gp_toolbox/handler_draw_cam.py

import bpy
import gpu
import bgl
# import blf
from gpu_extras.batch import batch_for_shader
from bpy_extras.view3d_utils import location_3d_to_region_2d

from bpy.app.handlers import persistent

def view3d_camera_border(context, cam):
    ## based on https://blender.stackexchange.com/questions/6377/coordinates-of-corners-of-camera-view-border
    # cam = context.scene.camera
    frame = cam.data.view_frame(scene=context.scene)
    # to world-space 
    frame = [cam.matrix_world @ v for v in frame]
    # to pixelspace
    region, rv3d = context.region, context.space_data.region_3d
    frame_px = [location_3d_to_region_2d(region, rv3d, v) for v in frame]
    return frame_px

def draw_cam_frame_callback(self, context):
    if context.region_data.view_perspective != 'CAMERA':
        return
    if context.scene.camera.name != 'draw_cam':
        return
    
    main_cam = context.scene.camera.parent
    if not main_cam:
        return
    # if context.area != self._draw_area:
    #     return
    
    # green -> (0.06, 0.4, 0.040, 0.6)
    # orange -> (0.45, 0.18, 0.03, 1.0)
    osd_color = (0.06, 0.4, 0.040, 0.4)
    
    frame_point = view3d_camera_border(context, main_cam)
    self.shader_2d = gpu.shader.from_builtin('2D_UNIFORM_COLOR')
    self.screen_framing = batch_for_shader(
    self.shader_2d, 'LINE_LOOP', {"pos": frame_point})

    bgl.glLineWidth(1)
    self.shader_2d.bind()
    self.shader_2d.uniform_float("color", osd_color)
    self.screen_framing.draw(self.shader_2d)
    
    # Reset
    # bgl.glLineWidth(1)

    # # Display Text
    # if self.use_osd_text:
    #     font_id = 0
    #     dpi = context.preferences.system.dpi
    #     # Display current frame text
    #     blf.color(font_id, *osd_color) # unpack color in argument
    #     blf.position(font_id, context.region.width/3, 15, 0) # context.region.height-
    #     blf.size(font_id, 16, dpi)
    #     blf.draw(font_id, f'Draw cam')


## As a modal for tests
class GPTB_OT_cam_frame_draw(bpy.types.Operator):
    bl_idname = "gp.draw_cam_frame"
    bl_label = "Draw Cam Frame"
    bl_description = "Draw the camera frame using a modal"
    bl_options = {"REGISTER"} # , "INTERNAL"

    # @classmethod
    # def poll(cls, context):
    #     return True

    def invoke(self, context, event):
        ## screen color frame
        # r = bpy.context.region
        # w = r.width
        # h = r.height

        # self.shader_2d = gpu.shader.from_builtin('2D_UNIFORM_COLOR')
        # self.screen_framing = batch_for_shader(
        # self.shader_2d, 'LINE_LOOP', {"pos": [(0,0), (0,h), (w,h), (w,0)]})
        
        ## OpenGL handler
        self._draw_area = context.area
        args = (self, context)
        self._handle = bpy.types.SpaceView3D.draw_handler_add(
            draw_cam_frame_callback, args, "WINDOW", "POST_PIXEL")

        context.window_manager.modal_handler_add(self)
        return {'RUNNING_MODAL'}
    

    def exit(self, context):
        bpy.types.SpaceView3D.draw_handler_remove(self._handle, 'WINDOW')
        context.area.tag_redraw()

    def modal(self, context, event):
        if event.type in {'ESC'}:
            self.exit(context)
            return {"CANCELLED"}
        return {'PASS_THROUGH'}
        # return {'RUNNING_MODAL'}


class DrawClass:
    def __init__(self, context):
        # print("INIT")
        self._handle = bpy.types.SpaceView3D.draw_handler_add(
            draw_cam_frame_callback, args, "WINDOW", "POST_PIXEL")

    def remove_handle(self):
        bpy.types.SpaceView3D.draw_handler_remove(self._handle, 'WINDOW')


### --- REGISTER ---

def register():
    if not bpy.app.background:
        bpy.utils.register_class(GPTB_OT_cam_frame_draw)
        
        # ha = DrawClass()

        # _handle = bpy.types.SpaceView3D.draw_handler_add(
        #     draw_cam_frame_callback, args, "WINDOW", "POST_PIXEL")

def unregister():
    if not bpy.app.background:
        bpy.utils.unregister_class(GPTB_OT_cam_frame_draw)
        
        # ha.remove_handle()

        # bpy.types.SpaceView3D.draw_handler_remove(_handle, 'WINDOW')


        # if 'draw_cam_frame_callback' in [hand.__name__ for hand in bpy.app.handlers.save_pre]:
        # bpy.app.handlers.save_pre.remove(remap_relative)


if __name__ == "__main__":
    register()