Compose numbered lists

app/src/main/java/eu/faircode/email/NumberSpan.java

@@ -0,0 +1,64 @@
+package eu.faircode.email;
+
+/*
+    This file is part of FairEmail.
+
+    FairEmail is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    FairEmail is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with FairEmail.  If not, see <http://www.gnu.org/licenses/>.
+
+    Copyright 2018-2020 by Marcel Bokhorst (M66B)
+*/
+
+import android.graphics.Canvas;
+import android.graphics.Paint;
+import android.graphics.Typeface;
+import android.text.Layout;
+import android.text.Spanned;
+import android.text.TextPaint;
+import android.text.style.BulletSpan;
+
+public class NumberSpan extends BulletSpan {
+    private TextPaint tp;
+    private String number;
+    private int margin;
+
+    public NumberSpan(int gapWidth, int color, float textSize, int index) {
+        tp = new TextPaint();
+        tp.setStyle(Paint.Style.FILL);
+        tp.setColor(color);
+        tp.setTypeface(Typeface.MONOSPACE);
+        tp.setTextSize(textSize);
+
+        number = index + ".";
+        margin = Math.round(tp.measureText(number) + gapWidth);
+    }
+
+    @Override
+    public int getLeadingMargin(boolean first) {
+        // https://issuetracker.google.com/issues/36956124
+        // This is called before drawLeadingMargin to justify the text
+        return margin;
+    }
+
+    @Override
+    public void drawLeadingMargin(Canvas c, Paint p, int x, int dir, int top, int baseline, int bottom, CharSequence text, int start, int end, boolean first, Layout layout) {
+        if (text instanceof Spanned &&
+                ((Spanned) text).getSpanStart(this) == start) {
+            float textSize = tp.getTextSize();
+            if (textSize > p.getTextSize())
+                tp.setTextSize(p.getTextSize());
+            c.drawText(number, x + dir, baseline, tp);
+            tp.setTextSize(textSize);
+        }
+    }
+}