In Initial load the SharePoint calculate the size (Width and Height) and  assigned to the #S4-workspace and #ms-designer-ribbon

Resize the window, the above same action is to be perform it again.

Steps :

  1. Using Chrome developer tools, I selected the #s4-workspace div and the selected “Break On…”, “Attributes modifications”:


  2. Then I resized the browser window and check, the function trigger


  3. So now that I know that the name of the function that SharePoint uses to calculate the size of the #s4-workspace div


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