Fix JS drop event not firing in the reviewer (#1906)

* Allow webviews to opt in to default D&D handling

* Remove redundant webview.js include

* Block default drag & drop behavior in reviewing screens

* Fix mypy error

qt/aqt/browser/previewer.py

@@ -132,6 +132,8 @@ class Previewer(QDialog):
             ],
             context=self,
         )
+        self._web.allow_drops = True
+        self._web.eval("_blockDefaultDragDropBehavior();")
         self._web.set_bridge_command(self._on_bridge_cmd, self)
 
     def _on_bridge_cmd(self, cmd: str) -> Any:

qt/aqt/clayout.py

@@ -355,6 +355,8 @@ class CardLayout(QDialog):
             ],
             context=self,
         )
+        self.preview_web.allow_drops = True
+        self.preview_web.eval("_blockDefaultDragDropBehavior();")
         self.preview_web.set_bridge_command(self._on_bridge_cmd, self)
 
         if self._isCloze():

qt/aqt/reviewer.py

@@ -313,6 +313,9 @@ class Reviewer:
             ],
             context=self,
         )
+        # block default drag & drop behavior while allowing drop events to be received by JS handlers
+        self.web.allow_drops = True
+        self.web.eval("_blockDefaultDragDropBehavior();")
         # show answer / ease buttons
         self.bottom.web.show()
         self.bottom.web.stdHtml(

qt/aqt/toolbar.py

@@ -47,7 +47,7 @@ class Toolbar:
         self.web.stdHtml(
             self._body % self._centerLinks(),
             css=["css/toolbar.css"],
-            js=["js/webview.js", "js/vendor/jquery.min.js", "js/toolbar.js"],
+            js=["js/vendor/jquery.min.js", "js/toolbar.js"],
             context=web_context,
         )
         self.web.adjustHeightToFit()

qt/aqt/webview.py

@@ -222,6 +222,8 @@ class WebContent:
 
 
 class AnkiWebView(QWebEngineView):
+    allow_drops = False
+
     def __init__(
         self,
         parent: Optional[QWidget] = None,
@@ -322,7 +324,8 @@ class AnkiWebView(QWebEngineView):
         m.popup(QCursor.pos())
 
     def dropEvent(self, evt: QDropEvent) -> None:
-        pass
+        if self.allow_drops:
+            super().dropEvent(evt)
 
     def setHtml(self, html: str) -> None:  #  type: ignore
         # discard any previous pending actions
@@ -331,6 +334,7 @@ class AnkiWebView(QWebEngineView):
         self._queueAction("setHtml", html)
         self.set_open_links_externally(True)
         self.setZoomFactor(1)
+        self.allow_drops = False
         self.show()
 
     def _setHtml(self, html: str) -> None:
@@ -357,6 +361,7 @@ class AnkiWebView(QWebEngineView):
     def load_url(self, url: QUrl) -> None:
         # allow queuing actions when loading url directly
         self._domDone = False
+        self.allow_drops = False
         super().load(url)
 
     def app_zoom_factor(self) -> float:

ts/reviewer/index.ts

@@ -227,3 +227,13 @@ export function _typeAnsPress(): void {
 export function _emulateMobile(enabled: boolean): void {
     document.documentElement.classList.toggle("mobile", enabled);
 }
+
+// Block Qt's default drag & drop behavior by default
+export function _blockDefaultDragDropBehavior(): void {
+    function handler(evt: DragEvent) {
+        evt.preventDefault();
+    }
+    document.ondragenter = handler;
+    document.ondragover = handler;
+    document.ondrop = handler;
+}