Display warning when resolution gets too low during zooming

frontend/javascripts/messages.ts

@@ -284,6 +284,8 @@ instead. Only enable this option if you understand its effect. All layers will n
     "This dataset location is marked as 'scratch' and meant for testing only. Please move this dataset to a permanent storage location and reimport it.",
   "dataset.resolution_mismatch":
     "This dataset contains multiple layers which differ in their resolution. Please convert the layers to make their resolutions match. Otherwise, rendering errors cannot be avoided.",
+  "dataset.z1_downsampling_hint":
+    "The currently rendered quality is not optimal due to the available magnifications and the viewport arrangement. To improve the quality try to increase the size of the XY viewport (e.g., by maximizing it).",
   "annotation.finish": "Are you sure you want to permanently finish this annotation?",
   "annotation.was_finished": "Annotation was archived",
   "annotation.no_fallback_data_included":

frontend/javascripts/oxalis/model/sagas/dataset_saga.ts

@@ -1,10 +1,11 @@
-/* eslint-disable import/prefer-default-export */
 import type { Saga } from "oxalis/model/sagas/effect-generators";
 import { select } from "oxalis/model/sagas/effect-generators";
-import { takeEvery } from "typed-redux-saga";
+import { call, takeEvery } from "typed-redux-saga";
+import { sleep } from "libs/utils";
 import { getEnabledLayers } from "oxalis/model/accessors/dataset_accessor";
 import Toast from "libs/toast";
 import messages from "messages";
+import { getCurrentResolution } from "../accessors/flycam_accessor";
 export function* watchMaximumRenderableLayers(): Saga<void> {
   function* warnMaybe(): Saga<void> {
     const maximumLayerCountToRender = yield* select(
@@ -31,3 +32,29 @@ export function* watchMaximumRenderableLayers(): Saga<void> {
 
   yield* takeEvery(["WK_READY", "UPDATE_LAYER_SETTING", "UPDATE_DATASET_SETTING"], warnMaybe);
 }
+
+let downsamplingWarningDidShow = false;
+export function* watchZ1Downsampling(): Saga<void> {
+  function* maybeShowWarning(): Saga<void> {
+    const currentRes = yield* select((state) => getCurrentResolution(state));
+    const currentZoomStep = yield* select((state) => state.flycam.zoomStep);
+    const minVoxelPerPixel = 0.5;
+
+    if (!downsamplingWarningDidShow) {
+      // checking the downsampled dimensions x and y
+      for (let i = 0; i < 2; i++) {
+        const voxelPerPixelXY = currentZoomStep / currentRes[i];
+        if (voxelPerPixelXY < minVoxelPerPixel) {
+          Toast.warning(messages["dataset.z1_downsampling_hint"]);
+          downsamplingWarningDidShow = false;
+        }
+      }
+    }
+  }
+  yield* takeEvery("WK_READY", maybeShowWarning);
+  yield* call(sleep, 2000);
+  yield* takeEvery(
+    ["ZOOM_IN", "ZOOM_OUT", "ZOOM_BY_DELTA", "SET_ZOOM_STEP", "SET_STORED_LAYOUTS"],
+    maybeShowWarning,
+  );
+}

frontend/javascripts/oxalis/model/sagas/root_saga.ts

@@ -9,7 +9,7 @@ import SkeletontracingSagas from "oxalis/model/sagas/skeletontracing_saga";
 import ErrorHandling from "libs/error_handling";
 import handleMeshChanges from "oxalis/model/sagas/handle_mesh_changes";
 import isosurfaceSaga from "oxalis/model/sagas/isosurface_saga";
-import { watchMaximumRenderableLayers } from "oxalis/model/sagas/dataset_saga";
+import { watchMaximumRenderableLayers, watchZ1Downsampling } from "oxalis/model/sagas/dataset_saga";
 import { watchToolDeselection } from "oxalis/model/sagas/annotation_tool_saga";
 import SettingsSaga from "oxalis/model/sagas/settings_saga";
 import watchTasksAsync, { warnAboutMagRestriction } from "oxalis/model/sagas/task_saga";
@@ -47,6 +47,7 @@ function* restartableSaga(): Saga<void> {
       ...AnnotationSagas.map((saga) => call(saga)),
       ...SaveSagas.map((saga) => call(saga)),
       ...VolumetracingSagas.map((saga) => call(saga)),
+      call(watchZ1Downsampling),
     ]);
   } catch (err) {
     rootSagaCrashed = true;