text: # ##### BEGIN GPL LICENSE BLOCK #####
  #
  #  This program is free software; you can redistribute it and/or
  #  modify it under the terms of the GNU General Public License
  #  as published by the Free Software Foundation; either version 2
  #  of the License, or (at your option) any later version.
  #
  #  This program is distributed in the hope that it will be useful,
  #  but WITHOUT ANY WARRANTY; without even the implied warranty of
  #  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  #  GNU General Public License for more details.
  #
  #  You should have received a copy of the GNU General Public License
  #  along with this program; if not, write to the Free Software Foundation,
  #  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  #
  # ##### END GPL LICENSE BLOCK #####
  
  # <pep8 compliant>
  import bpy
  from bpy.types import Menu, Panel, UIList
  from rna_prop_ui import PropertyPanel
  from bl_ui.utils import PresetPanel
  
  from bl_ui.properties_grease_pencil_common import (
      GreasePencilMaterialsPanel,
  )
  
  
  class GPENCIL_MT_color_context_menu(Menu):
      bl_label = "Material Specials"
  
      def draw(self, _context):
          layout = self.layout
  
          layout.operator("gpencil.color_reveal", icon='RESTRICT_VIEW_OFF', text="Show All")
          layout.operator("gpencil.color_hide", icon='RESTRICT_VIEW_ON', text="Hide Others").unselected = True
  
          layout.separator()
  
          layout.operator("gpencil.color_lock_all", icon='LOCKED', text="Lock All")
          layout.operator("gpencil.color_unlock_all", icon='UNLOCKED', text="UnLock All")
  
          layout.operator("gpencil.stroke_lock_color", text="Lock Unselected")
          layout.operator("gpencil.lock_layer", text="Lock Unused")
  
          layout.separator()
  
          layout.operator("object.material_slot_remove_unused")
          layout.operator("gpencil.stroke_merge_material", text="Merge Similar")
  
          layout.separator()
          layout.operator("gpencil.material_to_vertex_color", text="Convert Materials to Vertex Color")
          layout.operator("gpencil.extract_palette_vertex", text="Extract Palette from Vertex Color")
  
  
  class GPENCIL_UL_matslots(UIList):
      def draw_item(self, _context, layout, _data, item, icon, _active_data, _active_propname, _index):
          slot = item
          ma = slot.material
          if (ma is not None) and (ma.grease_pencil is not None):
              gpcolor = ma.grease_pencil
  
              if self.layout_type in {'DEFAULT', 'COMPACT'}:
                  if gpcolor.lock:
                      layout.active = False
  
                  row = layout.row(align=True)
                  row.enabled = not gpcolor.lock
                  row.prop(ma, "name", text="", emboss=False, icon_value=icon)
  
                  row = layout.row(align=True)
                  if gpcolor.ghost is True:
                      icon = 'ONIONSKIN_OFF'
                  else:
                      icon = 'ONIONSKIN_ON'
                  row.prop(gpcolor, "ghost", text="", icon=icon, emboss=False)
                  row.prop(gpcolor, "hide", text="", emboss=False)
                  row.prop(gpcolor, "lock", text="", emboss=False)
  
              elif self.layout_type == 'GRID':
                  layout.alignment = 'CENTER'
                  layout.label(text="", icon_value=icon)
  
  
  class GPMaterialButtonsPanel:
      bl_space_type = 'PROPERTIES'
      bl_region_type = 'WINDOW'
      bl_context = "material"
  
      @classmethod
      def poll(cls, context):
          ma = context.material
          return ma and ma.grease_pencil
  
  
  class MATERIAL_PT_gpencil_slots(GreasePencilMaterialsPanel, Panel):
      bl_label = "Grease Pencil Material Slots"
      bl_space_type = 'PROPERTIES'
      bl_region_type = 'WINDOW'
      bl_context = "material"
      bl_options = {'HIDE_HEADER'}
  
      @classmethod
      def poll(cls, context):
          ob = context.object
          ma = context.material
  
          return (ma and ma.grease_pencil) or (ob and ob.type == 'GPENCIL')
  
  
  # Used as parent for "Stroke" and "Fill" panels
  class MATERIAL_PT_gpencil_surface(GPMaterialButtonsPanel, Panel):
      bl_label = "Surface"
  
      def draw_header_preset(self, _context):
          MATERIAL_PT_gpencil_material_presets.draw_panel_header(self.layout)
  
      def draw(self, _context):
          layout = self.layout
          layout.use_property_split = True
  
  
  class MATERIAL_PT_gpencil_strokecolor(GPMaterialButtonsPanel, Panel):
      bl_label = "Stroke"
      bl_parent_id = 'MATERIAL_PT_gpencil_surface'
  
      def draw_header(self, context):
          ma = context.material
          if ma is not None and ma.grease_pencil is not None:
              gpcolor = ma.grease_pencil
              self.layout.enabled = not gpcolor.lock
              self.layout.prop(gpcolor, "show_stroke", text="")
  
      def draw(self, context):
          layout = self.layout
          layout.use_property_split = True
  
          ma = context.material
          if ma is not None and ma.grease_pencil is not None:
              gpcolor = ma.grease_pencil
  
              col = layout.column()
              col.enabled = not gpcolor.lock
  
              col.prop(gpcolor, "mode")
  
              col.prop(gpcolor, "stroke_style", text="Style")
  
              row = col.row()
              row.prop(gpcolor, "color", text="Base Color")
  
              if gpcolor.stroke_style == 'TEXTURE':
                  row = col.row()
                  row.enabled = not gpcolor.lock
                  col = row.column(align=True)
                  col.template_ID(gpcolor, "stroke_image", open="image.open")
  
              if gpcolor.stroke_style == 'TEXTURE':
                  row = col.row()
                  row.prop(gpcolor, "mix_stroke_factor", text="Blend", slider=True)
                  if gpcolor.mode == 'LINE':
                      col.prop(gpcolor, "pixel_size", text="UV Factor")
  
              if gpcolor.mode in {'DOTS', 'BOX'}:
                  col.prop(gpcolor, "alignment_mode")
  
              if gpcolor.mode == 'LINE':
                  col.prop(gpcolor, "use_overlap_strokes")
  
  
  class MATERIAL_PT_gpencil_fillcolor(GPMaterialButtonsPanel, Panel):
      bl_label = "Fill"
      bl_parent_id = 'MATERIAL_PT_gpencil_surface'
  
      def draw_header(self, context):
          ma = context.material
          gpcolor = ma.grease_pencil
          self.layout.enabled = not gpcolor.lock
          self.layout.prop(gpcolor, "show_fill", text="")
  
      def draw(self, context):
          layout = self.layout
          layout.use_property_split = True
  
          ma = context.material
          gpcolor = ma.grease_pencil
  
          # color settings
          col = layout.column()
          col.enabled = not gpcolor.lock
          col.prop(gpcolor, "fill_style", text="Style")
  
  
          if gpcolor.fill_style == 'SOLID':
              col.prop(gpcolor, "fill_color", text="Base Color")
  
          elif gpcolor.fill_style == 'GRADIENT':
              col.prop(gpcolor, "gradient_type")
  
              col.prop(gpcolor, "fill_color", text="Base Color")
              col.prop(gpcolor, "mix_color", text="Secondary Color")
              col.prop(gpcolor, "mix_factor", text="Blend in Fill Gradient", slider=True)
              col.prop(gpcolor, "flip", text="Flip Colors")
  
              col.prop(gpcolor, "texture_offset", text="Location")
              col.prop(gpcolor, "texture_scale", text="Scale")
              if gpcolor.gradient_type == 'LINEAR':
                  col.prop(gpcolor, "texture_angle", text="Rotation")
  
          elif gpcolor.fill_style == 'TEXTURE':
              col.template_ID(gpcolor, "fill_image", open="image.open")
  
              col.prop(gpcolor, "fill_color", text="Base Color")
              col.prop(gpcolor, "texture_opacity", slider=True)
              col.prop(gpcolor, "mix_factor", text="Blend in Fill Texture", slider=True)
  
              col.prop(gpcolor, "texture_offset", text="Location")
              col.prop(gpcolor, "texture_angle", text="Rotation")
              col.prop(gpcolor, "texture_scale", text="Scale")
              col.prop(gpcolor, "texture_clamp", text="Clip Image")
  
  
  class MATERIAL_PT_gpencil_preview(GPMaterialButtonsPanel, Panel):
      bl_label = "Preview"
      COMPAT_ENGINES = {'BLENDER_EEVEE'}
      bl_options = {'DEFAULT_CLOSED'}
  
      def draw(self, context):
          ma = context.material
          self.layout.label(text=ma.name)
          self.layout.template_preview(ma)
  
  
  class MATERIAL_PT_gpencil_custom_props(GPMaterialButtonsPanel, PropertyPanel, Panel):
      COMPAT_ENGINES = {'BLENDER_EEVEE', 'BLENDER_WORKBENCH'}
      _context_path = "object.active_material"
      _property_type = bpy.types.Material
  
  
  class MATERIAL_PT_gpencil_options(GPMaterialButtonsPanel, Panel):
      bl_label = "Options"
      bl_options = {'DEFAULT_CLOSED'}
  
      def draw(self, context):
          layout = self.layout
          layout.use_property_split = True
  
          ma = context.material
          gpcolor = ma.grease_pencil
          layout.prop(gpcolor, "pass_index")
  
  
  class MATERIAL_PT_gpencil_material_presets(PresetPanel, Panel):
      """Material settings"""
      bl_label = "Material Presets"
      preset_subdir = "gpencil_material"
      preset_operator = "script.execute_preset"
      preset_add_operator = "scene.gpencil_material_preset_add"
  
  
  classes = (
      GPENCIL_UL_matslots,
      GPENCIL_MT_color_context_menu,
      MATERIAL_PT_gpencil_slots,
      MATERIAL_PT_gpencil_preview,
      MATERIAL_PT_gpencil_material_presets,
      MATERIAL_PT_gpencil_surface,
      MATERIAL_PT_gpencil_strokecolor,
      MATERIAL_PT_gpencil_fillcolor,
      MATERIAL_PT_gpencil_options,
      MATERIAL_PT_gpencil_custom_props,
  )
  
  if __name__ == "__main__":  # only for live edit.
      from bpy.utils import register_class
  
      for cls in classes:
          register_class(cls)
  