Layout tiled using a width/height fraction

Instead of using container->width/height as both the input and output
of the layout calculation have container->width_fraction/height_fraction
as the share of the parent this container occupies and calculate the
layout based on that. That way the container arrangement can always be
recalculated even if width/height have been altered by things like
fullscreen.

To do this several parts are reworked:

- The vertical and horizontal arrangement code is ajusted to work with
  fractions instead of directly with width/height
- The resize code is then changed to manipulate the fractions when
  working on tiled containers.
- Finally the places that manipulated width/height are adjusted to
  match. The adjusted parts are container split, swap, and the input
  seat code.

It's possible that some parts of the code are now adjusting width and
height only for those to be immediately recalculated. That's harmless
and since non-tiled containers are still sized with width/height
directly it may avoid breaking other corner cases.

Fixes #3547
Fixes #4297

7 files changed, 85 insertions, 37 deletions

diff --git a/include/sway/tree/container.h b/include/sway/tree/container.h
index adeb85ae..4efde640 100644
--- a/include/sway/tree/container.h
+++ b/include/sway/tree/container.h
@@ -88,6 +88,10 @@ struct sway_container {
 	double saved_x, saved_y;
 	double saved_width, saved_height;
 
+	// The share of the space of parent container this container occupies
+	double width_fraction;
+	double height_fraction;
+
 	// These are in layout coordinates.
 	double content_x, content_y;
 	int content_width, content_height;
diff --git a/sway/commands/move.c b/sway/commands/move.c
index 6fd66f28..2a1993ae 100644
--- a/sway/commands/move.c
+++ b/sway/commands/move.c
@@ -131,6 +131,7 @@ static void container_move_to_container_from_direction(
 						container, index);
 			}
 			container->width = container->height = 0;
+			container->width_fraction = container->height_fraction = 0;
 		}
 		return;
 	}
@@ -142,6 +143,7 @@ static void container_move_to_container_from_direction(
 			0 : destination->children->length;
 		container_insert_child(destination, container, index);
 		container->width = container->height = 0;
+		container->width_fraction = container->height_fraction = 0;
 		return;
 	}
 
@@ -163,6 +165,7 @@ static void container_move_to_workspace_from_direction(
 		struct sway_container *container, struct sway_workspace *workspace,
 		enum wlr_direction move_dir) {
 	container->width = container->height = 0;
+	container->width_fraction = container->height_fraction = 0;
 
 	if (is_parallel(workspace->layout, move_dir)) {
 		sway_log(SWAY_DEBUG, "Reparenting container (parallel)");
@@ -206,7 +209,7 @@ static void container_move_to_workspace(struct sway_container *container,
 	} else {
 		container_detach(container);
 		container->width = container->height = 0;
-		container->saved_width = container->saved_height = 0;
+		container->width_fraction = container->height_fraction = 0;
 		workspace_add_tiling(workspace, container);
 		container_update_representation(container);
 	}
@@ -234,7 +237,7 @@ static void container_move_to_container(struct sway_container *container,
 	container_detach(container);
 	container_remove_gaps(container);
 	container->width = container->height = 0;
-	container->saved_width = container->saved_height = 0;
+	container->width_fraction = container->height_fraction = 0;
 
 	if (destination->view) {
 		container_add_sibling(destination, container, 1);
diff --git a/sway/commands/resize.c b/sway/commands/resize.c
index 440937f0..28f2552e 100644
--- a/sway/commands/resize.c
+++ b/sway/commands/resize.c
@@ -174,10 +174,14 @@ void container_resize_tiled(struct sway_container *con,
 		if (prev && prev->width - sibling_amount < MIN_SANE_W) {
 			return;
 		}
-		con->width += amount;
-		next->width -= sibling_amount;
+
+		con->width_fraction +=
+			((double)amount / con->width) * con->width_fraction;
+		next->width_fraction -=
+			((double)sibling_amount / con->width) * con->width_fraction;
 		if (prev) {
-			prev->width -= sibling_amount;
+			prev->width_fraction -=
+				((double)sibling_amount / con->width) * con->width_fraction;
 		}
 	} else {
 		if (con->height + amount < MIN_SANE_H) {
@@ -189,10 +193,14 @@ void container_resize_tiled(struct sway_container *con,
 		if (prev && prev->height - sibling_amount < MIN_SANE_H) {
 			return;
 		}
-		con->height += amount;
-		next->height -= sibling_amount;
+
+		con->height_fraction +=
+			((double)amount / con->height) * con->height_fraction;
+		next->height_fraction -=
+			((double)sibling_amount / con->height) * con->height_fraction;
 		if (prev) {
-			prev->height -= sibling_amount;
+			prev->height_fraction -=
+				((double)sibling_amount / con->height) * con->height_fraction;
 		}
 	}
 
@@ -280,10 +288,11 @@ static struct cmd_results *resize_adjust_tiled(uint32_t axis,
 		}
 	}
 
-	double old_width = current->width;
-	double old_height = current->height;
+	double old_width = current->width_fraction;
+	double old_height = current->height_fraction;
 	container_resize_tiled(current, axis, amount->amount);
-	if (current->width == old_width && current->height == old_height) {
+	if (current->width_fraction == old_width &&
+			current->height_fraction == old_height) {
 		return cmd_results_new(CMD_INVALID, "Cannot resize any further");
 	}
 	return cmd_results_new(CMD_SUCCESS, NULL);
diff --git a/sway/commands/swap.c b/sway/commands/swap.c
index f27aa7ed..a4a4108d 100644
--- a/sway/commands/swap.c
+++ b/sway/commands/swap.c
@@ -20,6 +20,8 @@ static void swap_places(struct sway_container *con1,
 	temp->y = con1->y;
 	temp->width = con1->width;
 	temp->height = con1->height;
+	temp->width_fraction = con1->width_fraction;
+	temp->height_fraction = con1->height_fraction;
 	temp->parent = con1->parent;
 	temp->workspace = con1->workspace;
 
@@ -27,11 +29,15 @@ static void swap_places(struct sway_container *con1,
 	con1->y = con2->y;
 	con1->width = con2->width;
 	con1->height = con2->height;
+	con1->width_fraction = con2->width_fraction;
+	con1->height_fraction = con2->height_fraction;
 
 	con2->x = temp->x;
 	con2->y = temp->y;
 	con2->width = temp->width;
 	con2->height = temp->height;
+	con2->width_fraction = temp->width_fraction;
+	con2->height_fraction = temp->height_fraction;
 
 	int temp_index = container_sibling_index(con1);
 	if (con2->parent) {
diff --git a/sway/input/seatop_move_tiling.c b/sway/input/seatop_move_tiling.c
index e1506175..4201ae37 100644
--- a/sway/input/seatop_move_tiling.c
+++ b/sway/input/seatop_move_tiling.c
@@ -291,6 +291,8 @@ static void handle_button(struct sway_seat *seat, uint32_t time_msec,
 			siblings->items[1] : siblings->items[index - 1];
 		con->width = sibling->width;
 		con->height = sibling->height;
+		con->width_fraction = sibling->width_fraction;
+		con->height_fraction = sibling->height_fraction;
 	}
 
 	arrange_workspace(old_ws);
diff --git a/sway/tree/arrange.c b/sway/tree/arrange.c
index fc5d49ed..dd0a72cd 100644
--- a/sway/tree/arrange.c
+++ b/sway/tree/arrange.c
@@ -18,39 +18,49 @@ static void apply_horiz_layout(list_t *children, struct wlr_box *parent) {
 		return;
 	}
 
-	// Count the number of new windows we are resizing
+	// Count the number of new windows we are resizing, and how much space
+	// is currently occupied
 	int new_children = 0;
+	double current_width_fraction = 0;
 	for (int i = 0; i < children->length; ++i) {
 		struct sway_container *child = children->items[i];
-		if (child->width <= 0) {
+		current_width_fraction += child->width_fraction;
+		if (child->width_fraction <= 0) {
 			new_children += 1;
 		}
 	}
 
-	// Calculate total width of children
-	double total_width = 0;
+	// Calculate each height fraction
+	double total_width_fraction = 0;
 	for (int i = 0; i < children->length; ++i) {
 		struct sway_container *child = children->items[i];
-		if (child->width <= 0) {
-			if (children->length > new_children) {
-				child->width = parent->width / (children->length - new_children);
+		if (child->width_fraction <= 0) {
+			if (current_width_fraction <= 0) {
+				child->width_fraction = 1.0;
+			} else if (children->length > new_children) {
+				child->width_fraction = current_width_fraction /
+					(children->length - new_children);
 			} else {
-				child->width = parent->width;
+				child->width_fraction = current_width_fraction;
 			}
 		}
-		container_remove_gaps(child);
-		total_width += child->width;
+		total_width_fraction += child->width_fraction;
+	}
+	// Normalize width fractions so the sum is 1.0
+	for (int i = 0; i < children->length; ++i) {
+		struct sway_container *child = children->items[i];
+		child->width_fraction /= total_width_fraction;
 	}
-	double scale = parent->width / total_width;
 
 	// Resize windows
 	sway_log(SWAY_DEBUG, "Arranging %p horizontally", parent);
 	double child_x = parent->x;
 	for (int i = 0; i < children->length; ++i) {
 		struct sway_container *child = children->items[i];
+		container_remove_gaps(child);
 		child->x = child_x;
 		child->y = parent->y;
-		child->width = floor(child->width * scale);
+		child->width = floor(child->width_fraction * parent->width);
 		child->height = parent->height;
 		child_x += child->width;
 
@@ -67,40 +77,50 @@ static void apply_vert_layout(list_t *children, struct wlr_box *parent) {
 		return;
 	}
 
-	// Count the number of new windows we are resizing
+	// Count the number of new windows we are resizing, and how much space
+	// is currently occupied
 	int new_children = 0;
+	double current_height_fraction = 0;
 	for (int i = 0; i < children->length; ++i) {
 		struct sway_container *child = children->items[i];
-		if (child->height <= 0) {
+		current_height_fraction += child->height_fraction;
+		if (child->height_fraction <= 0) {
 			new_children += 1;
 		}
 	}
 
-	// Calculate total height of children
-	double total_height = 0;
+	// Calculate each height fraction
+	double total_height_fraction = 0;
 	for (int i = 0; i < children->length; ++i) {
 		struct sway_container *child = children->items[i];
-		if (child->height <= 0) {
-			if (children->length > new_children) {
-				child->height = parent->height / (children->length - new_children);
+		if (child->height_fraction <= 0) {
+			if (current_height_fraction <= 0) {
+				child->height_fraction = 1.0;
+			} else if (children->length > new_children) {
+				child->height_fraction = current_height_fraction /
+					(children->length - new_children);
 			} else {
-				child->height = parent->height;
+				child->height_fraction = current_height_fraction;
 			}
 		}
-		container_remove_gaps(child);
-		total_height += child->height;
+		total_height_fraction += child->height_fraction;
+	}
+	// Normalize height fractions so the sum is 1.0
+	for (int i = 0; i < children->length; ++i) {
+		struct sway_container *child = children->items[i];
+		child->height_fraction /= total_height_fraction;
 	}
-	double scale = parent->height / total_height;
 
 	// Resize
 	sway_log(SWAY_DEBUG, "Arranging %p vertically", parent);
 	double child_y = parent->y;
 	for (int i = 0; i < children->length; ++i) {
 		struct sway_container *child = children->items[i];
+		container_remove_gaps(child);
 		child->x = parent->x;
 		child->y = child_y;
 		child->width = parent->width;
-		child->height = floor(child->height * scale);
+		child->height = floor(child->height_fraction * parent->height);
 		child_y += child->height;
 
 		// Make last child use remaining height of parent
diff --git a/sway/tree/container.c b/sway/tree/container.c
index 9046ae27..068dbb88 100644
--- a/sway/tree/container.c
+++ b/sway/tree/container.c
@@ -789,6 +789,8 @@ void container_set_floating(struct sway_container *container, bool enable) {
 				container->border = container->saved_border;
 			}
 		}
+		container->width_fraction = 0;
+		container->height_fraction = 0;
 	}
 
 	container_end_mouse_operation(container);
@@ -1022,9 +1024,9 @@ void container_fullscreen_disable(struct sway_container *con) {
 	if (container_is_floating(con)) {
 		con->x = con->saved_x;
 		con->y = con->saved_y;
+		con->width = con->saved_width;
+		con->height = con->saved_height;
 	}
-	con->width = con->saved_width;
-	con->height = con->saved_height;
 
 	if (con->fullscreen_mode == FULLSCREEN_WORKSPACE) {
 		if (con->workspace) {
@@ -1415,6 +1417,8 @@ struct sway_container *container_split(struct sway_container *child,
 	struct sway_container *cont = container_create(NULL);
 	cont->width = child->width;
 	cont->height = child->height;
+	cont->width_fraction = child->width_fraction;
+	cont->height_fraction = child->height_fraction;
 	cont->x = child->x;
 	cont->y = child->y;
 	cont->current_gaps = child->current_gaps;