Merge pull request #25 from discord/charles/rna-text-align

[RNA] Align text

Author: charlesx2013

ReactAndroid/src/main/java/com/facebook/react/views/text/CustomLineHeightSpan.java

@@ -24,6 +24,12 @@ public CustomLineHeightSpan(float height) {
   @Override
   public void chooseHeight(
       CharSequence text, int start, int end, int spanstartv, int v, Paint.FontMetricsInt fm) {
+
+    if (OVERRIDE_LINE_HEIGHT) {
+      overrideLineHeight(fm);
+      return;
+    }
+
     // This is more complicated that I wanted it to be. You can find a good explanation of what the
     // FontMetrics mean here: http://stackoverflow.com/questions/27631736.
     // The general solution is that if there's not enough height to show the full line height, we
@@ -56,4 +62,41 @@ public void chooseHeight(
       fm.descent = fm.bottom;
     }
   }
+
+  private final static boolean OVERRIDE_LINE_HEIGHT = true;
+
+  /**
+   * Discord Story time!
+   *
+   * So since we decided to be _very_ flexible with channel names, users have decided that they were gonna name their channels
+   * shit like ‧͙⁺˚･༓☾text☽༓･˚⁺‧͙ | l̶̟̦͚͎̦͑̎m̵̮̥̫͕͚̜̱̫̺̪͍̯̉̂̔͌́̚̕a̶͖̫͍͇̯̯̭͎͋̅́̿́̕͘͘͝͝ò̶̧̢͎̃̋͆̉͠ | and other fun non-standard channel names.
+   *
+   * This caused issues with line heights, because the RN implementation decided that it would try as best as possible to
+   * fit the text within the lineHeight that was given to it by the react component, causing text to be shifted upward
+   * and look terrible (see: https://canary.discord.com/channels/281683040739262465/912423796915462154/101286117376867126
+   * for an example).
+   *
+   * We (Jerry + Charles) decided that to fix this issue, we would instead ignore lineHeights _only_ if the text
+   * height was larger than the lineHeight provided to it.
+   *
+   * This is a much simpler implementation that what was previously here.
+   *
+   * _IF_ the lineHeight is larger than the text height, we default to centering the text as much as possible within
+   * that line height.
+   */
+  private void overrideLineHeight(Paint.FontMetricsInt fm) {
+    int realTextHeight = fm.bottom - fm.top;
+
+    if (mHeight >= realTextHeight) {
+      // Show proportionally additional ascent / top & descent / bottom
+      final int additional = mHeight - (-fm.top + fm.bottom);
+
+      // Round up for the negative values and down for the positive values  (arbitrary choice)
+      // So that bottom - top equals additional even if it's an odd number.
+      fm.top -= Math.ceil(additional / 2.0f);
+      fm.bottom += Math.floor(additional / 2.0f);
+      fm.ascent = fm.top;
+      fm.descent = fm.bottom;
+    }
+  }
 }