Calculate overlay position from window size

Previously, it was assumed that all monitors (and especially the primary
monitor, index 0) was inside the window when we calculate the position
of the overlay.

That might not always be the case, for example when using fullscreen
mode over a narrower set of monitors. This commit does so the overlay is
positioned correctly based on the actual window size, instead of what we
expect it to be.

diff --git a/vncviewer/DesktopWindow.cxx b/vncviewer/DesktopWindow.cxx
index e7f91f024cb9395b782c45505cba5f4ca6e0db28..8c85c4d9953818e0cecc105f7fa181e02ccd016a 100644 (file)
--- a/vncviewer/DesktopWindow.cxx
+++ b/vncviewer/DesktopWindow.cxx
@@ -465,9 +465,34 @@ void DesktopWindow::draw()
 
     // Make sure it's properly seen by adjusting it relative to the
     // primary screen rather than the entire window
-    if (fullscreen_active() && fullScreenAllMonitors) {
+    if (fullscreen_active()) {
       assert(Fl::screen_count() >= 1);
-      Fl::screen_xywh(sx, sy, sw, sh, 0);
+
+      rfb::Rect window_rect, screen_rect;
+      window_rect.setXYWH(x(), y(), w(), h());
+
+      bool found_enclosed_screen = false;
+      for (int i = 0; i < Fl::screen_count(); i++) {
+        Fl::screen_xywh(sx, sy, sw, sh, i);
+
+        // The screen with the smallest index that are enclosed by
+        // the viewport will be used for showing the overlay.
+        screen_rect.setXYWH(sx, sy, sw, sh);
+        if (screen_rect.enclosed_by(window_rect)) {
+          found_enclosed_screen = true;
+          break;
+        }
+      }
+
+      // If no monitor inside the viewport was found,
+      // use the one primary instead.
+      if (!found_enclosed_screen)
+        Fl::screen_xywh(sx, sy, sw, sh, 0);
+
+      // Adjust the coordinates so they are relative to the viewport.
+      sx -= x();
+      sy -= y();
+
     } else {
       sx = 0;
       sy = 0;