Decouple bisect from jumplist

Move some bisect state to zathura_t and manipulate the jumplist that much.
Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

shortcuts.c

@@ -19,6 +19,14 @@
 #include "page-widget.h"
 #include "adjustment.h"
 
+#ifndef MIN
+#define MIN(a,b) (((a)<(b))?(a):(b))
+#endif
+
+#ifndef MAX
+#define MAX(a,b) (((a)>(b))?(a):(b))
+#endif
+
 /* Helper function; see sc_display_link and sc_follow. */
 static bool
 draw_links(zathura_t* zathura)
@@ -786,123 +794,146 @@ sc_bisect(girara_session_t* session, girara_argument_t* argument,
   g_return_val_if_fail(argument != NULL, false);
   g_return_val_if_fail(zathura->document != NULL, false);
 
-  unsigned int number_of_pages, cur_page, prev_page, prev2_page;
-  bool have_prev, have_prev2;
-
-  zathura_jump_t* prev_jump = NULL;
-  zathura_jump_t* prev2_jump = NULL;
-
-  number_of_pages= zathura_document_get_number_of_pages(zathura->document);
-  cur_page = zathura_document_get_current_page_number(zathura->document);
-
-  prev_page = prev2_page = 0;
-  have_prev = have_prev2 = false;
+  const unsigned int num_pages = zathura_document_get_number_of_pages(zathura->document);
+  const unsigned int cur_page = zathura_document_get_current_page_number(zathura->document);
 
   /* process arguments */
   int direction;
-  if (t > 0 && t <= number_of_pages) {
-    /* jump to page t, and bisect between cur_page and t */
-    zathura_jumplist_add(zathura);
-    page_set(zathura, t-1);
-    zathura_jumplist_add(zathura);
-    if (t-1 > cur_page) {
+  if (t > 0 && t <= num_pages) {
+    /* bisect between cur_page and t */
+    t -= 1;
+    if (t == cur_page) {
+      /* nothing to do */
+      return false;
+    }
+    else if (t > cur_page) {
+      zathura->bisect.start = cur_page;
+      zathura->bisect.end = t;
       direction = BACKWARD;
     } else {
+      zathura->bisect.start = t;
+      zathura->bisect.end = cur_page;
       direction = FORWARD;
     }
-
   } else if (argument != NULL)  {
     direction = argument->n;
 
-  } else {
-    return false;
-  }
+    zathura_jump_t* jump = zathura_jumplist_current(zathura);
+    if (jump == NULL) {
+      girara_debug("bisecting between first and last page because there are no jumps");
+      zathura->bisect.start = 0;
+      zathura->bisect.end = num_pages - 1;
+    } else {
+      if (jump->page != cur_page || jump->page != zathura->bisect.last_jump) {
+        girara_debug("last jump doesn't match up, starting new bisecting");
+        zathura->bisect.start = 0;
+        zathura->bisect.end = num_pages - 1;
 
-  cur_page = zathura_document_get_current_page_number(zathura->document);
+        /* check if we have previous jumps */
+        if (zathura_jumplist_has_previous(zathura) == true) {
+          zathura_jumplist_backward(zathura);
+          jump = zathura_jumplist_current(zathura);
 
-  if (zathura_jumplist_has_previous(zathura)) {
-    /* If there is a previous jump, get its page */
-    zathura_jumplist_backward(zathura);
-    prev_jump = zathura_jumplist_current(zathura);
-    if (prev_jump) {
-      prev_page = prev_jump->page;
-      have_prev = true;
-    }
+          unsigned int prev_page = 0;
+          unsigned int prev_page2 = num_pages - 1;
+          if (jump != NULL) {
+            prev_page = jump->page;
+          }
 
-    if (zathura_jumplist_has_previous(zathura)) {
-      /* If there is a second previous jump, get its page. */
-      zathura_jumplist_backward(zathura);
-      prev2_jump = zathura_jumplist_current(zathura);
-      if (prev2_jump) {
-        prev2_page = prev2_jump->page;
-        have_prev2 = true;
+          prev_page2 = prev_page;
+          if (zathura_jumplist_has_previous(zathura) == true) {
+            zathura_jumplist_backward(zathura);
+            jump = zathura_jumplist_current(zathura);
+            if (jump != NULL) {
+              prev_page2 = jump->page;
+            }
+            zathura_jumplist_forward(zathura);
+          }
+          zathura_jumplist_forward(zathura);
+
+          if (prev_page == prev_page2) {
+            if (prev_page > cur_page) {
+              zathura->bisect.end = prev_page;
+            } else {
+              zathura->bisect.start = prev_page;
+            }
+          } else {
+            zathura->bisect.start = MIN(prev_page, prev_page2);
+            zathura->bisect.end = MAX(prev_page, prev_page2);
+          }
+        }
+
+        /* some sanity checks on new bounds */
+        if (cur_page < zathura->bisect.start) {
+          if (direction == FORWARD) {
+            zathura->bisect.start = cur_page;
+          } else {
+            zathura->bisect.start = cur_page;
+            zathura->bisect.end = 0;
+          }
+        } else if (cur_page > zathura->bisect.end) {
+          if (direction == BACKWARD) {
+            zathura->bisect.end = cur_page;
+          } else {
+            zathura->bisect.start = cur_page;
+            zathura->bisect.end = num_pages - 1;
+          }
+        }
       }
-      zathura_jumplist_forward(zathura);
     }
-    zathura_jumplist_forward(zathura);
+  } else {
+    return false;
+  }
+
+  girara_debug("bisecting between %d and %d, at %d", zathura->bisect.start, zathura->bisect.end, cur_page);
+  if (zathura->bisect.start == zathura->bisect.end) {
+    /* nothing to do */
+    return false;
   }
 
   /* now, we are back at the initial jump. prev_page and prev2_page contain
    the pages for previous and second previous jump if they exist. */
 
+  unsigned int next_page = cur_page;
+  unsigned int next_start = zathura->bisect.start;
+  unsigned int next_end = zathura->bisect.end;
+
   /* bisect */
   switch(direction) {
     case FORWARD:
-      if (have_prev && cur_page <= prev_page) {
-        /* add a new jump point */
-        if (cur_page < prev_page) {
-          zathura_jumplist_add(zathura);
-          page_set(zathura, (cur_page + prev_page)/2);
-          zathura_jumplist_add(zathura);
+      if (cur_page != zathura->bisect.end) {
+        next_page = (cur_page + zathura->bisect.end) / 2;
+        if (next_page == cur_page) {
+          ++next_page;
         }
-
-      } else if (have_prev2 && cur_page <= prev2_page) {
-        /* save current position at previous jump point */
-        if (cur_page < prev2_page) {
-          zathura_jumplist_backward(zathura);
-          zathura_jumplist_add(zathura);
-          zathura_jumplist_forward(zathura);
-
-          page_set(zathura, (cur_page + prev2_page)/2);
-          zathura_jumplist_add(zathura);
-        }
-      } else {
-        /* none of prev_page or prev2_page comes after cur_page */
-        zathura_jumplist_add(zathura);
-        page_set(zathura, (cur_page + number_of_pages - 1)/2);
-        zathura_jumplist_add(zathura);
+        next_start = cur_page;
       }
       break;
 
     case BACKWARD:
-      if (have_prev && prev_page <= cur_page) {
-        /* add a new jump point */
-        if (prev_page < cur_page) {
-          zathura_jumplist_add(zathura);
-          page_set(zathura, (cur_page + prev_page)/2);
-          zathura_jumplist_add(zathura);
+      if (cur_page != zathura->bisect.start) {
+        next_page = (cur_page + zathura->bisect.start) / 2;
+        if (next_page == cur_page) {
+          --next_page;
         }
-
-      } else if (have_prev2 && prev2_page <= cur_page) {
-        /* save current position at previous jump point */
-        if (prev2_page < cur_page) {
-          zathura_jumplist_backward(zathura);
-          zathura_jumplist_add(zathura);
-          zathura_jumplist_forward(zathura);
-
-          page_set(zathura, (cur_page + prev2_page)/2);
-          zathura_jumplist_add(zathura);
-        }
-
-      } else {
-        /* none of prev_page or prev2_page comes before cur_page */
-        zathura_jumplist_add(zathura);
-        page_set(zathura, cur_page/2);
-        zathura_jumplist_add(zathura);
+        next_end = cur_page;
       }
       break;
   }
 
+  if (next_page == cur_page) {
+    /* nothing to do */
+    return false;
+  }
+
+  girara_debug("bisecting between %d and %d, jumping to %d", zathura->bisect.start, zathura->bisect.end, next_page);
+  zathura->bisect.last_jump = next_page;
+  zathura->bisect.start = next_start;
+  zathura->bisect.end = next_end;
+
+  page_set(zathura, next_page);
+  zathura_jumplist_add(zathura);
+
   /* adjust horizontal position */
   GtkAdjustment* hadjustment = gtk_scrolled_window_get_hadjustment(GTK_SCROLLED_WINDOW(session->gtk.view));
   cb_view_hadjustment_changed(hadjustment, zathura);

zathura.h

@@ -163,6 +163,15 @@ struct zathura_s
     unsigned int size;
     unsigned int num_cached_pages;
   } page_cache;
+
+  /**
+   * Bisect stage
+   */
+  struct {
+    unsigned int last_jump; /**< Page jumped to by bisect */
+    unsigned int start; /**< Bisection range - start */
+    unsigned int end; /**< Bisection range - end */
+  } bisect;
 };
 
 /**