diff --git a/src/canvas.c b/src/canvas.c
index 7febdb3..0168639 100644
--- a/src/canvas.c
+++ b/src/canvas.c
@@ -1 +1,99 @@
+/*
+ * canvas.c
+ *
+ * This file is a part of logdiag.
+ * Copyright Přemysl Janouch 2010. All rights reserved.
+ *
+ * See the file LICENSE for licensing information.
+ *
+ */
+
+#include <gtk/gtk.h>
+
+#include "config.h"
+
+#include "canvas.h"
+#include "document.h"
+
 /* http://www.gnomejournal.org/article/34/writing-a-widget-using-cairo-and-gtk28 */
+
+/**
+ * SECTION:canvas
+ * @short_description: A canvas.
+ * @see_also: #LogdiagDocument
+ *
+ * #LogdiagCanvas is used for displaying #LogdiagDocument objects.
+ */
+
+/*
+ * LogdiagCanvasPrivate:
+ * @document: A document object assigned to this canvas as a model.
+ */
+struct _LogdiagCanvasPrivate
+{
+	LogdiagDocument *document;
+};
+
+G_DEFINE_TYPE (LogdiagCanvas, logdiag_canvas, GTK_TYPE_DRAWING_AREA);
+
+static void
+logdiag_canvas_finalize (GObject *gobject);
+
+
+static void
+logdiag_canvas_class_init (LogdiagCanvasClass *klass)
+{
+	GObjectClass *object_class;
+	GtkWidgetClass *widget_class;
+
+	object_class = G_OBJECT_CLASS (klass);
+	object_class->finalize = logdiag_canvas_finalize;
+
+	widget_class = GTK_WIDGET_CLASS (klass);
+
+/**
+ * LogdiagCanvas::set-scroll-adjustments:
+ * @canvas: The canvas object.
+ *
+ * Contents of the library have changed.
+ */
+/*
+	widget_class->set_scroll_adjustments_signal = g_signal_new
+		("set-scroll-adjustments", G_TYPE_FROM_CLASS (widget_class),
+		G_SIGNAL_RUN_LAST | G_SIGNAL_ACTION,
+		0, // G_STRUCT_OFFSET (LogdiagCanvasClass, ...)
+		NULL, NULL,
+		gtk_marshal_NONE__POINTER_POINTER,
+		G_TYPE_NONE, 2, GTK_TYPE_ADJUSTMENT, GTK_TYPE_ADJUSTMENT);
+*/
+	g_type_class_add_private (klass, sizeof (LogdiagCanvasPrivate));
+}
+
+static void
+logdiag_canvas_init (LogdiagCanvas *self)
+{
+	self->priv = G_TYPE_INSTANCE_GET_PRIVATE
+		(self, LOGDIAG_TYPE_CANVAS, LogdiagCanvasPrivate);
+}
+
+static void
+logdiag_canvas_finalize (GObject *gobject)
+{
+	LogdiagCanvas *self;
+
+	self = LOGDIAG_CANVAS (gobject);
+
+	/* Chain up to the parent class. */
+	G_OBJECT_CLASS (logdiag_canvas_parent_class)->finalize (gobject);
+}
+
+/**
+ * logdiag_canvas_new:
+ *
+ * Create an instance.
+ */
+LogdiagCanvas *
+logdiag_canvas_new (void)
+{
+	return g_object_new (LOGDIAG_TYPE_CANVAS, NULL);
+}
diff --git a/src/canvas.h b/src/canvas.h
index e69de29..be3539a 100644
--- a/src/canvas.h
+++ b/src/canvas.h
@@ -0,0 +1,59 @@
+/*
+ * canvas.h
+ *
+ * This file is a part of logdiag.
+ * Copyright Přemysl Janouch 2010. All rights reserved.
+ *
+ * See the file LICENSE for licensing information.
+ *
+ */
+
+#ifndef __CANVAS_H__
+#define __CANVAS_H__
+
+G_BEGIN_DECLS
+
+
+#define LOGDIAG_TYPE_CANVAS (logdiag_canvas_get_type ())
+#define LOGDIAG_CANVAS(obj) (G_TYPE_CHECK_INSTANCE_CAST \
+	((obj), LOGDIAG_TYPE_CANVAS, LogdiagCanvas))
+#define LOGDIAG_CANVAS_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST \
+	((klass), LOGDIAG_TYPE_CANVAS, LogdiagCanvasClass))
+#define LOGDIAG_IS_CANVAS(obj) (G_TYPE_CHECK_INSTANCE_TYPE \
+	((obj), LOGDIAG_TYPE_CANVAS))
+#define LOGDIAG_IS_CANVAS_CLASS(klass) (G_TYPE_CHECK_INSTANCE_TYPE \
+	((klass), LOGDIAG_TYPE_CANVAS))
+#define LOGDIAG_CANVAS_GET_CLASS(obj) (G_TYPE_INSTANCE_GET_CLASS \
+	((obj), LOGDIAG_CANVAS, LogdiagCanvasClass))
+
+typedef struct _LogdiagCanvas LogdiagCanvas;
+typedef struct _LogdiagCanvasPrivate LogdiagCanvasPrivate;
+typedef struct _LogdiagCanvasClass LogdiagCanvasClass;
+
+
+/**
+ * LogdiagCanvas:
+ */
+struct _LogdiagCanvas
+{
+/*< private >*/
+	GtkDrawingArea parent_instance;
+	LogdiagCanvasPrivate *priv;
+
+/*< public >*/
+};
+
+struct _LogdiagCanvasClass
+{
+	GtkDrawingAreaClass parent_class;
+};
+
+
+GType logdiag_canvas_get_type (void) G_GNUC_CONST;
+
+LogdiagCanvas *logdiag_canvas_new (void);
+
+
+G_END_DECLS
+
+#endif /* ! __CANVAS_H__ */
diff --git a/src/document.h b/src/document.h
index e69de29..198d8f8 100644
--- a/src/document.h
+++ b/src/document.h
@@ -0,0 +1,91 @@
+/*
+ * document.h
+ *
+ * This file is a part of logdiag.
+ * Copyright Přemysl Janouch 2010. All rights reserved.
+ *
+ * See the file LICENSE for licensing information.
+ *
+ */
+
+#ifndef __DOCUMENT_H__
+#define __DOCUMENT_H__
+
+G_BEGIN_DECLS
+
+
+#define LOGDIAG_TYPE_DOCUMENT (logdiag_symbol_library_get_type ())
+#define LOGDIAG_DOCUMENT(obj) (G_TYPE_CHECK_INSTANCE_CAST \
+	((obj), LOGDIAG_TYPE_DOCUMENT, LogdiagDocument))
+#define LOGDIAG_DOCUMENT_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST \
+	((klass), LOGDIAG_TYPE_DOCUMENT, LogdiagDocumentClass))
+#define LOGDIAG_IS_DOCUMENT(obj) (G_TYPE_CHECK_INSTANCE_TYPE \
+	((obj), LOGDIAG_TYPE_DOCUMENT))
+#define LOGDIAG_IS_DOCUMENT_CLASS(klass) (G_TYPE_CHECK_INSTANCE_TYPE \
+	((klass), LOGDIAG_TYPE_DOCUMENT))
+#define LOGDIAG_DOCUMENT_GET_CLASS(obj) (G_TYPE_INSTANCE_GET_CLASS \
+	((obj), LOGDIAG_DOCUMENT, LogdiagDocumentClass))
+
+typedef struct _LogdiagDocument LogdiagDocument;
+/*typedef struct _LogdiagDocumentPrivate LogdiagDocumentPrivate;*/
+typedef struct _LogdiagDocumentClass LogdiagDocumentClass;
+
+
+/**
+ * LogdiagDocument:
+ */
+struct _LogdiagDocument
+{
+/*< private >*/
+	GObject parent_instance;
+
+/*< public >*/
+};
+
+struct _LogdiagDocumentClass
+{
+	GObjectClass parent_class;
+};
+
+
+GType logdiag_document_get_type (void) G_GNUC_CONST;
+
+LogdiagDocument *logdiag_document_new (void);
+gboolean logdiag_document_new_from_file (const char *file_name, GError *error);
+gboolean logdiag_document_save_to_file (const char *file_name, GError *error);
+
+#if 0
+/*
+ * LogdiagDocumentPrivate:
+ * @objects: All the objects in the document.
+ */
+struct _LogdiagDocumentPrivate
+{
+	GSList *objects;
+};
+
+/** The contents of the document have changed. */
+signal documentChanged (...);
+
+/* TODO: A list of objects: */
+LogdiagDocumentSymbol
+LogdiagDocumentLabel
+
+logdiag_document_add_symbol (LogdiagSymbol *symbol, x, y);
+
+/* XXX: Separated lists of objects
+ *      or a single list for all objects?
+ */
+/* TODO: Wires. */
+logdiag_document_selection_...
+logdiag_document_selection_get_json (LogdiagDocument *self);
+logdiag_document_insert_json (LogdiagDocument *self);
+/** Go back or forward in the history of changes. */
+/* TODO: An interface that informs about the history. */
+logdiag_document_history_go (LogdiagDocument *self);
+#endif /* 0 */
+
+
+G_END_DECLS
+
+#endif /* ! __DOCUMENT_H__ */
diff --git a/src/symbol-category.h b/src/symbol-category.h
index e6b1b75..51ccb78 100644
--- a/src/symbol-category.h
+++ b/src/symbol-category.h
@@ -35,7 +35,7 @@ typedef struct _LogdiagSymbolCategoryClass LogdiagSymbolCategoryClass;
  * @parent: The parent object, may be LogdiagSymbolLibrary
  * or another LogdiagSymbolCategory.
  * @name: The name of the category.
- * @image_path: Path to the image of the category.
+ * @image_path: Path to the image for this category.
  * @children: Children of this category.
  */
 struct _LogdiagSymbolCategory
@@ -52,7 +52,7 @@ struct _LogdiagSymbolCategory
 
 struct _LogdiagSymbolCategoryClass
 {
-	GtkObjectClass parent_class;
+	GObjectClass parent_class;
 };
 
 
diff --git a/src/symbol-library.c b/src/symbol-library.c
index 869e3f2..679a068 100644
--- a/src/symbol-library.c
+++ b/src/symbol-library.c
@@ -177,6 +177,7 @@ logdiag_symbol_library_load (LogdiagSymbolLibrary *self, const char *path)
 
 /**
  * logdiag_symbol_library_clear:
+ * @self: A symbol library object.
  *
  * Clears all the contents.
  */
@@ -246,6 +247,7 @@ logdiag_symbol_category_finalize (GObject *gobject)
 
 /**
  * logdiag_symbol_category_new:
+ * @parent: The parent library for this category.
  *
  * Create an instance.
  */
@@ -276,16 +278,72 @@ logdiag_symbol_category_new (LogdiagSymbolLibrary *parent)
 
 /*
  * LogdiagSymbolPrivate:
- * @parent_library: The parent LogdiagSymbolLibrary.
+ * @library: The parent LogdiagSymbolLibrary.
  * The library contains the real function for rendering.
  */
 struct _LogdiagSymbolPrivate
 {
-	LogdiagSymbolLibrary *parent_library;
+	LogdiagSymbolLibrary *library;
 };
 
+G_DEFINE_TYPE (LogdiagSymbol, logdiag_symbol, G_TYPE_OBJECT);
+
+static void
+logdiag_symbol_finalize (GObject *gobject);
+
+
+static void
+logdiag_symbol_class_init (LogdiagSymbolClass *klass)
+{
+	GObjectClass *object_class;
+
+	object_class = G_OBJECT_CLASS (klass);
+	object_class->finalize = logdiag_symbol_finalize;
+
+	g_type_class_add_private (klass, sizeof (LogdiagSymbolPrivate));
+}
+
+static void
+logdiag_symbol_init (LogdiagSymbol *self)
+{
+	self->priv = G_TYPE_INSTANCE_GET_PRIVATE
+		(self, LOGDIAG_TYPE_SYMBOL_LIBRARY, LogdiagSymbolPrivate);
+}
+
+static void
+logdiag_symbol_finalize (GObject *gobject)
+{
+	LogdiagSymbol *self;
+
+	self = LOGDIAG_SYMBOL (gobject);
+	g_object_unref (self->priv->library);
+
+	/* Chain up to the parent class. */
+	G_OBJECT_CLASS (logdiag_symbol_parent_class)->finalize (gobject);
+}
+
+/**
+ * logdiag_symbol_new:
+ * @library: A library object.
+ * @filename: The file from which the symbol will be loaded.
+ *
+ * Load a symbol from a file into the library.
+ */
+LogdiagSymbol *logdiag_symbol_new (LogdiagSymbolLibrary *library,
+	const gchar *filename)
+{
+	LogdiagSymbol *symbol;
+
+	symbol = g_object_new (LOGDIAG_TYPE_SYMBOL, NULL);
+	/* TODO: Use the filename, Luke. */
+
+	symbol->priv->library = library;
+	g_object_ref (library);
+}
+
 /**
  * logdiag_symbol_build_identifier:
+ * @self: A symbol object.
  *
  * Build an identifier for the symbol.
  * The identifier is in the format "Category/Category/Symbol".
@@ -298,6 +356,12 @@ logdiag_symbol_build_identifier (LogdiagSymbol *self)
 
 /**
  * logdiag_symbol_draw:
+ * @self: A symbol object.
+ * @surface: A cairo surface to be drawn on.
+ * @param: Parameters for the symbol in a table.
+ * @x: The X coordinate on the surface.
+ * @y: The Y coordinate on the surface.
+ * @zoom: Zoom ratio.
  *
  * Draw the symbol onto a Cairo surface.
  */
diff --git a/src/symbol.h b/src/symbol.h
index c8f851f..046786a 100644
--- a/src/symbol.h
+++ b/src/symbol.h
@@ -27,34 +27,34 @@ G_BEGIN_DECLS
 	((obj), LOGDIAG_SYMBOL, LogdiagSymbolClass))
 
 typedef struct _LogdiagSymbol LogdiagSymbol;
-/*typedef struct _LogdiagSymbolPrivate LogdiagSymbolPrivate;*/
+typedef struct _LogdiagSymbolPrivate LogdiagSymbolPrivate;
 typedef struct _LogdiagSymbolClass LogdiagSymbolClass;
 
 
 /**
  * LogdiagSymbol:
- * @parent: The parent category.
  * @name: The name of this symbol.
  */
 struct _LogdiagSymbol
 {
 /*< private >*/
 	GObject parent_instance;
-/*	LogdiagSymbolPrivate *priv;*/
+	LogdiagSymbolPrivate *priv;
 
 /*< public >*/
-	LogdiagSymbolCategory *parent;
-	char *name;
+	gchar *name;
 };
 
 struct _LogdiagSymbolClass
 {
-	GtkObjectClass parent_class;
+	GObjectClass parent_class;
 };
 
 
 GType logdiag_symbol_get_type (void) G_GNUC_CONST;
 
+LogdiagSymbol *logdiag_symbol_new (LogdiagSymbolLibrary *library,
+	const gchar *filename);
 char *logdiag_symbol_build_identifier (LogdiagSymbol *self);
 void logdiag_symbol_draw (LogdiagSymbol *self, cairo_t *surface,
 	GHashTable *param, gint x, gint y, gdouble zoom);
diff --git a/src/window-main.c b/src/window-main.c
index 43ce429..89714a5 100644
--- a/src/window-main.c
+++ b/src/window-main.c
@@ -13,8 +13,11 @@
 #include "config.h"
 
 #include "window-main.h"
+#include "canvas.h"
+#include "document.h"
 #include "symbol-library.h"
 #include "symbol-category.h"
+#include "symbol.h"
 
 
 /**
@@ -37,11 +40,19 @@ struct _LogdiagWindowMainPrivate
 	GtkWidget *toolbar;
 
 	LogdiagSymbolLibrary *library;
+	LogdiagCanvas *canvas;
 
 	GtkWidget *statusbar;
 	guint statusbar_menu_context_id;
 };
 
+struct DocumentData
+{
+	LogdiagDocument *document;
+	const gchar *file_name;
+	/* Canvas viewport settings (for multitabbed) */
+};
+
 /* Define the type. */
 G_DEFINE_TYPE (LogdiagWindowMain, logdiag_window_main, GTK_TYPE_WINDOW);
 
@@ -219,6 +230,11 @@ logdiag_window_main_init (LogdiagWindowMain *self)
 
 	load_toolbar (self);
 
+	/* Canvas. */
+	priv->canvas = logdiag_canvas_new ();
+	gtk_box_pack_start (GTK_BOX (priv->hbox), GTK_WIDGET (priv->canvas),
+		FALSE, FALSE, 0);
+
 	/* TODO: GtkHPaned */
 
 	priv->statusbar = gtk_statusbar_new ();
@@ -227,7 +243,7 @@ logdiag_window_main_init (LogdiagWindowMain *self)
 	gtk_box_pack_end (GTK_BOX (priv->vbox), priv->statusbar, FALSE, FALSE, 0);
 
 
-	/* Do this on disposal. */
+	/* TODO: Do this on disposal. */
 	/* g_object_unref(ui_manager); */
 
 	/* Proceed to showing the window. */