[dia] import: Implement DiaImportRenderer as a helper for further file import

[Hans Breuer <hans src gnome org>]

commit 06363f656f1491d8cefb6deb0445343d036947a6
Author: Hans Breuer <hans breuer org>
Date:   Sun Apr 20 11:11:21 2014 +0200

    import: Implement DiaImportRenderer as a helper for further file import
    
    This is finally the implementation of an old idea of mine: for file formats
    which are basically serialized drawing commands it should be relative
    straightforward to create the Dia objects via DiaRenderer interface. The WPG
    format is in this category and the respective plug-in had initial code for
    this idea for years. The following wpg-import.c is proof of concept and used
    to debug this code.

 lib/Makefile.am         |    2 +
 lib/diaimportrenderer.c |  811 +++++++++++++++++++++++++++++++++++++++++++++++
 lib/diaimportrenderer.h |   58 ++++
 lib/libdia.def          |    3 +
 lib/makefile.msc        |    1 +
 5 files changed, 875 insertions(+), 0 deletions(-)
---
diff --git a/lib/Makefile.am b/lib/Makefile.am
index 543a6eb..1475d5c 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -164,6 +164,8 @@ libdia_la_SOURCES =  \
                diatransform.c \
                diarenderer.h \
                diarenderer.c \
+               diaimportrenderer.c \
+               diaimportrenderer.h \
                diainteractiverenderer.c \
                diagdkrenderer.h \
                diagdkrenderer.c \
diff --git a/lib/diaimportrenderer.c b/lib/diaimportrenderer.c
new file mode 100644
index 0000000..9def10b
--- /dev/null
+++ b/lib/diaimportrenderer.c
@@ -0,0 +1,811 @@
+/* Dia -- an diagram creation/manipulation program
+ * Copyright (C) 1998 Alexander Larsson
+ *
+ * diaimportrenderer.c - Dia renderer class creating DiaObject(s)
+ *
+ * Copyright (C) 2014 Hans Breuer
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+#include <config.h>
+
+#include "diaimportrenderer.h"
+#include "object.h"
+#include "text.h"
+#include "create.h"
+#include "properties.h"
+#include "dia_image.h"
+#include "diatransformrenderer.h"
+#include "diapathrenderer.h"
+
+static void begin_render (DiaRenderer *, const Rectangle *update);
+static void end_render (DiaRenderer *);
+
+static void set_linewidth (DiaRenderer *renderer, real linewidth);
+static void set_linecaps (DiaRenderer *renderer, LineCaps mode);
+static void set_linejoin (DiaRenderer *renderer, LineJoin mode);
+static void set_linestyle (DiaRenderer *renderer, LineStyle mode);
+static void set_dashlength (DiaRenderer *renderer, real length);
+static void set_fillstyle (DiaRenderer *renderer, FillStyle mode);
+static void set_font (DiaRenderer *renderer, DiaFont *font, real height);
+
+static void draw_line (DiaRenderer *renderer,
+                      Point *start, Point *end,
+                      Color *color);
+static void fill_rect (DiaRenderer *renderer,
+                      Point *ul_corner, Point *lr_corner,
+                      Color *color);
+static void fill_polygon (DiaRenderer *renderer,
+                         Point *points, int num_points,
+                         Color *color);
+static void draw_arc (DiaRenderer *renderer,
+                     Point *center,
+                     real width, real height,
+                     real angle1, real angle2,
+                     Color *color);
+static void fill_arc (DiaRenderer *renderer,
+                     Point *center,
+                     real width, real height,
+                     real angle1, real angle2,
+                     Color *color);
+static void draw_ellipse (DiaRenderer *renderer,
+                         Point *center,
+                         real width, real height,
+                         Color *color);
+static void fill_ellipse (DiaRenderer *renderer,
+                         Point *center,
+                         real width, real height,
+                         Color *color);
+static void draw_bezier (DiaRenderer *renderer,
+                        BezPoint *points,
+                        int numpoints,
+                        Color *color);
+static void fill_bezier (DiaRenderer *renderer,
+                        BezPoint *points,
+                        int numpoints,
+                        Color *color);
+static void draw_string (DiaRenderer *renderer,
+                        const gchar *text,
+                        Point *pos,
+                        Alignment alignment,
+                        Color *color);
+static void draw_image (DiaRenderer *renderer,
+                       Point *point,
+                       real width, real height,
+                       DiaImage *image);
+
+static void draw_rect (DiaRenderer *renderer,
+                       Point *ul_corner, Point *lr_corner,
+                       Color *color);
+static void draw_polyline (DiaRenderer *renderer,
+                           Point *points, int num_points,
+                           Color *color);
+static void draw_rounded_polyline (DiaRenderer *renderer,
+                                  Point *points, int num_points,
+                                  Color *color, real radius);
+static void draw_polygon (DiaRenderer *renderer,
+                         Point *points, int num_points,
+                         Color *color);
+
+static void draw_rounded_rect (DiaRenderer *renderer,
+                              Point *ul_corner, Point *lr_corner,
+                              Color *color, real radius);
+static void fill_rounded_rect (DiaRenderer *renderer,
+                              Point *ul_corner, Point *lr_corner,
+                             Color *color, real radius);
+static void draw_line_with_arrows  (DiaRenderer *renderer, 
+                                   Point *start, Point *end, 
+                                   real line_width,
+                                   Color *line_color,
+                                   Arrow *start_arrow,
+                                   Arrow *end_arrow);
+static void draw_arc_with_arrows  (DiaRenderer *renderer, 
+                                  Point *start, 
+                                  Point *end,
+                                  Point *midpoint,
+                                  real line_width,
+                                  Color *color,
+                                  Arrow *start_arrow,
+                                  Arrow *end_arrow);
+static void draw_polyline_with_arrows (DiaRenderer *renderer, 
+                                      Point *points, int num_points,
+                                      real line_width,
+                                      Color *color,
+                                      Arrow *start_arrow,
+                                      Arrow *end_arrow);
+static void draw_rounded_polyline_with_arrows (DiaRenderer *renderer, 
+                                              Point *points, int num_points,
+                                              real line_width,
+                                              Color *color,
+                                              Arrow *start_arrow,
+                                              Arrow *end_arrow,
+                                              real radius);
+
+static void draw_bezier_with_arrows (DiaRenderer *renderer, 
+                                    BezPoint *points,
+                                    int num_points,
+                                    real line_width,
+                                    Color *color,
+                                    Arrow *start_arrow,
+                                    Arrow *end_arrow);
+
+static gboolean is_capable_to (DiaRenderer *renderer, RenderCapability cap);
+
+static void set_pattern (DiaRenderer *renderer, DiaPattern *pat);
+
+static gpointer parent_class = NULL;
+
+G_DEFINE_TYPE(DiaImportRenderer, dia_import_renderer, DIA_TYPE_RENDERER);
+
+static void
+renderer_finalize (GObject *object)
+{
+  DiaRenderer *renderer = DIA_RENDERER (object);
+
+  /* XXX: anything to destroy */
+
+  G_OBJECT_CLASS (parent_class)->finalize (object);
+}
+
+static void
+dia_import_renderer_class_init (DiaImportRendererClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+  DiaRendererClass *renderer_class = DIA_RENDERER_CLASS (klass);
+
+  parent_class = g_type_class_peek_parent (klass);
+
+  object_class->finalize = renderer_finalize;
+
+  renderer_class->begin_render = begin_render;
+  renderer_class->end_render   = end_render;
+
+  renderer_class->set_linewidth  = set_linewidth;
+  renderer_class->set_linecaps   = set_linecaps;
+  renderer_class->set_linejoin   = set_linejoin;
+  renderer_class->set_linestyle  = set_linestyle;
+  renderer_class->set_dashlength = set_dashlength;
+  renderer_class->set_fillstyle  = set_fillstyle;
+
+  renderer_class->draw_line    = draw_line;
+  renderer_class->fill_rect    = fill_rect;
+  renderer_class->fill_polygon = fill_polygon;
+  renderer_class->draw_arc     = draw_arc;
+  renderer_class->fill_arc     = fill_arc;
+  renderer_class->draw_ellipse = draw_ellipse;
+  renderer_class->fill_ellipse = fill_ellipse;
+  renderer_class->draw_string  = draw_string;
+  renderer_class->draw_image   = draw_image;
+
+  /* medium level functions */
+  renderer_class->draw_bezier  = draw_bezier;
+  renderer_class->fill_bezier  = fill_bezier;
+  renderer_class->draw_rect = draw_rect;
+  renderer_class->draw_rounded_polyline  = draw_rounded_polyline;
+  renderer_class->draw_polyline  = draw_polyline;
+  renderer_class->draw_polygon   = draw_polygon;
+
+  /* highest level functions */
+  renderer_class->draw_rounded_rect = draw_rounded_rect;
+  renderer_class->fill_rounded_rect = fill_rounded_rect;
+  renderer_class->draw_line_with_arrows = draw_line_with_arrows;
+  renderer_class->draw_arc_with_arrows  = draw_arc_with_arrows;
+  renderer_class->draw_polyline_with_arrows = draw_polyline_with_arrows;
+  renderer_class->draw_rounded_polyline_with_arrows = draw_rounded_polyline_with_arrows;
+  renderer_class->draw_bezier_with_arrows = draw_bezier_with_arrows;
+  
+  /* other */
+  renderer_class->is_capable_to = is_capable_to;
+  renderer_class->set_pattern = set_pattern;
+}
+
+static void
+dia_import_renderer_init (DiaImportRenderer *self)
+{
+  /* set all (non-null) defaults */
+  self->line_style = LINESTYLE_SOLID;
+  self->dash_length = 1.0;
+  self->line_caps = LINECAPS_BUTT;
+  self->line_join = LINEJOIN_MITER;
+
+  self->objects = NULL;
+}
+
+static void 
+begin_render (DiaRenderer *renderer, const Rectangle *update)
+{
+  g_warning ("%s::begin_render not implemented!", 
+             G_OBJECT_CLASS_NAME (G_OBJECT_GET_CLASS (renderer)));
+}
+
+static void 
+end_render (DiaRenderer *renderer)
+{
+  g_warning ("%s::end_render not implemented!", 
+             G_OBJECT_CLASS_NAME (G_OBJECT_GET_CLASS (renderer)));
+}
+
+static void 
+set_linewidth (DiaRenderer *renderer, real linewidth)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  self->line_width = linewidth;
+}
+
+static void 
+set_linecaps (DiaRenderer *renderer, LineCaps mode)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  self->line_caps = mode;
+}
+
+static void 
+set_linejoin (DiaRenderer *renderer, LineJoin mode)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  self->line_join = mode;
+}
+
+static void 
+set_linestyle (DiaRenderer *renderer, LineStyle mode)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  self->line_style = mode;
+}
+
+static void 
+set_dashlength (DiaRenderer *renderer, real length)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  self->dash_length = length;
+}
+
+static void 
+set_fillstyle (DiaRenderer *renderer, FillStyle mode)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  self->fill_style = mode;
+}
+
+/*!
+ * \brief Apply the current renderer's style to the given object
+ * \memberof _DiaImportRenderer
+ */
+static void
+_apply_style (DiaImportRenderer *self,
+             DiaObject *obj,
+             const Color *fill,
+             const Color *stroke,
+             real radius)
+{
+  GPtrArray *props = g_ptr_array_new ();
+
+  prop_list_add_line_width (props, self->line_width);
+  if (fill) {
+    prop_list_add_fill_colour (props, fill);
+    prop_list_add_show_background (props, TRUE);
+  } else {
+    prop_list_add_show_background (props, FALSE);
+  }
+  if (stroke) {
+    prop_list_add_line_style (props, self->line_style, self->dash_length);
+    /* XXX: line_join, line_caps */
+    prop_list_add_line_colour (props, stroke);
+  } else if (fill) {
+    /* line width to 0, line color to fill */
+    prop_list_add_line_width (props, 0.0);
+    prop_list_add_line_colour (props, fill);
+  }
+  if (radius > 0.0)
+    prop_list_add_real (props, "corner_radius", radius);
+  obj->ops->set_props (obj, props);
+  prop_list_free (props);
+}
+/*!
+ * \brief Remember the object for later use
+ * \memberof _DiaImportRenderer
+ */
+static void
+_push_object (DiaImportRenderer *self, DiaObject *obj)
+{
+  self->objects = g_list_append (self->objects, obj);
+}
+
+/*!
+ * \brief Draw a simple line
+ * \memberof _DiaImportRenderer
+ */
+static void 
+draw_line (DiaRenderer *renderer, Point *start, Point *end, Color *color)
+{
+  Point points[2];
+  points[0] = *start;
+  points[1] = *end;
+  draw_rounded_polyline (renderer, &points[0], 2, color, 0.0);
+}
+
+/*!
+ * \brief Fill the given ploygon
+ * \memberof _DiaImportRenderer
+ */
+static void 
+fill_polygon (DiaRenderer *renderer, Point *points, int num_points, Color *color)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  DiaObject *object = create_standard_polygon (num_points, points);
+
+  _apply_style (self, object, color, NULL, 0.0);
+  _push_object (self, object);
+}
+
+static DiaObject *
+_make_arc (Point *center, 
+          real width, real height,
+         real angle1, real angle2)
+{
+  DiaObject *object;
+  Point st, en;
+  real rx = width / 2, ry = height / 2;
+  real r = sqrt (rx*ry);
+  real a, b, d;
+  st.x = center->x + rx * cos(angle1*G_PI/180);
+  st.y = center->y - ry * sin(angle1*G_PI/180);
+  en.x = center->x + rx * cos(angle2*G_PI/180);
+  en.y = center->y - ry * sin(angle2*G_PI/180);
+  a = distance_point_point (&st, &en) / 2.0;
+  if (a < r)
+    b = sqrt(r*r - a*a); /* Pythagoras */
+  else
+    b = 0; /* half circle */
+  d = r - b;
+
+  object = create_standard_arc (st.x, st.y, en.x, en.y, d, NULL, NULL);
+  return object;
+}
+
+/*!
+ * \brief Draw an arc
+ * \memberof _DiaImportRenderer
+ */
+static void 
+draw_arc (DiaRenderer *renderer, Point *center, 
+          real width, real height, real angle1, real angle2,
+          Color *color)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  DiaObject *object = _make_arc (center, width, height, angle1, angle2);
+
+  _apply_style (self, object, NULL, color, 0.0);
+  _push_object (self, object);
+}
+
+/*!
+ * \brief Fill a rectangle
+ * \memberof _DiaImportRenderer
+ */
+static void 
+fill_rect (DiaRenderer *renderer,
+           Point *ul_corner, Point *lr_corner,
+           Color *color)
+{
+  fill_rounded_rect (renderer, ul_corner, lr_corner, color, 0.0);
+}
+
+/*!
+ * \brief Fill an arc
+ * As of this writing the Dia "Standard - Arc" (_Arc) object does not support
+ * filling. The created object is a filled _Beziergon because of this.
+ * \memberof _DiaImportRenderer
+ */
+static void
+fill_arc (DiaRenderer *renderer, Point *center,
+          real width, real height, real angle1, real angle2,
+          Color *color)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+#if 0 /* does not work till 'Standard - Arc' supports filling */
+  DiaObject *object = _make_arc (center, width, height, angle1, angle2);
+
+  _apply_style (self, object, color, NULL, 0.0);
+  _push_object (self, object);
+#else
+  GArray *path = g_array_new (FALSE, FALSE, sizeof(BezPoint));
+  path_build_arc (path, center, width, height, angle1, angle2, TRUE);
+  DIA_RENDERER_GET_CLASS(renderer)->fill_bezier (renderer,
+                                                &g_array_index (path, BezPoint, 0),
+                                                path->len, color);
+  g_array_free (path, TRUE);
+#endif
+}
+
+/*!
+ * \brief Draw an ellipse
+ * Creates a hollow _Ellipse object.
+ * \memberof _DiaImportRenderer
+ */
+static void 
+draw_ellipse (DiaRenderer *renderer, Point *center,
+              real width, real height, 
+              Color *color)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  DiaObject *object = create_standard_ellipse (center->x - width / 2, center->y - height / 2, width, height);
+
+  _apply_style (self, object, NULL, color, 0.0);
+  _push_object (self, object);
+}
+
+/*!
+ * \brief Fill an ellipse
+ * Creates a filled _Ellipse object.
+ * \memberof _DiaImportRenderer
+ */
+static void 
+fill_ellipse (DiaRenderer *renderer, Point *center,
+              real width, real height, Color *color)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  DiaObject *object = create_standard_ellipse (center->x - width / 2, center->y - height / 2, width, height);
+
+  _apply_style (self, object, color, NULL, 0.0);
+  _push_object (self, object);
+}
+
+/*!
+ * \brief Draw a string
+ * Creates a _Text object with the properties given by _DiaImportRenderer::set_font().
+ * \memberof _DiaImportRenderer
+ */
+static void 
+draw_string (DiaRenderer *renderer,
+             const gchar *text, Point *pos, Alignment alignment,
+             Color *color)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  DiaObject *object = create_standard_text (pos->x, pos->y);
+  GPtrArray *props = g_ptr_array_new ();
+
+  prop_list_add_font (props, "text_font", renderer->font);
+  prop_list_add_text_colour (props, color);
+  prop_list_add_fontsize (props, PROP_STDNAME_TEXT_HEIGHT, renderer->font_height);
+  prop_list_add_enum (props, "text_alignment", alignment);
+  prop_list_add_text (props, "text", text); /* must be last! */
+
+  object->ops->set_props (object, props);
+  prop_list_free (props);
+
+  _push_object (self, object);
+}
+
+/*!
+ * \brief Draw an image
+ * Creates an _Image object. Ownership of the passed in image is _not_ transferred,
+ * but it's pixbuf is referenced. The caller is responsible to destroy the image
+ * with dia_image_unref() when it is no longer needed.
+ * \memberof _DiaImportRenderer
+ */
+static void
+draw_image (DiaRenderer *renderer,
+            Point *point, real width, real height,
+            DiaImage *image)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  DiaObject *object = create_standard_image (point->x, point->y, width, height, "");
+  GPtrArray *props = g_ptr_array_new ();
+
+  prop_list_add_filename (props, "image_file", dia_image_filename (image));
+  /* XXX: reset or merge border? */
+  object->ops->set_props (object, props);
+  prop_list_free (props);
+
+  dia_object_set_pixbuf (object, dia_image_pixbuf (image));
+  _push_object (self, object);
+}
+
+/*
+ * medium level functions, implemented by the above
+ */
+
+/*!
+ * \brief Draw a bezier line
+ * Creates a _Bezierline object.
+ * \memberof _DiaImportRenderer
+ */
+static void 
+draw_bezier (DiaRenderer *renderer,
+             BezPoint *points, int numpoints,
+             Color *color)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  DiaObject *object = create_standard_bezierline (numpoints, points, NULL, NULL);
+
+  _apply_style (self, object, NULL, color, 0.0);
+  _push_object (self, object);
+}
+
+/*!
+ * \brief Fill a bezier shape
+ * Creates a _Beziergon object.
+ * \memberof _DiaImportRenderer
+ */
+static void
+fill_bezier (DiaRenderer *renderer,
+             BezPoint *points, int numpoints,
+             Color *color)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  DiaObject *object = create_standard_beziergon (numpoints, points);
+
+  _apply_style (self, object, color, NULL, 0.0);
+  _push_object (self, object);
+}
+
+/*!
+ * \brief Draw a simple rectangle
+ * Creates a _Box object.
+ * \memberof _DiaImportRenderer
+ */
+static void
+draw_rect (DiaRenderer *renderer,
+           Point *ul_corner, Point *lr_corner,
+           Color *color)
+{
+  draw_rounded_rect (renderer, ul_corner, lr_corner, color, 0.0);
+}
+
+/*!
+ * \brief Draw a polyline
+ * Creates a _Polyline object.
+ * \memberof _DiaImportRenderer
+ */
+static void 
+draw_polyline (DiaRenderer *renderer,
+              Point *points, int num_points,
+              Color *color)
+{
+  draw_rounded_polyline (renderer, points, num_points, color, 0.0);
+}
+
+/*! 
+ * \brief Create a polyline with optionally rounded corners
+ * Creates a _Polyline object.
+ * \memberof DiaImportRenderer
+ */
+static void
+draw_rounded_polyline (DiaRenderer *renderer,
+                        Point *points, int num_points,
+                        Color *color, real radius)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  DiaObject *object = create_standard_polyline (num_points, points, NULL, NULL);
+  /* XXX: radius */
+  _apply_style (self, object, NULL, color, 0.0);
+  _push_object (self, object);
+}
+
+/*!
+ * \brief Draw a polygon
+ * Creates a _Polygon object.
+ * \memberof _DiaImportRenderer
+ */
+static void
+draw_polygon (DiaRenderer *renderer,
+              Point *points, int num_points,
+              Color *color)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  DiaObject *object = create_standard_polygon (num_points, points);
+  _apply_style (self, object, NULL, color, 0.0);
+  _push_object (self, object);
+}
+
+/*!
+ * \brief Draw a rectangle with rounded corners.
+ * Creates a _Box object.
+ * \memberof _DiaImportRenderer
+ */
+static void
+draw_rounded_rect (DiaRenderer *renderer, 
+                   Point *ul_corner, Point *lr_corner,
+                   Color *color, real radius) 
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  DiaObject *object = create_standard_box (ul_corner->x, ul_corner->y,
+                                          lr_corner->x - ul_corner->x,
+                                          lr_corner->y - ul_corner->y);
+  _apply_style (self, object, NULL, color, radius);
+  _push_object (self, object);
+}
+
+/*!
+ * \brief Fill a rectangle with rounded corners.
+ * Creates a _Box object.
+ * \memberof _DiaImportRenderer
+ */
+static void
+fill_rounded_rect(DiaRenderer *renderer, 
+                  Point *ul_corner, Point *lr_corner,
+                  Color *color, real radius)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  DiaObject *object = create_standard_box (ul_corner->x, ul_corner->y,
+                                          lr_corner->x - ul_corner->x,
+                                          lr_corner->y - ul_corner->y);
+  _apply_style (self, object, color, NULL, radius);
+  _push_object (self, object);
+}
+
+/*!
+ * \brief Draw a line with optional arrows.
+ * Creates a _Polyine object.
+ * \memberof _DiaImportRenderer
+ */
+static void
+draw_line_with_arrows(DiaRenderer *renderer, 
+                      Point *startpoint, 
+                      Point *endpoint,
+                      real line_width,
+                      Color *color,
+                      Arrow *start_arrow,
+                      Arrow *end_arrow)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  DiaObject *object;
+  Point points[2];
+  points[0] = *startpoint;
+  points[1] = *endpoint;
+  object = create_standard_polyline (2, points, start_arrow, end_arrow);
+  _apply_style (self, object, NULL, color, 0.0);
+  _push_object (self, object);
+}
+
+/*!
+ * \brief Draw a polyline with optional arrows.
+ * Creates a _Polyline object.
+ * \memberof _DiaImportRenderer
+ */
+static void
+draw_polyline_with_arrows(DiaRenderer *renderer, 
+                          Point *points, int num_points,
+                          real line_width,
+                          Color *color,
+                          Arrow *start_arrow,
+                          Arrow *end_arrow)
+{
+  draw_rounded_polyline_with_arrows(renderer, points, num_points,
+                                   line_width, color,
+                                   start_arrow, end_arrow,
+                                   0.0);
+}
+
+/*!
+ * \brief Draw a polyline with rounded corners and optional arrows.
+ * Creates a _Polyline object.
+ * \memberof _DiaImportRenderer
+ */
+static void
+draw_rounded_polyline_with_arrows(DiaRenderer *renderer, 
+                                 Point *points, int num_points,
+                                 real line_width,
+                                 Color *color,
+                                 Arrow *start_arrow,
+                                 Arrow *end_arrow,
+                                 real radius)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  DiaObject *object = create_standard_polyline (num_points, points,
+                                               start_arrow, end_arrow);
+  _apply_style (self, object, NULL, color, radius);
+  _push_object (self, object);
+}
+
+/*!
+ * \brief Draw an arc with optional arrows.
+ * Creates a _Arc object.
+ * \memberof _DiaImportRenderer
+ */
+static void
+draw_arc_with_arrows (DiaRenderer *renderer, 
+                      Point *startpoint, 
+                      Point *endpoint,
+                      Point *midpoint,
+                      real line_width,
+                      Color *color,
+                      Arrow *start_arrow,
+                      Arrow *end_arrow)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  DiaObject *object;
+  Point chord_point = { (startpoint->x + endpoint->x) / 2.0,
+                       (startpoint->y + endpoint->y) / 2.0 };
+  real d = distance_point_point (&chord_point, midpoint);
+  object = create_standard_arc (startpoint->x, startpoint->y,
+                               endpoint->x, endpoint->y,
+                               d, start_arrow, end_arrow);
+
+  _apply_style (self, object, NULL, color, 0.0);
+  _push_object (self, object);
+}
+
+/*!
+ * \brief Draw a bezier line with optional arrows.
+ * Creates a _Bezierline object.
+ * \memberof _DiaImportRenderer
+ */
+static void
+draw_bezier_with_arrows(DiaRenderer *renderer, 
+                        BezPoint *points,
+                        int num_points,
+                        real line_width,
+                        Color *color,
+                        Arrow *start_arrow,
+                        Arrow *end_arrow)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  DiaObject *object = create_standard_bezierline (num_points, points,
+                                                start_arrow, end_arrow);
+  _apply_style (self, object, NULL, color, 0.0);
+  _push_object (self, object);
+}
+
+/*!
+ * \brief Advertize renderer capabilities.
+ * Everything has to be possible with DiaObject, but there might be some
+ * limitation with this renderer's implementation.
+ * \memberof _DiaImportRenderer
+ */
+static gboolean 
+is_capable_to (DiaRenderer *renderer, RenderCapability cap)
+{
+  return TRUE;
+}
+
+/*!
+ * \brief Remember the pattern for later reference
+ * \memberof _DiaImportRenderer
+ */
+static void
+set_pattern (DiaRenderer *renderer, DiaPattern *pat)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  if (self->pattern && self->pattern != pat) {
+    g_object_unref (self->pattern);
+    self->pattern = g_object_ref (pat);
+  }
+}
+
+/*!
+ * \brief Take ownership of the objects created so far
+ * This function return a _Group object containing all DiaObject created
+ * through the renderer interface so far. Ownership is transferred to the
+ * caller so the internal list is emptied by this call. If only a single
+ * object was created it is returned without the containing group.
+ */
+DiaObject *
+dia_import_renderer_get_objects (DiaRenderer *renderer)
+{
+  DiaImportRenderer *self = DIA_IMPORT_RENDERER (renderer);
+  if (!self || !self->objects)
+    return NULL;
+  if (g_list_length (self->objects) > 1) {
+    DiaObject *group = create_standard_group (self->objects);
+    self->objects = NULL;
+    return group;
+  } else {
+    DiaObject *object = self->objects->data;
+    g_list_free (self->objects);
+    return object;
+  }
+}
diff --git a/lib/diaimportrenderer.h b/lib/diaimportrenderer.h
new file mode 100644
index 0000000..e21e6a4
--- /dev/null
+++ b/lib/diaimportrenderer.h
@@ -0,0 +1,58 @@
+#ifndef DIA_IMPORT_RENDERER_H
+#define DIA_IMPORT_RENDERER_H
+
+#include "diatypes.h"
+#include "diarenderer.h"
+
+G_BEGIN_DECLS
+
+#define DIA_TYPE_IMPORT_RENDERER           (dia_import_renderer_get_type ())
+#define DIA_IMPORT_RENDERER(obj)           (G_TYPE_CHECK_INSTANCE_CAST ((obj), DIA_TYPE_IMPORT_RENDERER, 
DiaImportRenderer))
+#define DIA_IMPORT_RENDERER_CLASS(klass)   (G_TYPE_CHECK_CLASS_CAST ((klass), DIA_TYPE_IMPORT_RENDERER, 
DiaImportRendererClass))
+#define DIA_IS_IMPORT_RENDERER(obj)        (G_TYPE_CHECK_INSTANCE_TYPE ((obj), DIA_TYPE_IMPORT_RENDERER))
+#define DIA_IMPORT_RENDERER_GET_CLASS(obj) (G_TYPE_INSTANCE_GET_CLASS ((obj), DIA_TYPE_IMPORT_RENDERER, 
DiaImportRendererClass))
+
+GType dia_import_renderer_get_type (void) G_GNUC_CONST;
+
+typedef struct _DiaImportRenderer DiaImportRenderer;
+typedef struct _DiaImportRendererClass DiaImportRendererClass;
+
+/*!
+ * \brief Creation of Dia's standard objects via renderer interface
+ *
+ * To be used for import plug-ins which want to support a file format with a similar
+ * rendering model as Dia internal. Complex rendering models like SVG and PDF are not
+ * not in the intended scope.
+ *
+ * \extends _DiaRenderer
+ */
+struct _DiaImportRenderer
+{
+  DiaRenderer parent_instance;
+
+  /*! \protected state variables should not be set directly but with the rendering interface */
+  LineStyle   line_style;
+  FillStyle   fill_style;
+  real        dash_length;
+
+  real        line_width;
+  LineCaps    line_caps;
+  LineJoin    line_join;
+
+  /*! \private */
+  /*! \private pattern set by set_pattern */
+  DiaPattern *pattern;
+  /*! \private all patterns seen between begin_render and end_render */
+  GList      *objects;
+};
+
+struct _DiaImportRendererClass
+{
+  DiaRendererClass parent_class;
+};
+
+DiaObject *dia_import_renderer_get_objects (DiaRenderer *renderer);
+
+G_END_DECLS
+
+#endif /* DIA_IMPORT_RENDERER_H */
diff --git a/lib/libdia.def b/lib/libdia.def
index 58b621c..4bb03e2 100644
--- a/lib/libdia.def
+++ b/lib/libdia.def
@@ -291,6 +291,9 @@ EXPORTS
  dia_image_pixbuf
  dia_image_new_from_pixbuf
 
+ dia_import_renderer_get_type
+ dia_import_renderer_get_objects
+
  pixbuf_encode_base64
  pixbuf_decode_base64
 
diff --git a/lib/makefile.msc b/lib/makefile.msc
index 01bbb9e..7727296 100644
--- a/lib/makefile.msc
+++ b/lib/makefile.msc
@@ -71,6 +71,7 @@ OBJECTS = \
        diaerror.obj \
        diagramdata.obj \
        diagdkrenderer.obj \
+       diaimportrenderer.obj \
        diainteractiverenderer.obj \
        diarenderer.obj \
        diapathrenderer.obj \