Merge branch 'sys-appearance'

Add wxSystemAppearance for dark mode checks under macOS.

Closes https://github.com/wxWidgets/wxWidgets/pull/1292

include/wx/settings.h

@@ -162,6 +162,39 @@ enum wxSystemScreenType
     wxSYS_SCREEN_DESKTOP    //   >= 800x600
 };
 
+// ----------------------------------------------------------------------------
+// wxSystemAppearance: describes the global appearance used for the UI
+// ----------------------------------------------------------------------------
+
+class WXDLLIMPEXP_CORE wxSystemAppearance
+{
+public:
+    // Return the name if available or empty string otherwise.
+    wxString GetName() const;
+
+    // Return true if the current system there is explicitly recognized as
+    // being a dark theme or if the default window background is dark.
+    bool IsDark() const;
+
+    // Return true if the background is darker than foreground. This is used by
+    // IsDark() if there is no platform-specific way to determine whether a
+    // dark mode is being used.
+    bool IsUsingDarkBackground() const;
+
+private:
+    friend class wxSystemSettingsNative;
+
+    // Ctor is private, even though it's trivial, because objects of this type
+    // are only supposed to be created by wxSystemSettingsNative.
+    wxSystemAppearance() { }
+
+    // Currently this class doesn't have any internal state because the only
+    // available implementation doesn't need it. If we do need it later, we
+    // could add some "wxSystemAppearanceImpl* const m_impl" here, which we'd
+    // forward our public functions to (we'd also need to add the copy ctor and
+    // dtor to clone/free it).
+};
+
 // ----------------------------------------------------------------------------
 // wxSystemSettingsNative: defines the API for wxSystemSettings class
 // ----------------------------------------------------------------------------
@@ -185,6 +218,9 @@ public:
     // get a system-dependent metric
     static int GetMetric(wxSystemMetric index, wxWindow * win = NULL);
 
+    // get the object describing the current system appearance
+    static wxSystemAppearance GetAppearance();
+
     // return true if the port has certain feature
     static bool HasFeature(wxSystemFeature index);
 };

interface/wx/settings.h

@@ -254,6 +254,55 @@ enum wxSystemScreenType
 };
 
 
+/**
+    Provides information about the current system appearance.
+
+    An object of this class can be retrieved using
+    wxSystemSettings::GetAppearance() and can then be queried for some aspects
+    of the current system appearance, notably whether the system is using a
+    dark theme, i.e. a theme with predominantly dark background.
+
+    This is useful for custom controls that don't use the standard system
+    colours, as they need to adjust the colours used for drawing them to fit in
+    the system look.
+
+    @since 3.1.3
+ */
+class wxSystemAppearance
+{
+public:
+    /**
+        Return the name if available or empty string otherwise.
+
+        This is currently only implemented for macOS 10.9 or later and returns
+        a not necessarily user-readable string such as "NSAppearanceNameAqua"
+        there and an empty string under all the other platforms.
+     */
+    wxString GetName() const;
+
+    /**
+        Return true if the current system there is explicitly recognized as
+        being a dark theme or if the default window background is dark.
+
+        This method should be used to check whether custom colours more
+        appropriate for the default (light) or dark appearance should be used.
+     */
+    bool IsDark() const;
+
+    /**
+        Return true if the default window background is significantly darker
+        than foreground.
+
+        This is used by IsDark() if there is no platform-specific way to
+        determine whether a dark mode is being used and is generally not very
+        useful to call directly.
+
+        @see wxColour::GetLuminance()
+     */
+    bool IsUsingDarkBackground() const;
+};
+
+
 /**
     @class wxSystemSettings
 
@@ -327,6 +376,13 @@ public:
     */
     static wxSystemScreenType GetScreenType();
 
+    /**
+        Returns the object describing the current system appearance.
+
+        @since 3.1.3
+     */
+    static wxSystemAppearance GetAppearance();
+
     /**
         Returns @true if the port has certain feature.
         See the ::wxSystemFeature enum values.

samples/drawing/drawing.cpp

@@ -1623,6 +1623,22 @@ void MyCanvas::DrawSystemColours(wxDC& dc)
     int lineHeight = textSize.GetHeight();
     wxRect r(textSize.GetWidth() + 10, 10, 100, lineHeight);
 
+    wxString title = "System colours";
+
+    const wxSystemAppearance appearance = wxSystemSettings::GetAppearance();
+    const wxString appearanceName = appearance.GetName();
+    if ( !appearanceName.empty() )
+        title += wxString::Format(" for \"%s\"", appearanceName);
+    if ( appearance.IsDark() )
+        title += " (using dark system theme)";
+    dc.DrawText(title, 10, r.y);
+    r.y += 2*lineHeight;
+    dc.DrawText(wxString::Format("Window background is %s",
+                                 appearance.IsUsingDarkBackground() ? "dark"
+                                                                    : "light"),
+                10, r.y);
+    r.y += 3*lineHeight;
+
     dc.SetPen(*wxTRANSPARENT_PEN);
 
     static const struct {

src/common/settcmn.cpp

@@ -66,3 +66,36 @@ void wxSystemSettings::SetScreenType( wxSystemScreenType screen )
 {
     ms_screen = screen;
 }
+
+// ----------------------------------------------------------------------------
+// Trivial wxSystemAppearance implementation
+// ----------------------------------------------------------------------------
+
+#if !defined(__WXOSX__)
+
+wxString wxSystemAppearance::GetName() const
+{
+    return wxString();
+}
+
+bool wxSystemAppearance::IsDark() const
+{
+    return IsUsingDarkBackground();
+}
+
+#endif // !__WXOSX__
+
+bool wxSystemAppearance::IsUsingDarkBackground() const
+{
+    const wxColour bg = wxSystemSettings::GetColour(wxSYS_COLOUR_WINDOW);
+    const wxColour fg = wxSystemSettings::GetColour(wxSYS_COLOUR_WINDOWTEXT);
+
+    // The threshold here is rather arbitrary, but it seems that using just
+    // inequality would be wrong as it could result in false positivies.
+    return fg.GetLuminance() - bg.GetLuminance() > 0.2;
+}
+
+wxSystemAppearance wxSystemSettingsNative::GetAppearance()
+{
+    return wxSystemAppearance();
+}

src/osx/carbon/renderer.cpp

@@ -173,11 +173,9 @@ int wxRendererMac::DrawHeaderButton( wxWindow *win,
     wxHeaderSortIconType sortArrow,
     wxHeaderButtonParams* params )
 {
-    if ( WX_IS_MACOS_AVAILABLE(10, 14) )
-    {
-        if ( wxSystemSettings::GetColour(wxSYS_COLOUR_WINDOW).Red() < 128 )
-            return wxRendererNative::GetGeneric().DrawHeaderButton(win, dc,  rect, flags, sortArrow, params);
-    }
+    if ( wxSystemSettings::GetAppearance().IsDark() )
+        return wxRendererNative::GetGeneric().DrawHeaderButton(win, dc,  rect, flags, sortArrow, params);
+
     const wxCoord x = rect.x;
     const wxCoord y = rect.y;
     const wxCoord w = rect.width;
@@ -391,13 +389,7 @@ void wxRendererMac::DrawSplitterSash( wxWindow *win,
 
         if ( win->HasFlag(wxSP_3DSASH) )
         {
-            bool doDraw;
-            if ( WX_IS_MACOS_AVAILABLE(10, 14) )
-                doDraw = wxSystemSettings::GetColour(wxSYS_COLOUR_WINDOW).Red() > 128;
-            else
-                doDraw = true;
-
-            if ( doDraw )
+            if ( !wxSystemSettings::GetAppearance().IsDark() )
             {
                 HIThemeSplitterDrawInfo drawInfo;
                 drawInfo.version = 0;

src/osx/carbon/statbrma.cpp

@@ -88,7 +88,7 @@ void wxStatusBarMac::InitColours()
             m_textActive = wxSystemSettings::GetColour(wxSYS_COLOUR_BTNTEXT);
             m_textInactive = wxSystemSettings::GetColour(wxSYS_COLOUR_GRAYTEXT);
 
-            if ( bg.Red() < 128 )
+            if ( wxSystemSettings::GetAppearance().IsDark() )
             {
                 // dark mode appearance
                 m_textActive = wxColour(0xB0, 0xB0, 0xB0);

src/osx/cocoa/settings.mm

@@ -42,6 +42,39 @@ static int wxOSXGetUserDefault(NSString* key, int defaultValue)
     return [setting intValue];
 }
 
+// ----------------------------------------------------------------------------
+// wxSystemAppearance
+// ----------------------------------------------------------------------------
+
+wxString wxSystemAppearance::GetName() const
+{
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_9
+    if ( WX_IS_MACOS_AVAILABLE(10, 9) )
+    {
+        return wxStringWithNSString([[NSApp effectiveAppearance] name]);
+    }
+#endif
+
+    return wxString();
+}
+
+bool wxSystemAppearance::IsDark() const
+{
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_14
+    if ( WX_IS_MACOS_AVAILABLE(10, 14) )
+    {
+        const NSAppearanceName
+            appearanceName = [[NSApp effectiveAppearance]
+                                bestMatchFromAppearancesWithNames:
+                                @[NSAppearanceNameAqua, NSAppearanceNameDarkAqua]];
+
+        return [appearanceName isEqualToString:NSAppearanceNameDarkAqua];
+    }
+#endif
+
+    // Fall back on the generic method when not running under 10.14.
+    return IsUsingDarkBackground();
+}
 
 // ----------------------------------------------------------------------------
 // wxSystemSettingsNative