How to resize a buffer so it only takes a small part of the screen?

In Emacs how can I resize a buffer so it only takes a small part of the screen ?

Is there any way ?

I would like to have the src taking 70% of the screen and a file manager in the othe开发者_StackOverflow中文版r 30%

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Set width of current window on current frame to ~ 70%:

(window-resize nil (- (truncate (* 0.7 (frame-width))) (window-width)) t)

The other windows are shrunk automatically. If you want to adjust more than one it gets more difficult.

As command:

(defun window-resize-to-70-percent ()
  (interactive)
  (window-resize nil (- (truncate (* 0.7 (frame-width))) (window-width)) t))

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Use separate window-manager frames for individual buffers (by default). Automatically shrink-fit the frames to fit the buffer content.

See One-On-One Emacs, in particular, libraries fit-frame.el and autofit-frame.el.