import hou

class TestTemplate(object):
    def __init__(self, scene_viewer, state_name):
        self.scene_viewer = scene_viewer
        self.state_name = state_name

    def onGenerate(self, kwargs):
        self.scene_viewer.setPromptMessage('Hello World!')
        self._drag_started = False

    def onMouseEvent(self, kwargs):
        event = kwargs["ui_event"]
        reason = event.reason()

        # MOUSE MOVE
        if reason == hou.uiEventReason.Active and self._drag_started:
            print 'mouse drag'

        # MOUSE PRESS
        elif reason == hou.uiEventReason.Start:
            print 'mouse press'
            self._drag_started = True

        # MOUSE CLICK
        elif reason == hou.uiEventReason.Picked:
            print 'click'

        # MOUSE RELEASE
        elif reason == hou.uiEventReason.Changed and self._drag_started:
            print 'mouse release'
            self._drag_started = False


template = hou.ViewerStateTemplate('test_state', 'Test State', hou.sopNodeTypeCategory())
template.bindFactory(TestTemplate)

hou.ui.registerViewerState(template)