Getting area (region.view2d) pixel coordinates of 2D views (VSE, NLA)

Question

I am looking to overlay a sound vis, using bgl, over strips in the NLA, VSE, like

How can I find the area.region.view2d x,y, width and height of strips in the NLA and VSE editors using python?

Answer 1

Yes, this can be done, using the API call View2D.view_to_region.

Heres a "hello world" example, drawing Hello World under the active strip.

import bpy
import bgl
import blf


def draw_callback_px(self, context):
    print("mouse points", len(self.mouse_path))

    region = context.region
    strip = context.scene.sequence_editor.active_strip
    if strip is None:
        return

    x = strip.frame_final_start
    y = strip.channel
    x, y = region.view2d.view_to_region(x, y)

    font_id = 0  # XXX, need to find out how best to get this.

    # draw some text
    blf.position(font_id, x, y, 0)
    blf.size(font_id, 20, 72)
    blf.draw(font_id, "Hello Word " + str(len(self.mouse_path)))


class ModalDrawOperator(bpy.types.Operator):
    """Draw a line with the mouse"""
    bl_idname = "sequencer.modal_operator"
    bl_label = "Simple Modal Sequencer Operator"

    def modal(self, context, event):
        context.area.tag_redraw()
        region = context.region

        if event.type == 'MOUSEMOVE':
            self.mouse_path.append((event.mouse_region_x, event.mouse_region_y))

        elif event.type == 'LEFTMOUSE':
            bpy.types.SpaceSequenceEditor.draw_handler_remove(self._handle, 'WINDOW')
            return {'FINISHED'}

        elif event.type in {'RIGHTMOUSE', 'ESC'}:
            bpy.types.SpaceSequenceEditor.draw_handler_remove(self._handle, 'WINDOW')
            return {'CANCELLED'}

        return {'RUNNING_MODAL'}

    def invoke(self, context, event):
        if context.area.type == 'SEQUENCE_EDITOR':
            # the arguments we pass the the callback
            args = (self, context)
            # Add the region OpenGL drawing callback
            # draw in view space with 'POST_VIEW' and 'PRE_VIEW'
            self._handle = bpy.types.SpaceSequenceEditor.draw_handler_add(draw_callback_px, args, 'WINDOW', 'POST_PIXEL')

            self.mouse_path = []

            context.window_manager.modal_handler_add(self)
            return {'RUNNING_MODAL'}
        else:
            self.report({'WARNING'}, "SequenceEditor not found, cannot run operator")
            return {'CANCELLED'}


def register():
    bpy.utils.register_class(ModalDrawOperator)


def unregister():
    bpy.utils.unregister_class(ModalDrawOperator)

if __name__ == "__main__":
    register()

Note that this is the template operator_modal_draw.py with minor edits.

The draw_callback_px can be added without having to be connected to a modal operator, if you want this to display continuously.

Also see: https://github.com/armadillica/attract-blender-addon/blob/master/draw.py for example use cases.