Fix for STR#3475: X11 platform, re-use current screen scaling factor when processing a screen reconfiguration event.

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.4@12939 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

1 files changed, 46 insertions, 6 deletions

diff --git a/src/Fl_x.cxx b/src/Fl_x.cxx
index 752924593..f911793cc 100644
--- a/src/Fl_x.cxx
+++ b/src/Fl_x.cxx
@@ -1220,6 +1220,51 @@ static KeySym fl_KeycodeToKeysym(Display *d, KeyCode k, unsigned i) {
   return XKeycodeToKeysym(d, k, i);
 }
 
+#if USE_XRANDR
+static void react_to_screen_reconfiguration() {
+#if USE_XFT
+  // memorize previous screen sizes and scales
+  int old_count = Fl::screen_count();
+  int (*sizes)[4] =  new int[old_count][4];
+  float *scales = new float[old_count];
+  for (int screen = 0; screen < old_count; screen++) {
+    Fl::screen_xywh(sizes[screen][0], sizes[screen][1], sizes[screen][2], sizes[screen][3], screen);
+    scales[screen] = Fl::screen_scale(screen);
+  }
+#endif // USE_XFT
+  Fl::call_screen_init(); // compute new screen sizes
+#if USE_XFT
+  // detect whether screen sizes were unchanged
+  bool nochange = (old_count == Fl::screen_count());
+  if (nochange) {
+    for (int screen = 0; screen < old_count; screen++) {
+      int X,Y,W,H;
+      Fl::screen_xywh(X,Y,W,H, screen);
+      X /= scales[screen];
+      Y /= scales[screen];
+      W /= scales[screen];
+      H /= scales[screen];
+      if (X != sizes[screen][0] || Y != sizes[screen][1] || W != sizes[screen][2] || H != sizes[screen][3]) {
+        nochange = false;
+        break;
+      }
+    }
+  }
+  delete[] sizes;
+  if (nochange) { // screen sizes did not change: re-use previous screen scale values
+    for (int screen = 0; screen < old_count; screen++)
+      Fl::screen_driver()->scale(screen, scales[screen]);
+  } else {
+    float factor = Fl::screen_driver()->use_startup_scale_factor();
+    for (int screen = 0; screen < Fl::screen_count(); screen++)
+      Fl::screen_driver()->rescale_all_windows_from_screen(screen, factor);
+  }
+  delete[] scales;
+#endif // USE_XFT
+}
+#endif // USE_XRANDR
+
+
 int fl_handle(const XEvent& thisevent)
 {
   XEvent xevent = thisevent;
@@ -1251,12 +1296,7 @@ int fl_handle(const XEvent& thisevent)
 #if USE_XRANDR  
   if( XRRUpdateConfiguration_f && xevent.type == randrEventBase + RRScreenChangeNotify) {
     XRRUpdateConfiguration_f(&xevent);
-    Fl::call_screen_init();
-#if USE_XFT
-    float factor = Fl::screen_driver()->desktop_scale_factor();
-    for (int screen = 0; screen <= Fl::screen_count(); screen++)
-      Fl::screen_driver()->rescale_all_windows_from_screen(screen, factor);
-#endif // USE_XFT
+    react_to_screen_reconfiguration();
     Fl::handle(FL_SCREEN_CONFIGURATION_CHANGED, NULL);
   }
 #endif // USE_XRANDR