From 014bd2ae54b6224dc01b18c313353231f4b539f6 Mon Sep 17 00:00:00 2001
From: Artur Wieczorek <artwik@wp.pl>
Date: Sun, 13 Sep 2020 23:47:26 +0200
Subject: [PATCH] Implement platform-specific coordinate conversion functions

Generic wxDC::DeviceToLogical{X|Y}() and wxDC::LogicalToDevice{X|Y}()
functions don't take into account transformations applied with
wxDC::SetTransformMatrix() so conversion results are invalid if wxDC is
transformed with both e.g. wxDC::SetUserScale() and
wxDC::SetTransformMatrix().
We need to implement functions in wxDCImpl and its platform-specific
derivates to do this conversion with taking into account all applied
transformations.

See #18916.
---
 include/wx/dc.h        |  4 ++++
 include/wx/dcgraph.h   |  5 +++++
 include/wx/msw/dc.h    |  3 +++
 src/common/dcbase.cpp  | 10 ++++++++++
 src/common/dcgraph.cpp | 19 +++++++++++++++++++
 src/msw/dc.cpp         | 18 ++++++++++++++++++
 6 files changed, 59 insertions(+)

diff --git a/include/wx/dc.h b/include/wx/dc.h
index a9e901ae22..492d4e5405 100644
--- a/include/wx/dc.h
+++ b/include/wx/dc.h
@@ -323,6 +323,10 @@ public:
     // flushing the content of this dc immediately eg onto screen
     virtual void Flush() { }
 
+    // coordinates conversions and transforms
+    virtual wxPoint DeviceToLogical(wxCoord x, wxCoord y) const;
+    virtual wxPoint LogicalToDevice(wxCoord x, wxCoord y) const;
+
     // bounding box
 
     virtual void CalcBoundingBox(wxCoord x, wxCoord y)
diff --git a/include/wx/dcgraph.h b/include/wx/dcgraph.h
index fd413d0835..4622a3534a 100644
--- a/include/wx/dcgraph.h
+++ b/include/wx/dcgraph.h
@@ -121,6 +121,10 @@ public:
     virtual void ResetTransformMatrix() wxOVERRIDE;
 #endif // wxUSE_DC_TRANSFORM_MATRIX
 
+    // coordinates conversions and transforms
+    virtual wxPoint DeviceToLogical(wxCoord x, wxCoord y) const wxOVERRIDE;
+    virtual wxPoint LogicalToDevice(wxCoord x, wxCoord y) const wxOVERRIDE;
+
     // the true implementations
     virtual bool DoFloodFill(wxCoord x, wxCoord y, const wxColour& col,
                              wxFloodFillStyle style = wxFLOOD_SURFACE) wxOVERRIDE;
@@ -225,6 +229,7 @@ protected:
     bool m_logicalFunctionSupported;
     wxGraphicsMatrix m_matrixOriginal;
     wxGraphicsMatrix m_matrixCurrent;
+    wxGraphicsMatrix m_matrixCurrentInv;
 #if wxUSE_DC_TRANSFORM_MATRIX
     wxAffineMatrix2D m_matrixExtTransform;
 #endif // wxUSE_DC_TRANSFORM_MATRIX
diff --git a/include/wx/msw/dc.h b/include/wx/msw/dc.h
index a27b70dab3..faaab34283 100644
--- a/include/wx/msw/dc.h
+++ b/include/wx/msw/dc.h
@@ -86,6 +86,9 @@ public:
     virtual void SetDeviceOrigin(wxCoord x, wxCoord y) wxOVERRIDE;
     virtual void SetAxisOrientation(bool xLeftRight, bool yBottomUp) wxOVERRIDE;
 
+    virtual wxPoint DeviceToLogical(wxCoord x, wxCoord y) const wxOVERRIDE;
+    virtual wxPoint LogicalToDevice(wxCoord x, wxCoord y) const wxOVERRIDE;
+
 #if wxUSE_DC_TRANSFORM_MATRIX
     virtual bool CanUseTransformMatrix() const wxOVERRIDE;
     virtual bool SetTransformMatrix(const wxAffineMatrix2D& matrix) wxOVERRIDE;
diff --git a/src/common/dcbase.cpp b/src/common/dcbase.cpp
index beededefe7..59f61bce0a 100644
--- a/src/common/dcbase.cpp
+++ b/src/common/dcbase.cpp
@@ -502,6 +502,16 @@ wxCoord wxDCImpl::LogicalToDeviceYRel(wxCoord y) const
     return wxRound((double)(y) * m_scaleY);
 }
 
+wxPoint wxDCImpl::DeviceToLogical(wxCoord x, wxCoord y) const
+{
+    return wxPoint(DeviceToLogicalX(x), DeviceToLogicalY(y));
+}
+
+wxPoint wxDCImpl::LogicalToDevice(wxCoord x, wxCoord y) const
+{
+    return wxPoint(LogicalToDeviceX(x), LogicalToDeviceY(y));
+}
+
 void wxDCImpl::ComputeScaleAndOrigin()
 {
     m_scaleX = m_logicalScaleX * m_userScaleX;
diff --git a/src/common/dcgraph.cpp b/src/common/dcgraph.cpp
index 1ab8f4c494..a731de53bc 100644
--- a/src/common/dcgraph.cpp
+++ b/src/common/dcgraph.cpp
@@ -487,6 +487,8 @@ void wxGCDCImpl::ComputeScaleAndOrigin()
         m_matrixCurrent.Concat(mtxExt);
 #endif // wxUSE_DC_TRANSFORM_MATRIX
         m_graphicContext->ConcatTransform( m_matrixCurrent );
+        m_matrixCurrentInv = m_matrixCurrent;
+        m_matrixCurrentInv.Invert();
         m_isClipBoxValid = false;
     }
 }
@@ -594,6 +596,23 @@ void wxGCDCImpl::ResetTransformMatrix()
 
 #endif // wxUSE_DC_TRANSFORM_MATRIX
 
+// coordinates conversions and transforms
+wxPoint wxGCDCImpl::DeviceToLogical(wxCoord x, wxCoord y) const
+{
+    wxDouble px = x;
+    wxDouble py = y;
+    m_matrixCurrentInv.TransformPoint(&px, &py);
+    return wxPoint(wxRound(px), wxRound(py));
+}
+
+wxPoint wxGCDCImpl::LogicalToDevice(wxCoord x, wxCoord y) const
+{
+    wxDouble px = x;
+    wxDouble py = y;
+    m_matrixCurrent.TransformPoint(&px, &py);
+    return wxPoint(wxRound(px), wxRound(py));
+}
+
 bool wxGCDCImpl::DoFloodFill(wxCoord WXUNUSED(x), wxCoord WXUNUSED(y),
                              const wxColour& WXUNUSED(col),
                              wxFloodFillStyle WXUNUSED(style))
diff --git a/src/msw/dc.cpp b/src/msw/dc.cpp
index 39ac13ec3d..6ebc77b68e 100644
--- a/src/msw/dc.cpp
+++ b/src/msw/dc.cpp
@@ -2100,6 +2100,24 @@ void wxMSWDCImpl::SetDeviceOrigin(wxCoord x, wxCoord y)
     m_isClipBoxValid = false;
 }
 
+wxPoint wxMSWDCImpl::DeviceToLogical(wxCoord x, wxCoord y) const
+{
+    POINT p[1];
+    p[0].x = x;
+    p[0].y = y;
+    ::DPtoLP(GetHdc(), p, WXSIZEOF(p));
+    return wxPoint(p[0].x, p[0].y);
+}
+
+wxPoint wxMSWDCImpl::LogicalToDevice(wxCoord x, wxCoord y) const
+{
+    POINT p[1];
+    p[0].x = x;
+    p[0].y = y;
+    ::LPtoDP(GetHdc(), p, WXSIZEOF(p));
+    return wxPoint(p[0].x, p[0].y);
+}
+
 // ----------------------------------------------------------------------------
 // Transform matrix
 // ----------------------------------------------------------------------------