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libtxt: make the min/max intrinsic width calculations match expectations of the framework (flutter/engine#4220)

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maxIntrinsicWidth is the sum of the width of all lines in the input
(if the width were any smaller, the renderer might have to wrap a line)

minIntrinsicWidth is the maximum width of a word (if the paragraph were
any narrower, the renderer would have to truncate a word)
This commit is contained in:
Jason Simmons 2017-10-16 15:31:15 -07:00 committed by GitHub
parent 16934d4f9e
commit df55d4f337
2 changed files with 27 additions and 26 deletions
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51
engine/src/flutter/third_party/txt/src/txt/paragraph.cc vendored
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@ -249,6 +249,7 @@ void Paragraph::Layout(double width, bool force) {
records_.clear();
line_heights_.clear();
glyph_position_x_.clear();
minikin::Layout layout;
SkTextBlobBuilder builder;
@ -256,6 +257,7 @@ void Paragraph::Layout(double width, bool force) {
size_t run_index = 0;
double y_offset = 0;
double prev_max_descent = 0;
double max_word_width = 0;
for (size_t line_number = 0; line_number < line_limit; ++line_number) {
size_t line_start = (line_number > 0) ? breaks[line_number - 1] : 0;
@ -268,8 +270,8 @@ void Paragraph::Layout(double width, bool force) {
bool justify_line =
(paragraph_style_.text_align == TextAlign::justify &&
line_number != line_limit - 1 && text_[line_end - 1] != '\n');
FindWords(text_, line_start, line_end, &words);
if (justify_line) {
FindWords(text_, line_start, line_end, &words);
if (words.size() > 1) {
word_gap_width =
(width_ - breaker_.getWidths()[line_number]) / (words.size() - 1);
@ -370,6 +372,7 @@ void Paragraph::Layout(double width, bool force) {
double justify_x_offset = 0;
size_t code_unit_index = 0;
double word_start_position = std::numeric_limits<double>::quiet_NaN();
for (const Range& glyph_blob : glyph_blobs) {
paint.setTypeface(GetTypefaceForGlyph(layout, glyph_blob.start));
@ -386,6 +389,11 @@ void Paragraph::Layout(double width, bool force) {
blob_buffer.pos[pos_index] = glyph_x_offset;
blob_buffer.pos[pos_index + 1] = layout.getY(glyph_index);
if (word_index < words.size() &&
code_unit_index == words[word_index].start) {
word_start_position = run_x_offset + glyph_x_offset;
}
float glyph_advance = layout.getCharAdvance(code_unit_index);
// The glyph may be a ligature. Determine how many input characters
@ -416,10 +424,19 @@ void Paragraph::Layout(double width, bool force) {
subglyph_advance, subglyph_code_unit_counts[i]);
}
if (justify_line && word_index < words.size() &&
if (word_index < words.size() &&
code_unit_index == words[word_index].end) {
justify_x_offset += word_gap_width;
if (justify_line)
justify_x_offset += word_gap_width;
word_index++;
if (!isnan(word_start_position)) {
double word_width =
glyph_single_line_position_x.back().glyph_end() -
word_start_position;
max_word_width = std::max(word_width, max_word_width);
word_start_position = std::numeric_limits<double>::quiet_NaN();
}
}
}
}
@ -470,12 +487,17 @@ void Paragraph::Layout(double width, bool force) {
glyph_position_x_.emplace_back(std::move(glyph_single_line_position_x));
}
CalculateIntrinsicWidths();
max_intrinsic_width_ = 0;
for (size_t i = 0; i < breaks_count_; ++i) {
max_intrinsic_width_ += breaker_.getWidths()[i];
}
min_intrinsic_width_ = std::min(max_word_width, max_intrinsic_width_);
breaker_.finish();
}
double Paragraph::GetLineXOffset(size_t line) {
if (line >= breaks_count_)
if (line >= breaks_count_ || isinf(width_))
return 0;
TextAlign align = paragraph_style_.text_align;
@ -506,25 +528,6 @@ double Paragraph::GetIdeographicBaseline() const {
return ideographic_baseline_;
}
void Paragraph::CalculateIntrinsicWidths() {
max_intrinsic_width_ = 0;
for (size_t i = 0; i < GetLineCount(); ++i) {
max_intrinsic_width_ += breaker_.getWidths()[i];
}
// TODO(garyq): Investigate correctness of the following implementation of min
// intrinsic width. This is currently the longest line in the text after
// layout.
min_intrinsic_width_ = 0;
for (size_t i = 0; i < GetLineCount(); ++i) {
min_intrinsic_width_ = fmax(min_intrinsic_width_, breaker_.getWidths()[i]);
}
// Ensure that min < max widths.
min_intrinsic_width_ = std::min(max_intrinsic_width_, min_intrinsic_width_);
max_intrinsic_width_ = std::max(max_intrinsic_width_, min_intrinsic_width_);
}
double Paragraph::GetMaxIntrinsicWidth() const {
return max_intrinsic_width_;
}

2
engine/src/flutter/third_party/txt/src/txt/paragraph.h vendored
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@ -260,8 +260,6 @@ class Paragraph {
double y,
size_t record_index);
void CalculateIntrinsicWidths();
FXL_DISALLOW_COPY_AND_ASSIGN(Paragraph);
};