Glitchiness with Tab Characters (#8591)

Fix a bug that caused jumping and flashing when entering tab characters into a TextField.

third_party/txt/src/minikin/LineBreaker.cpp

@@ -32,8 +32,6 @@ using std::vector;
 
 namespace minikin {
 
-const int CHAR_TAB = 0x0009;
-
 // Large scores in a hierarchy; we prefer desperate breaks to an overfull line.
 // All these constants are larger than any reasonable actual width score.
 const float SCORE_INFTY = std::numeric_limits<float>::max();
@@ -159,22 +157,14 @@ float LineBreaker::addStyleRun(MinikinPaint* paint,
   size_t postSpaceCount = mSpaceCount;
   for (size_t i = start; i < end; i++) {
     uint16_t c = mTextBuf[i];
-    if (c == CHAR_TAB) {
-      mWidth = mPreBreak + mTabStops.nextTab(mWidth - mPreBreak);
-      if (mFirstTabIndex == INT_MAX) {
-        mFirstTabIndex = (int)i;
-      }
-      // fall back to greedy; other modes don't know how to deal with tabs
-      mStrategy = kBreakStrategy_Greedy;
-    } else {
-      if (isWordSpace(c))
-        mSpaceCount += 1;
-      mWidth += mCharWidths[i];
-      if (!isLineEndSpace(c)) {
-        postBreak = mWidth;
-        postSpaceCount = mSpaceCount;
-        afterWord = i + 1;
-      }
+    // libtxt: Tab handling was removed here.
+    if (isWordSpace(c))
+      mSpaceCount += 1;
+    mWidth += mCharWidths[i];
+    if (!isLineEndSpace(c)) {
+      postBreak = mWidth;
+      postSpaceCount = mSpaceCount;
+      afterWord = i + 1;
     }
     if (i + 1 == current) {
       size_t wordStart = mWordBreaker.wordStart();

third_party/txt/src/minikin/LineBreaker.h

@@ -85,30 +85,6 @@ class LineWidths {
   std::vector<float> mIndents;
 };
 
-class TabStops {
- public:
-  void set(const int* stops, size_t nStops, int tabWidth) {
-    if (stops != nullptr) {
-      mStops.assign(stops, stops + nStops);
-    } else {
-      mStops.clear();
-    }
-    mTabWidth = tabWidth;
-  }
-  float nextTab(float widthSoFar) const {
-    for (size_t i = 0; i < mStops.size(); i++) {
-      if (mStops[i] > widthSoFar) {
-        return mStops[i];
-      }
-    }
-    return floor(widthSoFar / mTabWidth + 1) * mTabWidth;
-  }
-
- private:
-  std::vector<int> mStops;
-  int mTabWidth;
-};
-
 class LineBreaker {
  public:
   const static int kTab_Shift =
@@ -143,10 +119,6 @@ class LineBreaker {
 
   void setIndents(const std::vector<float>& indents);
 
-  void setTabStops(const int* stops, size_t nStops, int tabWidth) {
-    mTabStops.set(stops, nStops, tabWidth);
-  }
-
   BreakStrategy getStrategy() const { return mStrategy; }
 
   void setStrategy(BreakStrategy strategy) { mStrategy = strategy; }
@@ -246,7 +218,6 @@ class LineBreaker {
   HyphenationFrequency mHyphenationFrequency = kHyphenationFrequency_Normal;
   bool mJustified;
   LineWidths mLineWidths;
-  TabStops mTabStops;
 
   // result of line breaking
   std::vector<int> mBreaks;