Move nav-flash from ui/doom to ui/nav-flash (#92)

modules/ui/nav-flash/README.org

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+* :ui nav-flash
+
+This module uses ~nav-flash~ to flash the line around the cursor after any motion command that might reasonably send the cursor somewhere the eyes can't follow.
+
+#+begin_quote
+Tremendously helpful on a 30" 2560x1600 display.
+#+end_quote
+
+** Install
+This module has no other dependencies.
+
+** Configure
+By default, ~nav-flash~ will be triggered whenever ~recenter~ is called. =:feature jump= attaches ~recenter~ to various hooks:
+
+#+BEGIN_SRC emacs-lisp
+(add-hook!
+  '(imenu-after-jump-hook evil-jumps-post-jump-hook
+    counsel-grep-post-action-hook dumb-jump-after-jump-hook)
+  #'recenter)
+#+END_SRC
+

modules/ui/nav-flash/config.el

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+;;; ui/nav-flash/config.el
+
+(def-package! nav-flash
+  :commands nav-flash-show
+  :init
+  (defun +doom*blink-cursor-maybe (orig-fn &rest args)
+    "Blink current line if the window has moved."
+    (let ((point (save-excursion (goto-char (window-start))
+                                 (point-marker))))
+      (apply orig-fn args)
+      (unless (equal point
+                     (save-excursion (goto-char (window-start))
+                                     (point-marker)))
+        (+doom/blink-cursor))))
+
+  (defun +doom/blink-cursor (&rest _)
+    "Blink current line using `nav-flash'."
+    (interactive)
+    (unless (minibufferp)
+      (nav-flash-show)
+      ;; only show in the current window
+      (overlay-put compilation-highlight-overlay 'window (selected-window))))
+
+  ;; NOTE In :feature jump `recenter' is hooked to a bunch of jumping commands,
+  ;; which will trigger nav-flash.
+
+  (advice-add #'windmove-do-window-select :around #'+doom*blink-cursor-maybe)
+  (advice-add #'recenter :around #'+doom*blink-cursor-maybe)
+
+  (after! evil
+    (advice-add #'evil-window-top    :after #'+doom/blink-cursor)
+    (advice-add #'evil-window-middle :after #'+doom/blink-cursor)
+    (advice-add #'evil-window-bottom :after #'+doom/blink-cursor)))
+
+

modules/ui/nav-flash/packages.el

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+;; -*- no-byte-compile: t; -*-
+;;; ui/nav-flash/packages.el
+
+(package! nav-flash)