Add wxWindow::GetDPIScaleFactor()

This function replaces some uses of GetContentScaleFactor(), where a
factor greater than 1 must be used even under the platforms not doing
any logical/physical pixel mapping, such as MSW.

For now GetContentScaleFactor() is still unchanged, but it will return 1
for such platforms in the future and adding GetDPIScaleFactor() allows
to avoid changing the behaviour of the code which relied on its current
behaviour.

include/wx/window.h

@@ -533,6 +533,10 @@ public:
     // e.g. 2.0 for a window on a retina screen
     virtual double GetContentScaleFactor() const;
 
+    // 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;
+
     // return the size of the left/right and top/bottom borders in x and y
     // components of the result respectively
     virtual wxSize GetWindowBorderSize() const;
@@ -957,7 +961,7 @@ public:
         // DPI-independent pixels, or DIPs, are pixel values for the standard
         // 96 DPI display, they are scaled to take the current resolution into
         // account (i.e. multiplied by the same factor as returned by
-        // GetContentScaleFactor()) if necessary for the current platform.
+        // GetDPIScaleFactor()) if necessary for the current platform.
         //
         // To support monitor-specific resolutions, prefer using the non-static
         // member functions or use a valid (non-null) window pointer.

interface/wx/window.h

@@ -1034,7 +1034,7 @@ public:
 
         A DPI-independent pixel is just a pixel at the standard 96 DPI
         resolution. To keep the same physical size at higher resolution, the
-        physical pixel value must be scaled by GetContentScaleFactor() but this
+        physical pixel value must be scaled by GetDPIScaleFactor() but this
         scaling may be already done by the underlying toolkit (GTK+, Cocoa,
         ...) automatically. This method performs the conversion only if it is
         not already done by the lower level toolkit and so by using it with
@@ -1110,7 +1110,7 @@ public:
 
     A DPI-independent pixel is just a pixel at the standard 96 DPI
     resolution. To keep the same physical size at higher resolution, the
-    physical pixel value must be scaled by GetContentScaleFactor() but this
+    physical pixel value must be scaled by GetDPIScaleFactor() but this
     scaling may be already done by the underlying toolkit (GTK+, Cocoa,
     ...) automatically. This method performs the conversion only if it is
     not already done by the lower level toolkit, For example, you may
@@ -1379,8 +1379,20 @@ public:
        Returns the magnification of the backing store of this window, eg 2.0
        for a window on a retina screen.
 
-       This factor should be used to determine the size of bitmaps and similar
+       @since 2.9.5
-       "content-containing" windows appropriate for the current resolution.
+    */
+    double GetContentScaleFactor() const;
+
+    /**
+       Returns the ratio of the DPI used by this window to the standard DPI.
+
+       The returned value is 1 for standard DPI screens or 2 for "200%
+       scaling".
+
+       This factor should be used to increase the size of icons and similar
+       windows whose best size is not based on text metrics when using DPI
+       scaling.
+
        E.g. the program may load a 32px bitmap if the content scale factor is
        1.0 or 64px version of the same bitmap if it is 2.0 or bigger.
 
@@ -1388,9 +1400,9 @@ public:
        are already scaled by this factor by the underlying toolkit under some
        platforms. Use FromDIP() for anything window-related instead.
 
-       @since 2.9.5
+        @since 3.1.4
      */
-    double GetContentScaleFactor() const;
+    double GetDPIScaleFactor() const;
 
     /**
         Returns the size of the left/right and top/bottom borders of this window in x

src/aui/dockart.cpp

@@ -802,7 +802,7 @@ void wxAuiDefaultDockArt::DrawPaneButton(wxDC& dc,
             break;
     }
 
-    wxAuiScaleBitmap(bmp, window->GetContentScaleFactor());
+    wxAuiScaleBitmap(bmp, window->GetDPIScaleFactor());
 
     wxRect rect = _rect;
 

src/aui/tabart.cpp

@@ -578,7 +578,7 @@ void wxAuiGenericTabArt::DrawTab(wxDC& dc,
             bmp = m_activeCloseBmp;
         }
 
-        wxAuiScaleBitmap(bmp, wnd->GetContentScaleFactor());
+        wxAuiScaleBitmap(bmp, wnd->GetDPIScaleFactor());
 
         int offsetY = tab_y-1;
         if (m_flags & wxAUI_NB_BOTTOM)
@@ -755,7 +755,7 @@ void wxAuiGenericTabArt::DrawButton(wxDC& dc,
     if (!bmp.IsOk())
         return;
 
-    wxAuiScaleBitmap(bmp, wnd->GetContentScaleFactor());
+    wxAuiScaleBitmap(bmp, wnd->GetDPIScaleFactor());
 
     rect = in_rect;
 
@@ -1125,7 +1125,7 @@ void wxAuiSimpleTabArt::DrawTab(wxDC& dc,
         else
             bmp = m_disabledCloseBmp;
 
-        wxAuiScaleBitmap(bmp, wnd->GetContentScaleFactor());
+        wxAuiScaleBitmap(bmp, wnd->GetDPIScaleFactor());
 
         wxRect rect(tab_x + tab_width - bmp.GetScaledWidth() - 1,
                     tab_y + (tab_height/2) - (bmp.GetScaledHeight()/2) + 1,
@@ -1273,7 +1273,7 @@ void wxAuiSimpleTabArt::DrawButton(wxDC& dc,
     if (!bmp.IsOk())
         return;
 
-    wxAuiScaleBitmap(bmp, wnd->GetContentScaleFactor());
+    wxAuiScaleBitmap(bmp, wnd->GetDPIScaleFactor());
 
     rect = in_rect;
 

src/common/sizer.cpp

@@ -111,7 +111,7 @@ float wxSizerFlags::DoGetDefaultBorderInPx()
     if ( s_defaultBorderInPx.HasChanged(win) )
     {
         s_defaultBorderInPx.SetAtNewDPI(
-            (float)(5 * (win ? win->GetContentScaleFactor() : 1)));
+            (float)(5 * (win ? win->GetDPIScaleFactor() : 1.0)));
     }
     return s_defaultBorderInPx.Get();
 }

src/common/wincmn.cpp

@@ -101,9 +101,12 @@ bool IsInCaptureStack(wxWindowBase* win);
 
 } // wxMouseCapture
 
-// We consider 96 DPI to be the standard value, this is correct at least for
+// Most platforms use 96 DPI by default, but Mac traditionally uses 72.
-// MSW, but could conceivably need adjustment for the other platforms.
+#ifdef __WXOSX__
+static const int BASELINE_DPI = 72;
+#else
 static const int BASELINE_DPI = 96;
+#endif
 
 // ----------------------------------------------------------------------------
 // static data
@@ -808,6 +811,11 @@ static wxSize GetDPIHelper(const wxWindowBase* w)
 }
 
 double wxWindowBase::GetContentScaleFactor() const
+{
+    return GetDPIScaleFactor();
+}
+
+double wxWindowBase::GetDPIScaleFactor() const
 {
     const wxSize dpi = GetDPIHelper(this);
 

src/html/htmlwin.cpp

@@ -493,7 +493,7 @@ bool wxHtmlWindow::DoSetPage(const wxString& source)
 
     double pixelScale = 1.0;
 #ifndef wxHAVE_DPI_INDEPENDENT_PIXELS
-    pixelScale = GetContentScaleFactor();
+    pixelScale = GetDPIScaleFactor();
 #endif
 
     m_Parser->SetDC(&dc, pixelScale, 1.0);

src/propgrid/propgrid.cpp

@@ -4610,7 +4610,7 @@ void wxPropertyGrid::OnResize( wxSizeEvent& event )
 
     if ( !HasExtraStyle(wxPG_EX_NATIVE_DOUBLE_BUFFERING) )
     {
-        double scaleFactor = GetContentScaleFactor();
+        double scaleFactor = GetDPIScaleFactor();
         int dblh = (m_lineHeight*2);
         if ( !m_doubleBuffer )
         {