[Nano-devel] [PATCH 2/2] scrolling: make the centering function behave like in Emacs

[Benno Schulenberg]

From: Benno Schulenberg <address@hidden>

One strike centers the cursor line, a second strike puts it at the top
of the screen, and a third strike at the bottom.  A fourth strike puts
it back at the center.
---
 src/global.c |  4 ++++
 src/move.c   | 15 +++++++++++++--
 src/nano.c   |  7 +++++++
 src/proto.h  |  2 ++
 src/winio.c  |  5 +++--
 5 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/src/global.c b/src/global.c
index b86014c5..300cb586 100644
--- a/src/global.c
+++ b/src/global.c
@@ -111,6 +111,10 @@ WINDOW *bottomwin = NULL;
 int editwinrows = 0;
                /* How many rows does the edit window take up? */
 
+int placement_mode = -1;
+               /* Whether to center the cursor line (0), put it at the top (1),
+                * or at the bottom (2). */
+
 filestruct *cutbuffer = NULL;
                /* The buffer where we store cut text. */
 filestruct *cutbottom = NULL;
diff --git a/src/move.c b/src/move.c
index 2613fd20..d9dfc5aa 100644
--- a/src/move.c
+++ b/src/move.c
@@ -559,10 +559,21 @@ void do_scroll_down(void)
        do_down(TRUE);
 }
 
-/* Scroll the line with the cursor to the center of the screen. */
+/* Scroll the line with the cursor to the center of the screen, or
+ * to the top, or to the bottom. */
 void do_center(void)
 {
-       adjust_viewport(CENTERING);
+       if (placement_mode == 0)
+                adjust_viewport(CENTERING);
+       else if (placement_mode == 1) {
+               /* Simulate the cursor being on the top row, then scroll there. 
*/
+               openfile->current_y = 0;
+               adjust_viewport(STATIONARY);
+       } else {
+               /* Simulate the cursor being on the bottom row, then scroll 
there. */
+               openfile->current_y = editwinrows - 1;
+               adjust_viewport(STATIONARY);
+       }
        total_refresh();
 }
 #endif
diff --git a/src/nano.c b/src/nano.c
index ad959256..e07f7cd6 100644
--- a/src/nano.c
+++ b/src/nano.c
@@ -1702,6 +1702,8 @@ int do_input(bool allow_funcs)
                        puddle[depth] = '\0';
                        do_output(puddle, depth, FALSE);
 
+                       placement_mode = -1;
+
                        /* Empty the input buffer. */
                        free(puddle);
                        puddle = NULL;
@@ -1748,6 +1750,11 @@ int do_input(bool allow_funcs)
 #ifdef ENABLE_WRAPPING
                        filestruct *was_next = openfile->current->next;
 #endif
+                       if (shortcut->func == do_center)
+                               placement_mode = (placement_mode + 1) % 3;
+                       else
+                               placement_mode = -1;
+
 #ifndef NANO_TINY
                        filestruct *was_current = openfile->current;
                        size_t was_x = openfile->current_x;
diff --git a/src/proto.h b/src/proto.h
index 9b179427..fe617c09 100644
--- a/src/proto.h
+++ b/src/proto.h
@@ -96,6 +96,8 @@ extern WINDOW *edit;
 extern WINDOW *bottomwin;
 extern int editwinrows;
 
+extern int placement_mode;
+
 extern filestruct *cutbuffer;
 extern filestruct *cutbottom;
 extern partition *filepart;
diff --git a/src/winio.c b/src/winio.c
index 9257fe79..34b966ed 100644
--- a/src/winio.c
+++ b/src/winio.c
@@ -3256,9 +3256,10 @@ void adjust_viewport(update_type manner)
 
        if (manner == STATIONARY)
                goal = openfile->current_y;
-       else if (manner == CENTERING)
+       else if (manner == CENTERING) {
                goal = editwinrows / 2;
-       else if (!current_is_above_screen())
+//             placement_mode = 0;
+       } else if (!current_is_above_screen())
                goal = editwinrows - 1;
 
        openfile->edittop = openfile->current;
-- 
2.16.2