Fix bug when the first display is not the main display on linux

modules/juce_gui_basics/native/juce_linux_Windowing.cpp

@@ -1189,7 +1189,7 @@ private:
                 ScopedPointer<XRRScreenResources> screens;
 
                 const int numMonitors = ScreenCount (dpy);
-                RROutput mainDisplay = xrandr.getOutputPrimary (dpy, RootWindow (dpy, 0));
+                RROutput mainDisplay = xrandr.getOutputPrimary (dpy, RootWindow (dpy, 0)) + 1;
 
                 for (int i = 0; i < numMonitors; ++i)
                 {
@@ -3722,12 +3722,45 @@ void Desktop::Displays::findDisplays (float masterScale)
 {
     DisplayGeometry& geometry = DisplayGeometry::getOrCreateInstance (display, masterScale);
 
+    // add the main display first
+    int mainDisplayIdx;
+    for (mainDisplayIdx = 0; mainDisplayIdx < geometry.infos.size(); ++mainDisplayIdx)
+    {
+        const DisplayGeometry::ExtendedInfo& info = geometry.infos.getReference (mainDisplayIdx);
+        if (info.isMain)
+        break;
+    }
+
+    // no main display found then use the first
+    if (mainDisplayIdx >= geometry.infos.size())
+        mainDisplayIdx = 0;
+
+    // add the main display
+    {
+        const DisplayGeometry::ExtendedInfo& info =
+      geometry.infos.getReference (mainDisplayIdx);
+        Desktop::Displays::Display d;
+
+        d.isMain = true;
+        d.scale = masterScale * info.scale;
+        d.dpi = info.dpi;
+
+        d.totalArea = DisplayGeometry::physicalToScaled (info.totalBounds);
+        d.userArea = (info.usableBounds / d.scale) + info.topLeftScaled;
+
+        displays.add (d);
+    }
+
     for (int i = 0; i < geometry.infos.size(); ++i)
     {
+        // don't add the main display a second time
+        if (i == mainDisplayIdx)
+            continue;
+
         const DisplayGeometry::ExtendedInfo& info = geometry.infos.getReference (i);
         Desktop::Displays::Display d;
 
-        d.isMain = info.isMain;
+        d.isMain = false;
         d.scale = masterScale * info.scale;
         d.dpi = info.dpi;