TextHeightBehavior implemented

Bug: skia:10201
Change-Id: I5398836d2068164282bab77fe8448654a72050d7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/286456
Commit-Queue: Julia Lavrova <jlavrova@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>

modules/skparagraph/include/DartTypes.h

@@ -126,6 +126,13 @@ enum class TextBaseline {
     kIdeographic,
 };
 
+enum TextHeightBehavior {
+    kAll = 0x0,
+    kDisableFirstAscent = 0x1,
+    kDisableLastDescent = 0x2,
+    kDisableAll = 0x1 | 0x2,
+};
+
 }  // namespace textlayout
 }  // namespace skia
 

modules/skparagraph/include/ParagraphStyle.h

@@ -91,6 +91,10 @@ struct ParagraphStyle {
     SkScalar getHeight() const { return fHeight; }
     void setHeight(SkScalar height) { fHeight = height; }
 
+
+    TextHeightBehavior getTextHeightBehavior() const { return fTextHeightBehavior; }
+    void setTextHeightBehavior(TextHeightBehavior v) { fTextHeightBehavior = v; }
+
     bool unlimited_lines() const {
         return fLinesLimit == std::numeric_limits<size_t>::max();
     }
@@ -107,6 +111,7 @@ private:
     size_t fLinesLimit;
     SkString fEllipsis;
     SkScalar fHeight;
+    TextHeightBehavior fTextHeightBehavior;
     bool fHintingIsOn;
 };
 }  // namespace textlayout

modules/skparagraph/src/ParagraphImpl.cpp

@@ -430,6 +430,7 @@ void ParagraphImpl::breakShapedTextIntoLines(SkScalar maxWidth) {
 
                 fLongestLine = std::max(fLongestLine, nearlyZero(advance.fX) ? widthWithSpaces : advance.fX);
             });
+
     fHeight = textWrapper.height();
     fWidth = maxWidth;
     fMaxIntrinsicWidth = textWrapper.maxIntrinsicWidth();
@@ -437,6 +438,26 @@ void ParagraphImpl::breakShapedTextIntoLines(SkScalar maxWidth) {
     fAlphabeticBaseline = fLines.empty() ? fEmptyMetrics.alphabeticBaseline() : fLines.front().alphabeticBaseline();
     fIdeographicBaseline = fLines.empty() ? fEmptyMetrics.ideographicBaseline() : fLines.front().ideographicBaseline();
     fExceededMaxLines = textWrapper.exceededMaxLines();
+
+    // Correct the first and the last line ascents/descents if required
+    if ((fParagraphStyle.getTextHeightBehavior() & TextHeightBehavior::kDisableFirstAscent) != 0) {
+        auto& firstLine = fLines.front();
+        auto delta = firstLine.metricsWithoutMultiplier(TextHeightBehavior::kDisableFirstAscent);
+        if (!SkScalarNearlyZero(delta)) {
+            fHeight += delta;
+            // Shift all the lines up
+            for (auto& line : fLines) {
+                line.shiftVertically(delta);
+            }
+        }
+    }
+
+    if ((fParagraphStyle.getTextHeightBehavior() & TextHeightBehavior::kDisableLastDescent) != 0) {
+        auto& lastLine = fLines.back();
+        auto delta = lastLine.metricsWithoutMultiplier(TextHeightBehavior::kDisableLastDescent);
+        // It's the last line. There is nothing below to shift
+        fHeight += delta;
+    }
 }
 
 void ParagraphImpl::formatLines(SkScalar maxWidth) {

modules/skparagraph/src/ParagraphStyle.cpp

@@ -21,6 +21,7 @@ ParagraphStyle::ParagraphStyle() {
     fTextDirection = TextDirection::kLtr;
     fLinesLimit = std::numeric_limits<size_t>::max();
     fHeight = 1;
+    fTextHeightBehavior = TextHeightBehavior::kAll;
     fHintingIsOn = true;
 }
 

modules/skparagraph/src/Run.h

@@ -81,6 +81,8 @@ public:
     }
     SkVector offset() const { return fOffset; }
     SkScalar ascent() const { return fFontMetrics.fAscent; }
+    SkScalar descent() const { return fFontMetrics.fDescent; }
+    SkScalar leading() const { return fFontMetrics.fLeading; }
     SkScalar correctAscent() const {
 
         if (fHeightMultiplier == 0) {
@@ -417,6 +419,7 @@ public:
     SkScalar descent() const { return fDescent; }
     SkScalar leading() const { return fLeading; }
     void setForceStrut(bool value) { fForceStrut = value; }
+    bool getForceStrut() const { return fForceStrut; }
 
 private:
 

modules/skparagraph/src/TextLine.cpp

@@ -305,6 +305,29 @@ SkRect TextLine::extendHeight(const ClipContext& context) const {
     return result;
 }
 
+SkScalar TextLine::metricsWithoutMultiplier(TextHeightBehavior correction) {
+
+    if (this->fSizes.getForceStrut()) {
+        return 0;
+    }
+
+    InternalLineMetrics result;
+    this->iterateThroughVisualRuns(true,
+        [&result](const Run* run, SkScalar runOffset, TextRange textRange, SkScalar* width) {
+        InternalLineMetrics runMetrics(run->ascent(), run->descent(), run->leading());
+        result.add(runMetrics);
+        return true;
+    });
+    SkScalar delta = 0;
+    if (correction  == TextHeightBehavior::kDisableFirstAscent) {
+        delta += (this->fSizes.ascent() - result.ascent());
+    } else if (correction  == TextHeightBehavior::kDisableLastDescent) {
+        delta -= (this->fSizes.descent() - result.descent());
+    }
+    fAdvance.fY += delta;
+    return delta;
+}
+
 void TextLine::paintText(SkCanvas* canvas, TextRange textRange, const TextStyle& style, const ClipContext& context) const {
 
     if (context.run->placeholderStyle() != nullptr) {

modules/skparagraph/src/TextLine.h

@@ -103,6 +103,9 @@ public:
 
     SkRect extendHeight(const ClipContext& context) const;
 
+    SkScalar metricsWithoutMultiplier(TextHeightBehavior correction);
+    void shiftVertically(SkScalar shift) { fOffset.fY += shift; }
+
 private:
 
     Run* shapeEllipsis(const SkString& ellipsis, Run* run);