(image-forward-hscroll, image-backward-hscroll)

(image-next-line, image-previous-line, image-scroll-up)
(image-scroll-down, image-bol, image-eol, image-bob, image-eob):
New functions.
(image-mode-map): Remap motion commands.
(image-mode-text-map): New keymap for viewing images as text.
(image-mode): Use image-mode-map.
(image-toggle-display): Toggle auto-hscroll-mode and mode keymaps.

1 files changed, 156 insertions, 2 deletions

diff --git a/lisp/image-mode.el b/lisp/image-mode.el
index eb08de1d6bb..18246b8dc90 100644
--- a/lisp/image-mode.el
+++ b/lisp/image-mode.el
@@ -43,11 +43,160 @@
 ;;;###autoload (push '("\\.p[bpgn]m\\'" . image-mode) auto-mode-alist)
 ;;;###autoload (push '("\\.x[bp]m\\'"   . image-mode-maybe) auto-mode-alist)
 
+;;; Image scrolling functions
+
+(defun image-forward-hscroll (&optional n)
+  "Scroll image in current window to the left by N character widths.
+Stop if the right edge of the image is reached."
+  (interactive "p")
+  (cond ((= n 0) nil)
+        ((< n 0)
+         (set-window-hscroll nil (max 0 (+ (window-hscroll) n))))
+        (t
+         (let* ((image (get-text-property 1 'display))
+                (img-width (ceiling (car (image-size image))))
+                (edges (window-inside-edges))
+                (win-width (- (nth 2 edges) (nth 0 edges))))
+           (set-window-hscroll nil
+                               (min (max 0 (- img-width win-width))
+                                    (+ n (window-hscroll))))))))
+
+(defun image-backward-hscroll (&optional n)
+  "Scroll image in current window to the right by N character widths.
+Stop if the left edge of the image is reached."
+  (interactive "p")
+  (image-forward-hscroll (- n)))
+
+(defun image-next-line (&optional n)
+  "Scroll image in current window upward by N lines.
+Stop if the bottom edge of the image is reached."
+  (interactive "p")
+  (cond ((= n 0) nil)
+        ((< n 0)
+         (set-window-vscroll nil (max 0 (+ (window-vscroll) n))))
+        (t
+         (let* ((image (get-text-property 1 'display))
+                (img-height (ceiling (cdr (image-size image))))
+                (edges (window-inside-edges))
+                (win-height (- (nth 3 edges) (nth 1 edges))))
+           (set-window-vscroll nil
+                               (min (max 0 (- img-height win-height))
+                                    (+ n (window-vscroll))))))))
+
+(defun image-previous-line (&optional n)
+  "Scroll image in current window downward by N lines.
+Stop if the top edge of the image is reached."
+  (interactive "p")
+  (image-next-line (- n)))
+
+(defun image-scroll-up (&optional n)
+  "Scroll image in current window upward by N lines.
+Stop if the bottom edge of the image is reached.
+If ARG is omitted or nil, scroll upward by a near full screen.
+A near full screen is `next-screen-context-lines' less than a full screen.
+Negative ARG means scroll downward.
+If ARG is the atom `-', scroll downward by nearly full screen.
+When calling from a program, supply as argument a number, nil, or `-'."
+  (interactive "P")
+  (cond ((null n)
+         (let* ((edges (window-inside-edges))
+                (win-height (- (nth 3 edges) (nth 1 edges))))
+           (image-next-line
+            (max 0 (- win-height next-screen-context-lines)))))
+        ((eq n '-)
+         (let* ((edges (window-inside-edges))
+                (win-height (- (nth 3 edges) (nth 1 edges))))
+           (image-next-line
+            (min 0 (- next-screen-context-lines win-height)))))
+        (t (image-next-line (prefix-numeric-value n)))))
+
+(defun image-scroll-down (&optional n)
+  "Scroll image in current window downward by N lines
+Stop if the top edge of the image is reached.
+If ARG is omitted or nil, scroll downward by a near full screen.
+A near full screen is `next-screen-context-lines' less than a full screen.
+Negative ARG means scroll upward.
+If ARG is the atom `-', scroll upward by nearly full screen.
+When calling from a program, supply as argument a number, nil, or `-'."
+  (interactive "P")
+  (cond ((null n)
+         (let* ((edges (window-inside-edges))
+                (win-height (- (nth 3 edges) (nth 1 edges))))
+           (image-next-line
+            (min 0 (- next-screen-context-lines win-height)))))
+        ((eq n '-)
+         (let* ((edges (window-inside-edges))
+                (win-height (- (nth 3 edges) (nth 1 edges))))
+           (image-next-line
+            (max 0 (- win-height next-screen-context-lines)))))
+        (t (image-next-line (- (prefix-numeric-value n))))))
+
+(defun image-bol (arg)
+  "Scroll horizontally to the left edge of the image in the current window.
+With argument ARG not nil or 1, move forward ARG - 1 lines first,
+stopping if the top or bottom edge of the image is reached."
+  (interactive "p")
+  (and arg
+       (/= (setq arg (prefix-numeric-value arg)) 1)
+       (image-next-line (- arg 1)))
+  (set-window-hscroll (selected-window) 0))
+
+(defun image-eol (arg)
+  "Scroll horizontally to the right edge of the image in the current window.
+With argument ARG not nil or 1, move forward ARG - 1 lines first,
+stopping if the top or bottom edge of the image is reached."
+  (interactive "p")
+  (and arg
+       (/= (setq arg (prefix-numeric-value arg)) 1)
+       (image-next-line (- arg 1)))
+  (let* ((image (get-text-property 1 'display))
+         (edges (window-inside-edges))
+         (win-width (- (nth 2 edges) (nth 0 edges)))
+         (img-width (ceiling (car (image-size image)))))
+    (set-window-hscroll (selected-window)
+                        (max 0 (- img-width win-width)))))
+
+(defun image-bob ()
+  "Scroll to the top-left corner of the image in the current window."
+  (interactive)
+  (set-window-hscroll (selected-window) 0)
+  (set-window-vscroll (selected-window) 0))
+
+(defun image-eob ()
+  "Scroll to the bottom-right corner of the image in the current window."
+  (interactive)
+  (let* ((image (get-text-property 1 'display))
+         (edges (window-inside-edges))
+         (win-width (- (nth 2 edges) (nth 0 edges)))
+         (img-width (ceiling (car (image-size image))))
+         (win-height (- (nth 3 edges) (nth 1 edges)))
+         (img-height (ceiling (cdr (image-size image)))))
+    (set-window-hscroll (selected-window) (max 0 (- img-width win-width)))
+    (set-window-vscroll (selected-window) (max 0 (- img-height win-height)))))
+
+;;; Image Mode setup
+
 (defvar image-mode-map
   (let ((map (make-sparse-keymap)))
     (define-key map "\C-c\C-c" 'image-toggle-display)
+    (define-key map [remap forward-char] 'image-forward-hscroll)
+    (define-key map [remap backward-char] 'image-backward-hscroll)
+    (define-key map [remap previous-line] 'image-previous-line)
+    (define-key map [remap next-line] 'image-next-line)
+    (define-key map [remap scroll-up] 'image-scroll-up)
+    (define-key map [remap scroll-down] 'image-scroll-down)
+    (define-key map [remap move-beginning-of-line] 'image-bol)
+    (define-key map [remap move-end-of-line] 'image-eol)
+    (define-key map [remap beginning-of-buffer] 'image-bob)
+    (define-key map [remap end-of-buffer] 'image-eob)
+    map)
+  "Major mode keymap for viewing images in Image mode.")
+
+(defvar image-mode-text-map
+  (let ((map (make-sparse-keymap)))
+    (define-key map "\C-c\C-c" 'image-toggle-display)
     map)
-  "Major mode keymap for Image mode.")
+  "Major mode keymap for viewing images as text in Image mode.")
 
 ;;;###autoload
 (defun image-mode ()
@@ -58,13 +207,13 @@ to toggle between display as an image and display as text."
   (kill-all-local-variables)
   (setq mode-name "Image")
   (setq major-mode 'image-mode)
-  (use-local-map image-mode-map)
   (add-hook 'change-major-mode-hook 'image-toggle-display-text nil t)
   (if (and (display-images-p)
            (not (get-text-property (point-min) 'display)))
       (image-toggle-display)
     ;; Set next vars when image is already displayed but local
     ;; variables were cleared by kill-all-local-variables
+    (use-local-map image-mode-map)
     (setq cursor-type nil truncate-lines t))
   (run-mode-hooks 'image-mode-hook)
   (if (display-images-p)
@@ -140,6 +289,8 @@ and showing the image as an image."
         (set-buffer-modified-p modified)
         (kill-local-variable 'cursor-type)
         (kill-local-variable 'truncate-lines)
+        (kill-local-variable 'auto-hscroll-mode)
+        (use-local-map image-mode-text-map)
         (if (called-interactively-p)
             (message "Repeat this command to go back to displaying the image")))
     ;; Turn the image data into a real image, but only if the whole file
@@ -177,6 +328,9 @@ and showing the image as an image."
       ;; This just makes the arrow displayed in the right fringe
       ;; area look correct when the image is wider than the window.
       (setq truncate-lines t)
+      ;; Allow navigation of large images
+      (set (make-local-variable 'auto-hscroll-mode) nil)
+      (use-local-map image-mode-map)
       (if (called-interactively-p)
           (message "Repeat this command to go back to displaying the file as text")))))