From 2ac44709bd9a9ec8d3ab60a40a81ac7ca3ad1b57 Mon Sep 17 00:00:00 2001
From: Nick Hanley <nicholasjhanley@gmail.com>
Date: Sat, 15 Jan 2022 17:51:31 -0500
Subject: [PATCH] Add keybind to scroll to image center (#203)

There are keybinds for scrolling to the edges of an image but there's no way back to the center. This is particularly annoying while zooming.
---
 commands.c   | 5 +++++
 commands.h   | 2 ++
 config.def.h | 1 +
 image.c      | 8 ++++++++
 nsxiv.1      | 3 +++
 nsxiv.h      | 1 +
 6 files changed, 20 insertions(+)

diff --git a/commands.c b/commands.c
index aafc510..7b7be62 100644
--- a/commands.c
+++ b/commands.c
@@ -325,6 +325,11 @@ bool ci_scroll(arg_t dir)
 	return img_pan(&img, dir, prefix);
 }
 
+bool ci_scroll_to_center(arg_t _)
+{
+	return img_pan_center(&img);
+}
+
 bool ci_scroll_to_edge(arg_t dir)
 {
 	return img_pan_edge(&img, dir);
diff --git a/commands.h b/commands.h
index 70af13a..b78157d 100644
--- a/commands.h
+++ b/commands.h
@@ -30,6 +30,7 @@ bool ci_navigate(arg_t);
 bool ci_navigate_frame(arg_t);
 bool ci_rotate(arg_t);
 bool ci_scroll(arg_t);
+bool ci_scroll_to_center(arg_t);
 bool ci_scroll_to_edge(arg_t);
 bool ci_set_zoom(arg_t);
 bool ci_slideshow(arg_t);
@@ -72,6 +73,7 @@ bool ct_select(arg_t);
 #define i_navigate_frame { ci_navigate_frame, MODE_IMAGE }
 #define i_rotate { ci_rotate, MODE_IMAGE }
 #define i_scroll { ci_scroll, MODE_IMAGE }
+#define i_scroll_to_center { ci_scroll_to_center, MODE_IMAGE }
 #define i_scroll_to_edge { ci_scroll_to_edge, MODE_IMAGE }
 #define i_set_zoom { ci_set_zoom, MODE_IMAGE }
 #define i_slideshow { ci_slideshow, MODE_IMAGE }
diff --git a/config.def.h b/config.def.h
index b328305..0973ff4 100644
--- a/config.def.h
+++ b/config.def.h
@@ -158,6 +158,7 @@ static const keymap_t keys[] = {
 	{ 0,            XK_J,             i_scroll_to_edge,     DIR_DOWN },
 	{ 0,            XK_K,             i_scroll_to_edge,     DIR_UP },
 	{ 0,            XK_L,             i_scroll_to_edge,     DIR_RIGHT },
+	{ 0,            XK_z,             i_scroll_to_center,   None },
 	{ 0,            XK_equal,         i_set_zoom,           100 },
 	{ 0,            XK_w,             i_fit_to_win,         SCALE_DOWN },
 	{ 0,            XK_W,             i_fit_to_win,         SCALE_FIT },
diff --git a/image.c b/image.c
index 2c4eec1..6b30731 100644
--- a/image.c
+++ b/image.c
@@ -744,6 +744,14 @@ bool img_pan(img_t *img, direction_t dir, int d)
 	return false;
 }
 
+bool img_pan_center(img_t *img)
+{
+	float x, y;
+	x = (img->win->w - img->w * img->zoom) / 2.0;
+	y = (img->win->h - img->h * img->zoom) / 2.0;
+	return img_pos(img, x, y);
+}
+
 bool img_pan_edge(img_t *img, direction_t dir)
 {
 	float ox, oy;
diff --git a/nsxiv.1 b/nsxiv.1
index f032327..6c8d8e6 100644
--- a/nsxiv.1
+++ b/nsxiv.1
@@ -318,6 +318,9 @@ Scroll to top image edge.
 .B L
 Scroll to right image edge.
 .TP
+.B z
+Scroll to image center.
+.TP
 Zooming:
 .TP
 .B =
diff --git a/nsxiv.h b/nsxiv.h
index eb5b398..a9a9b8a 100644
--- a/nsxiv.h
+++ b/nsxiv.h
@@ -229,6 +229,7 @@ bool img_zoom(img_t*, int);
 bool img_zoom_to(img_t*, float);
 bool img_pos(img_t*, float, float);
 bool img_pan(img_t*, direction_t, int);
+bool img_pan_center(img_t*);
 bool img_pan_edge(img_t*, direction_t);
 void img_rotate(img_t*, degree_t);
 void img_flip(img_t*, flipdir_t);