From 61618a9a1452903a54a5577b247e8671baddf834 Mon Sep 17 00:00:00 2001
From: Thomas Wilshaw <thomaswilshaw@gmail.com>
Date: Fri, 19 Jun 2020 16:41:29 +0100
Subject: [PATCH] Use a world transform for QPainter

World transform is based of the view matrix and can be used on any
QPainter that needs to draw on the canvas and move with the mouse/
zoom.
---
 app/widget/viewer/viewerdisplay.cpp | 40 ++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 15 deletions(-)

diff --git a/app/widget/viewer/viewerdisplay.cpp b/app/widget/viewer/viewerdisplay.cpp
index a078b2f58..1ceb97c8f 100644
--- a/app/widget/viewer/viewerdisplay.cpp
+++ b/app/widget/viewer/viewerdisplay.cpp
@@ -313,6 +313,25 @@ void ViewerDisplayWidget::paintGL()
 
   }
 
+  /*
+  * Get matrix elements (roughly) as below in column major order
+  *
+  * | Sx 0  0  Tx |
+  * | 0  Sy 0  Ty |
+  * | 0  0  Sz Tz |
+  * | 0  0  0  1  |
+  */
+  float *data = GetCompleteMatrix().data();
+  QTransform world;
+  // Move corner of canvas to correct point
+  world.translate(width() * 0.5 - width() * *(data)*0.5,
+                  height() * 0.5 - height() * *(data + 5) * 0.5);
+  // Scale
+  world.scale(*(data), *(data + 5));
+  // Translate for mouse movement
+  world.translate(*(data + 12) * width() * 0.5 / *(data),
+                  *(data + 13) * height() * -0.5 / *(data + 5));
+
   // Draw gizmos if we have any
   if (gizmos_) {
     GizmoTraverser gt(QSize(gizmo_params_.width(), gizmo_params_.height()));
@@ -322,19 +341,16 @@ void ViewerDisplayWidget::paintGL()
     gizmo_db_ = gt.GenerateDatabase(gizmos_, TimeRange(node_time, node_time));
 
     QPainter p(this);
+    p.setWorldTransform(world);
     gizmos_->DrawGizmos(gizmo_db_, &p, QVector2D(GetTexturePosition(size())), size());
   }
 
   // Draw action/title safe areas
   if (safe_margin_.is_enabled()) {
     QPainter p(this);
-    float* data = GetCompleteMatrix().data();
-    QMatrix mat;
-    mat.translate(data[12], data[13]);
-    mat.scale(data[0], data[5]);
-    //p.setTransform(GetCompleteMatrix().toTransform());
-    
-    printf("Data[12]: %f\n", *(data+12));
+    p.setWorldTransform(world);
+
+
     p.setPen(Qt::lightGray);
     p.setBrush(Qt::NoBrush);
 
@@ -352,14 +368,8 @@ void ViewerDisplayWidget::paintGL()
         y = height() / 2 - h / 2;
       }
     }
-    QRect rect1(w / 20 + x, h / 20 + y, w / 10 * 9, h / 10 * 9);
-    //p.drawRect(w / 20 + x, h / 20 + y, w / 10 * 9, h / 10 * 9);
-    // scale translation by width(), height() and halve
-    // scale should already be correct, but needs offsetting
-    rect1.translate(*(data + 12)*width()*0.5, *(data + 13)*height()*-0.5);
-    rect1.setWidth(rect1.width() * *(data));
-    rect1.setHeight(rect1.height() * *(data + 5));
-    p.drawRect(rect1);
+
+    p.drawRect(w / 20 + x, h / 20 + y, w / 10 * 9, h / 10 * 9);
     p.drawRect(w / 10 + x, h / 10 + y, w / 10 * 8, h / 10 * 8);
 
     int cross = qMin(w, h) / 32;