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Apply dark theme to PDF by inverting colors #574

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16 changes: 15 additions & 1 deletion app/src/main/java/app/grapheneos/pdfviewer/PdfViewer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -130,6 +130,7 @@ public class PdfViewer extends AppCompatActivity implements LoaderManager.Loader
private String mEncryptedDocumentPassword;
private List<CharSequence> mDocumentProperties;
private InputStream mInputStream;
private boolean invertedMode = false;

private PdfviewerBinding binding;
private TextView mTextView;
Expand Down Expand Up @@ -416,8 +417,17 @@ public void onPageFinished(WebView view, String url) {
mDocumentState = STATE_LOADED;
invalidateOptionsMenu();
loadPdfWithPassword(mEncryptedDocumentPassword);

if (invertedMode) injectDarkThemeCss(view);
}
private void injectDarkThemeCss(WebView view) {
String js = "javascript:(function() {" +
"document.body.style.filter = 'invert(1) hue-rotate(180deg)';" +
"})()";
view.evaluateJavascript(js, null);
}


@Override
public boolean onRenderProcessGone(WebView view, RenderProcessGoneDetail detail) {
if (detail.didCrash()) {
Expand Down Expand Up @@ -730,7 +740,7 @@ public boolean onPrepareOptionsMenu(@NonNull Menu menu) {
R.id.action_next, R.id.action_previous, R.id.action_first, R.id.action_last,
R.id.action_rotate_clockwise, R.id.action_rotate_counterclockwise,
R.id.action_view_document_properties, R.id.action_share, R.id.action_save_as,
R.id.action_outline));
R.id.action_toggle_inverted_mode, R.id.action_outline));
if (BuildConfig.DEBUG) {
ids.add(R.id.debug_action_toggle_text_layer_visibility);
ids.add(R.id.debug_action_crash_webview);
Expand Down Expand Up @@ -759,6 +769,7 @@ public boolean onPrepareOptionsMenu(@NonNull Menu menu) {
enableDisableMenuItem(menu.findItem(R.id.action_next), mPage < mNumPages);
enableDisableMenuItem(menu.findItem(R.id.action_previous), mPage > 1);
enableDisableMenuItem(menu.findItem(R.id.action_save_as), mUri != null);
enableDisableMenuItem(menu.findItem(R.id.action_toggle_inverted_mode), mUri != null);
enableDisableMenuItem(menu.findItem(R.id.action_view_document_properties),
mDocumentProperties != null);

Expand Down Expand Up @@ -821,6 +832,9 @@ public boolean onOptionsItemSelected(MenuItem item) {
return true;
} else if (itemId == R.id.action_save_as) {
saveDocument();
}else if (itemId == R.id.action_toggle_inverted_mode) {
invertedMode = !invertedMode;
loadPdf();
} else if (itemId == R.id.debug_action_toggle_text_layer_visibility) {
binding.webview.evaluateJavascript("toggleTextLayerVisibility()", null);
return true;
Expand Down
6 changes: 6 additions & 0 deletions app/src/main/res/menu/pdf_viewer.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -72,6 +72,12 @@
android:icon="@drawable/ic_outline_bulletlist_24dp"
android:title="@string/action_outline" />

<item
android:id="@+id/action_toggle_inverted_mode"
android:icon="@drawable/ic_outline_bulletlist_24dp"
android:title="@string/action_toggle_inverted_mode" />


<item
android:id="@+id/action_view_document_properties"
android:title="@string/action_view_document_properties"
Expand Down
1 change: 1 addition & 0 deletions app/src/main/res/values/strings.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@
<string name="action_share">Share</string>
<string name="action_save_as">Save as</string>
<string name="action_outline">Outline</string>
<string name="action_toggle_inverted_mode">Toggle inverted mode</string>
<string name="action_view_document_properties">Properties</string>
<string name="action_close">Close</string>

Expand Down