add snap when finishing search

app/UI.hs

@@ -201,14 +201,14 @@ wireEvents ctx = do
     case keyval of
       Gdk.KEY_Down -> WebKit.findControllerSearchNext fc >> pure True
       Gdk.KEY_Up -> WebKit.findControllerSearchPrevious fc >> pure True
-      Gdk.KEY_Escape -> Gtk.setEditableText entry "" >> WebKit.findControllerSearchFinish fc >> Gtk.widgetGrabFocus (appWebView (ctxWidgets ctx)) >> pure True
+      Gdk.KEY_Escape -> Gtk.setEditableText entry "" >> WebKit.findControllerSearchFinish fc >> Gtk.widgetGrabFocus (appWebView (ctxWidgets ctx)) >> snapPagination ctx >> pure True
       _ -> pure False
   Gtk.widgetAddController entry searchKeys
 
   _ <- on entry #searchChanged $ do
     q <- Gtk.editableGetText entry
     if T.null q
-      then WebKit.findControllerSearchFinish fc
+      then WebKit.findControllerSearchFinish fc >> snapPagination ctx
       else WebKit.findControllerSearch fc q findOpts maxBound
   let runfwd = runSearch ctx nextMatch
   _ <- on entry #activate $ runfwd -- pressing enter while having search text
@@ -525,6 +525,26 @@ wrapHtml (Html body) start mode =
       let safe = T.filter (\c -> c /= '"' && c /= '\\') f
        in "<script>var el=document.getElementById(\"" <> safe <> "\");if(el)goToPage(Math.floor(el.offsetLeft/window.innerWidth));</script>"
 
+
+-- | Re-align the paginated view after an in-page find. WebKit reveals a match
+-- by scrolling the (multi-column) layout, which leaves the transform-based
+-- pager out of sync so several half-pages show at once once the search ends.
+-- Reset the scroll offset back to zero and re-apply the current page transform.
+-- No-op in scrolling mode, which scrolls natively and needs no fix-up.
+snapPagination :: Ctx -> IO ()
+snapPagination ctx = do
+  mode <- getMode ctx
+  when (mode == Paginated) $
+    evalJSBool
+      (appWebView (ctxWidgets ctx))
+      ( T.concat
+          [ "var d=document.documentElement,b=document.body;",
+            "d.scrollLeft=0;d.scrollTop=0;if(b){b.scrollLeft=0;b.scrollTop=0;}",
+            "window.scrollTo(0,0);if(typeof apply==='function'){apply();}true"
+          ]
+      )
+      (\_ -> pure ())
+
 evalJSBool :: WebKit.WebView -> T.Text -> (Bool -> IO ()) -> IO ()
 evalJSBool wv src k =
   WebKit.webViewEvaluateJavascript wv src (-1) Nothing Nothing (Nothing :: Maybe Gio.Cancellable)