Linux: Fail more gracefully on systems which don't support 32-, 24-, or 16-bit RGB displays

modules/juce_gui_basics/native/juce_linux_Windowing.cpp

@@ -41,6 +41,9 @@ public:
         // it's dangerous to create a window on a thread other than the message thread.
         JUCE_ASSERT_MESSAGE_MANAGER_IS_LOCKED
 
+        if (! XWindowSystem::getInstance()->isX11Available())
+            return;
+
         if (isAlwaysOnTop)
             ++numAlwaysOnTopPeers;
 
@@ -262,12 +265,14 @@ public:
     //==============================================================================
     void repaint (const Rectangle<int>& area) override
     {
-        repainter->repaint (area.getIntersection (bounds.withZeroOrigin()));
+        if (repainter != nullptr)
+            repainter->repaint (area.getIntersection (bounds.withZeroOrigin()));
     }
 
     void performAnyPendingRepaintsNow() override
     {
-        repainter->performAnyPendingRepaintsNow();
+        if (repainter != nullptr)
+            repainter->performAnyPendingRepaintsNow();
     }
 
     void setIcon (const Image& newIcon) override

modules/juce_gui_basics/native/x11/juce_linux_XWindowSystem.cpp

@@ -1983,7 +1983,7 @@ bool XWindowSystem::canUseARGBImages() const
                                                                          X11Symbols::getInstance()->xDefaultVisual (display, X11Symbols::getInstance()->xDefaultScreen (display)),
                                                                          24, ZPixmap, nullptr, &segmentinfo, 64, 64);
 
-            canUseARGB = (testImage->bits_per_pixel == 32);
+            canUseARGB = testImage != nullptr && testImage->bits_per_pixel == 32;
             X11Symbols::getInstance()->xDestroyImage (testImage);
         }
         else
@@ -3013,7 +3013,7 @@ bool XWindowSystem::initialiseXDisplay()
     if (! displayVisuals->isValid())
     {
         Logger::outputDebugString ("ERROR: System doesn't support 32, 24 or 16 bit RGB display.\n");
-        Process::terminate();
+        return false;
     }
 
     // Setup input event handler

modules/juce_gui_basics/native/x11/juce_linux_XWindowSystem.h

@@ -164,6 +164,8 @@ public:
     ::Display* getDisplay()                    { return display; }
     XWindowSystemUtilities::Atoms& getAtoms()  { return atoms; }
 
+    bool isX11Available() const noexcept       { return xIsAvailable; }
+
     //==============================================================================
     void handleWindowMessage (LinuxComponentPeer*, XEvent&) const;
     bool isParentWindowOf (::Window, ::Window possibleChild) const;