Merge branch 'per-monitor-dpi-aware-controls-1' of https://github.com/MaartenBent/wxWidgets

Update the font of some buddy controls when the DPI changes. Fix the
position of the statusbar after a DPI change. Add some changes that were
suggested in https://github.com/wxWidgets/wxWidgets/pull/1499 but left
out from it.

Some sizes are cached to improve the speed of the library. These sizes
become incorrect when the DPI changes. And are incorrect when a window
is created on a display with a different DPI. Fix this by checking if
the current DPI is the same as the DPI that was used when calculating
the size, otherwise recalculate the size.

Closes https://github.com/wxWidgets/wxWidgets/pull/1530

include/wx/button.h

@@ -39,8 +39,9 @@ public:
     // returns the old default item (possibly NULL)
     virtual wxWindow *SetDefault();
 
-    // returns the default button size for this platform
-    static wxSize GetDefaultSize();
+    // returns the default button size for this platform, and optionally for a
+    // specific window when the platform supports per-monitor DPI
+    static wxSize GetDefaultSize(wxWindow* win = NULL);
 
 protected:
     wxDECLARE_NO_COPY_CLASS(wxButtonBase);

include/wx/fontutil.h

@@ -34,6 +34,7 @@
 #endif
 
 class WXDLLIMPEXP_FWD_BASE wxArrayString;
+class WXDLLIMPEXP_FWD_CORE wxWindow;
 struct WXDLLIMPEXP_FWD_CORE wxNativeEncodingInfo;
 
 #if defined(_WX_X_FONTLIKE)
@@ -118,11 +119,16 @@ public:
     // set the XFLD
     void SetXFontName(const wxString& xFontName);
 #elif defined(__WXMSW__)
-    wxNativeFontInfo(const LOGFONT& lf_)
-        : lf(lf_),
-          pointSize(GetPointSizeAtPPI(lf.lfHeight))
-    {
-    }
+    // Preserve compatibility in the semi-public (i.e. private, but still
+    // unfortunately used by some existing code outside of the library) API
+    // by allowing to create wxNativeFontInfo from just LOGFONT, but ensure
+    // that we always specify the window, to use the correct DPI, when creating
+    // fonts inside the library itself.
+    wxNativeFontInfo(const LOGFONT& lf_, const wxWindow* win
+#ifndef WXBUILDING
+        = NULL
+#endif
+    );
 
     // MSW-specific: get point size from LOGFONT height using specified DPI,
     // or screen DPI when 0.

include/wx/msw/radiobox.h

@@ -162,6 +162,8 @@ protected:
 
     virtual WXHRGN MSWGetRegionWithoutChildren() wxOVERRIDE;
 
+    virtual void MSWUpdateFontOnDPIChange(const wxSize& newDPI) wxOVERRIDE;
+
     // resolve ambiguity in base classes
     virtual wxBorder GetDefaultBorder() const wxOVERRIDE { return wxRadioBoxBase::GetDefaultBorder(); }
 

include/wx/msw/slider.h

@@ -122,6 +122,9 @@ protected:
 
     WXHBRUSH DoMSWControlColor(WXHDC pDC, wxColour colBg, WXHWND hWnd) wxOVERRIDE;
 
+    virtual void MSWUpdateFontOnDPIChange(const wxSize& newDPI) wxOVERRIDE;
+
+    void OnDPIChanged(wxDPIChangedEvent& event);
 
     // the labels windows, if any
     wxSubwindows  *m_labels;

include/wx/msw/statusbar.h

@@ -72,6 +72,8 @@ protected:
     // implementation of the public SetStatusWidths()
     void MSWUpdateFieldsWidths();
 
+    virtual void MSWUpdateFontOnDPIChange(const wxSize& newDPI) wxOVERRIDE;
+
     // used by DoUpdateStatusText()
     wxClientDC *m_pDC;
 

include/wx/private/window.h

@@ -11,6 +11,7 @@
 #define _WX_PRIVATE_WINDOW_H_
 
 #include "wx/gdicmn.h"
+#include "wx/dynlib.h"
 
 namespace wxPrivate
 {
@@ -33,6 +34,67 @@ inline wxSize GetAverageASCIILetterSize(const T& of_what)
     return s;
 }
 
+namespace
+{
+
+inline bool SupportsPerMonitorDPI()
+{
+    static bool s_checkDPI =
+#if defined(__WXMSW__) && wxUSE_DYNLIB_CLASS
+        // Only check the DPI when GetDpiForWindow is available because the old
+        // method (GetDeviceCaps) is a lot slower (about 1500 times).
+        // And when GetDpiForWindow is not available (for example older Windows
+        // versions), per-monitor DPI (V2) is also not available.
+        wxLoadedDLL("user32.dll").HasSymbol("GetDpiForWindow");
+#else
+        false;
+#endif
+    return s_checkDPI;
+}
+
+}
+
+template <typename T>
+class DpiDependentValue
+{
+public:
+    // Explicit initialization is needed if T is a primitive type.
+    DpiDependentValue()
+        : m_value(), m_dpi()
+    { }
+
+    bool HasChanged(const wxWindowBase* win)
+    {
+        if ( win && SupportsPerMonitorDPI() )
+        {
+            const wxSize dpi = win->GetDPI();
+            if ( dpi != m_dpi )
+            {
+                m_dpi = dpi;
+                return true;
+            }
+        }
+
+        // Ensure that we return true the first time we're called,
+        // asuming that the value will always be set to a non-default value.
+        return m_value == T();
+    }
+
+    void SetAtNewDPI(const T& value)
+    {
+        m_value = value;
+    }
+
+    T& Get()
+    {
+        return m_value;
+    }
+
+private:
+    T m_value;
+    wxSize m_dpi;
+};
+
 } // namespace wxPrivate
 
 #endif // _WX_PRIVATE_WINDOW_H_

include/wx/sizer.h

@@ -120,13 +120,7 @@ public:
         // current DPI, do it once (and cache the result) in another function.
         #define wxNEEDS_BORDER_IN_PX
 
-        // We don't react to dynamic DPI changes, so we can cache the values of
-        // the border in on-screen pixels after computing it once. This
-        // could/should change in the future.
-        if ( !ms_defaultBorderInPx )
-            ms_defaultBorderInPx = DoGetDefaultBorderInPx();
-
-        return ms_defaultBorderInPx;
+        return DoGetDefaultBorderInPx();
     #endif
 #else
         return 0;
@@ -230,8 +224,6 @@ public:
 private:
 #ifdef wxNEEDS_BORDER_IN_PX
     static int DoGetDefaultBorderInPx();
-
-    static int ms_defaultBorderInPx;
 #endif // wxNEEDS_BORDER_IN_PX
 
     int m_proportion;