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.

interface/wx/display.h

@@ -143,6 +143,46 @@ public:
      */
     wxSize GetPPI() const;
 
+    /**
+        Returns scaling factor used by this display.
+
+        The scaling factor is the ratio between GetPPI() and GetStdPPI()
+        (it is implicitly assumed that this ratio is the same for both
+        horizontal and vertical components).
+
+        @see wxWindow::GetContentScaleFactor(), wxWindow::GetDPIScaleFactor()
+
+        @since 3.1.5
+     */
+    double GetScaleFactor() const;
+
+    /**
+        Returns default display resolution for the current platform in pixels
+        per inch.
+
+        This function mostly used internally, use GetPPI() to get the actual
+        display resolution.
+
+        Currently the standard PPI is the same in both horizontal and vertical
+        directions on all platforms and its value is 96 everywhere except under
+        Apple devices (those running macOS, iOS, watchOS etc), where it is 72.
+
+        @see GetStdPPI()
+
+        @since 3.1.5
+     */
+    static int GetStdPPIValue();
+
+    /**
+        Returns default display resolution for the current platform as wxSize.
+
+        This function is equivalent to constructing wxSize object with both
+        components set to GetStdPPIValue().
+
+        @since 3.1.5
+     */
+    static wxSize GetStdPPI();
+
     /**
         Returns @true if the display is the primary display. The primary
         display is the one whose index is 0.