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36 id 1TI6vW-0006xx-GH; Sat, 29 Sep 2012 19:58:30 -0400
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37 Date: Sat, 29 Sep 2012 19:58:30 -0400
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38 From: Austin Clements <amdragon@MIT.EDU>
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39 To: Jani Nikula <jani@nikula.org>
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40 Subject: Re: [PATCH] emacs: simplify point placement in notmuch-hello refresh
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41 Message-ID: <20120929235830.GZ26662@mit.edu>
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42 References: <1348958664-1767-1-git-send-email-jani@nikula.org>
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77 LGTM. I wasn't aware notmuch-hello even attempted to maintain point,
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78 since I'd never seen it work.
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80 This patch could go a step further and remove found-target-pos from
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81 notmuch-hello-insert-saved-searches, target-pos from
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82 notmuch-hello-insert-searches, and found-target-pos from
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83 notmuch-hello-insert-buttons.
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85 It might be more stable to record the line number and column count and
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86 restore those, since point is sensitive to additions and removals of
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87 text within earlier lines.
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90 On a more abstract note, I feel like we have this same problem all
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91 over the Emacs UI: we "update" some UI by completely rebuilding it,
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92 and then we make some ad hoc, more-or-less (usually less) intelligent
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93 guess about where point should go. notmuch-hello has this problem,
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94 updating search-mode lines on tag change has this problem, refreshing
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95 the search buffer has this problem, and various buffer-rebuilding
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96 toggles in show have this problem.
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98 Proper incremental UI updates are simply not an option for some of
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99 these cases, because we have to call out to the CLI to get new data
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100 and that data might be completely different from what we're currently
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101 showing. We could restructure things to support this---for example,
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102 when toggling crypto, show could ask for the body of each message it's
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103 already showing---but this would complicate the code and I'm not sure
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104 we can restructure cases where the set of objects may change.
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106 But I wonder if there's an abstraction that would let us fully rebuild
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107 UIs or parts of UIs, but keep enough context to make this fluid. I'm
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108 imagining something like representing a buffer as a tree of UI nodes,
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109 where the buffer itself is simply the flattening of this tree, and
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110 each UI node has a identifier that's unique among its siblings. For
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111 example, the search buffer would have a root child for each search
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112 result, and then each piece of the result line would be a child of
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113 that line's node. This mechanism would give us a persistent context.
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114 Before an update, it could record the identifiers of all of the nodes
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115 in the path leading to the leaf node containing point, along with all
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116 of the prior siblings of each of these nodes and the offset of point
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117 within the leaf node. After and update, it could replay this path as
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118 best as possible: at each step in the path, if it can find a node with
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119 the same identifier as the node in the path, it would descend into it;
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120 otherwise, it would descend into the last recorded sibling it can find
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121 in the new tree. When this decent reaches a leaf, it can place point
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122 there. This same mechanism could be used to record and restore the
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123 window start position, as well as other markers we may need.
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125 Quoth Jani Nikula on Sep 30 at 1:44 am:
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126 > notmuch-hello (called also through notmuch-hello-update, bound to '='
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127 > by default) tries to find the widget under or following point before
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128 > refresh, and put the point back to the widget afterwards. The code has
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129 > grown quite complicated, and has at least the following issues:
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131 > 1) All the individual section functions have to include code to
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132 > support point placement. If there is no such support, point is
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133 > dropped to the search box. Only saved searches and all tags
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134 > sections support point placement.
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136 > 2) Point placement is based on widget-value. If there are two widgets
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137 > with the same widget-value (for example a saved search with the
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138 > same name as a tag) the point is moved to the earlier one, even if
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139 > point was on the later one.
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141 > 3) When first entering notmuch-hello notmuch-hello-target is nil, and
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142 > point is dropped to the search box.
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144 > Moving the point to the search box is annoying because the user is
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145 > required to move the point before being able to enter key bindings.
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147 > Simplify the code by removing all point placement based on widgets, as
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148 > it does not work properly, and trying to fix that would unnecessarily
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149 > complicate the code.
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151 > Point is simply saved before refresh, and put back to where it
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152 > was. Sometimes, if notmuch-show-empty-saved-searches is nil, and the
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153 > refresh adds or removes saved searches from the list, this has the
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154 > appearance of moving the point relative to the nearest widgets. This
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155 > is a much smaller and less frequent problem than the ones listed
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160 > I've sent this before months ago, and received comments starting at
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161 > id:"87aa2aohjs.fsf@gmail.com". I find the current behaviour annoying,
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162 > and I prefer this simple fix over complicating the existing
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163 > mess. Nobody has stood up to do anything better anyway. Perhaps we
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164 > could take a step forward with this while waiting for Someone(tm) to
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165 > come up with the perfect point placement?
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167 > emacs/notmuch-hello.el | 70 ++++++++++++------------------------------------
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168 > 1 file changed, 17 insertions(+), 53 deletions(-)
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170 > diff --git a/emacs/notmuch-hello.el b/emacs/notmuch-hello.el
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171 > index 684bedc..04d90cf 100644
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172 > --- a/emacs/notmuch-hello.el
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173 > +++ b/emacs/notmuch-hello.el
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174 > @@ -154,11 +154,6 @@ International Bureau of Weights and Measures."
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175 > (defvar notmuch-hello-url "http://notmuchmail.org"
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176 > "The `notmuch' web site.")
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178 > -(defvar notmuch-hello-search-pos nil
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179 > - "Position of search widget, if any.
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181 > -This should only be set by `notmuch-hello-insert-search'.")
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183 > (defvar notmuch-hello-custom-section-options
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184 > '((:filter (string :tag "Filter for each tag"))
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185 > (:filter-count (string :tag "Different filter to generate message counts"))
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186 > @@ -209,11 +204,8 @@ function produces a section simply by adding content to the current
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187 > buffer. A section should not end with an empty line, because a
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188 > newline will be inserted after each section by `notmuch-hello'.
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190 > -Each function should take no arguments. If the produced section
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191 > -includes `notmuch-hello-target' (i.e. cursor should be positioned
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192 > -inside this section), the function should return this element's
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194 > -Otherwise, it should return nil.
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195 > +Each function should take no arguments. The return value is
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198 > For convenience an element can also be a list of the form (FUNC ARG1
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199 > ARG2 .. ARGN) in which case FUNC will be applied to the rest of the
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200 > @@ -240,15 +232,6 @@ supported for \"Customized queries section\" items."
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201 > notmuch-hello-query-section
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202 > (function :tag "Custom section"))))
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204 > -(defvar notmuch-hello-target nil
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205 > - "Button text at position of point before rebuilding the notmuch-buffer.
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207 > -This variable contains the text of the button, if any, the
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208 > -point was positioned at before the notmuch-hello buffer was
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209 > -rebuilt. This should never actually be global and is defined as a
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210 > -defvar only for documentation purposes and to avoid a compiler
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211 > -warning about it occurring as a free variable.")
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213 > (defvar notmuch-hello-hidden-sections nil
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214 > "List of sections titles whose contents are hidden")
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216 > @@ -449,8 +432,6 @@ Such a list can be computed with `notmuch-hello-query-counts'."
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217 > (msg-count (third elem)))
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218 > (widget-insert (format "%8s "
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219 > (notmuch-hello-nice-number msg-count)))
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220 > - (if (string= name notmuch-hello-target)
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221 > - (setq found-target-pos (point-marker)))
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222 > (widget-create 'push-button
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223 > :notify #'notmuch-hello-widget-search
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224 > :notmuch-search-terms query
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225 > @@ -589,7 +570,6 @@ Complete list of currently available key bindings:
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226 > (defun notmuch-hello-insert-search ()
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227 > "Insert a search widget."
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228 > (widget-insert "Search: ")
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229 > - (setq notmuch-hello-search-pos (point-marker))
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230 > (widget-create 'editable-field
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231 > ;; Leave some space at the start and end of the
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233 > @@ -763,13 +743,7 @@ following:
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234 > (set-buffer "*notmuch-hello*")
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235 > (switch-to-buffer "*notmuch-hello*"))
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237 > - (let ((notmuch-hello-target (if (widget-at)
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238 > - (widget-value (widget-at))
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239 > - (condition-case nil
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241 > - (widget-forward 1)
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242 > - (widget-value (widget-at)))
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244 > + (let ((final-target-pos (point))
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245 > (inhibit-read-only t))
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247 > ;; Delete all editable widget fields. Editable widget fields are
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248 > @@ -788,30 +762,20 @@ following:
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249 > (mapc 'delete-overlay (car all))
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250 > (mapc 'delete-overlay (cdr all)))
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252 > - (let (final-target-pos)
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254 > - (lambda (section)
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255 > - (let ((point-before (point))
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256 > - (result (if (functionp section)
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257 > - (funcall section)
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258 > - (apply (car section) (cdr section)))))
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259 > - (if (and (not final-target-pos) (integer-or-marker-p result))
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260 > - (setq final-target-pos result))
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261 > - ;; don't insert a newline when the previous section didn't show
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263 > - (unless (eq (point) point-before)
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264 > - (widget-insert "\n"))))
\r
265 > - notmuch-hello-sections)
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268 > - (when final-target-pos
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269 > - (goto-char final-target-pos)
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270 > - (unless (widget-at)
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271 > - (widget-forward 1)))
\r
273 > - (unless (widget-at)
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274 > - (when notmuch-hello-search-pos
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275 > - (goto-char notmuch-hello-search-pos)))))
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277 > + (lambda (section)
\r
278 > + (let ((point-before (point)))
\r
279 > + (if (functionp section)
\r
280 > + (funcall section)
\r
281 > + (apply (car section) (cdr section)))
\r
282 > + ;; don't insert a newline when the previous section didn't
\r
283 > + ;; show anything.
\r
284 > + (unless (eq (point) point-before)
\r
285 > + (widget-insert "\n"))))
\r
286 > + notmuch-hello-sections)
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289 > + (goto-char final-target-pos))
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290 > (run-hooks 'notmuch-hello-refresh-hook)
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291 > (setq notmuch-hello-first-run nil))
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295 Austin Clements MIT/'06/PhD/CSAIL
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296 amdragon@mit.edu http://web.mit.edu/amdragon
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297 Somewhere in the dream we call reality you will find me,
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298 searching for the reality we call dreams.
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projects / notmuch-archives.git / blob