Carla/source/modules/juce_gui_basics/mouse/juce_ComponentDragger.cpp

/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2015 - ROLI Ltd.

   Permission is granted to use this software under the terms of either:
   a) the GPL v2 (or any later version)
   b) the Affero GPL v3

   Details of these licenses can be found at: www.gnu.org/licenses

   JUCE is distributed in the hope that it will be useful, but WITHOUT ANY
   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

   ------------------------------------------------------------------------------

   To release a closed-source product which uses JUCE, commercial licenses are
   available: visit www.juce.com for more information.

  ==============================================================================
*/

ComponentDragger::ComponentDragger() {}
ComponentDragger::~ComponentDragger() {}

//==============================================================================
void ComponentDragger::startDraggingComponent (Component* const componentToDrag, const MouseEvent& e)
{
    jassert (componentToDrag != nullptr);
    jassert (e.mods.isAnyMouseButtonDown()); // The event has to be a drag event!

    if (componentToDrag != nullptr)
        mouseDownWithinTarget = e.getEventRelativeTo (componentToDrag).getMouseDownPosition();
}

void ComponentDragger::dragComponent (Component* const componentToDrag, const MouseEvent& e,
                                      ComponentBoundsConstrainer* const constrainer)
{
    jassert (componentToDrag != nullptr);
    jassert (e.mods.isAnyMouseButtonDown()); // The event has to be a drag event!

    if (componentToDrag != nullptr)
    {
        Rectangle<int> bounds (componentToDrag->getBounds());

        // If the component is a window, multiple mouse events can get queued while it's in the same position,
        // so their coordinates become wrong after the first one moves the window, so in that case, we'll use
        // the current mouse position instead of the one that the event contains...
        if (componentToDrag->isOnDesktop())
            bounds += componentToDrag->getLocalPoint (nullptr, e.source.getScreenPosition()).roundToInt() - mouseDownWithinTarget;
        else
            bounds += e.getEventRelativeTo (componentToDrag).getPosition() - mouseDownWithinTarget;

        if (constrainer != nullptr)
            constrainer->setBoundsForComponent (componentToDrag, bounds, false, false, false, false);
        else
            componentToDrag->setBounds (bounds);
    }
}