Extract textrange

shell/platform/common/cpp/BUILD.gn

@@ -37,14 +37,19 @@ copy("publish_headers") {
 }
 
 source_set("common_cpp_input") {
-  public = [ "text_input_model.h" ]
+  public = [
+    "text_input_model.h",
+    "text_range.h",
+  ]
 
   sources = [ "text_input_model.cc" ]
 
   configs += [ ":desktop_library_implementation" ]
 
   public_configs = [ "//flutter:config" ]
 
+  deps = [ "//flutter/fml:fml" ]
+
   if (is_win) {
     # For wstring_conversion. See issue #50053.
     defines = [ "_SILENCE_CXX17_CODECVT_HEADER_DEPRECATION_WARNING" ]
@@ -137,6 +142,7 @@ if (enable_unittests) {
       "json_message_codec_unittests.cc",
       "json_method_codec_unittests.cc",
       "text_input_model_unittests.cc",
+      "text_range_unittests.cc",
     ]
 
     deps = [

shell/platform/common/cpp/text_input_model.cc

@@ -38,27 +38,24 @@ void TextInputModel::SetText(const std::string& text) {
   std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>
       utf16_converter;
   text_ = utf16_converter.from_bytes(text);
-  selection_base_ = 0;
-  selection_extent_ = 0;
+  selection_ = TextRange(0);
 }
 
 bool TextInputModel::SetSelection(size_t base, size_t extent) {
-  auto max_pos = text_.length();
+  size_t max_pos = text_.length();
   if (base > max_pos || extent > max_pos) {
     return false;
   }
-  selection_base_ = base;
-  selection_extent_ = extent;
+  selection_ = TextRange(base, extent);
   return true;
 }
 
 bool TextInputModel::DeleteSelected() {
-  if (selection_base_ == selection_extent_) {
+  if (selection_.collapsed()) {
     return false;
   }
-  text_.erase(selection_start(), selection_end() - selection_start());
-  selection_base_ = selection_start();
-  selection_extent_ = selection_base_;
+  text_.erase(selection_.start(), selection_.length());
+  selection_ = TextRange(selection_.start());
   return true;
 }
 
@@ -78,9 +75,9 @@ void TextInputModel::AddCodePoint(char32_t c) {
 
 void TextInputModel::AddText(const std::u16string& text) {
   DeleteSelected();
-  text_.insert(selection_extent_, text);
-  selection_extent_ += text.length();
-  selection_base_ = selection_extent_;
+  size_t position = selection_.position();
+  text_.insert(position, text);
+  selection_ = TextRange(position + text.length());
 }
 
 void TextInputModel::AddText(const std::string& text) {
@@ -90,38 +87,36 @@ void TextInputModel::AddText(const std::string& text) {
 }
 
 bool TextInputModel::Backspace() {
-  // If there's a selection, delete it.
   if (DeleteSelected()) {
     return true;
   }
-  // There's no selection; delete the preceding codepoint.
-  if (selection_base_ != 0) {
-    int count = IsTrailingSurrogate(text_.at(selection_base_ - 1)) ? 2 : 1;
-    text_.erase(selection_base_ - count, count);
-    selection_base_ -= count;
-    selection_extent_ = selection_base_;
+  // If there's no selection, delete the preceding codepoint.
+  size_t position = selection_.position();
+  if (position != 0) {
+    int count = IsTrailingSurrogate(text_.at(position - 1)) ? 2 : 1;
+    text_.erase(position - count, count);
+    selection_ = TextRange(position - count);
     return true;
   }
   return false;
 }
 
 bool TextInputModel::Delete() {
-  // If there's a selection, delete it.
   if (DeleteSelected()) {
     return true;
   }
-  // There's no selection; delete the following codepoint.
-  if (selection_base_ != text_.length()) {
-    int count = IsLeadingSurrogate(text_.at(selection_base_)) ? 2 : 1;
-    text_.erase(selection_base_, count);
-    selection_extent_ = selection_base_;
+  // If there's no selection, delete the preceding codepoint.
+  size_t position = selection_.position();
+  if (position != text_.length()) {
+    int count = IsLeadingSurrogate(text_.at(position)) ? 2 : 1;
+    text_.erase(position, count);
     return true;
   }
   return false;
 }
 
 bool TextInputModel::DeleteSurrounding(int offset_from_cursor, int count) {
-  auto start = selection_extent_;
+  size_t start = selection_.extent();
   if (offset_from_cursor < 0) {
     for (int i = 0; i < -offset_from_cursor; i++) {
       // If requested start is before the available text then reduce the
@@ -150,65 +145,53 @@ bool TextInputModel::DeleteSurrounding(int offset_from_cursor, int count) {
   text_.erase(start, end - start);
 
   // Cursor moves only if deleted area is before it.
-  if (offset_from_cursor <= 0) {
-    selection_base_ = start;
-  }
-
-  // Clear selection.
-  selection_extent_ = selection_base_;
+  selection_ = TextRange(offset_from_cursor <= 0 ? start : selection_.start());
 
   return true;
 }
 
 bool TextInputModel::MoveCursorToBeginning() {
-  if (selection_base_ == 0 && selection_extent_ == 0)
+  if (selection_.collapsed() && selection_.position() == 0)
     return false;
-
-  selection_base_ = 0;
-  selection_extent_ = 0;
+  selection_ = TextRange(0);
   return true;
 }
 
 bool TextInputModel::MoveCursorToEnd() {
-  auto max_pos = text_.length();
-  if (selection_base_ == max_pos && selection_extent_ == max_pos)
+  size_t max_pos = text_.length();
+  if (selection_.collapsed() && selection_.position() == max_pos)
     return false;
-
-  selection_base_ = max_pos;
-  selection_extent_ = max_pos;
+  selection_ = TextRange(max_pos);
   return true;
 }
 
 bool TextInputModel::MoveCursorForward() {
-  // If about to move set to the end of the highlight (when not selecting).
-  if (selection_base_ != selection_extent_) {
-    selection_base_ = selection_end();
-    selection_extent_ = selection_base_;
+  // If there's a selection, move to the end of the selection.
+  if (!selection_.collapsed()) {
+    selection_ = TextRange(selection_.end());
     return true;
   }
-  // If not at the end, move the extent forward.
-  if (selection_extent_ != text_.length()) {
-    int count = IsLeadingSurrogate(text_.at(selection_base_)) ? 2 : 1;
-    selection_base_ += count;
-    selection_extent_ = selection_base_;
+  // Otherwise, move the cursor forward.
+  size_t position = selection_.position();
+  if (position != text_.length()) {
+    int count = IsLeadingSurrogate(text_.at(position)) ? 2 : 1;
+    selection_ = TextRange(position + count);
     return true;
   }
   return false;
 }
 
 bool TextInputModel::MoveCursorBack() {
-  // If about to move set to the beginning of the highlight
-  // (when not selecting).
-  if (selection_base_ != selection_extent_) {
-    selection_base_ = selection_start();
-    selection_extent_ = selection_base_;
+  // If there's a selection, move to the beginning of the selection.
+  if (!selection_.collapsed()) {
+    selection_ = TextRange(selection_.start());
     return true;
   }
-  // If not at the start, move the beginning backward.
-  if (selection_base_ != 0) {
-    int count = IsTrailingSurrogate(text_.at(selection_base_ - 1)) ? 2 : 1;
-    selection_base_ -= count;
-    selection_extent_ = selection_base_;
+  // Otherwise, move the cursor backward.
+  size_t position = selection_.position();
+  if (position != 0) {
+    int count = IsTrailingSurrogate(text_.at(position - 1)) ? 2 : 1;
+    selection_ = TextRange(position - count);
     return true;
   }
   return false;
@@ -221,9 +204,9 @@ std::string TextInputModel::GetText() const {
 }
 
 int TextInputModel::GetCursorOffset() const {
-  // Measure the length of the current text up to the cursor.
+  // Measure the length of the current text up to the selection extent.
   // There is probably a much more efficient way of doing this.
-  auto leading_text = text_.substr(0, selection_extent_);
+  auto leading_text = text_.substr(0, selection_.extent());
   std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>
       utf8_converter;
   return utf8_converter.to_bytes(leading_text).size();

shell/platform/common/cpp/text_input_model.h

@@ -5,11 +5,13 @@
 #ifndef FLUTTER_SHELL_PLATFORM_CPP_TEXT_INPUT_MODEL_H_
 #define FLUTTER_SHELL_PLATFORM_CPP_TEXT_INPUT_MODEL_H_
 
-#include <algorithm>
 #include <memory>
 #include <string>
 
+#include "flutter/shell/platform/common/cpp/text_range.h"
+
 namespace flutter {
+
 // Handles underlying text input state, using a simple ASCII model.
 //
 // Ignores special states like "insert mode" for now.
@@ -104,10 +106,10 @@ class TextInputModel {
   int GetCursorOffset() const;
 
   // The position where the selection starts.
-  int selection_base() const { return selection_base_; }
+  int selection_base() const { return selection_.base(); }
 
   // The position of the cursor.
-  int selection_extent() const { return selection_extent_; }
+  int selection_extent() const { return selection_.extent(); }
 
  private:
   // Deletes the current selection, if any.
@@ -117,18 +119,7 @@ class TextInputModel {
   bool DeleteSelected();
 
   std::u16string text_;
-  size_t selection_base_ = 0;
-  size_t selection_extent_ = 0;
-
-  // Returns the left hand side of the selection.
-  size_t selection_start() const {
-    return std::min(selection_base_, selection_extent_);
-  }
-
-  // Returns the right hand side of the selection.
-  size_t selection_end() const {
-    return std::max(selection_base_, selection_extent_);
-  }
+  TextRange selection_ = TextRange(0);
 };
 
 }  // namespace flutter

shell/platform/common/cpp/text_range.h

@@ -0,0 +1,53 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <algorithm>
+
+#include "flutter/fml/logging.h"
+
+// A directional range of text.
+//
+// A |TextRange| describes a range of text with |base| and |extent| positions.
+// In the case where |base| == |extent|, the range is said to be collapsed, and
+// when |base| > |extent|, the range is said to be reversed.
+class TextRange {
+ public:
+  explicit TextRange(size_t position) : base_(position), extent_(position) {}
+  explicit TextRange(size_t base, size_t extent)
+      : base_(base), extent_(extent) {}
+  TextRange(const TextRange&) = default;
+  TextRange& operator=(const TextRange&) = default;
+
+  virtual ~TextRange() = default;
+
+  // Returns the base position of the range.
+  size_t base() const { return base_; }
+
+  // Returns the extent position of the range.
+  size_t extent() const { return extent_; }
+
+  // Returns the lesser of the base and extent positions.
+  size_t start() const { return std::min(base_, extent_); }
+
+  // Returns the greater of the base and extent positions.
+  size_t end() const { return std::max(base_, extent_); }
+
+  // Returns the position of a collapsed range.
+  //
+  // Asserts that the range is of length 0.
+  size_t position() const {
+    FML_DCHECK(base_ == extent_);
+    return extent_;
+  }
+
+  // Returns the length of the range.
+  size_t length() const { return end() - start(); }
+
+  // Returns true if the range is of length 0.
+  bool collapsed() const { return base_ == extent_; }
+
+ private:
+  size_t base_;
+  size_t extent_;
+};

shell/platform/common/cpp/text_range_unittests.cc

@@ -0,0 +1,53 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/shell/platform/common/cpp/text_range.h"
+
+#include "gtest/gtest.h"
+
+namespace flutter {
+
+TEST(TextRange, TextRangeFromPositionZero) {
+  TextRange range(0);
+  EXPECT_EQ(range.base(), size_t(0));
+  EXPECT_EQ(range.extent(), size_t(0));
+  EXPECT_EQ(range.start(), size_t(0));
+  EXPECT_EQ(range.end(), size_t(0));
+  EXPECT_EQ(range.length(), size_t(0));
+  EXPECT_EQ(range.position(), size_t(0));
+  EXPECT_TRUE(range.collapsed());
+}
+
+TEST(TextRange, TextRangeFromPositionNonZero) {
+  TextRange range(3);
+  EXPECT_EQ(range.base(), size_t(3));
+  EXPECT_EQ(range.extent(), size_t(3));
+  EXPECT_EQ(range.start(), size_t(3));
+  EXPECT_EQ(range.end(), size_t(3));
+  EXPECT_EQ(range.length(), size_t(0));
+  EXPECT_EQ(range.position(), size_t(3));
+  EXPECT_TRUE(range.collapsed());
+}
+
+TEST(TextRange, TextRangeFromRange) {
+  TextRange range(3, 7);
+  EXPECT_EQ(range.base(), size_t(3));
+  EXPECT_EQ(range.extent(), size_t(7));
+  EXPECT_EQ(range.start(), size_t(3));
+  EXPECT_EQ(range.end(), size_t(7));
+  EXPECT_EQ(range.length(), size_t(4));
+  EXPECT_FALSE(range.collapsed());
+}
+
+TEST(TextRange, TextRangeFromReversedRange) {
+  TextRange range(7, 3);
+  EXPECT_EQ(range.base(), size_t(7));
+  EXPECT_EQ(range.extent(), size_t(3));
+  EXPECT_EQ(range.start(), size_t(3));
+  EXPECT_EQ(range.end(), size_t(7));
+  EXPECT_EQ(range.length(), size_t(4));
+  EXPECT_FALSE(range.collapsed());
+}
+
+}  // namespace flutter