JUCE/modules/juce_gui_basics/mouse/juce_ComponentDragger.cpp

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

   This file is part of the JUCE 6 technical preview.
   Copyright (c) 2020 - Raw Material Software Limited

   You may use this code under the terms of the GPL v3
   (see www.gnu.org/licenses).

   For this technical preview, this file is not subject to commercial licensing.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

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

namespace juce
{

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)
    {
        auto 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);
    }
}

} // namespace juce