[elpa] externals/topspace 42353585e0 005/181: Minor code improvements from the "low hanging fruit" in initial commit:

[ELPA Syncer]

branch: externals/topspace
commit 42353585e048ef2998c5050bc6ffee5e169e6e41
Author: Trevor Pogue <poguete@mcmaster.ca>
Commit: Trevor Pogue <poguete@mcmaster.ca>

    Minor code improvements from the "low hanging fruit" in initial commit:
    - made text start closer to dead centered by changing division constant in 
the vcm--center-offset function/property
    - simplified the control of vcm-scroll-offset by removing an unnecessary 
conditional and making it strictly a variable instead of a property
    - rearranged order in which the code sections appear
    - added window-resizing hook, but it is not a complete window-resizing 
solution because it only works for windows in focus
    - removed before-change-functions-hook which is made redundant by 
after-change-functions-hook
    - added comment clarifications for:
      - purpose of variable vcm-first-recenter-done
      - fact that the use of term "properties" in this code is inspired 
specifically from the definition of properties in Python
---
 vertical-center-mode.el | 166 ++++++++++++++++++++++++------------------------
 1 file changed, 82 insertions(+), 84 deletions(-)

diff --git a/vertical-center-mode.el b/vertical-center-mode.el
index 650cd7e158..b34cb773aa 100644
--- a/vertical-center-mode.el
+++ b/vertical-center-mode.el
@@ -24,10 +24,11 @@
 
 ;;; TODO:
 ;; - support scrolling above top line with page scrolling as well
+;; - wrapped lines being counted as single lines when centering
 ;; - cannot scroll above top line if buffer open in multiple windows and
 ;; one or more windows is scrolled above beginning of buffer
-;; - centering is a bit lower than dead center
-;; - support recentering on window resize
+;; - recentering on window resize only occurs in selected buffer
+;; - issues if enabling when top line in window is > line 1
 ;; - submit to MELPA? (after optimizing/cleaning up code more)
 
 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -69,13 +70,19 @@ another window unless user has previously adjusted its 
height with scrolling.
 (defun vcm--turn-on ()
   (setq-local vcm-on t)
   (setq-local vcm-overlay (make-overlay (point-min) (point-max)))
+  ;; vcm-scroll-offset: the overlay portion that the user adjusts with 
scrolling
   (setq-local vcm-scroll-offset 0)
   (setq-local vcm-user-scrolled nil)
   (vcm--add-hooks)
   (if (not (boundp 'vcm-first-recenter-done))
+      ;; vcm-first-recenter-done is used to block too many recenterings 
occuring
+      ;; that are triggered by window-based hooks,
       (setq-local vcm-first-recenter-done nil))
-  (if vcm-first-recenter-done
-      (vcm--recenter-reset-scroll)))
+  ;; Below: let user turn the mode off then on again to recenter while 
preventing
+  ;; recentering here on initial mode turn-on. This avoids a bug with buffer
+  ;; not being centered on emacs startup, but need to investigate further to
+  ;; understand the root cause behind this bug/solution relationship.
+  (if vcm-first-recenter-done (vcm--recenter-reset-scroll)))
 
 (defun vcm--turn-off ()
   "Delete/unset data structures when the mode is turned off."
@@ -86,7 +93,6 @@ another window unless user has previously adjusted its height 
with scrolling.
   (makunbound 'vcm-scroll-offset)
   (makunbound 'vcm-user-scrolled))
 
-;; handle insertions into the buffer
 (defun vcm--kill-buffer ()
   (makunbound 'vcm-first-recenter-done)
   (vcm--turn-off))
@@ -95,32 +101,63 @@ another window unless user has previously adjusted its 
height with scrolling.
 
 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
-;;; Hooks
+;;; Properties (inspired specifically by definition of properties from Python)
 
-(defvar vcm--hook-alist
-  '(
-    (window-configuration-change-hook . vcm--recenter-reset-scroll-conditional)
-    (kill-buffer-hook . vcm--kill-buffer)
-    (before-change-functions . vcm--recenter-keep-scroll)
-    (after-change-functions . vcm--recenter-keep-scroll)
-    (pre-command-hook . vcm--scroll-increase-overlay)
-    (post-command-hook . vcm--scroll-decrease-overlay))
-  "A list of hooks so they only need to be written in one spot.
-List of cons cells in format (hook-variable . function).")
+(defun vcm--center-offset ()
+  "Portion of the overlay that makes small buffers centered."
+  ;; dividing by slightly less than 2 here made buffers more dead centered
+  (let ((center-offset (/ (* (- (window-height) (vcm--buf-size)) 31) 64)))
+    (when (< center-offset 0) (setq center-offset 0))
+    center-offset)) ; return center-offset
 
-(defun vcm--add-hooks ()
-  "Add hooks defined in variable `vcm-hook-alist'."
-  (mapc (lambda (entry) (add-hook (car entry) (cdr entry) t t))
-        vcm--hook-alist))
+(defun vcm--add-to-scroll-offset (direction)
+  (let ((pos (+ (- (line-number-at-pos) (vcm--top-line)) (vcm--overlay-size)))
+        (bottom (- (window-height) 5)))
+    ;; avoids a bug with cursor suddenly scrolling up
+    (when (> pos bottom) (previous-line)))
+  ;; only put overlay when top line is 1
+  (when (= (vcm--top-line) 1)
+    ;; block scrolling text fully below bottom of window
+    (unless (and (> direction 0)
+                 (>= (vcm--overlay-size) (- (window-height) 5)))
+      (setq vcm-scroll-offset (+ vcm-scroll-offset direction)))))
 
-(defun vcm--remove-hooks ()
-  "Remove hooks defined in variable `vcm-hook-alist'."
-  (mapc (lambda (entry) (remove-hook (car entry) (cdr entry) t))
-        vcm--hook-alist))
+(defun vcm--overlay-size ()
+  "The total overlay size."
+  (+ vcm-scroll-offset (vcm--center-offset)))
+
+(defun vcm--buf-size ()
+  "Size of the buffer text in lines."
+  (count-lines (point-min) (point-max)))
+
+(defun vcm--top-line ()
+  "Line number of the top line of text shown in the window."
+  (line-number-at-pos (window-start)))
 
 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
-;;; Scrolling
+;;; Overlay dislaying and recentering hooks
+
+;; the optional unused args in this section are just for hook compatibility
+
+(defun vcm--recenter-keep-scroll (&optional arg0 arg1 arg2)
+  "Use an overlay to display empty lines at the beginning of the buffer.
+This emulates the ability to scroll above the top line."
+  (let ((overlay-size (vcm--overlay-size)))
+    (overlay-put vcm-overlay 'before-string
+                 (when (> overlay-size 0) (make-string overlay-size ?\n))))
+  (setq vcm-first-recenter-done t))
+
+(defun vcm--recenter-reset-scroll (&optional arg0 arg1 arg2)
+  (setq vcm-scroll-offset 0)
+  (vcm--recenter-keep-scroll))
+
+(defun vcm--recenter-reset-scroll-conditional (&optional arg0 arg1 arg2)
+  (unless (and vcm-user-scrolled) (vcm--recenter-reset-scroll)))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;;; Scrolling hooks
 
 (defun vcm--scroll (scroll-list ccm-list scroll-direction)
   "Emulate scrolling if user command was a scrolling command."
@@ -131,7 +168,7 @@ List of cons cells in format (hook-variable . function).")
         (centering-cursor (member this-command ccm-list)))
     ;; shouldn't scroll from moving cursor unless in centered-cursor-mode
     (unless (bound-and-true-p centered-cursor-mode) (setq centering-cursor 
nil))
-    (when (and (or user-is-scrolling centering-cursor))
+    (when (or user-is-scrolling centering-cursor)
       (vcm--add-to-scroll-offset scroll-direction)
       (setq vcm-user-scrolled t)
       (vcm--recenter-keep-scroll))))
@@ -148,64 +185,25 @@ List of cons cells in format (hook-variable . function).")
 
 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
-;;; Overlay dislaying and recentering
-
-(defun vcm--recenter-keep-scroll (&optional arg0 arg1 arg2)
-  "Use an overlay to display empty lines at the beginning of the buffer.
-This emulates the ability to scroll above the top line."
-  (let ((overlay-size (vcm--overlay-size)))
-    (overlay-put vcm-overlay 'before-string
-                 (when (> overlay-size 0) (make-string overlay-size ?\n))))
-  (setq vcm-first-recenter-done t))
-
-(defun vcm--recenter-reset-scroll (&optional arg0 arg1 arg2)
-  (vcm--reset-scroll)
-  (vcm--recenter-keep-scroll))
-
-(defun vcm--recenter-reset-scroll-conditional (&optional arg0 arg1 arg2)
-  (unless (and vcm-user-scrolled)
-    (vcm--recenter-reset-scroll)))
-
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-
-;;; Properties
-
-(defun vcm--center-offset ()
-  "Portion of the overlay that makes small buffer centered."
-  (let ((center-offset
-         (/ (- (window-height) (vcm--buf-size)) 2)))
-    (when (< center-offset 0) (setq center-offset 0))
-    center-offset)) ; return center-offset
-
-(defun vcm--scroll-offset ()
-  "Portion of the overlay the user adjusts with scrolling."
-  (let ((top-line (vcm--top-line)))
-    (if (> top-line 2)
-        (setq vcm-scroll-offset (- (*(vcm--center-offset) -1) 1))))
-  vcm-scroll-offset) ; return vcm-scroll-offset
-
-(defun vcm--add-to-scroll-offset (direction)
-  (let ((pos (+ (- (line-number-at-pos) (vcm--top-line)) (vcm--overlay-size)))
-        (bottom (- (window-height) 5)))
-    ;; avoids a bug with cursor suddenly scrolling up
-    (when (> pos bottom) (previous-line)))
-  ;; only put overlay when top line is 1
-  (when (= (vcm--top-line) 1)
-    ;; block scrolling text fully below bottom of window
-    (unless (and (> direction 0)
-                 (>= (vcm--overlay-size) (- (window-height) 5)))
-      (setq vcm-scroll-offset (+ (vcm--scroll-offset) direction)))))
-
-(defun vcm--reset-scroll () (setq vcm-scroll-offset 0))
+;;; Hooks
 
-(defun vcm--overlay-size ()
-  "The total overlay size."
-  (+ (vcm--scroll-offset) (vcm--center-offset)))
+(defvar vcm--hook-alist
+  '(
+    (window-configuration-change-hook . vcm--recenter-reset-scroll-conditional)
+    (window-size-change-functions . vcm--recenter-reset-scroll)
+    (kill-buffer-hook . vcm--kill-buffer)
+    (after-change-functions . vcm--recenter-keep-scroll)
+    (pre-command-hook . vcm--scroll-increase-overlay)
+    (post-command-hook . vcm--scroll-decrease-overlay))
+  "A list of hooks so they only need to be written in one spot.
+List of cons cells in format (hook-variable . function).")
 
-(defun vcm--buf-size ()
-  "Size of the buffer text in lines."
-  (count-lines (point-min) (point-max)))
+(defun vcm--add-hooks ()
+  "Add hooks defined in variable `vcm-hook-alist'."
+  (mapc (lambda (entry) (add-hook (car entry) (cdr entry) t t))
+        vcm--hook-alist))
 
-(defun vcm--top-line ()
-  "Line number of the top line of text shown in the window."
-  (line-number-at-pos (window-start)))
+(defun vcm--remove-hooks ()
+  "Remove hooks defined in variable `vcm-hook-alist'."
+  (mapc (lambda (entry) (remove-hook (car entry) (cdr entry) t))
+        vcm--hook-alist))