Implement wxColourDisplay() in terms of wxDisplay::GetDepth()

Get rid of another global display-related function, even though this one
only had non-trivial implementation under MSW.

interface/wx/gdicmn.h

@@ -1183,6 +1183,10 @@ const wxSize wxDefaultSize;
 /**
     Returns @true if the display is colour, @false otherwise.
 
+    @note Use of this function is not recommended in the new code as it only
+        works for the primary display. Use wxDisplay::GetDepth() to retrieve
+        the depth of the appropriate display and compare it with 1 instead.
+
     @header{wx/gdicmn.h}
 */
 bool wxColourDisplay();

src/common/gdicmn.cpp

@@ -850,6 +850,13 @@ int wxDisplayDepth()
     return wxDisplay().GetDepth();
 }
 
+bool wxColourDisplay()
+{
+    // If GetDepth() returns 0, meaning unknown, we assume it's a colour
+    // display, hence the use of "!=" rather than ">" here.
+    return wxDisplay().GetDepth() != 1;
+}
+
 void wxDisplaySize(int *width, int *height)
 {
     const wxSize size = wxGetDisplaySize();

src/dfb/utils.cpp

@@ -89,12 +89,6 @@ wxDisplayFactory* wxDisplay::CreateFactory()
     return new wxDisplayFactorySingleDFB;
 }
 
-bool wxColourDisplay()
-{
-    #warning "FIXME: wxColourDisplay"
-    return true;
-}
-
 void wxDisplaySizeMM(int *width, int *height)
 {
     // FIXME: there's no way to get physical resolution using the DirectDB

src/gtk/utilsgtk.cpp

@@ -90,11 +90,6 @@ void wxDisplaySizeMM( int *width, int *height )
 #endif
 }
 
-bool wxColourDisplay()
-{
-    return true;
-}
-
 wxWindow* wxFindWindowAtPoint(const wxPoint& pt)
 {
     return wxGenericFindWindowAtPoint(pt);

src/gtk1/utilsgtk.cpp

@@ -97,11 +97,6 @@ void wxGetMousePosition( int* x, int* y )
     gdk_window_get_pointer( NULL, x, y, NULL );
 }
 
-bool wxColourDisplay()
-{
-    return true;
-}
-
 wxWindow* wxFindWindowAtPoint(const wxPoint& pt)
 {
     return wxGenericFindWindowAtPoint(pt);

src/motif/utils.cpp

@@ -225,12 +225,6 @@ void wxGetMousePosition( int* x, int* y )
 #endif
 }
 
-// Return true if we have a colour display
-bool wxColourDisplay()
-{
-    return wxDisplayDepth() > 1;
-}
-
 void wxDisplaySizeMM(int *width, int *height)
 {
     Display *dpy = wxGlobalDisplay();

src/msw/utilsgui.cpp

@@ -117,27 +117,6 @@ void wxGetMousePosition( int* x, int* y )
     if ( y ) *y = pt.y;
 }
 
-// Return true if we have a colour display
-bool wxColourDisplay()
-{
-    // this function is called from wxDC ctor so it is called a *lot* of times
-    // hence we optimize it a bit but doing the check only once
-    //
-    // this should be MT safe as only the GUI thread (holding the GUI mutex)
-    // can call us
-    static int s_isColour = -1;
-
-    if ( s_isColour == -1 )
-    {
-        ScreenHDC dc;
-        int noCols = ::GetDeviceCaps(dc, NUMCOLORS);
-
-        s_isColour = (noCols == -1) || (noCols > 2);
-    }
-
-    return s_isColour != 0;
-}
-
 void wxDisplaySizeMM(int *width, int *height)
 {
     ScreenHDC dc;

src/osx/utils_osx.cpp

@@ -53,14 +53,6 @@ bool wxCheckForInterrupt(wxWindow *WXUNUSED(wnd))
     return false;
 }
 
-// Return true if we have a colour display
-bool wxColourDisplay()
-{
-    // always the case on OS X
-    return true;
-}
-
-
 #if wxOSX_USE_COCOA_OR_CARBON
 
 #if wxUSE_GUI

src/qt/utils.cpp

@@ -140,11 +140,6 @@ wxWindow *wxGetActiveWindow()
     return NULL;
 }
 
-bool wxColourDisplay()
-{
-    return QApplication::desktop()->depth() > 1;
-}
-
 bool wxLaunchDefaultApplication(const wxString& path, int WXUNUSED( flags ) )
 {
     return QDesktopServices::openUrl( QUrl::fromLocalFile( wxQtConvertString( path ) ) );

src/x11/utils.cpp

@@ -148,12 +148,6 @@ void wxGetMousePosition( int* x, int* y )
 #endif
 };
 
-// Return true if we have a colour display
-bool wxColourDisplay()
-{
-    return wxDisplayDepth() > 1;
-}
-
 void wxDisplaySizeMM(int *width, int *height)
 {
     Display *dpy = (Display*) wxGetDisplay();