### Method

# Gtk Snapshot push_gl_shader

#### Declaration [src]

    void
    gtk_snapshot_push_gl_shader (
      GtkSnapshot* snapshot,
      GskGLShader* shader,
      const graphene_rect_t* bounds,
      GBytes* take_args
    )

#### Description [src]

Push a `GskGLShaderNode`.

The node uses the given `GskGLShader` and uniform values Additionally this takes a list of `n_children` other nodes which will be passed to the `GskGLShaderNode`.

The `take_args` argument is a block of data to use for uniform arguments, as per types and offsets defined by the `shader`. Normally this is generated by `gsk_gl_shader_format_args()` or `GskShaderArgsBuilder`.

The snapshotter takes ownership of `take_args`, so the caller should not free it after this.

If the renderer doesn’t support GL shaders, or if there is any problem when compiling the shader, then the node will draw pink. You should use `gsk_gl_shader_compile()` to ensure the `shader` will work for the renderer before using it.

If the shader requires textures (see `gsk_gl_shader_get_n_textures()`), then it is expected that you call `gtk_snapshot_gl_shader_pop_texture()` the number of times that are required. Each of these calls will generate a node that is added as a child to the `GskGLShaderNode`, which in turn will render these offscreen and pass as a texture to the shader.

Once all textures (if any) are pop:ed, you must call the regular `gtk_snapshot_pop()`.

If you want to use pre-existing textures as input to the shader rather than rendering new ones, use `gtk_snapshot_append_texture()` to push a texture node. These will be used directly rather than being re-rendered.

For details on how to write shaders, see `GskGLShader`.

#### Parameters

`shader`

  Type: `GskGLShader`

  The code to run.

  The data is owned by the caller of the method.

`bounds`

  Type: `graphene_rect_t`

  The rectangle to render into.

  The data is owned by the caller of the method.

`take_args`

  Type: `GBytes`

  Data block with arguments for the shader.

  The instance takes ownership of the data, and is responsible for freeing it.