// 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.
type SurfaceRelation = struct {
    /// Advice on arranging these surfaces on the screen together.
    @allow_deprecated_struct_defaults
    arrangement SurfaceArrangement = SurfaceArrangement.NONE;

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

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

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

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