gds-render/preview-rendering/src/preview-rendering-gui.c

#include <preview-rendering/preview-rendering-gui.h>
#include <epoxy/gl.h>

struct _OpenGlPreviewGui {
	GObject super;
	GtkWindow *main_window;
	GtkGLArea *gl_area;
	unsigned int polygon_shader_prog;
	unsigned int vao;
	unsigned int vbo;
	float color[4];
};

G_DEFINE_TYPE(OpenGlPreviewGui, opengl_preview_gui, G_TYPE_OBJECT)

static void opengl_preview_gui_dispose(GObject *gobj)
{
	OpenGlPreviewGui *self;

	self = GDS_RENDER_OPENGL_PREVIEW_GUI(gobj);

	g_clear_object(&self->gl_area);

	if (self->main_window) {
		gtk_widget_destroy(GTK_WIDGET(self->main_window));
		self->main_window = NULL;
	}

	G_OBJECT_CLASS(opengl_preview_gui_parent_class)->dispose(gobj);
}

static void opengl_preview_gui_class_init(OpenGlPreviewGuiClass *klass)
{
	GObjectClass *oclass = G_OBJECT_CLASS(klass);

	oclass->dispose = opengl_preview_gui_dispose;
}

static gboolean gl_area_render(GtkGLArea *area, GdkGLContext *context, gpointer user)
{
	OpenGlPreviewGui *gui;

	int loc;

	gui = GDS_RENDER_OPENGL_PREVIEW_GUI(user);
	gtk_gl_area_make_current(area);

	glClearColor (0, 0, 0, 1.0);
	glClear (GL_COLOR_BUFFER_BIT);
	glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
	glUseProgram(gui->polygon_shader_prog);
	glBindVertexArray(gui->vao);
	loc = glGetUniformLocation(gui->polygon_shader_prog, "const_color");
	glUniform4fv(loc, 1, gui->color);
	glDrawArrays(GL_TRIANGLES, 0, 3);

	glFlush();

	return TRUE;
}

static int compile_shader_from_resource(GLenum shader_type, const char *res_name, unsigned int *shader)
{
	int success;
	GBytes *res_bytes;
	const char *data;
	gsize size;
	int size_int;
	int sh;

	res_bytes = g_resources_lookup_data(res_name, G_RESOURCE_LOOKUP_FLAGS_NONE, NULL);
	data = g_bytes_get_data(res_bytes, &size);
	sh = glCreateShader(shader_type);
	size_int = (int)size;
	glShaderSource(sh, 1, &data, &size_int);
	glCompileShader(sh);
	glGetShaderiv(sh, GL_COMPILE_STATUS, &success);
	g_bytes_unref(res_bytes);
	if (shader)
		*shader = sh;
	return success;
}

static gboolean gl_area_realize(GtkGLArea *area, gpointer user)
{
	unsigned int vbo;
	unsigned int vs;
	unsigned int fs;
	unsigned int prog;
	unsigned int vao;
	OpenGlPreviewGui *gui;
	int success;

	gui = GDS_RENDER_OPENGL_PREVIEW_GUI(user);

	gui->color[0] = 0.6f;
	gui->color[1] = 0.5f;
	gui->color[2] = 0.12f;
	gui->color[3] = 1.0f;

	gtk_gl_area_make_current(area);

	if (!compile_shader_from_resource(GL_VERTEX_SHADER, "/shaders/polygon.vs", &vs)) {
		g_warning("Error compiling vertex shader");
	}
	if (!compile_shader_from_resource(GL_FRAGMENT_SHADER, "/shaders/polygon.fs", &fs)) {
		g_warning("Error compiling fragment shader");
	}

	prog = glCreateProgram();
	glAttachShader(prog, vs);
	glAttachShader(prog, fs);
	glLinkProgram(prog);
	glGetProgramiv(prog, GL_LINK_STATUS, &success);
	if (!success) {
		g_warning("Error linking shader");
	}
	glUseProgram(prog);
	glDeleteShader(vs);
	glDeleteShader(fs);


	float vertices[] = {
		-0.5f, -0.5f,
		0.5f, -0.5f,
		0.0f, 0.5f,
	};

	glGenVertexArrays(1, &vao);
	glBindVertexArray(vao);
	glGenBuffers(1, &vbo);
	glBindBuffer(GL_ARRAY_BUFFER, vbo);
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
	glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 2*sizeof(float), (void *)0);
	glEnableVertexAttribArray(0);



	gui->polygon_shader_prog = prog;
	gui->vao = vao;
	gui->vbo = vbo;

	return TRUE;

}

static void opengl_preview_gui_init(OpenGlPreviewGui *self)
{
	GtkBuilder *builder;

	builder = gtk_builder_new_from_resource("/gui/preview-window.glade");
	self->main_window = GTK_WINDOW(gtk_builder_get_object(builder, "main-window"));
	self->gl_area = GTK_GL_AREA(gtk_builder_get_object(builder, "gl-area"));
	g_signal_connect(self->gl_area, "render", G_CALLBACK(gl_area_render), self);
	g_signal_connect(self->gl_area, "realize", G_CALLBACK(gl_area_realize), self);
	g_object_ref(self->gl_area);
}

OpenGlPreviewGui *opengl_preview_gui_new(void)
{
	return GDS_RENDER_OPENGL_PREVIEW_GUI(g_object_new(TYPE_GDS_RENDER_OPENGL_PREVIEW_GUI, NULL));
}

void opengl_preview_gui_show(OpenGlPreviewGui *self)
{
	gtk_widget_show(GTK_WIDGET(self->main_window));
}