RTL handling for ghost runs, NotoNaskhArabic test font (#8638)

Author: GaryQian

third_party/txt/src/txt/paragraph.cc

@@ -17,14 +17,15 @@
 #include "paragraph.h"
 
 #include <hb.h>
+#include <minikin/Layout.h>
+
 #include <algorithm>
 #include <limits>
 #include <map>
 #include <numeric>
 #include <utility>
 #include <vector>
 
-#include <minikin/Layout.h>
 #include "flutter/fml/logging.h"
 #include "font_collection.h"
 #include "font_skia.h"
@@ -34,9 +35,6 @@
 #include "minikin/LayoutUtils.h"
 #include "minikin/LineBreaker.h"
 #include "minikin/MinikinFont.h"
-#include "unicode/ubidi.h"
-#include "unicode/utf16.h"
-
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkFont.h"
 #include "third_party/skia/include/core/SkFontMetrics.h"
@@ -46,6 +44,8 @@
 #include "third_party/skia/include/core/SkTypeface.h"
 #include "third_party/skia/include/effects/SkDashPathEffect.h"
 #include "third_party/skia/include/effects/SkDiscretePathEffect.h"
+#include "unicode/ubidi.h"
+#include "unicode/utf16.h"
 
 namespace txt {
 namespace {
@@ -552,28 +552,39 @@ void Paragraph::Layout(double width, bool force) {
     // Find the runs comprising this line.
     std::vector<BidiRun> line_runs;
     for (const BidiRun& bidi_run : bidi_runs) {
-      if (bidi_run.start() < line_end_index &&
-          bidi_run.end() > line_range.start) {
-        line_runs.emplace_back(std::max(bidi_run.start(), line_range.start),
-                               std::min(bidi_run.end(), line_end_index),
-                               bidi_run.direction(), bidi_run.style());
-      }
       // A "ghost" run is a run that does not impact the layout, breaking,
-      // alignment, width, etc but is still "visible" though getRectsForRange.
+      // alignment, width, etc but is still "visible" through getRectsForRange.
       // For example, trailing whitespace on centered text can be scrolled
       // through with the caret but will not wrap the line.
       //
       // Here, we add an additional run for the whitespace, but dont
       // let it impact metrics. After layout of the whitespace run, we do not
       // add its width into the x-offset adjustment, effectively nullifying its
       // impact on the layout.
+      std::unique_ptr<BidiRun> ghost_run = nullptr;
       if (paragraph_style_.ellipsis.empty() &&
           line_range.end_excluding_whitespace < line_range.end &&
           bidi_run.start() <= line_range.end &&
           bidi_run.end() > line_end_index) {
-        line_runs.emplace_back(std::max(bidi_run.start(), line_end_index),
-                               std::min(bidi_run.end(), line_range.end),
-                               bidi_run.direction(), bidi_run.style(), true);
+        ghost_run = std::make_unique<BidiRun>(
+            std::max(bidi_run.start(), line_end_index),
+            std::min(bidi_run.end(), line_range.end), bidi_run.direction(),
+            bidi_run.style(), true);
+      }
+      // Include the ghost run before normal run if RTL
+      if (bidi_run.direction() == TextDirection::rtl && ghost_run != nullptr) {
+        line_runs.push_back(*ghost_run);
+      }
+      // Emplace a normal line run.
+      if (bidi_run.start() < line_end_index &&
+          bidi_run.end() > line_range.start) {
+        line_runs.emplace_back(std::max(bidi_run.start(), line_range.start),
+                               std::min(bidi_run.end(), line_end_index),
+                               bidi_run.direction(), bidi_run.style());
+      }
+      // Include the ghost run after normal run if LTR
+      if (bidi_run.direction() == TextDirection::ltr && ghost_run != nullptr) {
+        line_runs.push_back(*ghost_run);
       }
     }
     bool line_runs_all_rtl =
@@ -661,6 +672,17 @@ void Paragraph::Layout(double width, bool force) {
       if (layout.nGlyphs() == 0)
         continue;
 
+      // When laying out RTL ghost runs, shift the run_x_offset here by the
+      // advance so that the ghost run is positioned to the left of the first
+      // real run of text in the line. However, since we do not want it to
+      // impact the layout of real text, this advance is subsequently added
+      // back into the run_x_offset after the ghost run positions have been
+      // calcuated and before the next real run of text is laid out, ensuring
+      // later runs are laid out in the same position as if there were no ghost
+      // run.
+      if (run.is_ghost() && run.is_rtl())
+        run_x_offset -= layout.getAdvance();
+
       std::vector<float> layout_advances(text_count);
       layout.getAdvances(layout_advances.data());
 
@@ -808,21 +830,25 @@ void Paragraph::Layout(double width, bool force) {
                   [](const GlyphPosition& a, const GlyphPosition& b) {
                     return a.code_units.start < b.code_units.start;
                   });
+
         line_code_unit_runs.emplace_back(
             std::move(code_unit_positions),
             Range<size_t>(run.start(), run.end()),
             Range<double>(glyph_positions.front().x_pos.start,
                           glyph_positions.back().x_pos.end),
             line_number, metrics, run.direction());
 
-        min_left_ = std::min(min_left_, glyph_positions.front().x_pos.start);
-        max_right_ = std::max(max_right_, glyph_positions.back().x_pos.end);
+        if (!run.is_ghost()) {
+          min_left_ = std::min(min_left_, glyph_positions.front().x_pos.start);
+          max_right_ = std::max(max_right_, glyph_positions.back().x_pos.end);
+        }
       }  // for each in glyph_blobs
-
-      // Do not increase x offset for trailing ghost runs as it should not
-      // impact the layout of visible glyphs. We do keep the record though so
-      // GetRectsForRange() can find metrics for trailing spaces.
-      if (!run.is_ghost()) {
+      // Do not increase x offset for LTR trailing ghost runs as it should not
+      // impact the layout of visible glyphs. RTL tailing ghost runs have the
+      // advance subtracted, so we do add the advance here to reset the
+      // run_x_offset. We do keep the record though so GetRectsForRange() can
+      // find metrics for trailing spaces.
+      if (!run.is_ghost() || run.is_rtl()) {
         run_x_offset += layout.getAdvance();
       }
     }  // for each in line_runs

third_party/txt/tests/paragraph_unittests.cc

@@ -706,6 +706,7 @@ TEST_F(ParagraphTest, DISABLE_ON_WINDOWS(JustifyRTL)) {
   txt::ParagraphStyle paragraph_style;
   paragraph_style.max_lines = 14;
   paragraph_style.text_align = TextAlign::justify;
+  paragraph_style.text_direction = TextDirection::rtl;
   txt::ParagraphBuilder builder(paragraph_style, GetTestFontCollection());
 
   txt::TextStyle text_style;
@@ -725,16 +726,33 @@ TEST_F(ParagraphTest, DISABLE_ON_WINDOWS(JustifyRTL)) {
 
   paragraph->Paint(GetCanvas(), 0, 0);
 
-  ASSERT_TRUE(Snapshot());
-
   auto glyph_line_width = [&paragraph](int index) {
     size_t second_to_last_position_index =
-        paragraph->glyph_lines_[index].positions.size() - 2;
+        paragraph->glyph_lines_[index].positions.size() - 1;
     return paragraph->glyph_lines_[index]
         .positions[second_to_last_position_index]
         .x_pos.end;
   };
 
+  SkPaint paint;
+  paint.setStyle(SkPaint::kStroke_Style);
+  paint.setAntiAlias(true);
+  paint.setStrokeWidth(1);
+
+  // Tests for GetRectsForRange()
+  Paragraph::RectHeightStyle rect_height_style =
+      Paragraph::RectHeightStyle::kMax;
+  Paragraph::RectWidthStyle rect_width_style =
+      Paragraph::RectWidthStyle::kTight;
+  paint.setColor(SK_ColorRED);
+  std::vector<txt::Paragraph::TextBox> boxes =
+      paragraph->GetRectsForRange(0, 100, rect_height_style, rect_width_style);
+  for (size_t i = 0; i < boxes.size(); ++i) {
+    GetCanvas()->drawRect(boxes[i].rect, paint);
+  }
+  ASSERT_EQ(boxes.size(), 5ull);
+  ASSERT_TRUE(Snapshot());
+
   // All lines except the last should be justified to the width of the
   // paragraph.
   for (size_t i = 0; i < paragraph->glyph_lines_.size() - 1; ++i) {
@@ -971,6 +989,74 @@ TEST_F(ParagraphTest, DISABLED_ArabicParagraph) {
   ASSERT_TRUE(Snapshot());
 }
 
+// Checks if the rects are in the correct positions after typing spaces in
+// Arabic.
+TEST_F(ParagraphTest, DISABLE_ON_WINDOWS(ArabicRectsParagraph)) {
+  const char* text = "بمباركة التقليدية قام عن. تصفح يد    ";
+  auto icu_text = icu::UnicodeString::fromUTF8(text);
+  std::u16string u16_text(icu_text.getBuffer(),
+                          icu_text.getBuffer() + icu_text.length());
+
+  txt::ParagraphStyle paragraph_style;
+  paragraph_style.max_lines = 14;
+  paragraph_style.text_align = TextAlign::right;
+  paragraph_style.text_direction = TextDirection::rtl;
+  txt::ParagraphBuilder builder(paragraph_style, GetTestFontCollection());
+
+  txt::TextStyle text_style;
+  text_style.font_families = std::vector<std::string>(1, "Noto Naskh Arabic");
+  text_style.font_size = 26;
+  text_style.letter_spacing = 1;
+  text_style.word_spacing = 5;
+  text_style.color = SK_ColorBLACK;
+  text_style.height = 1;
+  text_style.decoration = TextDecoration::kUnderline;
+  text_style.decoration_color = SK_ColorBLACK;
+  builder.PushStyle(text_style);
+
+  builder.AddText(u16_text);
+
+  builder.Pop();
+
+  auto paragraph = builder.Build();
+  paragraph->Layout(GetTestCanvasWidth() - 100);
+
+  paragraph->Paint(GetCanvas(), 0, 0);
+
+  SkPaint paint;
+  paint.setStyle(SkPaint::kStroke_Style);
+  paint.setAntiAlias(true);
+  paint.setStrokeWidth(1);
+
+  // Tests for GetRectsForRange()
+  Paragraph::RectHeightStyle rect_height_style =
+      Paragraph::RectHeightStyle::kMax;
+  Paragraph::RectWidthStyle rect_width_style =
+      Paragraph::RectWidthStyle::kTight;
+  paint.setColor(SK_ColorRED);
+  std::vector<txt::Paragraph::TextBox> boxes =
+      paragraph->GetRectsForRange(0, 100, rect_height_style, rect_width_style);
+  for (size_t i = 0; i < boxes.size(); ++i) {
+    GetCanvas()->drawRect(boxes[i].rect, paint);
+  }
+  EXPECT_EQ(boxes.size(), 2ull);
+
+  EXPECT_FLOAT_EQ(boxes[0].rect.left(), 556.54688);
+  EXPECT_FLOAT_EQ(boxes[0].rect.top(), -0.26855469);
+  EXPECT_FLOAT_EQ(boxes[0].rect.right(), 900);
+  EXPECT_FLOAT_EQ(boxes[0].rect.bottom(), 44);
+
+  EXPECT_FLOAT_EQ(boxes[1].rect.left(), 510.09375);
+  EXPECT_FLOAT_EQ(boxes[1].rect.top(), -0.26855469);
+  EXPECT_FLOAT_EQ(boxes[1].rect.right(), 557.04688);
+  EXPECT_FLOAT_EQ(boxes[1].rect.bottom(), 44);
+
+  ASSERT_EQ(paragraph_style.text_align,
+            paragraph->GetParagraphStyle().text_align);
+
+  ASSERT_TRUE(Snapshot());
+}
+
 TEST_F(ParagraphTest, GetGlyphPositionAtCoordinateParagraph) {
   const char* text =
       "12345 67890 12345 67890 12345 67890 12345 67890 12345 67890 12345 "

third_party/txt/third_party/fonts/NotoNaskhArabic-LICENSE.txt

@@ -0,0 +1,92 @@
+This Font Software is licensed under the SIL Open Font License,
+Version 1.1.
+
+This license is copied below, and is also available with a FAQ at:
+http://scripts.sil.org/OFL
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font
+creation efforts of academic and linguistic communities, and to
+provide a free and open framework in which fonts may be shared and
+improved in partnership with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded,
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply to
+any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software
+components as distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to,
+deleting, or substituting -- in part or in whole -- any of the
+components of the Original Version, by changing formats or by porting
+the Font Software to a new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION & CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed,
+modify, redistribute, and sell modified and unmodified copies of the
+Font Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components, in
+Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the
+corresponding Copyright Holder. This restriction only applies to the
+primary font name as presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created using
+the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.