Drag and drop from python panel into viewport

[satara]

Hi,

 

I'm currently working on an asset browser implemented as a python panel using PySide.

The main part of it is a QListWidget containing one items per asset. I'm trying to implement drag and drop functionality to place items directly in viewport at drop position.

 

For dragging I'm using the itemPressed signal, which is sent by QListWidget when holding the mouse button over an item. Then I want to check if a drop is allowed on mouseMoveEvent() by traversing all viewports and checking if the mouse cursor is located inside. But can't find a way to check if the mouse cursor is over the viewport. Also I need the exact drop position when releasing the mouse button.

 

I found this related topic http://forums.odforce.net/topic/20382-geometry-point-under-the-mouse/ and tried to adopt the first block to get the drop position in world space. For testing I just created a default Mouse CHOP and called hou.evalParm('/obj/chopnet/mouse") from withi mouseReleaseEvent(), but it always fails (the path is definetely correct) with hou.OperationFailed exception. Also calling hou.GeometryViewport.mapFromMouseChop() always fails for me, even if I just pass (0.0, 0.0).

 

Here is some code:

class AssetListWidget(QtGui.QListWidget):
  def __init__(self, parent=None):
        QtGui.QListWidget.__init__(self, parent)
        # doing some initialization here
        self.itemPressed.connect(self.onItemPressed)

    def onItemPressed(self, item):
        self.draggedItem = item
        # cache sceneviewers
        for paneTab in hou.ui.curDesktop().paneTabs():
            if paneTab.type() == hou.paneTabType.SceneViewer:
                self.sceneViewers.append(paneTab)
   
    def mouseMoveEvent(self, ev):
        allowDrag = False
        for sceneViewer in self.sceneViewers:
            for viewport in sceneViewer.viewports():
                try:
                    mx, my = hou.evalParmTuple("/obj/chopnet/mouse") # always fails
                    vx, vy = v.mapFromMouseChop(mx, my) # screen to view
                    direction, position =v.mapToWorld(vx,vy) # view to world 
                except hou.OperationFailed as err:
                    print err
                """
                try:
                    print viewport.mapFromMouseChop(0.0, 0.0) # always fails
                except hou.OperationFailed as err:
                    print err
                """
                
    def mouseReleaseEvent(self, ev):
        # will be similiar to above
        QtGui.QListWidget.mouseReleaseEvent(self, ev)

What am I doing wrong? How do I have to set up the Mouse CHOP properly? Does someone have a better advice for implementing this feature (if it is even possible using hom)?

 

Thanks for any help!

 

Best,

Satara

 

 

 

 

[Stalkerx777]

You could use this, for example:

    def mouseReleaseEvent(self, event):
        sc = toolutils.sceneViewer()
        try:
            res = sc.selectPositions()
            origin = res[0]
        except hou.OperationInterrupted:
            return

        n = hou.node('/obj').createNode('null')
        n.parmTuple('t').set(origin)

[satara]

Thanks Alexey, that's perfect for my case. Do you also have any idea, how to check if the cursor is inside the sceneviewer to adjust the mouse cursor inside mouseMoveEvent()?

[Stalkerx777]

Thanks Alexey, that's perfect for my case. Do you also have any idea, how to check if the cursor is inside the sceneviewer to adjust the mouse cursor inside mouseMoveEvent()?

 

You can get viewport QWidget like this:

QApplication.instance().widgetAt(QCursor.pos())

This will give you a widget under the cursor, BUT, i don't know how to check if this QWidget is actually a houdini viewport  

[satara]

Thanks again Alexey. Tried to get any useful information from the widgets to determine if it's the viewport, but wasn't succesfull. Will let you know if I find a solution.

[Guest mantragora]

... how to check if this QWidget is actually a houdini viewport

Maybe you could check if it's a window. I think that OpenGL will be a child of a window, not a window by itself.

EDIT: So in QT words, you can check if QWidget have any children. Viewport shouldn't contain any QWidget children since it's not a part of QT, so it should return only blank list. It can have only parent.

 

from PySide import QtGui as qtg 

widget = qtg.QApplication.instance().widgetAt(qtg.QCursor().pos())
print(len(widget.children()))

Edited April 23, 2015 by mantragora

[satara]

Hey thanks, it's a bit hacky but seems to work for most of the cases. Only the timeline and my own QListWidget failed in the test (also have zero children). I also added a check for the objectName() to filter my own widget. I think it will be sufficient for now, but improvements would be very welcome!

def mouseMoveEvent(self, ev):
    allowDrop = False
    widget = QtGui.QApplication.instance().widgetAt(ev.globalX(), ev.globalY())
    if widget:
        if widget.objectName() == 're_QGLWidget':
            if len(widget.children()) == 0:
                allowDrop = True

Edited April 23, 2015 by satara