Support for scrolling through the pager

pager.cpp

@@ -363,8 +363,13 @@ line_t pager_t::completion_print_item(const wcstring &prefix, const comp_t *c, s
    \param prefix The string to print before each completion
 */
 
-void pager_t::completion_print(int cols, int *width_per_column, int row_start, int row_stop, const wcstring &prefix, const comp_info_list_t &lst, page_rendering_t *rendering) const
+void pager_t::completion_print(size_t cols, int *width_per_column, size_t row_start, size_t row_stop, const wcstring &prefix, const comp_info_list_t &lst, page_rendering_t *rendering) const
 {
+    /* Teach the rendering about the rows it printed */
+    assert(row_start >= 0);
+    assert(row_stop >= row_start);
+    rendering->row_start = row_start;
+    rendering->row_end = row_stop;
 
     size_t rows = (lst.size()-1)/cols+1;
     
@@ -393,7 +398,7 @@ void pager_t::completion_print(int cols, int *width_per_column, int row_start, i
             }
             
             /* Append this to the real line */
-            rendering->screen_data.create_line(row).append_line(line);
+            rendering->screen_data.create_line(row - row_start).append_line(line);
         }
     }
 }
@@ -629,7 +634,7 @@ void pager_t::set_term_size(int w, int h)
    \return one of PAGER_RETRY, PAGER_DONE and PAGER_RESIZE
 */
 
-int pager_t::completion_try_print(int cols, const wcstring &prefix, const comp_info_list_t &lst, page_rendering_t *rendering) const
+int pager_t::completion_try_print(size_t cols, const wcstring &prefix, const comp_info_list_t &lst, page_rendering_t *rendering, size_t suggested_start_row) const
 {
     /*
       The calculated preferred width of each column
@@ -648,7 +653,7 @@ int pager_t::completion_try_print(int cols, const wcstring &prefix, const comp_i
     */
     int print=0;
 
-    int rows = (int)divide_round_up(lst.size(), cols);
+    size_t row_count = divide_round_up(lst.size(), cols);
 
     int pref_tot_width=0;
     int min_tot_width = 0;
@@ -661,14 +666,14 @@ int pager_t::completion_try_print(int cols, const wcstring &prefix, const comp_i
     /* Calculate how wide the list would be */
     for (long col = 0; col < cols; col++)
     {
-        for (long row = 0; row<rows; row++)
+        for (long row = 0; row<row_count; row++)
         {
             int pref,min;
             const comp_t *c;
-            if (lst.size() <= col*rows + row)
+            if (lst.size() <= col*row_count + row)
                 continue;
 
-            c = &lst.at(col*rows + row);
+            c = &lst.at(col*row_count + row);
             pref = c->pref_width;
             min = c->min_width;
 
@@ -714,7 +719,7 @@ int pager_t::completion_try_print(int cols, const wcstring &prefix, const comp_i
           pref_tot_width-term_width );
         */
         if (min_tot_width < term_width &&
-                (((rows < term_height) && (next_rows >= term_height)) ||
+                (((row_count < term_height) && (next_rows >= term_height)) ||
                  (pref_tot_width-term_width< 4 && cols < 3)))
         {
             /*
@@ -754,13 +759,39 @@ int pager_t::completion_try_print(int cols, const wcstring &prefix, const comp_i
 
     if (print)
     {
-        res=PAGER_DONE;
+        /* Determine the starting and stop row */
-        if (rows < term_height)
+        size_t start_row = 0, stop_row = 0;
+        if (row_count <= term_height)
         {
-            completion_print(cols, width, 0, rows, prefix, lst, rendering);
+            /* Easy, we can show everything */
+            start_row = 0;
+            stop_row = row_count;
         }
         else
         {
+            /* We can only show part of the full list. Determine which part based on the suggested_start_row */
+            assert(row_count > term_height);
+            size_t last_starting_row = row_count - term_height;
+            start_row = mini(suggested_start_row, last_starting_row);
+            stop_row = start_row + term_height;
+            assert(start_row >= 0 && start_row <= last_starting_row);
+        }
+        
+        assert(stop_row >= start_row);
+        assert(stop_row <= row_count);
+        assert(stop_row - start_row <= term_height);
+        completion_print(cols, width, start_row, stop_row, prefix, lst, rendering);
+        return PAGER_DONE;
+        
+        res=PAGER_DONE;
+        if (row_count < term_height)
+        {
+            completion_print(cols, width, 0, row_count, prefix, lst, rendering);
+        }
+        else
+        {
+            completion_print(cols, width, 0, term_height - 1, prefix, lst, rendering);
+            
             assert(0);
             int npos, pos = 0;
             int do_loop = 1;
@@ -771,7 +802,7 @@ int pager_t::completion_try_print(int cols, const wcstring &prefix, const comp_i
             while (do_loop)
             {
                 set_color(rgb_color_t::black(), highlight_get_color(highlight_spec_pager_progress, true));
-                wcstring msg = format_string(_(L" %d to %d of %d"), pos, pos+term_height-1, rows);
+                wcstring msg = format_string(_(L" %d to %d of %d"), pos, pos+term_height-1, row_count);
                 msg.append(L"   \r");
 
                 writestr(msg.c_str());
@@ -798,7 +829,7 @@ int pager_t::completion_try_print(int cols, const wcstring &prefix, const comp_i
 
                     case LINE_DOWN:
                     {
-                        if (pos <= (rows - term_height))
+                        if (pos <= (row_count - term_height))
                         {
                             pos++;
                             completion_print(cols, width, pos+term_height-2, pos+term_height-1, prefix, lst, rendering);
@@ -809,7 +840,7 @@ int pager_t::completion_try_print(int cols, const wcstring &prefix, const comp_i
                     case PAGE_DOWN:
                     {
 
-                        npos = mini((int)(rows - term_height+1), (int)(pos + term_height-1));
+                        npos = mini((int)(row_count - term_height+1), (int)(pos + term_height-1));
                         if (npos != pos)
                         {
                             pos = npos;
@@ -902,7 +933,7 @@ page_rendering_t pager_t::render() const
             rendering.selected_completion_idx = this->visual_selected_completion_index(rendering.rows, rendering.cols);
             
             bool done = false;
-            switch (completion_try_print(cols, prefix, completion_infos, &rendering))
+            switch (completion_try_print(cols, prefix, completion_infos, &rendering, suggested_row_start))
             {
                 case PAGER_RETRY:
                     break;
@@ -937,7 +968,7 @@ void pager_t::update_rendering(page_rendering_t *rendering) const
     }
 }
 
-pager_t::pager_t() : term_width(0), term_height(0), selected_completion_idx(PAGER_SELECTION_NONE)
+pager_t::pager_t() : term_width(0), term_height(0), selected_completion_idx(PAGER_SELECTION_NONE), suggested_row_start(0)
 {
 }
 
@@ -1001,7 +1032,7 @@ const completion_t *pager_t::select_next_completion_in_direction(selection_direc
     }
     else
     {
-        /* Cardinal directions. We have a completion index; we wish to compute its row and column. Completions are rendered column first, i.e. we go south before we go west. */
+        /* Cardinal directions. We have a completion index; we wish to compute its row and column. Completions are rendered column first, i.e. we go south before we go west. So if we have N rows, and our selected index is N + 2, then our row is 2 (mod by N) and our column is 1 (divide by N) */
         size_t current_row = selected_completion_idx % rendering.rows;
         size_t current_col = selected_completion_idx / rendering.rows;
         
@@ -1084,6 +1115,28 @@ const completion_t *pager_t::select_next_completion_in_direction(selection_direc
     if (new_selected_completion_idx != selected_completion_idx)
     {
         selected_completion_idx = new_selected_completion_idx;
+        
+        /* Update suggested_row_start to ensure the selection is visible. suggested_row_start * rendering.cols is the first suggested visible completion; add the visible completion count to that to get the last one */
+        size_t visible_row_count = rendering.row_end - rendering.row_start;
+        
+        if (visible_row_count > 0 && selected_completion_idx != PAGER_SELECTION_NONE) //paranoia
+        {
+            size_t row_containing_selection = selected_completion_idx % rendering.rows;
+            
+            /* Ensure our suggested row start is not past the selected row */
+            if (suggested_row_start > row_containing_selection)
+            {
+                suggested_row_start = row_containing_selection;
+            }
+            
+            /* Ensure our suggested row start is not too early before it */
+            if (suggested_row_start + visible_row_count <= row_containing_selection)
+            {
+                suggested_row_start = row_containing_selection - visible_row_count + 1;
+            }
+        }
+        
+        
         return selected_completion(rendering);
     }
     else
@@ -1131,6 +1184,6 @@ void pager_t::clear()
     selected_completion_idx = PAGER_SELECTION_NONE;
 }
 
-page_rendering_t::page_rendering_t() : term_width(-1), term_height(-1), rows(0), cols(0), selected_completion_idx(-1)
+page_rendering_t::page_rendering_t() : term_width(-1), term_height(-1), rows(0), cols(0), row_start(0), row_end(0), selected_completion_idx(-1)
 {
 }

pager.h

@@ -13,6 +13,8 @@ class page_rendering_t
     int term_height;
     size_t rows;
     size_t cols;
+    size_t row_start;
+    size_t row_end;
     size_t selected_completion_idx;
     screen_data_t screen_data;
     
@@ -35,6 +37,7 @@ class pager_t
     completion_list_t completions;
     
     size_t selected_completion_idx;
+    size_t suggested_row_start;
     
     /* Returns the index of the completion that should draw selected, using the given number of columns */
     size_t visual_selected_completion_index(size_t rows, size_t cols) const;
@@ -72,12 +75,12 @@ class pager_t
     
     wcstring prefix;
     
-    int completion_try_print(int cols, const wcstring &prefix, const comp_info_list_t &lst, page_rendering_t *rendering) const;
+    int completion_try_print(size_t cols, const wcstring &prefix, const comp_info_list_t &lst, page_rendering_t *rendering, size_t suggested_start_row) const;
     
     void recalc_min_widths(comp_info_list_t * lst) const;
     void measure_completion_infos(std::vector<comp_t> *infos, const wcstring &prefix) const;
     
-    void completion_print(int cols, int *width_per_column, int row_start, int row_stop, const wcstring &prefix, const comp_info_list_t &lst, page_rendering_t *rendering) const;
+    void completion_print(size_t cols, int *width_per_column, size_t row_start, size_t row_stop, const wcstring &prefix, const comp_info_list_t &lst, page_rendering_t *rendering) const;
     line_t completion_print_item(const wcstring &prefix, const comp_t *c, size_t row, size_t column, int width, bool secondary, bool selected, page_rendering_t *rendering) const;
 
     
@@ -95,7 +98,7 @@ class pager_t
     /* Sets the index of the selected completion */
     void set_selected_completion_index(size_t completion_idx);
     
-    /* Changes the selected completion in the given direction according to the layout of the given rendering. Returns true if the values changed. */
+    /* Changes the selected completion in the given direction according to the layout of the given rendering. Returns the newly selected completion if it changed, NULL if nothing was selected or it did not change. */
     const completion_t *select_next_completion_in_direction(selection_direction_t direction, const page_rendering_t &rendering);
     
     /* Returns the currently selected completion for the given rendering */

reader.cpp

@@ -546,7 +546,7 @@ static void reader_repaint()
     indents.resize(len);
     
     // Re-render our completions page if necessary
-    data->pager.set_term_size(common_get_width(), common_get_height());
+    data->pager.set_term_size(common_get_width(), 8 /* common_get_height() */);
     data->pager.update_rendering(&data->current_page_rendering);
 
     s_write(&data->screen,