Warn user they will lose changes if they pick a new PDF

Author: photown

src/Main.ts

@@ -31,11 +31,18 @@ function onPageLoad() {
 
   parsePageUrl();
 
-  view.setOnPdfFileChosenListener(async function (pdfFile: File) {
+  view.setOnPdfFileChosenListener(
+    () => true,
+    async function (pdfFile: File) {
+      await loadPdfFromFile(pdfFile);
+    }
+  );
+
+  async function loadPdfFromFile(pdfFile: File) {
     await readFileAsArrayBuffer(pdfFile).then(function (fileData: ArrayBuffer) {
       loadPdf(pdfFile.name, fileData);
     });
-  });
+  }
 
   function readFileAsArrayBuffer(file: File): Promise<ArrayBuffer> {
     return new Promise((resolve, reject) => {
@@ -155,6 +162,21 @@ function onPageLoad() {
 
     view.enableNavButtons();
 
+    view.setOnPdfFileChosenListener(
+      function () {
+        const overlays: Overlays = extractOverlays();
+        return (
+          overlays.pagesOverlays.size == 0 ||
+          confirm(
+            "If you load another PDF, all changes in the current PDF will be lost. Are you sure?"
+          )
+        );
+      },
+      async function (pdfFile: File) {
+        await loadPdfFromFile(pdfFile);
+      }
+    );
+
     view.setOnNextClickedListener(function () {
       if (currentPage + 1 <= pdfDocument.getPageCount()) {
         gotoPage(currentPage + 1);

src/View.ts

@@ -300,13 +300,17 @@ export class View {
   }
 
   public setOnPdfFileChosenListener(
+    canChoosePdfPrecheck: () => boolean,
     onPdfFileChosen: (pdfFile: File) => Promise<void>
   ) {
     const pdfInput = document.getElementById(
       "pdf-file-input"
     ) as HTMLInputElement;
-    pdfInput.onclick = function () {
+    pdfInput.onclick = function (e: Event) {
       pdfInput.value = "";
+      if (!canChoosePdfPrecheck()) {
+        e.preventDefault();
+      }
     };
     pdfInput.onchange = async function (ev: Event) {
       const input = ev.target as HTMLInputElement;