scroll by one line in textlist

to scroll by only one line, hold CONTROL key and scroll with
mouse wheel

common/utils/T/tracer/event_selector.c

@@ -34,11 +34,14 @@ static void scroll(void *private, gui *g,
   int number_of_lines;
   int new_line;
   int inc;
+  int *d = notification_data;
+  int key_modifiers = *d;
 
   textlist_state(g, w, &visible_lines, &start_line, &number_of_lines);
   inc = 10;
   if (inc > visible_lines - 2) inc = visible_lines - 2;
   if (inc < 1) inc = 1;
+  if (key_modifiers & KEY_CONTROL) inc = 1;
   if (!strcmp(notification, "scrollup")) inc = -inc;
 
   new_line = start_line + inc;

common/utils/T/tracer/gui/gui.h

@@ -83,8 +83,8 @@ int new_color(gui *gui, char *color);
 /* notifications */
 /* known notifications:
  * - textlist:
- *      - scrollup   { void *: NULL }
- *      - scrolldown { void *: NULL }
+ *      - scrollup   { int: key_modifiers }
+ *      - scrolldown { int: key_modifiers }
  *      - click      { int [2]: line, button }
  * - label:
  *      - click      { int: button } (if enabled)

common/utils/T/tracer/gui/textlist.c

@@ -54,11 +54,11 @@ static void button(gui *_g, widget *_this, int x, int y,
   x -= this->common.x;
   /* scroll up */
   if (button == 4 && up == 0) {
-    gui_notify(g, "scrollup", _this, NULL);
+    gui_notify(g, "scrollup", _this, &key_modifiers);
   }
   /* scroll down */
   if (button == 5 && up == 0) {
-    gui_notify(g, "scrolldown", _this, NULL);
+    gui_notify(g, "scrolldown", _this, &key_modifiers);
   }
   /* button 1/2/3 click */
   if (button >= 1 && button <= 3 && up == 0) {

common/utils/T/tracer/view/textlist.c

@@ -89,6 +89,8 @@ static void scroll(void *private, gui *g,
   int number_of_lines;
   int new_line;
   int inc;
+  int *d = notification_data;
+  int key_modifiers = *d;
 
   if (pthread_mutex_lock(&this->lock)) abort();
 
@@ -96,6 +98,7 @@ static void scroll(void *private, gui *g,
   inc = 10;
   if (inc > visible_lines - 2) inc = visible_lines - 2;
   if (inc < 1) inc = 1;
+  if (key_modifiers & KEY_CONTROL) inc = 1;
   if (!strcmp(notification, "scrollup")) inc = -inc;
 
   new_line = start_line + inc;