GMS2 Drawing Shaders Only Working in DrawGUI

So I am very new to shaders, and I am working with a free shader from the GMS2 marketplace> Anyways, I have run into an issue with this shader that I guess I am just too new at shaders to be knowledgeable about this. The code for the shader is:

shd_mosaic.vsh:

attribute vec3 in_Position;
attribute vec4 in_Colour;
attribute vec2 in_TextureCoord;

varying vec2 v_texcoord;

void main()
{
    gl_Position = gm_Matrices[MATRIX_WORLD_VIEW_PROJECTION] * vec4(in_Position, 1.0);
    v_texcoord = in_TextureCoord;
}

shd_mosaic.fsh:

varying vec2 v_texcoord;

uniform float time;
uniform vec2 mouse_pos;
uniform vec2 resolution;
uniform float pixel_amount;

void main()
{ 
    vec2 res = vec2(1.0, resolution.x/resolution.y);
    vec2 size = vec2(res.x/pixel_amount, res.y/pixel_amount);
    vec2 uv = v_texcoord - mod(v_texcoord,size);
    gl_FragColor = texture2D( gm_BaseTexture, uv );
}

And then I also have my object that manages the shader, obj_controller_mosaic:

create code:

draw_set_color(c_white);

uni_time = shader_get_uniform(shd_mosaic,"time");
var_time_var = 0;

uni_mouse_pos = shader_get_uniform(shd_mosaic,"mouse_pos");
var_mouse_pos_x = mouse_x - camera_get_view_x(view_get_camera(view_current));
var_mouse_pos_y = mouse_y - camera_get_view_y(view_get_camera(view_current));

uni_resolution = shader_get_uniform(shd_mosaic,"resolution");
var_resolution_x = room_width //camera_get_view_width(view_get_camera(view_current));
var_resolution_y = room_height //camera_get_view_height(view_get_camera(view_current));

uni_pixel_amount = shader_get_uniform(shd_mosaic, "pixel_amount");
var_pixel_amount = 700.0;

shader_enabled = true;
full_screen_effect = true;

surf = surface_create(camera_get_view_width(view_get_camera(view_current)), camera_get_view_height(view_get_camera(view_current)));
view_set_surface_id(view_get_camera(view_current), surf);

DrawGUI code:

var_time_var+=0.04;

var_resolution_x = camera_get_view_width(view_get_camera(view_current));
var_resolution_y = camera_get_view_height(view_get_camera(view_current)); 

if shader_enabled shader_set(shd_mosaic);
    shader_set_uniform_f(uni_time, var_time_var);
    shader_set_uniform_f(uni_mouse_pos, var_mouse_pos_x, var_mouse_pos_y);
    shader_set_uniform_f(uni_resolution, var_resolution_x, var_resolution_y);
    shader_set_uniform_f(uni_pixel_amount, var_pixel_amount);
    if full_screen_effect draw_surface(surf, 0, 0);
shader_reset();

Alright, now due to some issues with other objects in the game, I want the DrawGUI code to actually be just in the Draw event. The issue is that when I copy this code over the the Draw event instead, I just get a black screen (when the code is in the DrawGUI event it works fine). Is there something I can do to make this code work in the Draw event instead of DrawGUI? Thanks in advance for your answers!

view_set_surface_id causes the view to be rendered to a surface. As result, it will not be drawn to the screen automatically - you would have to do so yourself, like you do in Draw GUI.

If you direly need to draw the view in a normal draw event, you'll need a second view and filter based on view_current in a Draw event.