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