Most of us split Emacs horizontally by 2 windows so that we can easily edit and compare multi documents at the same time. However, the problem is that the two windows usually have the same size and sometimes difficult for you to work with files with long lines. Golden Ratio Mode is a small but useful package for Emacs that will automatically resize the focused window by golden ratio.

The window that has the main focus will have the perfect size for editing, while the ones that are not being actively edited will be re-sized to a smaller size that doesn’t get in the way, but at the same time will be readable enough to know it’s content.

You can install it using package.el. After finishing installation, just add this to your init.el file

(require 'golden-ratio)
(golden-ratio-mode 1)

To prevent Golden Ratio mode to be activated for certain mode, use this

(setq golden-ratio-exclude-modes '("ediff-mode"
                                   "eshell-mode"
                                   "dired-mode"))

On a high resolution screen, when the display width of the focused window resized by golden ratio is larger than 160 characters, opening any commands which call to pop-up-window will cause Emacs to create extra window instead of jump to an already existing window. TO prevent that, just set the variable split-width-threshold to nil

(setq split-width-threshold nil)