Merge branch 'display-ppi-from-scaling-factor'

Determine display DPI from scaling factor instead of trying to compute
it from the physical display dimensions.

See https://github.com/wxWidgets/wxWidgets/pull/2015

Closes #18855.

include/wx/display.h

@@ -87,6 +87,24 @@ public:
     // get the resolution of this monitor in pixels per inch
     wxSize GetPPI() const;
 
+    // get the default resolution for displays on this platform
+    static int GetStdPPIValue()
+    {
+#ifdef __WXOSX__
+        return 72;
+#else
+        return 96;
+#endif
+    }
+
+    static wxSize GetStdPPI()
+    {
+        return wxSize(GetStdPPIValue(), GetStdPPIValue());
+    }
+
+    // get the scaling used by this display
+    double GetScaleFactor() const;
+
     // name may be empty
     wxString GetName() const;
 

include/wx/gtk/window.h

@@ -97,6 +97,7 @@ public:
     virtual int GetCharHeight() const wxOVERRIDE;
     virtual int GetCharWidth() const wxOVERRIDE;
     virtual double GetContentScaleFactor() const wxOVERRIDE;
+    virtual double GetDPIScaleFactor() const wxOVERRIDE;
 
     virtual void SetScrollbar( int orient, int pos, int thumbVisible,
                                int range, bool refresh = true ) wxOVERRIDE;

include/wx/msw/window.h

@@ -100,6 +100,8 @@ public:
     virtual bool Reparent(wxWindowBase *newParent) wxOVERRIDE;
 
     virtual wxSize GetDPI() const wxOVERRIDE;
+    virtual double GetDPIScaleFactor() const wxOVERRIDE;
+
 
     virtual void WarpPointer(int x, int y) wxOVERRIDE;
     virtual bool EnableTouchEvents(int eventsMask) wxOVERRIDE;

include/wx/osx/window.h

@@ -121,6 +121,7 @@ public:
 #endif // wxUSE_HOTKEY
 
     virtual wxSize GetDPI() const wxOVERRIDE;
+    virtual double GetDPIScaleFactor() const wxOVERRIDE;
 
 #if wxUSE_DRAG_AND_DROP
     virtual void SetDropTarget( wxDropTarget *dropTarget ) wxOVERRIDE;

include/wx/private/display.h

@@ -115,14 +115,9 @@ public:
     // return the scale factor used to convert logical pixels to physical ones
     virtual double GetScaleFactor() const { return 1.0; }
 
-    // return the resolution of the display, uses GetSize(), GetScaleFactor()
-    // and GetSizeMM() by default but can be also overridden directly
-    virtual wxSize GetPPI() const;
-
-    // return the physical size of the display or (0, 0) if unknown: this is
-    // only used by GetPPI() implementation in the base class, so if GetPPI()
-    // is overridden, this one doesn't have to be implemented
-    virtual wxSize GetSizeMM() const { return wxSize(0, 0); }
+    // return the resolution of the display, by default uses GetScaleFactor(),
+    // but can be also overridden directly, as is done in wxMSW
+    virtual wxSize GetPPI() const { return wxDisplay::GetStdPPI()*GetScaleFactor(); }
 
     // return the name (may be empty)
     virtual wxString GetName() const { return wxString(); }
@@ -149,11 +144,6 @@ protected:
     // create the object providing access to the display with the given index
     wxDisplayImpl(unsigned n) : m_index(n) { }
 
-    // Compute PPI from the sizes in pixels and mm.
-    //
-    // Return (0, 0) if physical size (in mm) is not known, i.e. 0.
-    static wxSize ComputePPI(int pxX, int pxY, int mmX, int mmY);
-
 
     // the index of this display (0 is always the primary one)
     const unsigned m_index;

include/wx/window.h

@@ -537,7 +537,7 @@ public:
 
     // Return the ratio of the DPI used by this window to the standard DPI,
     // e.g. 1 for standard DPI screens and 2 for "200% scaling".
-    double GetDPIScaleFactor() const;
+    virtual double GetDPIScaleFactor() const;
 
     // return the size of the left/right and top/bottom borders in x and y
     // components of the result respectively