bug#42272: 27.0.91; [PATCH] Fix doc-view rescale

[Yuan Fu <ykf5041@psu.edu>]

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> On Aug 14, 2020, at 7:53 AM, Lars Ingebrigtsen <larsi@gnus.org> wrote:
> 
> "Fu, Yuan" <ykf5041@psu.edu> writes:
> 
>> Here is the fix patch:
> 
> Thanks; applied to Emacs 28.

Cool! Here is the centering patch.

Yuan


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From 216f20f3628900c5dc4ea98a14f38b326a71c480 Mon Sep 17 00:00:00 2001
From: Yuan Fu <casouri@gmail.com>
Date: Thu, 13 Aug 2020 15:57:47 -0400
Subject: [PATCH] Add centering commands to doc-view.el

* lisp/doc-view.el (doc-view-mode-map): Add binding for centering
commands.
(doc-view-center-page-horizontally, doc-view-center-page-vertically):
New functions.
---
 lisp/doc-view.el | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/lisp/doc-view.el b/lisp/doc-view.el
index 3e2b244326..77c06a8eaf 100644
--- a/lisp/doc-view.el
+++ b/lisp/doc-view.el
@@ -435,6 +435,9 @@ doc-view-mode-map
     (define-key map (kbd "c m")       'doc-view-set-slice-using-mouse)
     (define-key map (kbd "c b")       'doc-view-set-slice-from-bounding-box)
     (define-key map (kbd "c r")       'doc-view-reset-slice)
+    ;; Centering the image
+    (define-key map (kbd "c h")       'doc-view-center-page-horizontally)
+    (define-key map (kbd "c v")       'doc-view-center-page-vertically)
     ;; Searching
     (define-key map (kbd "C-s")       'doc-view-search)
     (define-key map (kbd "<find>")    'doc-view-search)
@@ -921,6 +924,32 @@ doc-view-fit-window-to-page
     (when new-frame-params
       (modify-frame-parameters (selected-frame) new-frame-params))))
 
+(defun doc-view-center-page-horizontally ()
+  "Center page horizontally when page is wider than window."
+  (interactive)
+  (let ((page-width (car (image-size (doc-view-current-image) 'pixel)))
+        (window-width (window-body-width nil 'pixel))
+        ;; How much do we scroll in order to center the page?
+        (pixel-hscroll 0)
+        ;; How many pixels are there in a column?
+        (col-in-pixel (/ (window-body-width nil 'pixel)
+                         (window-body-width nil))))
+    (when (> page-width window-width)
+      (setq pixel-hscroll (/ (- page-width window-width) 2))
+      (set-window-hscroll (selected-window)
+                          (/ pixel-hscroll col-in-pixel)))))
+
+(defun doc-view-center-page-vertically ()
+  "Center page vertically when page is wider than window."
+  (interactive)
+  (let ((page-height (cdr (image-size (doc-view-current-image) 'pixel)))
+        (window-height (window-body-height nil 'pixel))
+        ;; How much do we scroll in order to center the page?
+        (pixel-scroll 0))
+    (when (> page-height window-height)
+      (setq pixel-scroll (/ (- page-height window-height) 2))
+      (set-window-vscroll (selected-window) pixel-scroll 'pixel))))
+
 (defun doc-view-reconvert-doc ()
   "Reconvert the current document.
 Should be invoked when the cached images aren't up-to-date."
-- 
2.27.0