5812 - debugging an ancient niggle in browse_trace

The problem: when I hit 'G' to go to the bottom of the trace, if the bottom
is visible on screen, the screen scrolls so the bottom of the trace
is the bottom-most line on screen. But the cursor moves to where the trace
used to end rather than the new location of the bottom of the trace (the
bottom of the screen).

1 files changed, 5 insertions, 6 deletions

diff --git a/tools/browse_trace.cc b/tools/browse_trace.cc
index b15da9c8..f1d8b5c8 100644
--- a/tools/browse_trace.cc
+++ b/tools/browse_trace.cc
@@ -132,8 +132,7 @@ void load_trace(const char* filename) {
   cerr << "lines read: " << Trace_stream->past_lines.size() << '\n';
 }
 
-// update Trace_indices for each screen_row on the basis of Top_of_screen and Visible
-void refresh_screen_rows() {
+void refresh_screen_rows() {  // Top_of_screen, Visible -> Trace_index
   int screen_row = 0, index = 0;
   Trace_index.clear();
   for (screen_row = 0, index = Top_of_screen;  screen_row < tb_height() && index < SIZE(Trace_stream->past_lines);  ++screen_row, ++index) {
@@ -148,7 +147,7 @@ void refresh_screen_rows() {
 done:;
 }
 
-void clear_line(int screen_row) {
+void clear_line(int screen_row) {  // -> screen
   tb_set_cursor(0, screen_row);
   for (int col = 0;  col < tb_width();  ++col)
     tb_print(' ', TB_WHITE, TB_BLACK);
@@ -193,7 +192,7 @@ vector<pair<size_t, size_t> > find_all_occurrences(const string& s, const string
   return result;
 }
 
-void render_line(int screen_row, const string& s, bool cursor_line) {
+void render_line(int screen_row, const string& s, bool cursor_line) {  // -> screen
   int col = 0;
   int color = TB_WHITE;
   int background_color = cursor_line ? /*subtle grey*/240 : TB_BLACK;
@@ -337,7 +336,7 @@ bool start_search_editor(search_direction dir) {
   }
 }
 
-void render() {
+void render() {  // Trace_index -> Last_printed_row, screen
   int screen_row = 0;
   for (screen_row = 0;  screen_row < tb_height();  ++screen_row) {
     if (!contains_key(Trace_index, screen_row)) break;
@@ -469,7 +468,7 @@ int main(int argc, char* argv[]) {
         refresh_screen_rows();
     }
     else if (key == 'G' || key == TB_KEY_END) {
-      // go to bottom of screen; largely like page-up, interestingly
+      // go to bottom of trace; largely like page-up, interestingly
       Top_of_screen = SIZE(Trace_stream->past_lines)-1;
       for (int screen_row = tb_height();  screen_row > 0 && Top_of_screen > 0;  --screen_row) {
         --Top_of_screen;