Extract document resize planning

src/app_dialogs.cpp

@@ -1,6 +1,7 @@
 #include "pch.h"
 #include "app.h"
 #include "action.h"
+#include "app_core/document_resize.h"
 #include "app_core/document_export.h"
 #include "app_core/document_session.h"
 #include "settings.h"
@@ -558,9 +559,15 @@ void App::dialog_resize()
 
     dialog->btn_ok->on_click = [this,dialog](Node*)
     {
-        int res = dialog->get_resolution();
+        const auto plan = pp::app::plan_document_resize(
+            dialog->combo ? dialog->combo->m_current_index : 0);
+        if (!plan)
+        {
+            dialog->destroy();
+            return;
+        }
         if (canvas)
-            canvas->m_canvas->resize(res, res);
+            canvas->m_canvas->resize(plan.value().width, plan.value().height);
         App::I->title_update();
         ActionManager::clear();
         dialog->destroy();