Merge branch 'msw-dpi-handling-fixes'

Fixes to make processing wxEVT_DPI_CHANGED work better.

See wxWidgets#23510.

include/wx/event.h

@@ -3129,7 +3129,12 @@ class WXDLLIMPEXP_CORE wxDPIChangedEvent : public wxEvent
 
     // Scale the value by the ratio between new and old DPIs carried by this
     // event.
+    wxPoint Scale(wxPoint pt) const;
     wxSize Scale(wxSize sz) const;
+    wxRect Scale(wxRect r) const
+    {
+        return wxRect(Scale(r.GetPosition()), Scale(r.GetSize()));
+    }
 
     int ScaleX(int x) const { return Scale(wxSize(x, -1)).x; }
     int ScaleY(int y) const { return Scale(wxSize(-1, y)).y; }

include/wx/msw/frame.h

@@ -131,6 +131,8 @@ class WXDLLIMPEXP_CORE wxFrame : public wxFrameBase
     virtual void DoGetClientSize(int *width, int *height) const override;
     virtual void DoSetClientSize(int width, int height) override;
 
+    virtual void MSWBeforeDPIChangedEvent(const wxDPIChangedEvent& event) override;
+
 #if wxUSE_MENUS_NATIVE
     // perform MSW-specific action when menubar is changed
     virtual void AttachMenuBar(wxMenuBar *menubar) override;

include/wx/msw/slider.h

@@ -123,8 +123,8 @@ class WXDLLIMPEXP_CORE wxSlider : public wxSliderBase
     WXHBRUSH DoMSWControlColor(WXHDC pDC, wxColour colBg, WXHWND hWnd) override;
 
     virtual void MSWUpdateFontOnDPIChange(const wxSize& newDPI) override;
+    virtual void MSWBeforeDPIChangedEvent(const wxDPIChangedEvent& event) override;
 
-    void OnDPIChanged(wxDPIChangedEvent& event);
 
     // the labels windows, if any
     wxSubwindows  *m_labels;

include/wx/msw/window.h

@@ -605,6 +605,15 @@ class WXDLLIMPEXP_CORE wxWindowMSW : public wxWindowBase
     // controls. The default version updates m_font of this window.
     virtual void MSWUpdateFontOnDPIChange(const wxSize& newDPI);
 
+    // Also called from MSWUpdateOnDPIChange() but, unlike the function above,
+    // this one is called after updating all the children and just before
+    // letting the application handle the given wxDPIChangedEvent (whose
+    // Scale() functions may be useful for the overridden versions).
+    virtual void
+    MSWBeforeDPIChangedEvent(const wxDPIChangedEvent& WXUNUSED(event))
+    {
+    }
+
     // this allows you to implement standard control borders without
     // repeating the code in different classes that are not derived from
     // wxControl

interface/wx/event.h

@@ -3475,10 +3475,19 @@ class wxDPIChangedEvent : public wxEvent
         For example, the returned value will be twice bigger than the original
         one when switching from normal (96) DPI to high (2x, 192) DPI.
 
+        The overloads taking wxPoint and wxRect are only available in wxWidgets
+        3.3.0 and later.
+
         @since 3.1.6
      */
     wxSize Scale(wxSize sz) const;
 
+    /// @overload
+    wxPoint Scale(wxPoint pt) const;
+
+    /// @overload
+    wxRect Scale(wxRect rect) const;
+
     /**
         Rescale horizontal component to match the new DPI.
 

src/common/event.cpp

@@ -915,6 +915,11 @@ wxHelpEvent::Origin wxHelpEvent::GuessOrigin(Origin origin)
 // wxDPIChangedEvent
 // ----------------------------------------------------------------------------
 
+wxPoint wxDPIChangedEvent::Scale(wxPoint pt) const
+{
+    return wxRescaleCoord(pt).From(m_oldDPI).To(m_newDPI);
+}
+
 wxSize wxDPIChangedEvent::Scale(wxSize sz) const
 {
     return wxRescaleCoord(sz).From(m_oldDPI).To(m_newDPI);

src/msw/frame.cpp

@@ -947,3 +947,15 @@ wxPoint wxFrame::GetClientAreaOrigin() const
 
     return pt;
 }
+
+void wxFrame::MSWBeforeDPIChangedEvent(const wxDPIChangedEvent& WXUNUSED(event))
+{
+#if wxUSE_STATUSBAR
+    // If this frame uses a status bar, we need to adjust its height here
+    // before executing the user-defined wxEVT_DPI_CHANGED handler which may
+    // want to change the client size of the frame (e.g. using wxSizer::Fit()),
+    // because otherwise this wouldn't work correctly because the status bar
+    // would still have its old height, corresponding to the old DPI.
+    PositionStatusBar();
+#endif // wxUSE_STATUSBAR
+}

src/msw/slider.cpp

@@ -184,8 +184,6 @@ bool wxSlider::Create(wxWindow *parent,
         SetSize(size);
     }
 
-    Bind(wxEVT_DPI_CHANGED, &wxSlider::OnDPIChanged, this);
-
     return true;
 }
 
@@ -649,13 +647,14 @@ void wxSlider::MSWUpdateFontOnDPIChange(const wxSize& newDPI)
     }
 }
 
-void wxSlider::OnDPIChanged(wxDPIChangedEvent& event)
+void wxSlider::MSWBeforeDPIChangedEvent(const wxDPIChangedEvent& event)
 {
+    // We need to update the thumb before processing wxEVT_DPI_CHANGED in the
+    // user code, as it may update the slider size, which wouldn't work
+    // correctly if it still used the old thumb length.
     int thumbLen = GetThumbLength();
 
     SetThumbLength(event.ScaleX(thumbLen));
-
-    event.Skip();
 }
 
 // ----------------------------------------------------------------------------

src/msw/window.cpp

@@ -5030,6 +5030,11 @@ wxWindowMSW::MSWUpdateOnDPIChange(const wxSize& oldDPI, const wxSize& newDPI)
 
     wxDPIChangedEvent event(oldDPI, newDPI);
     event.SetEventObject(this);
+
+    // Another hook to give the derived window a chance to update itself after
+    // updating all the children, but before the user-defined event handler.
+    MSWBeforeDPIChangedEvent(event);
+
     return HandleWindowEvent(event);
 }