Use wxRescaleCoord() in wxMSW DPI update code too

Use the same scaling function as elsewhere instead of using
ceil/floor().

Provide wxRescaleCoordWithFrom specialization for int to allow using it
with just single coordinates too.

include/wx/private/rescale.h

@@ -29,8 +29,9 @@
 // order to allow calling To() on it.
 //
 // Another complication is that we want this to work for both wxSize and
-// wxPoint, so wxRescaleCoord() is a overloaded and the helper classes are
+// wxPoint, as well as for just plain coordinate values, so wxRescaleCoord() is
-// templates, with their template parameter being either one or the other.
+// an overloaded function and the helper classes are templates, with their
+// template parameter being either wxSize, wxPoint or int.
 
 namespace wxPrivate
 {
@@ -72,6 +73,31 @@ private:
     friend wxRescaleCoordWithValue<T>;
 };
 
+// Specialization for just a single value.
+template <>
+class wxRescaleCoordWithFrom<int>
+{
+public:
+    int To(wxSize newScale) const
+    {
+        return m_value == wxDefaultCoord
+                ? wxDefaultCoord
+                : wxMulDivInt32(m_value, newScale.x, m_oldScale.x);
+    }
+
+private:
+    wxRescaleCoordWithFrom(int value, wxSize oldScale)
+        : m_value(value), m_oldScale(oldScale)
+    {
+    }
+
+    const int m_value;
+    const wxSize m_oldScale;
+
+    // Only it can create objects of this class.
+    friend wxRescaleCoordWithValue<int>;
+};
+
 template <typename T>
 class wxRescaleCoordWithValue
 {
@@ -97,6 +123,11 @@ private:
 
 } // namespace wxPrivate
 
+inline wxPrivate::wxRescaleCoordWithValue<int> wxRescaleCoord(int coord)
+{
+    return wxPrivate::wxRescaleCoordWithValue<int>(coord);
+}
+
 inline wxPrivate::wxRescaleCoordWithValue<wxSize> wxRescaleCoord(wxSize sz)
 {
     return wxPrivate::wxRescaleCoordWithValue<wxSize>(sz);

src/msw/window.cpp

@@ -82,6 +82,7 @@
 #include "wx/msw/dcclient.h"
 #include "wx/msw/seh.h"
 #include "wx/private/textmeasure.h"
+#include "wx/private/rescale.h"
 
 #if wxUSE_TOOLTIPS
     #include "wx/tooltip.h"
@@ -4891,20 +4892,9 @@ void wxWindowMSW::MSWUpdateFontOnDPIChange(const wxSize& newDPI)
     }
 }
 
-// Helper function to update the given coordinate by the scaling factor if it
-// is set, i.e. different from wxDefaultCoord.
-static void ScaleCoordIfSet(int& coord, float scaleFactor)
-{
-    if ( coord != wxDefaultCoord )
-    {
-        const float coordScaled = coord * scaleFactor;
-        coord = int(scaleFactor > 1 ? std::ceil(coordScaled) : std::floor(coordScaled));
-    }
-}
-
 // Called from MSWUpdateonDPIChange() to recursively update the window
 // sizer and any child sizers and spacers.
-static void UpdateSizerOnDPIChange(wxSizer* sizer, float scaleFactor)
+static void UpdateSizerOnDPIChange(wxSizer* sizer, wxSize oldDPI, wxSize newDPI)
 {
     if ( !sizer )
     {
@@ -4919,27 +4909,25 @@ static void UpdateSizerOnDPIChange(wxSizer* sizer, float scaleFactor)
         wxSizerItem* sizerItem = node->GetData();
 
         int border = sizerItem->GetBorder();
-        ScaleCoordIfSet(border, scaleFactor);
+        border = wxRescaleCoord(border).From(oldDPI).To(newDPI);
         sizerItem->SetBorder(border);
 
         // only scale sizers and spacers, not windows
         if ( sizerItem->IsSizer() || sizerItem->IsSpacer() )
         {
             wxSize min = sizerItem->GetMinSize();
-            ScaleCoordIfSet(min.x, scaleFactor);
+            min = wxRescaleCoord(min).From(oldDPI).To(newDPI);
-            ScaleCoordIfSet(min.y, scaleFactor);
             sizerItem->SetMinSize(min);
 
             if ( sizerItem->IsSpacer() )
             {
                 wxSize size = sizerItem->GetSize();
-                ScaleCoordIfSet(size.x, scaleFactor);
+                size = wxRescaleCoord(size).From(oldDPI).To(newDPI);
-                ScaleCoordIfSet(size.y, scaleFactor);
                 sizerItem->SetDimension(wxDefaultPosition, size);
             }
 
             // Update any child sizers if this is a sizer
-            UpdateSizerOnDPIChange(sizerItem->GetSizer(), scaleFactor);
+            UpdateSizerOnDPIChange(sizerItem->GetSizer(), oldDPI, newDPI);
         }
     }
 }
@@ -4948,12 +4936,10 @@ void
 wxWindowMSW::MSWUpdateOnDPIChange(const wxSize& oldDPI, const wxSize& newDPI)
 {
     // update min and max size if necessary
-    const float scaleFactor = (float)newDPI.y / oldDPI.y;
+    m_minHeight = wxRescaleCoord(m_minHeight).From(oldDPI).To(newDPI);
-
+    m_minWidth = wxRescaleCoord(m_minWidth).From(oldDPI).To(newDPI);
-    ScaleCoordIfSet(m_minHeight, scaleFactor);
+    m_maxHeight = wxRescaleCoord(m_maxHeight).From(oldDPI).To(newDPI);
-    ScaleCoordIfSet(m_minWidth, scaleFactor);
+    m_maxWidth = wxRescaleCoord(m_maxWidth).From(oldDPI).To(newDPI);
-    ScaleCoordIfSet(m_maxHeight, scaleFactor);
-    ScaleCoordIfSet(m_maxWidth, scaleFactor);
 
     InvalidateBestSize();
 
@@ -4961,7 +4947,7 @@ wxWindowMSW::MSWUpdateOnDPIChange(const wxSize& oldDPI, const wxSize& newDPI)
     MSWUpdateFontOnDPIChange(newDPI);
 
     // update sizers
-    UpdateSizerOnDPIChange(GetSizer(), scaleFactor);
+    UpdateSizerOnDPIChange(GetSizer(), oldDPI, newDPI);
 
     // update children
     for ( wxWindowList::compatibility_iterator node = GetChildren().GetFirst();