--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/OrthancStone/Sources/Scene2D/Internals/CairoInfoPanelRenderer.cpp	Tue Jul 07 16:21:02 2020 +0200
@@ -0,0 +1,132 @@
+/**
+ * Stone of Orthanc
+ * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
+ * Department, University Hospital of Liege, Belgium
+ * Copyright (C) 2017-2020 Osimis S.A., Belgium
+ *
+ * This program is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU Affero General Public License
+ * as published by the Free Software Foundation, either version 3 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
+ * Affero General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ **/
+
+
+#include "CairoInfoPanelRenderer.h"
+
+#include "../InfoPanelSceneLayer.h"
+
+namespace OrthancStone
+{
+  namespace Internals
+  {
+    void CairoInfoPanelRenderer::Update(const ISceneLayer& layer)
+    {
+      const InfoPanelSceneLayer& l = dynamic_cast<const InfoPanelSceneLayer&>(layer);
+
+      texture_.Copy(l.GetTexture(), true);
+      anchor_ = l.GetAnchor();
+      isLinearInterpolation_ = l.IsLinearInterpolation();
+      applySceneRotation_ = l.ShouldApplySceneRotation();
+    }
+
+    void CairoInfoPanelRenderer::Render(const AffineTransform2D& transform,
+                                        unsigned int canvasWidth,
+                                        unsigned int canvasHeight)
+    {
+      int dx, dy;
+      InfoPanelSceneLayer::ComputeAnchorLocation(
+        dx, dy, anchor_, texture_.GetWidth(), texture_.GetHeight(),
+        canvasWidth, canvasHeight);
+
+      cairo_t* cr = target_.GetCairoContext();
+      cairo_save(cr);
+
+      if (applySceneRotation_)
+      {
+        // the transformation is as follows:
+        // - originally, the image is aligned so that its top left corner
+        // is at 0,0
+        // - first, we translate the image by -w/2,-h/2 
+        // - then we rotate it, so that the next rotation will make the  
+        //   image rotate around its center.
+        // - then, we translate the image by +w/2,+h/2 to put it
+        //   back in place
+        // - the fourth and last transform is the one that brings the 
+        //   image to its desired anchored location.
+
+        int32_t halfWidth =
+          static_cast<int32_t>(0.5 * texture_.GetWidth());
+
+        int32_t halfHeight =
+          static_cast<int32_t>(0.5 * texture_.GetHeight());
+
+        AffineTransform2D translation1 =
+          AffineTransform2D::CreateOffset(-halfWidth, -halfHeight);
+
+        const Matrix& sceneTransformM = transform.GetHomogeneousMatrix();
+        Matrix r;
+        Matrix q;
+        LinearAlgebra::RQDecomposition3x3(r, q, sceneTransformM);
+
+        // first, put the scene rotation in a cairo matrix
+        cairo_matrix_t m;
+        cairo_matrix_init(
+          &m, q(0, 0), q(1, 0), q(0, 1), q(1, 1), q(0, 2), q(1, 2));
+
+        // now let's build the transform piece by piece
+        // first translation (directly written in `transform`)
+        cairo_matrix_t transform;
+        cairo_matrix_init_identity(&transform);
+        cairo_matrix_translate(&transform, -halfWidth, -halfHeight);
+
+        // then the rotation
+        cairo_matrix_multiply(&transform, &transform, &m);
+
+        // then the second translation
+        {
+          cairo_matrix_t translation2;
+          cairo_matrix_init_translate(&translation2, halfWidth, halfHeight);
+          cairo_matrix_multiply(&transform, &transform, &m);
+        }
+
+        // then the last translation
+        {
+          cairo_matrix_t translation3;
+          cairo_matrix_init_translate(&translation3, dx, dy);
+          cairo_matrix_multiply(&transform, &transform, &translation3);
+        }
+        cairo_transform(cr, &transform);
+      } 
+      else
+      {
+        cairo_matrix_t t;
+        cairo_matrix_init_identity(&t);
+        cairo_matrix_translate(&t, dx, dy);
+        cairo_transform(cr, &t);
+      }
+      cairo_set_operator(cr, CAIRO_OPERATOR_OVER);
+      cairo_set_source_surface(cr, texture_.GetObject(), 0, 0);
+
+      if (isLinearInterpolation_)
+      {
+        cairo_pattern_set_filter(cairo_get_source(cr), CAIRO_FILTER_BILINEAR);
+      }
+      else
+      {
+        cairo_pattern_set_filter(cairo_get_source(cr), CAIRO_FILTER_NEAREST);
+      }
+
+      cairo_paint(cr);
+
+      cairo_restore(cr);
+    }
+  }
+}