From 277f9c58a17b8ef486f721d7d2b3cb47120433b9 Mon Sep 17 00:00:00 2001
From: Artur Wieczorek <artwik@wp.pl>
Date: Fri, 16 Sep 2016 22:04:53 +0200
Subject: [PATCH] Fix retrieving bounding box coordinates

Bounding box coordinates have to be calculated and stored internally in device units to be independent on changes of logical coordinates between calls to wxDC::CalcBoundingBox.
These stored coordinates are converted to the logical units on demand when they are retrieved with call to wxDC::MinX, MinY, MaxX or MaxY.

Closes #17667.
---
 docs/changes.txt |  1 +
 include/wx/dc.h  | 16 ++++++++++------
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/docs/changes.txt b/docs/changes.txt
index b6eb8f14fa..04d9ce5629 100644
--- a/docs/changes.txt
+++ b/docs/changes.txt
@@ -105,6 +105,7 @@ All (GUI):
 - Add wxGraphicsContext::Flush() for Cairo renderer.
 - Add wxStyledTextEvent::GetListCompletionMethod() (NewPagodi).
 - Add wxEVT_STC_AUTOCOMP_COMPLETED event (NewPagodi).
+- Fix retrieving bounding box for wxDC with transformed coordinates.
 
 wxGTK:
 
diff --git a/include/wx/dc.h b/include/wx/dc.h
index c61498724f..7cfe17fb14 100644
--- a/include/wx/dc.h
+++ b/include/wx/dc.h
@@ -325,6 +325,9 @@ public:
 
     virtual void CalcBoundingBox(wxCoord x, wxCoord y)
     {
+      // Bounding box is internally stored in device units.
+      x = LogicalToDeviceX(x);
+      y = LogicalToDeviceY(y);
       if ( m_isBBoxValid )
       {
          if ( x < m_minX ) m_minX = x;
@@ -349,10 +352,11 @@ public:
         m_minX = m_maxX = m_minY = m_maxY = 0;
     }
 
-    wxCoord MinX() const { return m_minX; }
-    wxCoord MaxX() const { return m_maxX; }
-    wxCoord MinY() const { return m_minY; }
-    wxCoord MaxY() const { return m_maxY; }
+    // Get bounding box in logical units.
+    wxCoord MinX() const { return m_isBBoxValid ? DeviceToLogicalX(m_minX) : 0; }
+    wxCoord MaxX() const { return m_isBBoxValid ? DeviceToLogicalX(m_maxX) : 0; }
+    wxCoord MinY() const { return m_isBBoxValid ? DeviceToLogicalY(m_minY) : 0; }
+    wxCoord MaxY() const { return m_isBBoxValid ? DeviceToLogicalY(m_maxY) : 0; }
 
     // setters and getters
 
@@ -712,8 +716,8 @@ protected:
                  m_mm_to_pix_y;
 
     // bounding and clipping boxes
-    wxCoord m_minX, m_minY, m_maxX, m_maxY;
-    wxCoord m_clipX1, m_clipY1, m_clipX2, m_clipY2;
+    wxCoord m_minX, m_minY, m_maxX, m_maxY; // Bounding box is stored in device units.
+    wxCoord m_clipX1, m_clipY1, m_clipX2, m_clipY2;  // Clipping box is stored in logical units.
 
     wxRasterOperationMode m_logicalFunction;
     int m_backgroundMode;