src/kits/shared/LongAndDragTrackingFilter.cpp

   1 /*
   2  * Copyright 2011, Alexandre Deckner, alex@zappotek.com
   3  * Distributed under the terms of the MIT License.
   4  */
   5
   6 /*!
   7         \class LongAndDragTrackingFilter
   8         \brief A simple long mouse down and drag detection filter
   9         *
  10         * A simple mouse filter that detects long clicks and pointer drags.
  11         * A long click message is sent when the mouse button is kept down
  12         * for a duration longer than a given threshold while the pointer stays
  13         * within the limits of a given threshold radius.
  14         * A drag message is triggered if the mouse goes further than the
  15         * threshold radius before the duration threshold elapsed.
  16         *
  17         * The messages contain the pointer position and the buttons state at
  18         * the moment of the click. The drag message is ready to use with the
  19         * be/haiku drag and drop API cf. comment in code.
  20         *
  21         * Current limitation: A long mouse down or a drag can be detected for
  22         * any mouse button, but any released button cancels the tracking.
  23         *
  24 */
  25
  26
  27 #include <LongAndDragTrackingFilter.h>
  28
  29 #include <Message.h>
  30 #include <Messenger.h>
  31 #include <MessageRunner.h>
  32 #include <View.h>
  33
  34 #include <new>
  35
  36
  37 LongAndDragTrackingFilter::LongAndDragTrackingFilter(uint32 longMessageWhat,
  38         uint32 dragMessageWhat, float radiusThreshold,
  39         bigtime_t durationThreshold)
  40         :
  41         BMessageFilter(B_ANY_DELIVERY, B_ANY_SOURCE),
  42         fLongMessageWhat(longMessageWhat),
  43         fDragMessageWhat(dragMessageWhat),
  44         fMessageRunner(NULL),
  45         fClickButtons(0),
  46         fSquaredRadiusThreshold(radiusThreshold * radiusThreshold),
  47         fDurationThreshold(durationThreshold)
  48 {
  49         if (durationThreshold == 0) {
  50                 get_click_speed(&fDurationThreshold);
  51                         // use system's doubleClickSpeed as default threshold
  52         }
  53 }
  54
  55
  56 LongAndDragTrackingFilter::~LongAndDragTrackingFilter()
  57 {
  58         delete fMessageRunner;
  59 }
  60
  61
  62 void
  63 LongAndDragTrackingFilter::_StopTracking()
  64 {
  65         delete fMessageRunner;
  66         fMessageRunner = NULL;
  67 }
  68
  69
  70 filter_result
  71 LongAndDragTrackingFilter::Filter(BMessage* message, BHandler** target)
  72 {
  73         if (*target == NULL)
  74                 return B_DISPATCH_MESSAGE;
  75
  76         switch (message->what) {
  77                 case B_MOUSE_DOWN:
  78
  79                         message->FindInt32("buttons", (int32*)&fClickButtons);
  80
  81                         if (fClickButtons != 0) {
  82
  83                                 BView* targetView = dynamic_cast<BView*>(*target);
  84                                 if (targetView != NULL)
  85                                         targetView->SetMouseEventMask(B_POINTER_EVENTS);
  86
  87                                 message->FindPoint("where", &fClickPoint);
  88                                 BMessage message(fLongMessageWhat);
  89                                 message.AddPoint("where", fClickPoint);
  90                                 message.AddInt32("buttons", fClickButtons);
  91
  92                                 delete fMessageRunner;
  93                                 fMessageRunner = new (std::nothrow) BMessageRunner(
  94                                         BMessenger(*target), &message, fDurationThreshold, 1);
  95                         }
  96                         return B_DISPATCH_MESSAGE;
  97
  98                 case B_MOUSE_UP:
  99                         _StopTracking();
 100                         message->AddInt32("last_buttons", (int32)fClickButtons);
 101                         return B_DISPATCH_MESSAGE;
 102
 103                 case B_MOUSE_MOVED:
 104                 {
 105                         if (fMessageRunner != NULL) {
 106                                 BPoint where;
 107                                 message->FindPoint("be:view_where", &where);
 108
 109                                 BPoint delta(fClickPoint - where);
 110                                 float squaredDelta = (delta.x * delta.x) + (delta.y * delta.y);
 111
 112                                 if (squaredDelta >= fSquaredRadiusThreshold) {
 113                                         BMessage dragMessage(fDragMessageWhat);
 114                                         dragMessage.AddPoint("be:view_where", fClickPoint);
 115                                                 // name it "be:view_where" since BView::DragMessage
 116                                                 // positions the dragging frame/bitmap by retrieving
 117                                                 // the current message and reading that field
 118                                         dragMessage.AddInt32("buttons", (int32)fClickButtons);
 119                                         BMessenger messenger(*target);
 120                                         messenger.SendMessage(&dragMessage);
 121
 122                                         _StopTracking();
 123                                 }
 124                         }
 125                         return B_DISPATCH_MESSAGE;
 126                 }
 127
 128                 default:
 129                         if (message->what == fLongMessageWhat) {
 130                                 _StopTracking();
 131                                 return B_DISPATCH_MESSAGE;
 132                         }
 133                         break;
 134         }
 135
 136         return B_DISPATCH_MESSAGE;
 137 }