// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

library fuchsia.examples.shadertoy;

using fuchsia.images;
using fuchsia.ui.gfx;

// Shadertoy (www.shadertoy.com) is an online community and tool for creating
// and sharing GLSL shaders.  The genius of Shadertoy is that it side-steps the
// need for tedious glue code to bind assets such and meshs to GPU shader code.
// Instead, users simply provide GLSL fragment shader coder, which is bound to
// a predefined set of inputs (see https://www.shadertoy.com/howto).
//
// Shadertoy is also a FIDL interface to a Fuchsia service which provides a host
// environment for GLSL shaders conforming to the specification defined by the
// website (again, see https://www.shadertoy.com/howto), and for binding input
// data to these shaders.
//
// This interface does not concern itself with how to display the images
// rendered by the GLSL code; this is the responsibility of |ShadertoyFactory|,
// which is used to create Shadertoy instances.
protocol Shadertoy {
    // Set whether rendering is paused or not.
    SetPaused(bool paused);

    // Set the GLSL shader code for the Shadertoy.  Return true if compilation was
    // successful and false otherwise.
    // TODO: provide better error reporting when compilation fails.
    SetShaderCode(string glsl) -> (bool successful);

    // Corresponds to Shadertoy's 'iResolution' shader parameter.
    SetResolution(uint32 width, uint32 height);

    // Corresponds to Shadertoy's 'iMouse' shader parameter.  The value is
    // interpreted as follows:
    // i_mouse.xy:
    //   - the position of the last mouse-down event
    // i_mouse.zw
    //   - (when mouse is down) the current position of the mouse
    //   - (when mouse is up) the position of the last mouse-up event
    SetMouse(fuchsia.ui.gfx.vec4 i_mouse);

    // Corresponds to Shadertoy's 'iChannel0..3' parameters.  Currently only 2D
    // samplers are supported (no cubemaps).  |channel| must be one of 0, 1, 2, 3.
    // TODO: implement cubemap support.
    SetImage(uint32 channel, request<fuchsia.images.ImagePipe> image_pipe);
};