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libtxt: Remove postprocess_line and improve tracking of X offsets for glyphs and PaintRecords (flutter/engine#4153)

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This commit is contained in:
Jason Simmons
2017-09-28 17:46:25 -07:00
committed by GitHub
parent 7dc9b08d3c
commit 9439d431b5
2 changed files with 34 additions and 75 deletions
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104
engine/src/flutter/third_party/txt/src/txt/paragraph.cc vendored
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@@ -201,7 +201,7 @@ void Paragraph::Layout(double width, bool force) {
breaker_.setJustified(paragraph_style_.text_align == TextAlign::justify);
breaker_.setStrategy(paragraph_style_.break_strategy);
size_t breaks_count = breaker_.computeBreaks();
breaks_count_ = breaker_.computeBreaks();
const int* breaks = breaker_.getBreaks();
// Create a copy of text_ to use locally so that any changes made to the
@@ -226,12 +226,9 @@ void Paragraph::Layout(double width, bool force) {
glyph_position_x_ = std::vector<std::vector<GlyphPosition>>();
std::vector<GlyphPosition> glyph_single_line_position_x;
// Track the x of the previous run to maintain accurate xposition when
// multiple SkTextBlobs make up a single line.
double previous_run_x_position = 0.0f;
SkScalar x = 0.0f;
SkScalar y = 0.0f;
SkScalar x_offset = GetLineXOffset(0);
SkScalar y_offset = 0.0f;
size_t break_index = 0;
double max_line_spacing = 0.0f;
double max_descent = 0.0f;
@@ -240,71 +237,13 @@ void Paragraph::Layout(double width, bool force) {
double justify_spacing = 0.0f;
double prev_word_pos = 0.0f;
double prev_char_advance = 0.0f;
double current_x_position = previous_run_x_position;
double current_x_position = 0.0f;
std::vector<const SkTextBlobBuilder::RunBuffer*> buffers;
std::vector<size_t> buffer_sizes;
int word_count = 0;
size_t max_lines = paragraph_style_.max_lines;
auto postprocess_line = [this, &x_queue, &y]() -> void {
size_t record_index = 0;
for (size_t i = 0; i < x_queue.size(); ++i) {
record_index = records_.size() - (x_queue.size() - i);
records_[record_index].SetOffset(SkPoint::Make(x_queue[i], y));
// Adjust the offsets for each of the different alignments.
switch (paragraph_style_.text_align) {
case TextAlign::left:
break;
case TextAlign::right: {
records_[record_index].SetOffset(SkPoint::Make(
records_[record_index].offset().x() + width_ -
breaker_.getWidths()[records_[record_index].line()],
records_[record_index].offset().y()));
break;
}
case TextAlign::center: {
records_[record_index].SetOffset(SkPoint::Make(
records_[record_index].offset().x() +
(width_ -
breaker_.getWidths()[records_[record_index].line()]) /
2,
records_[record_index].offset().y()));
break;
}
case TextAlign::justify: {
break;
}
}
}
// Correct positions stored in the member vars.
for (size_t y_index = 0; y_index < lines_; ++y_index) {
switch (paragraph_style_.text_align) {
case TextAlign::left:
break;
case TextAlign::right: {
for (size_t i = 0; i < glyph_position_x_[y_index].size(); ++i) {
glyph_position_x_[y_index][i].start +=
width_ - breaker_.getWidths()[y_index];
}
break;
}
case TextAlign::center: {
for (size_t i = 0; i < glyph_position_x_[y_index].size(); ++i) {
glyph_position_x_[y_index][i].start +=
(width_ - breaker_.getWidths()[y_index]) / 2;
}
break;
}
case TextAlign::justify: {
// TODO(garyq): Track position changes due to justify in justify
// method.
break;
}
}
}
x_queue.clear();
};
for (size_t run_index = 0; run_index < runs_.size(); ++run_index) {
auto run = runs_.GetRun(run_index);
bool is_newline = text_[run.start] == '\n' && run.end - run.start == 1;
@@ -319,7 +258,7 @@ void Paragraph::Layout(double width, bool force) {
size_t layout_start = run.start;
// Layout until the end of the run or too many lines.
while (layout_start < run.end && lines_ < max_lines) {
const size_t next_break = (break_index > breaks_count - 1)
const size_t next_break = (break_index > breaks_count_ - 1)
? std::numeric_limits<size_t>::max()
: breaks[break_index];
const size_t layout_end = std::min(run.end, next_break);
@@ -441,8 +380,7 @@ void Paragraph::Layout(double width, bool force) {
size_t ligature_width = ligature_end - character_index;
float subglyph_advance = glyph_advance / ligature_width;
glyph_single_line_position_x.emplace_back(
current_x_position + previous_run_x_position + letter_spacing,
subglyph_advance);
x_offset + current_x_position + letter_spacing, subglyph_advance);
// Compute positions for the additional characters in the ligature.
for (size_t i = 1; i < ligature_width; ++i) {
@@ -469,7 +407,6 @@ void Paragraph::Layout(double width, bool force) {
}
}
blob_start += blob_length;
previous_run_x_position += current_x_position + letter_spacing;
}
// TODO(abarth): We could keep the same SkTextBlobBuilder as long as the
@@ -486,7 +423,7 @@ void Paragraph::Layout(double width, bool force) {
// Must adjust each line to the largest text in the line, so cannot
// directly push the offset property of PaintRecord until line is
// finished.
x_queue.push_back(x);
x_queue.push_back(x_offset);
temp_line_spacing = lines_ == 0 ? -metrics.fAscent * run.style.height
: (-metrics.fAscent + metrics.fLeading) *
@@ -506,27 +443,31 @@ void Paragraph::Layout(double width, bool force) {
max_descent = temp_line_spacing;
if (layout_end == next_break || is_newline) {
y += roundf(max_line_spacing + prev_max_descent);
y_offset += roundf(max_line_spacing + prev_max_descent);
for (size_t i = 0; i < x_queue.size(); ++i) {
PaintRecord& record = records_[records_.size() - x_queue.size() + i];
record.SetOffset(SkPoint::Make(x_queue[i], y_offset));
}
x_queue.clear();
line_heights_.push_back(
(line_heights_.empty() ? 0 : line_heights_.back()) +
roundf(max_line_spacing + max_descent));
glyph_position_x_.push_back(glyph_single_line_position_x);
prev_max_descent = max_descent;
postprocess_line();
// Reset Variables for next line.
max_line_spacing = 0.0f;
max_descent = 0.0f;
x = 0.0f;
prev_word_pos = 0;
prev_char_advance = 0.0f;
previous_run_x_position = 0.0f;
current_x_position = 0.0f;
break_index += 1;
lines_++;
x_offset = GetLineXOffset(lines_);
glyph_single_line_position_x.clear();
} else {
x += layout.getAdvance();
x_offset += layout.getAdvance();
}
layout_start = layout_end;
@@ -542,6 +483,19 @@ void Paragraph::Layout(double width, bool force) {
breaker_.finish();
}
double Paragraph::GetLineXOffset(size_t line) {
if (line >= breaks_count_)
return 0;
if (paragraph_style_.text_align == TextAlign::right) {
return width_ - breaker_.getWidths()[line];
} else if (paragraph_style_.text_align == TextAlign::center) {
return (width_ - breaker_.getWidths()[line]) / 2;
} else {
return 0;
}
}
// Amends the buffers to incorporate justification.
void Paragraph::JustifyLine(
std::vector<const SkTextBlobBuilder::RunBuffer*>& buffers,

5
engine/src/flutter/third_party/txt/src/txt/paragraph.h vendored
View File

@@ -179,6 +179,7 @@ class Paragraph {
std::shared_ptr<FontCollection> font_collection_;
minikin::LineBreaker breaker_;
size_t breaks_count_ = 0;
// Stores the result of Layout().
std::vector<PaintRecord> records_;
@@ -243,6 +244,10 @@ class Paragraph {
// justifying.
void FillWhitespaceSet(size_t start, size_t end, hb_font_t* hb_font);
// Calculate the starting X offset of a line based on the line's width and
// alignment.
double GetLineXOffset(size_t line);
// Calculates and amends the layout for one line to be justified.
void JustifyLine(std::vector<const SkTextBlobBuilder::RunBuffer*>& buffers,
std::vector<size_t>& buffer_sizes,