input: Add shortcut to cycle first page column

Add mapping cycle_first_column (default 'D') to cycle the column
in which to display the first page.

doc/man/zathura.1.rst

@@ -127,6 +127,8 @@ General
     Show index and switch to **Index mode**
   d
     Toggle dual page view
+  D
+    Cycle opening column in dual page view
   F5
     Switch to presentation mode
   F11

doc/man/zathurarc.5.rst

@@ -225,6 +225,10 @@ They can also be combined with modifiers:
 
     Change current mode. Pass the desired mode as argument.
 
+  * ``cycle_first_page``
+
+    In multiple page layout, cycle the column in which the first page is displayed.
+
   * ``display_link``:
 
     Display link target.

zathura/config.c

@@ -443,6 +443,7 @@ void config_load_default(zathura_t* zathura) {
   girara_shortcut_add(gsession, GDK_CONTROL_MASK, GDK_KEY_n, NULL, girara_sc_toggle_statusbar, (mode), 0, NULL);       \
   girara_shortcut_add(gsession, GDK_CONTROL_MASK, GDK_KEY_m, NULL, girara_sc_toggle_inputbar, (mode), 0, NULL);        \
   girara_shortcut_add(gsession, 0, GDK_KEY_d, NULL, sc_toggle_page_mode, (mode), 0, NULL);                             \
+  girara_shortcut_add(gsession, 0, GDK_KEY_D, NULL, sc_cycle_first_column, (mode), 0, NULL);                           \
                                                                                                                        \
   girara_shortcut_add(gsession, 0, GDK_KEY_q, NULL, sc_quit, (mode), 0, NULL);                                         \
                                                                                                                        \
@@ -596,6 +597,7 @@ void config_load_default(zathura_t* zathura) {
   girara_shortcut_mapping_add(gsession, "adjust_window",       sc_adjust_window);
   girara_shortcut_mapping_add(gsession, "bisect",              sc_bisect);
   girara_shortcut_mapping_add(gsession, "change_mode",         sc_change_mode);
+  girara_shortcut_mapping_add(gsession, "cycle_first_column",  sc_cycle_first_column);
   girara_shortcut_mapping_add(gsession, "display_link",        sc_display_link);
   girara_shortcut_mapping_add(gsession, "copy_link",           sc_copy_link);
   girara_shortcut_mapping_add(gsession, "copy_filepath",       sc_copy_filepath);

zathura/shortcuts.c

@@ -150,6 +150,34 @@ sc_change_mode(girara_session_t* session, girara_argument_t* argument,
   return false;
 }
 
+bool
+sc_cycle_first_column(girara_session_t* session, girara_argument_t* UNUSED(argument),
+                      girara_event_t* UNUSED(event), unsigned int t)
+{
+  g_return_val_if_fail(session != NULL, false);
+  g_return_val_if_fail(session->global.data != NULL, false);
+  zathura_t* zathura = session->global.data;
+
+  if (zathura->document == NULL) {
+    girara_notify(session, GIRARA_WARNING, _("No document opened."));
+    return false;
+  }
+
+  int pages_per_row = 1;
+  girara_setting_get(session, "pages-per-row", &pages_per_row);
+  char* first_page_column_list = NULL;
+  girara_setting_get(session, "first-page-column", &first_page_column_list);
+
+  if (t == 0) t = 1;
+  char* new_column_list = increment_first_page_column(first_page_column_list, pages_per_row, t);
+  g_free(first_page_column_list);
+
+  girara_setting_set(session, "first-page-column", new_column_list);
+  g_free(new_column_list);
+
+  return true;
+}
+
 bool
 sc_display_link(girara_session_t* session, girara_argument_t* UNUSED(argument),
                 girara_event_t* UNUSED(event), unsigned int UNUSED(t))

zathura/shortcuts.h

@@ -38,6 +38,17 @@ bool sc_adjust_window(girara_session_t* session, girara_argument_t* argument, gi
  */
 bool sc_change_mode(girara_session_t* session, girara_argument_t* argument, girara_event_t* event, unsigned int t);
 
+/**
+ * Cycle the column the first page is displayed in
+ *
+ * @param session The used girara session
+ * @param argument The used argument
+ * @param event Girara event
+ * @param t Number of executions
+ * @return true if no error occurred otherwise false
+ */
+bool sc_cycle_first_column(girara_session_t* session, girara_argument_t* argument, girara_event_t* event, unsigned int t);
+
 /**
  * Display a link
  *

zathura/utils.c

@@ -313,6 +313,54 @@ find_first_page_column(const char* first_page_column_list,
   return first_page_column;
 }
 
+char*
+increment_first_page_column(const char* first_page_column_list,
+                            const unsigned int pages_per_row, int incr)
+{
+  /* sanity checks */
+  if (first_page_column_list == NULL)
+    first_page_column_list = "";
+  /* This function is a no-op for 1 column layout */
+  if (pages_per_row <= 1)
+    return g_strdup(first_page_column_list);
+
+  unsigned int size = 0;
+  unsigned int* settings = parse_first_page_column_list(first_page_column_list, &size);
+
+  /* Lookup current setting. Signed value to avoid negative overflow when modifying it later. */
+  int column = 1;
+  if (pages_per_row <= size) {
+    column = settings[pages_per_row - 1];
+  } else if (size > 0) {
+    column = settings[size - 1];
+  }
+
+  /* increment and normalise to [1,pages_per_row]. */
+  column += incr;
+  column %= pages_per_row;    /* range [-pages_per_row+1, pages_per_row-1] */
+  if (column <= 0)
+    column += pages_per_row;  /* range [1, pages_per_row] */
+
+  /* Write back, creating the new cell if necessary. */
+  if (pages_per_row <= size) {
+    settings[pages_per_row - 1] = column;
+  } else {
+    /* extend settings array */
+    settings = g_realloc_n(settings, pages_per_row, sizeof(*settings));
+    for (unsigned int i=size; i<pages_per_row-1; i++) {
+      /* The value of the last set cell is normally used for all largers pages_per_row,
+       * so duplicate it to the newly created cells. */
+      settings[i] = settings[size - 1];
+    }
+    settings[pages_per_row-1] = column;
+    size = pages_per_row;
+  }
+
+  char* new_column_list = write_first_page_column_list(settings, size);
+  g_free(settings);
+  return new_column_list;
+}
+
 bool
 parse_color(GdkRGBA* color, const char* str)
 {

zathura/utils.h

@@ -143,6 +143,18 @@ unsigned int* parse_first_page_column(const char* first_page_column_list, unsign
 unsigned int find_first_page_column(const char* first_page_column_list,
                                     const unsigned int pages_per_row);
 
+/**
+ * Cycle the column the first page should be rendered in.
+ *
+ * @param[in] first_page_column_list The settings list
+ * @param[in] pages_per_row The current pages per row
+ * @param[in] incr The value added to the current first page column setting
+ *
+ * @return The new modified settings list
+ */
+char* increment_first_page_column(const char* first_page_column_list,
+                                  const unsigned int pages_per_row, int incr);
+
 /**
  * Parse color string and print warning if color cannot be parsed.
  *