Bug 803633 - Add basic support for new scrollbar behavior in GTK+ [Part 1]. r=mstange, r=karlt

layout/xul/nsSliderFrame.cpp

@@ -534,6 +534,21 @@ nsSliderFrame::HandleEvent(nsPresContext* aPresContext,
 
     mDragStart = pos - mThumbStart;
   }
+#ifdef MOZ_WIDGET_GTK
+  else if (ShouldScrollForEvent(aEvent) &&
+           aEvent->mClass == eMouseEventClass &&
+           aEvent->AsMouseEvent()->button == WidgetMouseEvent::eRightButton) {
+    // HandlePress and HandleRelease are usually called via
+    // nsFrame::HandleEvent, but only for the left mouse button.
+    if (aEvent->message == NS_MOUSE_BUTTON_DOWN) {
+      HandlePress(aPresContext, aEvent, aEventStatus);
+    } else if (aEvent->message == NS_MOUSE_BUTTON_UP) {
+      HandleRelease(aPresContext, aEvent, aEventStatus);
+    }
+
+    return NS_OK;
+  }
+#endif
 
   // XXX hack until handle release is actually called in nsframe.
 //  if (aEvent->message == NS_MOUSE_EXIT_SYNTH || aEvent->message == NS_MOUSE_RIGHT_BUTTON_UP || aEvent->message == NS_MOUSE_LEFT_BUTTON_UP)
@@ -955,8 +970,14 @@ nsSliderFrame::ShouldScrollForEvent(WidgetGUIEvent* aEvent)
     case NS_MOUSE_BUTTON_DOWN:
     case NS_MOUSE_BUTTON_UP: {
       uint16_t button = aEvent->AsMouseEvent()->button;
+#ifdef MOZ_WIDGET_GTK
+      return (button == WidgetMouseEvent::eLeftButton) ||
+             (button == WidgetMouseEvent::eRightButton && GetScrollToClick()) ||
+             (button == WidgetMouseEvent::eMiddleButton && gMiddlePref && !GetScrollToClick());
+#else
       return (button == WidgetMouseEvent::eLeftButton) ||
              (button == WidgetMouseEvent::eMiddleButton && gMiddlePref);
+#endif
     }
     default:
       return false;
@@ -978,8 +999,8 @@ nsSliderFrame::ShouldScrollToClickForEvent(WidgetGUIEvent* aEvent)
     return false;
   }
 
-#ifdef XP_MACOSX
+#if defined(XP_MACOSX) || defined(MOZ_WIDGET_GTK)
-  // On Mac, clicking the scrollbar thumb should never scroll to click.
+  // On Mac and Linux, clicking the scrollbar thumb should never scroll to click.
   if (IsEventOverThumb(aEvent)) {
     return false;
   }
@@ -995,6 +1016,12 @@ nsSliderFrame::ShouldScrollToClickForEvent(WidgetGUIEvent* aEvent)
     return GetScrollToClick() != invertPref;
   }
 
+#ifdef MOZ_WIDGET_GTK
+  if (mouseEvent->button == WidgetMouseEvent::eRightButton) {
+    return !GetScrollToClick();
+  }
+#endif
+
   return true;
 }
 

modules/libpref/init/all.js

@@ -574,16 +574,18 @@ pref("accessibility.browsewithcaret_shortcut.enabled", true);
 // unless accessibility.tabfocus is set by the user.
 pref("accessibility.tabfocus", 7);
 pref("accessibility.tabfocus_applies_to_xul", false);
-
-// On OS X, we follow the "Click in the scrollbar to:" system preference
-// unless this preference was set manually
-pref("ui.scrollToClick", 0);
-
 #else
 // Only on mac tabfocus is expected to handle UI widgets as well as web content
 pref("accessibility.tabfocus_applies_to_xul", true);
 #endif
 
+// We follow the "Click in the scrollbar to:" system preference on OS X and
+// "gtk-primary-button-warps-slider" property with GTK (since 2.24 / 3.6),
+// unless this preference is explicitly set.
+#if !defined(XP_MACOSX) && !defined(MOZ_WIDGET_GTK)
+pref("ui.scrollToClick", 0);
+#endif
+
 // provide ability to turn on support for canvas focus rings
 pref("canvas.focusring.enabled", true);
 pref("canvas.customfocusring.enabled", false);

widget/gtk/nsLookAndFeel.cpp

@@ -555,6 +555,26 @@ nsLookAndFeel::GetIntImpl(IntID aID, int32_t &aResult)
             g_object_unref(entry);
         }
         break;
+    case eIntID_ScrollToClick:
+        {
+            GtkSettings *settings;
+            gboolean warps_slider = FALSE;
+
+            settings = gtk_settings_get_default ();
+            if (g_object_class_find_property (G_OBJECT_GET_CLASS(settings),
+                                              "gtk-primary-button-warps-slider")) {
+                g_object_get (settings,
+                              "gtk-primary-button-warps-slider",
+                              &warps_slider,
+                              nullptr);
+            }
+
+            if (warps_slider)
+                aResult = 1;
+            else
+                aResult = 0;
+        }
+        break;
     case eIntID_SubmenuDelay:
         {
             GtkSettings *settings;