shape_result_view.h | Explore in Territory

// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/351564777): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif

#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_SHAPING_SHAPE_RESULT_VIEW_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_SHAPING_SHAPE_RESULT_VIEW_H_

#include "base/containers/span.h"
#include "third_party/blink/renderer/platform/fonts/shaping/glyph_data.h"
#include "third_party/blink/renderer/platform/fonts/shaping/shape_result.h"
#include "third_party/blink/renderer/platform/fonts/simple_font_data.h"
#include "third_party/blink/renderer/platform/geometry/layout_unit.h"
#include "third_party/blink/renderer/platform/heap/collection_support/heap_hash_set.h"
#include "third_party/blink/renderer/platform/platform_export.h"
#include "third_party/blink/renderer/platform/text/text_direction.h"
#include "third_party/blink/renderer/platform/wtf/forward.h"
#include "third_party/blink/renderer/platform/wtf/vector.h"

namespace blink {

class ShapeResult;

// Class representing a read-only composite of views into one or more existing
// shape results.
// Implemented as a list of ref counted RunInfo instances and a start/end
// offset for each, represented using the internal RunInfoPart struct.
// This allows lines to be reference sections of the overall paragraph shape
// results without the memory or computational overhead of a copy.
//
// The example below shows the shape result and the individual lines as
// ShapeResultView instances pointing to the original paragraph results for
// the string "Pack my box with five dozen liquor jugs.":
//  ╔═════════════════════════════════════════════════════╗
//  ║ Paragraph with single run, no re-shaping for lines. ║
//  ╟─────────────────────────────────────────────────────╢
//  ║ runs_ ╭───────────────────────────────────────────╮ ║
//  ║   1:  │ Pack my box with five dozen liquor jugs.  │ ║
//  ║       ╰───────────────────────────────────────────╯ ║
//  ║ lines ╭───────────────────────────────────────────╮ ║
//  ║   1:  │ Pack my box with    -> view, run 1:  0-16 │ ║
//  ║   2:  │ five dozen liquor   -> view, run 1: 17-34 │ ║
//  ║   3:  │ jugs.               -> view, run 1: 35-40 │ ║
//  ║       ╰───────────────────────────────────────────╯ ║
//  ╚═════════════════════════════════════════════════════╝
//
// In cases where a portion of the line needs re-shaping the new results are
// added as separate runs at the beginning and/or end of the runs_ vector with a
// reference to zero or more sub-runs in the middle representing the original
// content that could be reused.
//
// In the example below the end of the first line "Jack!" needs to be re-shaped:
//  ╔═════════════════════════════════════════════════════╗
//  ║ Paragraph with single run, requiring re-shape.      ║
//  ╟─────────────────────────────────────────────────────╢
//  ║ runs_ ╭───────────────────────────────────────────╮ ║
//  ║   1:  │ "Now fax quiz Jack!" my brave ghost pled. │ ║
//  ║       ╰───────────────────────────────────────────╯ ║
//  ║ lines ╭───────────────────────────────────────────╮ ║
//  ║   1:  │ "Now fax quiz     -> view, run 1:  0-14   │ ║
//  ║   1:  │ Jack!             -> new result/run       │ ║
//  ║   2:  │ my brave ghost    -> view, run 1: 21-35   │ ║
//  ║   3:  │ pled.             -> view, run 1: 41-36   │ ║
//  ║       ╰───────────────────────────────────────────╯ ║
//  ╚═════════════════════════════════════════════════════╝
//
// In this case the beginning of the first line would be represented as a part
// referencing a range in the original ShapeResult while the last word
// would be a separate result owned by the ShapeResultView instance. The second
// and third lines would again be represented as parts.
class PLATFORM_EXPORT ShapeResultView final
    : public GarbageCollected<ShapeResultView> { … };

}  // namespace blink

WTF_ALLOW_CLEAR_UNUSED_SLOTS_WITH_MEM_FUNCTIONS(…)

#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_SHAPING_SHAPE_RESULT_VIEW_H_
chromium/third_party/blink/renderer/platform/fonts/shaping/shape_result_view.h
