Use list_find in more places and refactor/fix workspace prev_next functions

The original purpose of this commit is to replace some for loops with
list_find. But while doing this I found the workspace_prev_next_impl
functions to be difficult to read and also contained a bug, so I
refactored them and fixed the bug.

To reproduce the bug:

* Have two outputs, where the left output has workspaces 1, 2, 3 and the
right output has workspaces 4, 5, 6. Make workspace 2 focused_inactive
and workspace 4 focused.
* Run `workspace prev`.
* Previously it would visit the left output, then apply `workspace prev`
to workspace 2, which focuses workspace 1.
* Now it will focus the rightmost workspace on the left output
(workspace 3).

The refactoring I made to the workspace functions are:

* Added the static keyword.
* They now accept an int dir rather than bool, to avoid an unnecessary
conversion.
* Rather than preparing start and end variables for the purpose of
iterating, just iterate everything.
* Replace for loops with list_find.
* Don't call workspace_output_prev_next_impl (this fixes the bug).

common/list.c

@@ -77,7 +77,7 @@ int list_seq_find(list_t *list, int compare(const void *item, const void *data),
 	return -1;
 }
 
-int list_find(list_t *list, void *item) {
+int list_find(list_t *list, const void *item) {
 	for (int i = 0; i < list->length; i++) {
 		if (list->items[i] == item) {
 			return i;

include/list.h

@@ -20,7 +20,7 @@ void list_qsort(list_t *list, int compare(const void *left, const void *right));
 // Return index for first item in list that returns 0 for given compare
 // function or -1 if none matches.
 int list_seq_find(list_t *list, int compare(const void *item, const void *cmp_to), const void *cmp_to);
-int list_find(list_t *list, void *item);
+int list_find(list_t *list, const void *item);
 // stable sort since qsort is not guaranteed to be stable
 void list_stable_sort(list_t *list, int compare(const void *a, const void *b));
 // swap two elements in a list

sway/tree/layout.c

@@ -20,14 +20,7 @@
 #include "log.h"
 
 static int index_child(const struct sway_container *child) {
-	struct sway_container *parent = child->parent;
-	for (int i = 0; i < parent->children->length; ++i) {
-		if (parent->children->items[i] == child) {
-			return i;
-		}
-	}
-	// This happens if the child is a floating container
-	return -1;
+	return list_find(child->parent->children, child);
 }
 
 static void container_handle_fullscreen_reparent(struct sway_container *con,
@@ -125,11 +118,9 @@ struct sway_container *container_remove_child(struct sway_container *child) {
 	}
 
 	struct sway_container *parent = child->parent;
-	for (int i = 0; i < parent->children->length; ++i) {
-		if (parent->children->items[i] == child) {
-			list_del(parent->children, i);
-			break;
-		}
+	int index = index_child(child);
+	if (index != -1) {
+		list_del(parent->children, index);
 	}
 	child->parent = NULL;
 	container_notify_subtree_changed(parent);

sway/tree/root.c

@@ -84,11 +84,9 @@ void root_scratchpad_remove_container(struct sway_container *con) {
 		return;
 	}
 	con->scratchpad = false;
-	for (int i = 0; i < root_container.sway_root->scratchpad->length; ++i) {
-		if (root_container.sway_root->scratchpad->items[i] == con) {
-			list_del(root_container.sway_root->scratchpad, i);
-			break;
-		}
+	int index = list_find(root_container.sway_root->scratchpad, con);
+	if (index != -1) {
+		list_del(root_container.sway_root->scratchpad, index);
 	}
 }
 

sway/tree/workspace.c

@@ -286,8 +286,8 @@ struct sway_container *workspace_by_name(const char *name) {
  * the end and beginning.  If next is false, the previous workspace is returned,
  * otherwise the next one is returned.
  */
-struct sway_container *workspace_output_prev_next_impl(
-		struct sway_container *output, bool next) {
+static struct sway_container *workspace_output_prev_next_impl(
+		struct sway_container *output, int dir) {
 	if (!output) {
 		return NULL;
 	}
@@ -302,27 +302,17 @@ struct sway_container *workspace_output_prev_next_impl(
 			focus :
 			container_parent(focus, C_WORKSPACE));
 
-	int i;
-	for (i = 0; i < output->children->length; i++) {
-		if (output->children->items[i] == workspace) {
-			return output->children->items[
-				wrap(i + (next ? 1 : -1), output->children->length)];
-		}
-	}
-
-	// Doesn't happen, at worst the for loop returns the previously active
-	// workspace
-	return NULL;
+	int index = list_find(output->children, workspace);
+	size_t new_index = wrap(index + dir, output->children->length);
+	return output->children->items[new_index];
 }
 
 /**
  * Get the previous or next workspace. If the first/last workspace on an output
- * is active, proceed to the previous/next output's previous/next workspace. If
- * next is false, the previous workspace is returned, otherwise the next one is
- * returned.
+ * is active, proceed to the previous/next output's previous/next workspace.
  */
-struct sway_container *workspace_prev_next_impl(
-		struct sway_container *workspace, bool next) {
+static struct sway_container *workspace_prev_next_impl(
+		struct sway_container *workspace, int dir) {
 	if (!workspace) {
 		return NULL;
 	}
@@ -331,52 +321,40 @@ struct sway_container *workspace_prev_next_impl(
 		return NULL;
 	}
 
-	struct sway_container *current_output = workspace->parent;
-	int offset = next ? 1 : -1;
-	int start = next ? 0 : 1;
-	int end;
-	if (next) {
-		end = current_output->children->length - 1;
-	} else {
-		end = current_output->children->length;
-	}
-	int i;
-	for (i = start; i < end; i++) {
-		if (current_output->children->items[i] == workspace) {
-			return current_output->children->items[i + offset];
-		}
-	}
+	struct sway_container *output = workspace->parent;
+	int index = list_find(output->children, workspace);
+	int new_index = index + dir;
 
-	// Given workspace is the first/last on the output, jump to the
-	// previous/next output
-	int num_outputs = root_container.children->length;
-	for (i = 0; i < num_outputs; i++) {
-		if (root_container.children->items[i] == current_output) {
-			struct sway_container *next_output = root_container.children->items[
-				wrap(i + offset, num_outputs)];
-			return workspace_output_prev_next_impl(next_output, next);
-		}
+	if (new_index >= 0 && new_index < output->children->length) {
+		return output->children->items[index + dir];
 	}
 
-	// Doesn't happen, at worst the for loop returns the previously active
-	// workspace on the active output
-	return NULL;
+	// Look on a different output
+	int output_index = list_find(root_container.children, output);
+	new_index = wrap(output_index + dir, root_container.children->length);
+	output = root_container.children->items[new_index];
+
+	if (dir == 1) {
+		return output->children->items[0];
+	} else {
+		return output->children->items[output->children->length - 1];
+	}
 }
 
 struct sway_container *workspace_output_next(struct sway_container *current) {
-	return workspace_output_prev_next_impl(current, true);
+	return workspace_output_prev_next_impl(current, 1);
 }
 
 struct sway_container *workspace_next(struct sway_container *current) {
-	return workspace_prev_next_impl(current, true);
+	return workspace_prev_next_impl(current, 1);
 }
 
 struct sway_container *workspace_output_prev(struct sway_container *current) {
-	return workspace_output_prev_next_impl(current, false);
+	return workspace_output_prev_next_impl(current, -1);
 }
 
 struct sway_container *workspace_prev(struct sway_container *current) {
-	return workspace_prev_next_impl(current, false);
+	return workspace_prev_next_impl(current, -1);
 }
 
 bool workspace_switch(struct sway_container *workspace,