使用OpenGL编译GTK +

Question

Context : I am learning development of GUI using GTK+. I also wanted to draw lines and circles on the GUI. So I started with the tutorials and I am stuck with the part of GtkGLArea. I am following the code given in the GTK+ documentation

The error :

glTrial.cpp:32:13: error: variable or field ‘on_realize’ declared void
 on_realize (GtkGLarea *area)
             ^
glTrial.cpp:32:13: error: ‘GtkGLarea’ was not declared in this scope
glTrial.cpp:32:24: error: ‘area’ was not declared in this scope
 on_realize (GtkGLarea *area)

I believe I am not compiling properly and the compiler is not able to find correct headers.

Compilation :

g++ -std=c++14 \`pkg-config --cflags gtk+-3.0\` -o glTrial glTrial.cpp \`pkg-config --libs gtk+-3.0\` 

The code :

#include <gtk/gtk.h>
#include <gtkgl-2.0/gtkgl/gdkgl.h>
#include <gtkgl-2.0/gtkgl/gtkglarea.h>

static void
print_hello (GtkWidget *widget,
         gpointer user_data)
{
  g_print ("Hello World\n");
}

static gboolean
render (GtkGLArea *area, GdkGLContext *context)
{
  // inside this function it's safe to use GL; the given
  // #GdkGLContext has been made current to the drawable
  // surface used by the #GtkGLArea and the viewport has
  // already been set to be the size of the allocation

  // we can start by clearing the buffer
  //glClearColor (0, 0, 0, 0);
  // glClear (GL_COLOR_BUFFER_BIT);

  // draw your object
  // draw_an_object ();

  // we completed our drawing; the draw commands will be
  // flushed at the end of the signal emission chain, and
  // the buffers will be drawn on the window
  return TRUE;
}
static void
on_realize (GtkGLarea *area)
{
  // We need to make the context current if we want to
  // call GL API
  gtk_gl_area_make_current (area);

  // If there were errors during the initialization or
  // when trying to make the context current, this
  // function will return a #GError for you to catch
  if (gtk_gl_area_get_error (area) != NULL)
    return;

  // You can also use gtk_gl_area_set_error() in order
  // to show eventual initialization errors on the
  // GtkGLArea widget itself
  GError *internal_error = NULL;
  init_buffer_objects (&error);
  if (error != NULL)
    {
      gtk_gl_area_set_error (area, error);
      g_error_free (error);
      return;
    }

  init_shaders (&error);
  if (error != NULL)
    {
      gtk_gl_area_set_error (area, error);
      g_error_free (error);
      return;
    }
}

static void
activate (GtkApplication* app,
      gpointer user_data)
{
  GtkWidget *window;
  GtkWidget *grid;
  GtkWidget *button;
  GtkWidget *gl_area =gtk_gl_area_new();

  /* Create a new window, and set its title */
  window = gtk_application_window_new(app);
  gtk_window_set_title(GTK_WINDOW(window), "Window");
  gtk_container_set_border_width(GTK_CONTAINER(window), 10);
  //  gtk_window_set_default_size(GTK_WINDOW(window), 200, 200);

  /* Here we construct the container that is going to pack the buttons*/
  grid = gtk_grid_new();

  /* Pack the container in the window */
  gtk_container_add (GTK_CONTAINER (window), grid);


  button = gtk_button_new_with_label ("Quit");
  g_signal_connect_swapped (button, "clicked", G_CALLBACK (gtk_widget_destroy), window);

  gtk_grid_attach (GTK_GRID (grid), button, 0, 0, 2, 1);

  button = gtk_button_new_with_label ("Hello");
  g_signal_connect_swapped (button, "clicked", G_CALLBACK (print_hello), NULL);

  gtk_grid_attach (GTK_GRID (grid), button, 0, 1, 2, 1);

  /* Trial for GL area*/
  g_signal_connect (gl_area, "render", G_CALLBACK(render), NULL);
  gtk_grid_attach (GTK_GRID (grid), gl_area, 0, 2, 10, 10);

  gtk_widget_show_all (window);
}


int
main (int argc,
      char **argv)
{
  GtkApplication *app;
  int status;
  g_application_run (G_APPLICATION (app), argc, argv);
  //  app = gtk_application_new("org.gtk.example", G_APPLICATION_FLAGS_NONE);
  g_signal_connect(app, "activate", G_CALLBACK (activate), NULL);
  status = g_application_run (G_APPLICATION (app), argc, argv);
  g_object_unref (app);
  return status;

}

Answer 1

According to a fast google, you are looking for GtkGLArea , note the uppercase . – derhass

Answer 2

you need:

sudo apt install *epoxy* and

c++ t.c --target=arm-linux-gnu  `pkg-config --libs --cflags  gtk+-3.0 epoxy ` -o op