From 88f7f5f8675a15d567837bd076e39e09bfe1aa74 Mon Sep 17 00:00:00 2001
From: Leo Tenenbaum <pommicket@gmail.com>
Date: Tue, 23 Feb 2021 14:30:49 -0500
Subject: goto line preview

---
 buffer.c | 10 +++++++++-
 main.c   |  2 --
 math.c   | 10 ++++++++++
 menu.c   | 14 +++++++++-----
 ted.h    |  3 +++
 5 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/buffer.c b/buffer.c
index 57325b8..0c226ea 100644
--- a/buffer.c
+++ b/buffer.c
@@ -864,7 +864,15 @@ void buffer_scroll_to_pos(TextBuffer *buffer, BufferPos pos) {
 }
 
 // scroll in such a way that this position is in the center of the screen
-void buffer_scroll_center_pos(TextBuffer *buffer) {
+void buffer_scroll_center_pos(TextBuffer *buffer, BufferPos pos) {
+	double line = pos.line;
+	double col = buffer_index_to_column(buffer, pos.line, pos.index);
+	
+	double display_lines = buffer_display_lines(buffer);
+	double display_cols = buffer_display_cols(buffer);
+	buffer->scroll_x = col - display_cols * 0.5;
+	buffer->scroll_y = line - display_lines * 0.5;
+	buffer_correct_scroll(buffer);
 }
 
 // if the cursor is offscreen, this will scroll to make it onscreen.
diff --git a/main.c b/main.c
index 72e3ff1..3063ffe 100644
--- a/main.c
+++ b/main.c
@@ -1,6 +1,4 @@
 // @TODO:
-// - goto line
-
 // - :run -- if .html file, open in browser, otherwise figure out a way of sending a command to shell
 // running in terminal emulator?? (don't want to implement stdin/ANSI codes/etc.)
 
diff --git a/math.c b/math.c
index b76c049..7d16a52 100644
--- a/math.c
+++ b/math.c
@@ -456,6 +456,16 @@ static void v4_print(v4 v) {
 	printf("(%f, %f, %f, %f)\n", v.x, v.y, v.z, v.w);
 }
 
+typedef struct {
+	double x, y;
+} v2d;
+
+static v2d V2D(double x, double y) {
+	v2d v;
+	v.x = x;
+	v.y = y;
+	return v;
+}
 
 // matrices are column-major, because that's what they are in OpenGL 
 typedef struct {
diff --git a/menu.c b/menu.c
index fb9eb56..497fbba 100644
--- a/menu.c
+++ b/menu.c
@@ -1,7 +1,9 @@
 static void menu_open(Ted *ted, Menu menu) {
 	if (ted->find) find_close(ted);
 	ted->menu = menu;
-	ted->prev_active_buffer = ted->active_buffer;
+	TextBuffer *prev_buf = ted->prev_active_buffer = ted->active_buffer;
+	ted->prev_active_buffer_scroll = V2D(prev_buf->scroll_x, prev_buf->scroll_y);
+	
 	ted->active_buffer = NULL;
 	*ted->warn_overwrite = 0; // clear warn_overwrite
 	buffer_clear(&ted->line_buffer);
@@ -31,8 +33,10 @@ static void menu_open(Ted *ted, Menu menu) {
 }
 
 static void menu_close(Ted *ted) {
-	ted->active_buffer = ted->prev_active_buffer;
+	TextBuffer *buffer = ted->active_buffer = ted->prev_active_buffer;
 	ted->prev_active_buffer = NULL;
+	buffer->scroll_x = ted->prev_active_buffer_scroll.x;
+	buffer->scroll_y = ted->prev_active_buffer_scroll.y;
 	switch (ted->menu) {
 	case MENU_NONE: assert(0); break;
 	case MENU_OPEN:
@@ -207,16 +211,16 @@ static void menu_update(Ted *ted) {
 		long line_number = strtol(contents, &end, 0);
 		TextBuffer *buffer = ted->prev_active_buffer;
 		if (line_number > 0 && *end == '\0' && line_number <= (long)buffer->nlines) {
+			BufferPos pos = {line_number - 1, 0};
+			
 			if (line_buffer->line_buffer_submitted) {
 				// let's go there!
-				BufferPos pos = {line_number - 1, 0};
-					
 				menu_close(ted);
 				buffer_cursor_move_to_pos(buffer, pos);
 				buffer_center_cursor(buffer);
 			} else {
 				// scroll to the line
-				
+				buffer_scroll_center_pos(buffer, pos);
 			}
 		}
 		line_buffer->line_buffer_submitted = false;
diff --git a/ted.h b/ted.h
index 2ca308f..d629dd5 100644
--- a/ted.h
+++ b/ted.h
@@ -272,6 +272,9 @@ typedef struct Ted {
 	
 	BuildError *build_errors; // dynamic array of build errors
 	u32 build_error; // build error we are currently "on"
+	
+	// used by menus to keep track of the scroll position so we can return to it.
+	v2d prev_active_buffer_scroll;
 
 	char **tag_selector_entries; // an array of all tags (see tag_selector_open)
 
-- 
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