描述

With this function you can assign a script to a layer and it will be called before the layer is rendered. When adding a script to a layer, in this way it will be run at the start of each of the different draw events so you may want to check in the script assigned which event is currently rendering and adapt the code to suit. This can be done by checking the event_type and/or the event_number (see the extended example below). Note that the function is not meant to be called in any draw events or step events, but rather only needs to be called at the start of the room in the Room Creation Code or in the Create Event/Room Start Event of an instance.

语法：

layer_script_begin

参数	描述
layer_id	The unique ID value of the layer to target (or the layer name as a string)
script	The script index to assign to the layer

返回：

N/A（无返回值）

Extended 举例：

In this extended example, we will first show you how a simple script is structured to set some shader uniform data so that when the given layer is drawn, this script will be run and the shader will work correctly. In the example, it is worth noting how we check which event is being called so that the rest of the script is only run on the specific event that we require it to work on - in this case, only on the main draw event:

/// scr_LayerShader_Start();
if event_type == ev_draw
   {
   if event_number == 0
      {
      colour_to_find = shader_get_uniform(sShaderDemo5, "f_Colour1");
      colour_to_set = shader_get_uniform(sShaderDemo5, "f_Colour2");
      shader_set(s_ColourChanger);
      shader_set_uniform_f(colour_to_find, 1,1,1 );
      shader_set_uniform_f(colour_to_set, 1,0,0 );
      }
   }

We would then have a companion script to reset the shader after all the drawing is done:

/// scr_LayerShader_End();
if event_type == ev_draw
   {
   if event_number == 0
      {
      shader_reset();
      }
   }

Now that we have defined our scripts for setting the shader, we then have to assign them to a specific layer so that the layer knows to call them. This would be done in the room creation code, or in the create event or room start event of some controller object (they do not need to be set every step, but rather once at the start of the room, or when the layer is initially created):

var lay_id = layer_get_id("Instances");
layer_script_begin(lay_id, scr_LayerShader_Start);
layer_script_end(lay_id, scr_LayerShader_End);

This final code block assigns the scripts to the layer.