fix: select all checkbox inconsistent (#76)

When no migrators is available, "selectAll" check box shouldn't be
visible cause there's nothing to select. Just disable item is not
friendly for user, add message to notify user that there is no migrator
available.

Author: asterwyx

src/migrator/app/taskpage.cpp

@@ -83,15 +83,16 @@ class TaskModel : public QAbstractListModel {
         migrators_ = factory_->list(availableAddons);
         migratorStatesCache_.resize(migrators_.size());
         int idx = 0;
-        availMigrators_ = 0;
+        auto tmpAvailMigrators = 0;
         for (const auto &migrator : migrators_) {
             migratorStatesCache_[idx] = migrator->check();
             if (migratorStatesCache_[idx]) {
-                availMigrators_++;
+                tmpAvailMigrators++;
             }
             idx++;
         }
         selected_.clear();
+        setAvailMigrators(tmpAvailMigrators);
         endResetModel();
         Q_EMIT selectedChanged();
     }
@@ -116,7 +117,7 @@ class TaskModel : public QAbstractListModel {
     }
 
     bool allSelected() const {
-        return static_cast<int>(availMigrators_) == selected_.size();
+        return availMigrators_ != 0 && static_cast<int>(availMigrators_) == selected_.size();
     }
 
     bool someSelected() const { return !selected_.isEmpty(); }
@@ -129,8 +130,16 @@ class TaskModel : public QAbstractListModel {
         return result;
     }
 
+    void setAvailMigrators(int availMigrators) {
+        if (availMigrators == static_cast<int>(availMigrators_))
+            return;
+        availMigrators_ = availMigrators;
+        Q_EMIT availMigratorsChanged(availMigrators_);
+    }
+
 Q_SIGNALS:
     void selectedChanged();
+    void availMigratorsChanged(int);
 
 private:
     const MigratorFactory *factory_;
@@ -148,7 +157,8 @@ TaskPage::TaskPage(MainWindow *parent)
     taskView->setModel(model_);
     fcitxNotRunningMessage->setVisible(!parent_->dbus()->available());
 
-    descriptionLabel->setText(_("Click on an item for more details."));
+    selectAllBox->hide();
+    descriptionLabel->setText(_("No available migrators."));
     connect(taskView->selectionModel(), &QItemSelectionModel::currentChanged,
             this, [this](const QModelIndex &current) {
                 if (current.isValid()) {
@@ -163,6 +173,15 @@ TaskPage::TaskPage(MainWindow *parent)
         selectAllBox->setChecked(model_->allSelected());
         Q_EMIT completeChanged();
     });
+    connect(model_, &TaskModel::availMigratorsChanged, this, [this](int availMigrators) {
+        if (!availMigrators) {
+            selectAllBox->hide();
+            descriptionLabel->setText(_("No available migrators."));
+        } else {
+            selectAllBox->show();
+            descriptionLabel->setText(_("Click on an item for more details."));
+        }
+    });
     connect(selectAllBox, &QCheckBox::clicked, this, [this](bool checked) {
         if (checked) {
             model_->selectAll();