
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}
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// Get pointers to uniforms and attributes
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positionUniform = glGetUniformLocation(shaderProgram, "p");
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colourAttribute = glGetAttribLocation(shaderProgram, "colour");
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positionAttribute = glGetAttribLocation(shaderProgram, "position");
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glDeleteShader(vs);
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glDeleteShader(fs);
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// Upload vertices (1st four values in a row) and colours (following four values)
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GLfloat vertexData[]= { -0.5,-0.5,0.0,1.0, 1.0,0.0,0.0,1.0,
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-0.5, 0.5,0.0,1.0, 0.0,1.0,0.0,1.0,
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0.5, 0.5,0.0,1.0, 0.0,0.0,1.0,1.0,
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0.5,-0.5,0.0,1.0, 1.0,1.0,1.0,1.0};
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glGenVertexArrays(1, &vertexArrayObject);
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glBindVertexArray(vertexArrayObject);
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glGenBuffers(1, &vertexBuffer);
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glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
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glBufferData(GL_ARRAY_BUFFER, 4*8*sizeof(GLfloat), vertexData, GL_STATIC_DRAW);
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glEnableVertexAttribArray((GLuint)positionAttribute);
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glEnableVertexAttribArray((GLuint)colourAttribute );
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glVertexAttribPointer((GLuint)positionAttribute, 4, GL_FLOAT, GL_FALSE, 8*sizeof(GLfloat), 0);
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glVertexAttribPointer((GLuint)colourAttribute , 4, GL_FLOAT, GL_FALSE, 8*sizeof(GLfloat), (char*)0+4*sizeof(GLfloat));
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glUseProgram(shaderProgram);
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}
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else if ((!valid())) {
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glViewport(0, 0, pixel_w(), pixel_h());
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}
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glClearColor(0.08f, 0.8f, 0.8f, 1.0f);
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glClear(GL_COLOR_BUFFER_BIT);
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if (shaderProgram) {
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GLfloat p[]={0,0};
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glUniform2fv(positionUniform, 1, (const GLfloat *)&p);
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glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
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}
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Fl_Gl_Window::draw(); // Draw FLTK child widgets.
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}
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int handle(int event) FL_OVERRIDE {
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static int first = 1;
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if (first && event == FL_SHOW && shown()) {
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first = 0;
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make_current();
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#ifndef __APPLE__
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GLenum err = glewInit(); // defines pters to functions of OpenGL V 1.2 and above
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# ifdef FLTK_USE_WAYLAND
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// glewInit returns GLEW_ERROR_NO_GLX_DISPLAY with Wayland
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// see https://github.com/nigels-com/glew/issues/273
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if (fl_wl_display() && err == GLEW_ERROR_NO_GLX_DISPLAY) err = GLEW_OK;
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# endif
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if (err) Fl::warning("glewInit() failed returning %u", err);
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else add_output("Using GLEW %s\n", glewGetString(GLEW_VERSION));
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#endif
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const uchar *glv = glGetString(GL_VERSION);
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add_output("GL_VERSION=%s\n", glv);
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sscanf((const char *)glv, "%d", &gl_version_major);
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if (gl_version_major < 3) {
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add_output("\nThis platform does not support OpenGL V3 :\n"
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"FLTK widgets will appear but the programmed "
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"rendering pipeline will not run.\n");
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mode(mode() & ~FL_OPENGL3);
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}
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redraw();
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}
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int retval = Fl_Gl_Window::handle(event);
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if (retval) return retval;
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if (event == FL_PUSH && gl_version_major >= 3) {
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static float factor = 1.1f;
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GLfloat data[4];
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glGetBufferSubData(GL_ARRAY_BUFFER, 0, 4*sizeof(GLfloat), data);
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if (data[0] < -0.88 || data[0] > -0.5) factor = 1/factor;
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data[0] *= factor;
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glBufferSubData(GL_ARRAY_BUFFER, 0, 4*sizeof(GLfloat), data);
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glGetBufferSubData(GL_ARRAY_BUFFER, 24*sizeof(GLfloat), 4*sizeof(GLfloat), data);
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data[0] *= factor;
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glBufferSubData(GL_ARRAY_BUFFER, 24*sizeof(GLfloat), 4*sizeof(GLfloat), data);
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redraw();
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add_output("push Fl_Gl_Window::pixels_per_unit()=%.1f\n", pixels_per_unit());
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return 1;
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}
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return retval;
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}
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void reset(void) { shaderProgram = 0; gl_texture_reset(); }
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};
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void toggle_double(Fl_Widget *wid, void *data) {
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static bool doublebuff = true;
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doublebuff = !doublebuff;
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SimpleGL3Window *glwin = (SimpleGL3Window*)data;
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int flags = glwin->mode();
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if (doublebuff) flags |= FL_DOUBLE; else flags &= ~FL_DOUBLE;
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glwin->reset();
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glwin->hide();
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glwin->mode(flags);
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glwin->show();
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}
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Fl_Text_Display *output; // shared between output_win() and add_output()
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void output_win(SimpleGL3Window *gl)
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{
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output = new Fl_Text_Display(300,0,500, 280);
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Fl_Light_Button *lb = new Fl_Light_Button(300, 280, 500, 20, "Double-Buffered");
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lb->callback(toggle_double);
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lb->user_data(gl);
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lb->value(1);
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output->buffer(new Fl_Text_Buffer());
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}
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void add_output(const char *format, ...)
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{
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va_list args;
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char line_buffer[10000];
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va_start(args, format);
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vsnprintf(line_buffer, sizeof(line_buffer)-1, format, args);
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va_end(args);
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output->buffer()->append(line_buffer);
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output->scroll(10000, 0);
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output->redraw();
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}
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void button_cb(Fl_Widget *widget, void *) {
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add_output("run %s callback\n", widget->label());
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}
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void add_widgets(Fl_Gl_Window *g) {
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Fl::set_color(FL_FREE_COLOR, 255, 255, 255, 140); // partially transparent white
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g->begin();
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// Create here widgets to go above the GL3 scene
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Fl_Button* b = new Fl_Button( 0, 0, 60, 30, "button");
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b->color(FL_FREE_COLOR);
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b->box(FL_DOWN_BOX );
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b->callback(button_cb, NULL);
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Fl_Button* b2 = new Fl_Button( 0, 170, 60, 30, "button2");
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b2->color(FL_FREE_COLOR);
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b2->box(FL_BORDER_BOX );
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b2->callback(button_cb, NULL);
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g->end();
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}
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int main(int argc, char **argv)
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{
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Fl::use_high_res_GL(1);
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Fl_Window *topwin = new Fl_Window(800, 300);
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SimpleGL3Window *win = new SimpleGL3Window(0, 0, 300, 300);
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win->end();
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output_win(win);
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add_widgets(win);
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topwin->end();
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topwin->resizable(win);
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topwin->label("Click GL panel to reshape");
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topwin->show(argc, argv);
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Fl::run();
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}
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