427 lines
10 KiB
C
427 lines
10 KiB
C
/* OpenGL Area
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*
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* GtkGLArea is a widget that allows custom drawing using OpenGL calls.
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*/
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#include <math.h>
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#include <gtk/gtk.h>
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#include <epoxy/gl.h>
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static GtkWidget *demo_window = NULL;
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/* the GtkGLArea widget */
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static GtkWidget *gl_area = NULL;
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enum {
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X_AXIS,
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Y_AXIS,
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Z_AXIS,
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N_AXIS
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};
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/* Rotation angles on each axis */
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static float rotation_angles[N_AXIS] = { 0.0 };
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/* The object we are drawing */
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static const GLfloat vertex_data[] = {
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0.f, 0.5f, 0.f, 1.f,
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0.5f, -0.366f, 0.f, 1.f,
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-0.5f, -0.366f, 0.f, 1.f,
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};
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/* Initialize the GL buffers */
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static void
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init_buffers (GLuint *vao_out,
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GLuint *buffer_out)
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{
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GLuint vao, buffer;
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/* We only use one VAO, so we always keep it bound */
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glGenVertexArrays (1, &vao);
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glBindVertexArray (vao);
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/* This is the buffer that holds the vertices */
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glGenBuffers (1, &buffer);
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glBindBuffer (GL_ARRAY_BUFFER, buffer);
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glBufferData (GL_ARRAY_BUFFER, sizeof (vertex_data), vertex_data, GL_STATIC_DRAW);
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glBindBuffer (GL_ARRAY_BUFFER, 0);
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if (vao_out != NULL)
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*vao_out = vao;
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if (buffer_out != NULL)
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*buffer_out = buffer;
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}
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/* Create and compile a shader */
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static GLuint
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create_shader (int type,
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const char *src)
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{
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GLuint shader;
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int status;
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shader = glCreateShader (type);
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glShaderSource (shader, 1, &src, NULL);
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glCompileShader (shader);
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glGetShaderiv (shader, GL_COMPILE_STATUS, &status);
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if (status == GL_FALSE)
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{
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int log_len;
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char *buffer;
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glGetShaderiv (shader, GL_INFO_LOG_LENGTH, &log_len);
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buffer = g_malloc (log_len + 1);
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glGetShaderInfoLog (shader, log_len, NULL, buffer);
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g_warning ("Compile failure in %s shader:\n%s\n",
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type == GL_VERTEX_SHADER ? "vertex" : "fragment",
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buffer);
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g_free (buffer);
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glDeleteShader (shader);
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return 0;
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}
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return shader;
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}
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/* Initialize the shaders and link them into a program */
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static void
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init_shaders (GLuint *program_out,
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GLuint *mvp_out)
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{
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GLuint vertex, fragment;
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GLuint program = 0;
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GLuint mvp = 0;
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int status;
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GBytes *source;
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source = g_resources_lookup_data ("/glarea/glarea-vertex.glsl", 0, NULL);
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vertex = create_shader (GL_VERTEX_SHADER, g_bytes_get_data (source, NULL));
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g_bytes_unref (source);
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if (vertex == 0)
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{
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*program_out = 0;
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return;
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}
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source = g_resources_lookup_data ("/glarea/glarea-fragment.glsl", 0, NULL);
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fragment = create_shader (GL_FRAGMENT_SHADER, g_bytes_get_data (source, NULL));
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g_bytes_unref (source);
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if (fragment == 0)
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{
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glDeleteShader (vertex);
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*program_out = 0;
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return;
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}
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program = glCreateProgram ();
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glAttachShader (program, vertex);
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glAttachShader (program, fragment);
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glLinkProgram (program);
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glGetProgramiv (program, GL_LINK_STATUS, &status);
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if (status == GL_FALSE)
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{
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int log_len;
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char *buffer;
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glGetProgramiv (program, GL_INFO_LOG_LENGTH, &log_len);
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buffer = g_malloc (log_len + 1);
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glGetProgramInfoLog (program, log_len, NULL, buffer);
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g_warning ("Linking failure:\n%s\n", buffer);
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g_free (buffer);
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glDeleteProgram (program);
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program = 0;
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goto out;
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}
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/* Get the location of the "mvp" uniform */
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mvp = glGetUniformLocation (program, "mvp");
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glDetachShader (program, vertex);
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glDetachShader (program, fragment);
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out:
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glDeleteShader (vertex);
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glDeleteShader (fragment);
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if (program_out != NULL)
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*program_out = program;
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if (mvp_out != NULL)
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*mvp_out = mvp;
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}
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static void
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compute_mvp (float *res,
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float phi,
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float theta,
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float psi)
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{
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float x = phi * (G_PI / 180.f);
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float y = theta * (G_PI / 180.f);
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float z = psi * (G_PI / 180.f);
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float c1 = cosf (x), s1 = sinf (x);
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float c2 = cosf (y), s2 = sinf (y);
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float c3 = cosf (z), s3 = sinf (z);
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float c3c2 = c3 * c2;
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float s3c1 = s3 * c1;
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float c3s2s1 = c3 * s2 * s1;
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float s3s1 = s3 * s1;
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float c3s2c1 = c3 * s2 * c1;
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float s3c2 = s3 * c2;
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float c3c1 = c3 * c1;
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float s3s2s1 = s3 * s2 * s1;
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float c3s1 = c3 * s1;
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float s3s2c1 = s3 * s2 * c1;
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float c2s1 = c2 * s1;
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float c2c1 = c2 * c1;
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/* initialize to the identity matrix */
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res[0] = 1.f; res[4] = 0.f; res[8] = 0.f; res[12] = 0.f;
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res[1] = 0.f; res[5] = 1.f; res[9] = 0.f; res[13] = 0.f;
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res[2] = 0.f; res[6] = 0.f; res[10] = 1.f; res[14] = 0.f;
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res[3] = 0.f; res[7] = 0.f; res[11] = 0.f; res[15] = 1.f;
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/* apply all three rotations using the three matrices:
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*
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* ⎡ c3 s3 0 ⎤ ⎡ c2 0 -s2 ⎤ ⎡ 1 0 0 ⎤
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* ⎢ -s3 c3 0 ⎥ ⎢ 0 1 0 ⎥ ⎢ 0 c1 s1 ⎥
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* ⎣ 0 0 1 ⎦ ⎣ s2 0 c2 ⎦ ⎣ 0 -s1 c1 ⎦
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*/
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res[0] = c3c2; res[4] = s3c1 + c3s2s1; res[8] = s3s1 - c3s2c1; res[12] = 0.f;
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res[1] = -s3c2; res[5] = c3c1 - s3s2s1; res[9] = c3s1 + s3s2c1; res[13] = 0.f;
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res[2] = s2; res[6] = -c2s1; res[10] = c2c1; res[14] = 0.f;
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res[3] = 0.f; res[7] = 0.f; res[11] = 0.f; res[15] = 1.f;
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}
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static GLuint position_buffer;
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static GLuint program;
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static GLuint mvp_location;
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/* We need to set up our state when we realize the GtkGLArea widget */
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static void
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realize (GtkWidget *widget)
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{
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gtk_gl_area_make_current (GTK_GL_AREA (widget));
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if (gtk_gl_area_get_error (GTK_GL_AREA (widget)) != NULL)
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return;
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init_buffers (&position_buffer, NULL);
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init_shaders (&program, &mvp_location);
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}
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/* We should tear down the state when unrealizing */
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static void
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unrealize (GtkWidget *widget)
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{
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gtk_gl_area_make_current (GTK_GL_AREA (widget));
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if (gtk_gl_area_get_error (GTK_GL_AREA (widget)) != NULL)
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return;
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glDeleteBuffers (1, &position_buffer);
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glDeleteProgram (program);
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}
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static void
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draw_triangle (void)
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{
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float mvp[16];
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/* Compute the model view projection matrix using the
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* rotation angles specified through the GtkRange widgets
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*/
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compute_mvp (mvp,
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rotation_angles[X_AXIS],
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rotation_angles[Y_AXIS],
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rotation_angles[Z_AXIS]);
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/* Use our shaders */
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glUseProgram (program);
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/* Update the "mvp" matrix we use in the shader */
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glUniformMatrix4fv (mvp_location, 1, GL_FALSE, &mvp[0]);
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/* Use the vertices in our buffer */
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glBindBuffer (GL_ARRAY_BUFFER, position_buffer);
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glEnableVertexAttribArray (0);
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glVertexAttribPointer (0, 4, GL_FLOAT, GL_FALSE, 0, 0);
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/* Draw the three vertices as a triangle */
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glDrawArrays (GL_TRIANGLES, 0, 3);
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/* We finished using the buffers and program */
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glDisableVertexAttribArray (0);
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glBindBuffer (GL_ARRAY_BUFFER, 0);
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glUseProgram (0);
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}
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static gboolean
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render (GtkGLArea *area,
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GdkGLContext *context)
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{
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if (gtk_gl_area_get_error (area) != NULL)
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return FALSE;
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/* Clear the viewport */
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glClearColor (0.5, 0.5, 0.5, 1.0);
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glClear (GL_COLOR_BUFFER_BIT);
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/* Draw our object */
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draw_triangle ();
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/* Flush the contents of the pipeline */
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glFlush ();
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return TRUE;
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}
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static void
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on_axis_value_change (GtkAdjustment *adjustment,
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gpointer data)
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{
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int axis = GPOINTER_TO_INT (data);
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g_assert (axis >= 0 && axis < N_AXIS);
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/* Update the rotation angle */
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rotation_angles[axis] = gtk_adjustment_get_value (adjustment);
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/* Update the contents of the GL drawing area */
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gtk_widget_queue_draw (gl_area);
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}
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static GtkWidget *
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create_axis_slider (int axis)
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{
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GtkWidget *box, *label, *slider;
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GtkAdjustment *adj;
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const char *text;
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box = gtk_box_new (GTK_ORIENTATION_HORIZONTAL, FALSE);
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switch (axis)
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{
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case X_AXIS:
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text = "X axis";
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break;
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case Y_AXIS:
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text = "Y axis";
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break;
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case Z_AXIS:
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text = "Z axis";
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break;
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default:
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g_assert_not_reached ();
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}
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label = gtk_label_new (text);
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gtk_container_add (GTK_CONTAINER (box), label);
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gtk_widget_show (label);
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adj = gtk_adjustment_new (0.0, 0.0, 360.0, 1.0, 12.0, 0.0);
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g_signal_connect (adj, "value-changed",
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G_CALLBACK (on_axis_value_change),
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GINT_TO_POINTER (axis));
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slider = gtk_scale_new (GTK_ORIENTATION_HORIZONTAL, adj);
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gtk_container_add (GTK_CONTAINER (box), slider);
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gtk_widget_set_hexpand (slider, TRUE);
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gtk_widget_show (slider);
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gtk_widget_show (box);
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return box;
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}
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static void
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close_window (GtkWidget *widget)
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{
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/* Reset the state */
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demo_window = NULL;
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gl_area = NULL;
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rotation_angles[X_AXIS] = 0.0;
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rotation_angles[Y_AXIS] = 0.0;
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rotation_angles[Z_AXIS] = 0.0;
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}
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GtkWidget *
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create_glarea_window (GtkWidget *do_widget)
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{
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GtkWidget *window, *box, *button, *controls;
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int i;
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window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
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gtk_window_set_screen (GTK_WINDOW (window), gtk_widget_get_screen (do_widget));
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gtk_window_set_title (GTK_WINDOW (window), "OpenGL Area");
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gtk_window_set_default_size (GTK_WINDOW (window), 400, 600);
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gtk_container_set_border_width (GTK_CONTAINER (window), 12);
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g_signal_connect (window, "destroy", G_CALLBACK (close_window), NULL);
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box = gtk_box_new (GTK_ORIENTATION_VERTICAL, FALSE);
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gtk_box_set_spacing (GTK_BOX (box), 6);
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gtk_container_add (GTK_CONTAINER (window), box);
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gl_area = gtk_gl_area_new ();
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gtk_widget_set_hexpand (gl_area, TRUE);
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gtk_widget_set_vexpand (gl_area, TRUE);
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gtk_container_add (GTK_CONTAINER (box), gl_area);
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/* We need to initialize and free GL resources, so we use
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* the realize and unrealize signals on the widget
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*/
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g_signal_connect (gl_area, "realize", G_CALLBACK (realize), NULL);
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g_signal_connect (gl_area, "unrealize", G_CALLBACK (unrealize), NULL);
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/* The main "draw" call for GtkGLArea */
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g_signal_connect (gl_area, "render", G_CALLBACK (render), NULL);
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controls = gtk_box_new (GTK_ORIENTATION_VERTICAL, FALSE);
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gtk_container_add (GTK_CONTAINER (box), controls);
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gtk_widget_set_hexpand (controls, TRUE);
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for (i = 0; i < N_AXIS; i++)
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gtk_container_add (GTK_CONTAINER (controls), create_axis_slider (i));
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button = gtk_button_new_with_label ("Quit");
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gtk_widget_set_hexpand (button, TRUE);
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gtk_container_add (GTK_CONTAINER (box), button);
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g_signal_connect_swapped (button, "clicked", G_CALLBACK (gtk_widget_destroy), window);
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return window;
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}
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GtkWidget*
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do_glarea (GtkWidget *do_widget)
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{
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if (demo_window == NULL)
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demo_window = create_glarea_window (do_widget);
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if (!gtk_widget_get_visible (demo_window))
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gtk_widget_show_all (demo_window);
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else
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gtk_widget_destroy (demo_window);
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return demo_window;
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}
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