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diff --git a/devdocs/elisp/abstract-display-example.html b/devdocs/elisp/abstract-display-example.html new file mode 100644 index 00000000..4e9c36ea --- /dev/null +++ b/devdocs/elisp/abstract-display-example.html @@ -0,0 +1,96 @@ + <h4 class="subsection">Abstract Display Example</h4> <p>Here is a simple example using functions of the ewoc package to implement a <em>color components</em> display, an area in a buffer that represents a vector of three integers (itself representing a 24-bit RGB value) in various ways. </p> <div class="example"> <pre class="example">(setq colorcomp-ewoc nil + colorcomp-data nil + colorcomp-mode-map nil + colorcomp-labels ["Red" "Green" "Blue"]) + +(defun colorcomp-pp (data) + (if data + (let ((comp (aref colorcomp-data data))) + (insert (aref colorcomp-labels data) "\t: #x" + (format "%02X" comp) " " + (make-string (ash comp -2) ?#) "\n")) + (let ((cstr (format "#%02X%02X%02X" + (aref colorcomp-data 0) + (aref colorcomp-data 1) + (aref colorcomp-data 2))) + (samp " (sample text) ")) + (insert "Color\t: " + (propertize samp 'face + `(foreground-color . ,cstr)) + (propertize samp 'face + `(background-color . ,cstr)) + "\n")))) + +(defun colorcomp (color) + "Allow fiddling with COLOR in a new buffer. +The buffer is in Color Components mode." + (interactive "sColor (name or #RGB or #RRGGBB): ") + (when (string= "" color) + (setq color "green")) + (unless (color-values color) + (error "No such color: %S" color)) + (switch-to-buffer + (generate-new-buffer (format "originally: %s" color))) + (kill-all-local-variables) + (setq major-mode 'colorcomp-mode + mode-name "Color Components") + (use-local-map colorcomp-mode-map) + (erase-buffer) + (buffer-disable-undo) + (let ((data (apply 'vector (mapcar (lambda (n) (ash n -8)) + (color-values color)))) + (ewoc (ewoc-create 'colorcomp-pp + "\nColor Components\n\n" + (substitute-command-keys + "\n\\{colorcomp-mode-map}")))) + (set (make-local-variable 'colorcomp-data) data) + (set (make-local-variable 'colorcomp-ewoc) ewoc) + (ewoc-enter-last ewoc 0) + (ewoc-enter-last ewoc 1) + (ewoc-enter-last ewoc 2) + (ewoc-enter-last ewoc nil))) +</pre> +</div> <p>This example can be extended to be a color selection widget (in other words, the “controller” part of the “model–view–controller” design paradigm) by defining commands to modify <code>colorcomp-data</code> and to finish the selection process, and a keymap to tie it all together conveniently. </p> <div class="example"> <pre class="example">(defun colorcomp-mod (index limit delta) + (let ((cur (aref colorcomp-data index))) + (unless (= limit cur) + (aset colorcomp-data index (+ cur delta))) + (ewoc-invalidate + colorcomp-ewoc + (ewoc-nth colorcomp-ewoc index) + (ewoc-nth colorcomp-ewoc -1)))) + +(defun colorcomp-R-more () (interactive) (colorcomp-mod 0 255 1)) +(defun colorcomp-G-more () (interactive) (colorcomp-mod 1 255 1)) +(defun colorcomp-B-more () (interactive) (colorcomp-mod 2 255 1)) +(defun colorcomp-R-less () (interactive) (colorcomp-mod 0 0 -1)) +(defun colorcomp-G-less () (interactive) (colorcomp-mod 1 0 -1)) +(defun colorcomp-B-less () (interactive) (colorcomp-mod 2 0 -1)) + +(defun colorcomp-copy-as-kill-and-exit () + "Copy the color components into the kill ring and kill the buffer. +The string is formatted #RRGGBB (hash followed by six hex digits)." + (interactive) + (kill-new (format "#%02X%02X%02X" + (aref colorcomp-data 0) + (aref colorcomp-data 1) + (aref colorcomp-data 2))) + (kill-buffer nil)) + +(setq colorcomp-mode-map + (let ((m (make-sparse-keymap))) + (suppress-keymap m) + (define-key m "i" 'colorcomp-R-less) + (define-key m "o" 'colorcomp-R-more) + (define-key m "k" 'colorcomp-G-less) + (define-key m "l" 'colorcomp-G-more) + (define-key m "," 'colorcomp-B-less) + (define-key m "." 'colorcomp-B-more) + (define-key m " " 'colorcomp-copy-as-kill-and-exit) + m)) +</pre> +</div> <p>Note that we never modify the data in each node, which is fixed when the ewoc is created to be either <code>nil</code> or an index into the vector <code>colorcomp-data</code>, the actual color components. </p><div class="_attribution"> + <p class="_attribution-p"> + Copyright © 1990-1996, 1998-2022 Free Software Foundation, Inc. <br>Licensed under the GNU GPL license.<br> + <a href="https://www.gnu.org/software/emacs/manual/html_node/elisp/Abstract-Display-Example.html" class="_attribution-link">https://www.gnu.org/software/emacs/manual/html_node/elisp/Abstract-Display-Example.html</a> + </p> +</div> |