the-btfash-foundation/Markwon
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Defensive copy in SpannableBuilder

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This commit is contained in:
Dimitry Ivanov 2017-11-02 19:20:33 +03:00
parent e37d6e1729
commit 1f403abeb0
3 changed files with 23 additions and 83 deletions
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54
app/src/main/java/ru/noties/markwon/MainActivity.java
View File

@ -2,12 +2,8 @@ package ru.noties.markwon;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.net.Uri;
import android.os.Bundle;
import android.text.Layout;
import android.text.style.LeadingMarginSpan;
import android.view.View;
import android.widget.TextView;
@ -62,56 +58,6 @@ public class MainActivity extends Activity {
appBarRenderer.render(appBarState());
if (false) {
final class Whatever {
CharSequence text() {
final SpannableBuilder builder = new SpannableBuilder();
builder.append("First line\n\n");
builder.append(Markwon.markdown(MainActivity.this, "* first\n* second\n* * third\n* * * forth\n\n"));
builder.setSpan(new LeadingMarginSpan() {
@Override
public int getLeadingMargin(boolean first) {
return 100;
}
@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) {
}
}, 0);
builder.append("Last line\n\n");
return builder.text();
}
}
final Whatever whatever = new Whatever();
final SpannableBuilder builder = new SpannableBuilder();
builder.append(whatever.text());
builder.append(whatever.text());
builder.setSpan(new LeadingMarginSpan() {
@Override
public int getLeadingMargin(boolean first) {
return 50;
}
@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) {
}
}, 0);
builder.append(whatever.text());
textView.setText(builder.text());
return;
}
markdownLoader.load(uri(), new MarkdownLoader.OnMarkdownTextLoaded() {
@Override
public void apply(final String text) {

47
library/src/main/java/ru/noties/markwon/SpannableBuilder.java
View File

@ -14,6 +14,8 @@ import java.util.Iterator;
* is using an array to store all the information about spans. So, a span that is added first
* will be drawn first, which leads to subtle bugs (spans receive wrong `x` values when
* requested to draw itself)
*
* @since 1.0.1
*/
@SuppressWarnings({"WeakerAccess", "unused"})
public class SpannableBuilder {
@ -23,6 +25,8 @@ public class SpannableBuilder {
// we will be using SpannableStringBuilder anyway as a backing store
// as it has tight connection with system (implements some hidden methods, etc)
private final SpannableStringBuilder builder;
// actually we might be just using ArrayList
private final Deque<Span> spans = new ArrayDeque<>(8);
public SpannableBuilder() {
@ -31,7 +35,7 @@ public class SpannableBuilder {
public SpannableBuilder(@NonNull CharSequence cs) {
this.builder = new SpannableStringBuilderImpl(cs.toString());
copySpans(cs);
copySpans(0, cs);
}
/**
@ -55,7 +59,7 @@ public class SpannableBuilder {
@NonNull
public SpannableBuilder append(@NonNull CharSequence cs) {
copySpans(cs);
copySpans(length(), cs);
builder.append(cs.toString());
@ -109,7 +113,8 @@ public class SpannableBuilder {
@NonNull
public CharSequence remove(int start, int end) {
// okay: here is what we will try to do:
// this method is intended to be used only by markdown visitor
// it's a workaround to allow tables
final SpannableStringBuilderImpl impl = new SpannableStringBuilderImpl(builder.subSequence(start, end));
@ -165,24 +170,26 @@ public class SpannableBuilder {
return builder.toString();
}
// Unfortunately I cannot see any way to NOT expose this internal value, which opens a gate
// to external modification (first of all InputFilters, that potentially break span indexes
// as we keep track of them independently). Must warn user to NOT apply inputFilters
@NonNull
public CharSequence text() {
// if called once, it will apply spans, which will modify our state
// okay, in order to not allow external modification and keep our spans order
// we should not return our builder
//
// plus, if this method was called -> all spans would be applied, which potentially
// breaks the order that we intend to use
// so, we will defensively copy builder
applySpans();
final SpannableStringBuilderImpl impl = new SpannableStringBuilderImpl(builder.toString());
// we could return here for example new SpannableStringBuilder(builder)
// but, if returned value will be used in other SpannableBuilder,
// we won't be able to detect in what order to store the spans
return builder;
for (Span span : spans) {
impl.setSpan(span.what, span.start, span.end, span.flags);
}
private void copySpans(@Nullable CharSequence cs) {
return impl;
}
private void copySpans(final int index, @Nullable CharSequence cs) {
// we must identify already reversed Spanned...
// and (!) iterate backwards when adding (to preserve order)
@ -191,7 +198,6 @@ public class SpannableBuilder {
final Spanned spanned = (Spanned) cs;
final boolean reverse = spanned instanceof SpannedReversed;
final int index = length();
final Object[] spans = spanned.getSpans(0, spanned.length(), Object.class);
@ -209,17 +215,6 @@ public class SpannableBuilder {
}
}
private void applySpans() {
// will apply appended spans in reverse order
// clear the stack (that keeps track of them)
Span span;
while ((span = spans.poll()) != null) {
builder.setSpan(span.what, span.start, span.end, span.flags);
}
}
private static class Span {
final Object what;

7
library/src/main/java/ru/noties/markwon/SpannableStringBuilderImpl.java
View File

@ -2,12 +2,11 @@ package ru.noties.markwon;
import android.text.SpannableStringBuilder;
/**
* @since 1.0.1
*/
class SpannableStringBuilderImpl extends SpannableStringBuilder implements SpannedReversed {
SpannableStringBuilderImpl() {
super();
}
SpannableStringBuilderImpl(CharSequence text) {
super(text);
}