selection: adjust start point when the selection changes direction

Without this, the initial cell will always be selected, regardless of
how the selection is moved to the left or right.

With this patch, the initial cell will only be selected while the
selection is being made in the original direction. Changing direction
of the selection moves the start point to next/previous character.

CHANGELOG.md

@@ -60,6 +60,8 @@
 * Viewport sometimes not moving when doing a scrollback search.
 * Crash when cancelling a scrollback search and the window had been
   resized while searching.
+* Selection start point not moving when the selection changes
+  direction.
 
 
 ### Security

selection.c

@@ -320,11 +320,47 @@ selection_update(struct terminal *term, int col, int row)
     struct coord new_start = term->selection.start;
     struct coord new_end = {col, term->grid->view + row};
 
+    /* Adjust start point if the selection has changed 'direction' */
+    if (!(new_end.row == new_start.row && new_end.col == new_start.col)) {
+        enum selection_direction new_direction;
+
+        if (new_end.row > new_start.row ||
+            (new_end.row == new_start.row && new_end.col > new_start.col))
+        {
+            /* New end point is before the start point */
+            new_direction = SELECTION_RIGHT;
+        } else {
+            /* The new end point is after the start point */
+            new_direction = SELECTION_LEFT;
+        }
+
+        if (term->selection.direction != new_direction) {
+            if (term->selection.direction != SELECTION_UNDIR) {
+                if (new_direction == SELECTION_LEFT) {
+                    new_start.col--;
+                    if (new_start.col < 0) {
+                        new_start.col = term->cols - 1;
+                        new_start.row--;
+                    }
+                } else {
+                    new_start.col++;
+                    if (new_start.col >= term->cols) {
+                        new_start.col = 0;
+                        new_start.row++;
+                    }
+                }
+            }
+
+            term->selection.direction = new_direction;
+        }
+    }
+
     size_t start_row_idx = new_start.row & (term->grid->num_rows - 1);
     size_t end_row_idx = new_end.row & (term->grid->num_rows - 1);
     const struct row *row_start = term->grid->rows[start_row_idx];
     const struct row *row_end = term->grid->rows[end_row_idx];
 
+
     /* Handle double-width characters */
     if (new_start.row < new_end.row ||
         (new_start.row == new_end.row && new_start.col <= new_end.col))
@@ -548,6 +584,7 @@ selection_cancel(struct terminal *term)
     term->selection.kind = SELECTION_NONE;
     term->selection.start = (struct coord){-1, -1};
     term->selection.end = (struct coord){-1, -1};
+    term->selection.direction = SELECTION_UNDIR;
 }
 
 void

terminal.h

@@ -181,6 +181,7 @@ enum mouse_reporting {
 enum cursor_style { CURSOR_BLOCK, CURSOR_UNDERLINE, CURSOR_BAR };
 
 enum selection_kind { SELECTION_NONE, SELECTION_NORMAL, SELECTION_BLOCK };
+enum selection_direction {SELECTION_UNDIR, SELECTION_LEFT, SELECTION_RIGHT};
 
 struct ptmx_buffer {
     void *data;
@@ -306,6 +307,7 @@ struct terminal {
 
     struct {
         enum selection_kind kind;
+        enum selection_direction direction;
         struct coord start;
         struct coord end;
     } selection;