improve the size of completions page to show the entire prompt

src/reader.cpp

@@ -434,9 +434,11 @@ static void reader_repaint() {
     std::vector<int> indents = data->indents;
     indents.resize(len);
 
-    // Re-render our completions page if necessary. We set the term size to 1 less than the true
-    // term height. This means we will always show the (bottom) line of the prompt.
-    data->pager.set_term_size(maxi(1, common_get_width()), maxi(1, common_get_height() - 1));
+    // Re-render our completions page if necessary. We set the term size to less than the true
+    // term height by the number of prompt lines. This means we will always show the entire line of
+    // the prompt.
+    data->pager.set_term_size(maxi(1, common_get_width()),
+                              maxi(1, common_get_height() - (int)calc_prompt_lines(full_line)));
     data->pager.update_rendering(&data->current_page_rendering);
 
     bool focused_on_pager = data->active_edit_line() == &data->pager.search_field_line;

src/screen.cpp

@@ -346,7 +346,7 @@ static prompt_layout_t calc_prompt_layout(const wchar_t *prompt, prompt_type_t w
     return prompt_layout;
 }
 
-static size_t calc_prompt_lines(const wcstring &prompt) {
+size_t calc_prompt_lines(const wcstring &prompt) {
     // Hack for the common case where there's no newline at all. I don't know if a newline can
     // appear in an escape sequence, so if we detect a newline we have to defer to
     // calc_prompt_width_and_lines.

src/screen.h

@@ -240,4 +240,7 @@ class cached_esc_sequences_t {
 // change by calling `cached_esc_sequences.clear()`.
 extern cached_esc_sequences_t cached_esc_sequences;
 
+// Calculates the number of prompt lines.
+size_t calc_prompt_lines(const wcstring &prompt);
+
 #endif