vis: add infrastructure to support multiple cursors/selections

This cleans up the existing selection handling code and adds the
necessary bits to eventually support multiple cursors/selections.

The cursor position is kept track of using marks, which means
retrieving the cursor position is no longer a constant time operation.
Furthermore the terminal cursor is no longer used, instead the whole
window is redrawn after every cursor movement.

1 files changed, 69 insertions, 35 deletions

diff --git a/view.h b/view.h
index 0adec05..d993fbd 100644
--- a/view.h
+++ b/view.h
@@ -8,6 +8,8 @@
 #include "syntax.h"
 
 typedef struct View View;
+typedef struct Cursor Cursor;
+typedef struct Selection Selection;
 
 typedef struct {
 	void *data;
@@ -24,7 +26,8 @@ typedef struct {
 			       the same as in the underlying text, for example tabs get expanded */
 	unsigned int attr;
 	bool istab;
-	bool selected;
+	bool selected;      /* whether this cell is part of a selected region */
+	bool cursor;        /* whether a cursor is currently locaated on the cell */
 } Cell;
 
 typedef struct Line Line;
@@ -55,13 +58,13 @@ void view_tabwidth_set(View*, int tabwidth);
 
 /* cursor movements which also update selection if one is active.
  * they return new cursor postion */
-size_t view_line_down(View*);
-size_t view_line_up(View*);
-size_t view_screenline_down(View*);
-size_t view_screenline_up(View*);
-size_t view_screenline_begin(View*);
-size_t view_screenline_middle(View*);
-size_t view_screenline_end(View*);
+size_t view_line_down(Cursor*);
+size_t view_line_up(Cursor*);
+size_t view_screenline_down(Cursor*);
+size_t view_screenline_up(Cursor*);
+size_t view_screenline_begin(Cursor*);
+size_t view_screenline_middle(Cursor*);
+size_t view_screenline_end(Cursor*);
 /* move window content up/down, but keep cursor position unchanged unless it is
  * on a now invisible line in which case we try to preserve the column position */
 size_t view_slide_up(View*, int lines);
@@ -73,38 +76,11 @@ size_t view_scroll_down(View*, int lines);
 /* place the cursor at the start ot the n-th window line, counting from 1 */
 size_t view_screenline_goto(View*, int n);
 
-/* get cursor position in bytes from start of the file */
-size_t view_cursor_get(View*);
-
-typedef struct {
-	int x, y;
-} ViewPos;
-
-ViewPos view_cursor_viewpos(View*);
-
 const Line *view_lines_get(View*);
-/* get cursor position in terms of screen coordinates */
-CursorPos view_cursor_getpos(View*);
-/* moves window viewport in direction until pos is visible. should only be
- * used for short distances between current cursor position and destination */
-void view_scroll_to(View*, size_t pos);
-/* move cursor to a given position. changes the viewport to make sure that
- * position is visible. if the position is in the middle of a line, try to
- * adjust the viewport in such a way that the whole line is displayed */
-void view_cursor_to(View*, size_t pos);
 /* redraw current cursor line at top/center/bottom of window */
 void view_redraw_top(View*);
 void view_redraw_center(View*);
 void view_redraw_bottom(View*);
-/* start selected area at current cursor position. further cursor movements will
- * affect the selected region. */
-void view_selection_start(View*);
-/* returns the currently selected text region, is either empty or well defined,
- * i.e. sel.start <= sel.end */
-Filerange view_selection_get(View*);
-void view_selection_set(View*, Filerange *sel);
-/* clear selection and redraw window */
-void view_selection_clear(View*);
 /* get the currently displayed area in bytes from the start of the file */
 Filerange view_viewport_get(View*);
 /* move visible viewport n-lines up/down, redraws the view but does not change
@@ -119,4 +95,62 @@ Syntax *view_syntax_get(View*);
 void view_symbols_set(View*, int flags);
 int view_symbols_get(View*);
 
+/* A view can manage multiple cursors, one of which (the main cursor) is always
+ * placed within the visible viewport. All functions named view_cursor_* operate
+ * on this cursor. Additional cursor can be created and manipulated using the
+ * functions named view_cursors_* */
+
+/* get main cursor position in terms of screen coordinates */
+CursorPos view_cursor_getpos(View*);
+/* get main cursor position in bytes from start of the file */
+size_t view_cursor_get(View*);
+/* moves window viewport in direction until pos is visible. should only be
+ * used for short distances between current cursor position and destination */
+void view_scroll_to(View*, size_t pos);
+/* move cursor to a given position. changes the viewport to make sure that
+ * position is visible. if the position is in the middle of a line, try to
+ * adjust the viewport in such a way that the whole line is displayed */
+void view_cursor_to(View*, size_t pos);
+/* create a new cursor */
+Cursor *view_cursors_new(View*);
+/* dispose an existing cursor */
+void view_cursors_free(Cursor*);
+/* only keep the main cursor, release all others together with their
+ * selections (if any) */
+void view_cursors_clear(View*);
+/* get the main cursor which is always in the visible viewport */
+Cursor *view_cursor(View*);
+/* get the first cursor */
+Cursor *view_cursors(View*);
+Cursor *view_cursors_prev(Cursor*);
+Cursor *view_cursors_next(Cursor*);
+/* get current position of cursor in bytes from the start of the file */
+size_t view_cursors_pos(Cursor*);
+/* place cursor at `pos' which should be in the interval [0, text-size] */
+void view_cursors_to(Cursor*, size_t pos);
+void view_cursors_scroll_to(Cursor*, size_t pos);
+/* start selected area at current cursor position. further cursor movements
+ * will affect the selected region. */
+void view_cursors_selection_start(Cursor*);
+/* detach cursor from selection, further cursor movements will not affect
+ * the selected region. */ 
+void view_cursors_selection_stop(Cursor*);
+/* clear selection associated with this cursor (if any) */
+void view_cursors_selection_clear(Cursor*);
+/* move cursor position from one end of the selection to the other */
+void view_cursors_selection_swap(Cursor*);
+/* get/set the selected region associated with this cursor */
+Filerange view_cursors_selection_get(Cursor*);
+void view_cursors_selection_set(Cursor*, Filerange*);
+
+Selection *view_selections_new(View*);
+void view_selections_free(Selection*);
+void view_selections_clear(View*);
+void view_selections_swap(Selection*);
+Selection *view_selections(View*);
+Selection *view_selections_prev(Selection*);
+Selection *view_selections_next(Selection*);
+Filerange view_selections_get(Selection*);
+void view_selections_set(Selection*, Filerange*);
+
 #endif