chromium/third_party/blink/renderer/core/css/try_tactic_transform.h

// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_CSS_TRY_TACTIC_TRANSFORM_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_CSS_TRY_TACTIC_TRANSFORM_H_

#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/style/position_try_fallbacks.h"
#include "third_party/blink/renderer/platform/text/writing_direction_mode.h"
#include "third_party/blink/renderer/platform/text/writing_mode_utils.h"

namespace blink {

// Represents a transform via <try-tactic>.
//
// Considering an element at some initial position (0), there are only seven
// different possible transformations represented by <try-tactic> flips:
//
//
//        4             5
//
//     ┌───────────────────┐
//     │.                  │
//  0  │  .                │  2
//     │    .              │
//     │      .            │
//     │        .          │
//     │          .        │
//     │            .      │
//     │              .    │
//  1  │                .  │  3
//     │                  .│
//     └───────────────────┘
//
//        6             7
//
//
// Note that the dotted line represents the start-start to end-end diagonal
// that we mirror across for flip-start.
//
// In many cases, there are multiple ways to compose flips together to reach
// a certain point. For example, first flipping block, then flipping inline
// both end up at (3). A less obvious example is block-start-inline being
// equivalent to just start (4).
//
// Although the specified order of flips within the <try-tactic> matters, any
// tactic can be converted to another corresponding tactic with a *fixed* order.
// This class represents the "canonical" tactic, with the following fixed
// flipping order: block, inline, then start.
//
// The following table shows the canonical tactics (N) vs. the diagram above,
// and also shows how non-canonical are transformed into canonical ones (=>N)).
//
// block                  (1)
// inline                 (2)
// block inline           (3)
// start                  (4)
// block start            (5)
// inline start           (6)
// block inline start     (7)
//
// inline block           (=>3)
// block start inline     (=>4)
// inline start block     (=>4)
// start inline           (=>5)
// start block            (=>6)
// inline block start     (=>7)
// start block inline     (=>7)
// start inline block     (=>7)
//
class CORE_EXPORT TryTacticTransform { … };

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_CSS_TRY_TACTIC_TRANSFORM_H_