// 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.

// This file contains the definition of SurfaceRelation and its properties.

library fuchsia.modular;

// Describes the relationship between two Surfaces.
// Provides information to the StoryShell for layout optimization.
struct SurfaceRelation {
    // Advice on arranging these surfaces on the screen together.
    SurfaceArrangement arrangement = NONE;

    // Advice for dismissal of surfaces to be linked.
    SurfaceDependency dependency = NONE;

    // Relative emphasis of the child surface, relative to the parent.
    // Influences relative areas of surfaces on screen.
    float32 emphasis = 1.0;
};

// Expresses arrangement type.
enum SurfaceArrangement {
    // No arrangement specified.
    NONE = 0;

    // Desire to present simultaneously.
    COPRESENT = 1;

    // The parent prefers to not be presented simultaneously with its child.
    // (The child may still become part of a simultaneous presentation depending
    // on the relationships between it and subsequently added surfaces).
    SEQUENTIAL = 2;

    // Place this surface on top of and obscuring the parent surface. This is a
    // complete replacement, not a modal or inset presentation.
    ONTOP = 3;
};

// Links surface dismissal.
enum SurfaceDependency {
    // No dependency specified.
    NONE = 0;

    // Child is dependent on parent.
    // If parent is dismissed, child is dismissed as well.
    DEPENDENT = 1;
};