From eddee965ffa29dc7681d12befa0cf90e4bf6d5c5 Mon Sep 17 00:00:00 2001
From: Nicola Fontana <ntd@entidi.it>
Date: Wed, 13 Aug 2008 22:07:14 +0200
Subject: [PATCH] Implemented adg_entity_build_{paper2model,model2paper}()

---
 adg/adg-entity.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 adg/adg-entity.h |  4 ++++
 2 files changed, 64 insertions(+)

diff --git a/adg/adg-entity.c b/adg/adg-entity.c
index 09b5dd61..0b33293a 100644
--- a/adg/adg-entity.c
+++ b/adg/adg-entity.c
@@ -387,6 +387,66 @@ adg_entity_scale_to_paper(AdgEntity *entity, cairo_t *cr)
 }
 
 /**
+ * adg_entity_build_paper2model:
+ * @entity: an #AdgEntity
+ * @matrix: the destination matrix
+ *
+ * Builds a matrix to translate from paper to model space and
+ * put the result in @matrix.
+ *
+ * Return value: %TRUE on success, %FALSE on errors
+ **/
+gboolean
+adg_entity_build_paper2model(AdgEntity *entity, AdgMatrix *matrix)
+{
+    cairo_status_t status;
+
+    g_return_val_if_fail(ADG_IS_ENTITY(entity), FALSE);
+    g_return_val_if_fail(matrix != NULL, FALSE);
+
+    adg_matrix_set(matrix, adg_entity_get_model_matrix(entity));
+    status = cairo_matrix_invert(matrix);
+    if (status != CAIRO_STATUS_SUCCESS) {
+        g_error("Unable to invert model matrix (cairo message: %s)",
+                cairo_status_to_string(status));
+        return FALSE;
+    }
+
+    cairo_matrix_multiply(matrix, matrix, adg_entity_get_paper_matrix(entity));
+    return TRUE;
+}
+
+/**
+ * adg_entity_build_model2paper:
+ * @entity: an #AdgEntity
+ * @matrix: the destination matrix
+ *
+ * Builds a matrix to translate from model to paper space and
+ * put the result in @matrix.
+ *
+ * Return value: %TRUE on success, %FALSE on errors
+ **/
+gboolean
+adg_entity_build_model2paper(AdgEntity *entity, AdgMatrix *matrix)
+{
+    cairo_status_t status;
+
+    g_return_val_if_fail(ADG_IS_ENTITY(entity), FALSE);
+    g_return_val_if_fail(matrix != NULL, FALSE);
+
+    adg_matrix_set(matrix, adg_entity_get_paper_matrix(entity));
+    status = cairo_matrix_invert(matrix);
+    if (status != CAIRO_STATUS_SUCCESS) {
+        g_error("Unable to invert paper matrix (cairo message: %s)",
+                cairo_status_to_string(status));
+        return FALSE;
+    }
+
+    cairo_matrix_multiply(matrix, matrix, adg_entity_get_model_matrix(entity));
+    return TRUE;
+}
+
+/**
  * adg_entity_model_matrix_changed:
  * @entity: an #AdgEntity
  * @parent_matrix: the parent #AdgMatrix
diff --git a/adg/adg-entity.h b/adg/adg-entity.h
index fd6df4c7..e1e05b05 100644
--- a/adg/adg-entity.h
+++ b/adg/adg-entity.h
@@ -85,6 +85,10 @@ void            adg_entity_set_context          (AdgEntity      *entity,
                                                  AdgContext     *context);
 const AdgMatrix*adg_entity_get_model_matrix     (AdgEntity      *entity);
 const AdgMatrix*adg_entity_get_paper_matrix     (AdgEntity      *entity);
+gboolean        adg_entity_build_paper2model    (AdgEntity      *entity,
+                                                 AdgMatrix      *matrix);
+gboolean        adg_entity_build_model2paper    (AdgEntity      *entity,
+                                                 AdgMatrix      *matrix);
 void            adg_entity_scale_to_model       (AdgEntity      *entity,
                                                  cairo_t        *cr);
 void            adg_entity_scale_to_paper       (AdgEntity      *entity,
-- 
2.11.4.GIT