import gpu
from gpu_extras.batch import batch_for_shader

import bpy
from bpy.types import Gizmo, GizmoGroup

class MyCustomShapeWidget(Gizmo):
    bl_idname = "VIEW3D_GT_custom_shape_widget"
    bl_target_properties = ()
    
    def draw(self, context):
        skew = 100.0
        x0 = 100.0
        y0 = 100.0
        x1 = 500.0
        y1 = 500.0
        z = 0.0
        color = (0.0, 0.0, 0.0, 0.9)
        verts = [(x0, y0, z), (x0+skew, y1, z), (x1, y1, z), (x1-skew, y0, z)]
        colors = [color, color, color, color]
        indices = [(0, 1, 2), (0, 2, 3)]
        content = {"pos":verts, "color":colors}
        
        gpu.state.blend_set('ALPHA')
        
        shader = gpu.shader.from_builtin('SMOOTH_COLOR')
        batch = batch_for_shader(shader, 'TRIS', content, indices=indices)
        batch.draw(shader)
        
        gpu.state.blend_set('NONE')

class MyCustomShapeWidgetGroup(GizmoGroup):
    bl_idname = "OBJECT_GGT_light_test"
    bl_label = "Test Light Widget"
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'WINDOW'
    
    # If bl_options has '3D' (like in the "Gizmo Custom Geometry" template),
    # there seem to be no gaps between triangles, even though they are
    # antialiased. If it's absent, there are gaps.
    #bl_options = {'3D', 'PERSISTENT'}
    bl_options = {'PERSISTENT'}

    def setup(self, context):
        gizmo = self.gizmos.new(MyCustomShapeWidget.bl_idname)
        gizmo.use_draw_modal = True

bpy.utils.register_class(MyCustomShapeWidget)
bpy.utils.register_class(MyCustomShapeWidgetGroup)