swayfx/sway/desktop/render.c

#define _POSIX_C_SOURCE 200809L
#include <assert.h>
#include <GLES2/gl2.h>
#include <stdlib.h>
#include <strings.h>
#include <time.h>
#include <wayland-server-core.h>
#include <wlr/render/gles2.h>
#include <wlr/render/wlr_renderer.h>
#include <wlr/types/wlr_box.h>
#include <wlr/types/wlr_buffer.h>
#include <wlr/types/wlr_matrix.h>
#include <wlr/types/wlr_output_damage.h>
#include <wlr/types/wlr_output_layout.h>
#include <wlr/types/wlr_output.h>
#include <wlr/types/wlr_surface.h>
#include <wlr/util/region.h>
#include "log.h"
#include "config.h"
#include "sway/config.h"
#include "sway/input/input-manager.h"
#include "sway/input/seat.h"
#include "sway/layers.h"
#include "sway/output.h"
#include "sway/server.h"
#include "sway/tree/arrange.h"
#include "sway/tree/container.h"
#include "sway/tree/root.h"
#include "sway/tree/view.h"
#include "sway/tree/workspace.h"

struct render_data {
	pixman_region32_t *damage;
	float alpha;
};

/**
 * Apply scale to a width or height.
 *
 * One does not simply multiply the width by the scale. We allow fractional
 * scaling, which means the resulting scaled width might be a decimal.
 * So we round it.
 *
 * But even this can produce undesirable results depending on the X or Y offset
 * of the box. For example, with a scale of 1.5, a box with width=1 should not
 * scale to 2px if its X coordinate is 1, because the X coordinate would have
 * scaled to 2px.
 */
static int scale_length(int length, int offset, float scale) {
	return round((offset + length) * scale) - round(offset * scale);
}

static void scissor_output(struct wlr_output *wlr_output,
		pixman_box32_t *rect) {
	struct wlr_renderer *renderer = wlr_backend_get_renderer(wlr_output->backend);
	assert(renderer);

	struct wlr_box box = {
		.x = rect->x1,
		.y = rect->y1,
		.width = rect->x2 - rect->x1,
		.height = rect->y2 - rect->y1,
	};

	int ow, oh;
	wlr_output_transformed_resolution(wlr_output, &ow, &oh);

	enum wl_output_transform transform =
		wlr_output_transform_invert(wlr_output->transform);
	wlr_box_transform(&box, &box, transform, ow, oh);

	wlr_renderer_scissor(renderer, &box);
}

static void set_scale_filter(struct wlr_output *wlr_output,
		struct wlr_texture *texture, enum scale_filter_mode scale_filter) {
	if (!wlr_texture_is_gles2(texture)) {
		return;
	}

	struct wlr_gles2_texture_attribs attribs;
	wlr_gles2_texture_get_attribs(texture, &attribs);

	glBindTexture(attribs.target, attribs.tex);

	switch (scale_filter) {
	case SCALE_FILTER_LINEAR:
		glTexParameteri(attribs.target, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
		break;
	case SCALE_FILTER_NEAREST:
		glTexParameteri(attribs.target, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
		break;
	case SCALE_FILTER_DEFAULT:
	case SCALE_FILTER_SMART:
		assert(false); // unreachable
	}
}

static void render_texture(struct wlr_output *wlr_output,
		pixman_region32_t *output_damage, struct wlr_texture *texture,
		const struct wlr_box *box, const float matrix[static 9], float alpha) {
	struct wlr_renderer *renderer =
		wlr_backend_get_renderer(wlr_output->backend);
	struct sway_output *output = wlr_output->data;

	struct wlr_gles2_texture_attribs attribs;
	wlr_gles2_texture_get_attribs(texture, &attribs);

	pixman_region32_t damage;
	pixman_region32_init(&damage);
	pixman_region32_union_rect(&damage, &damage, box->x, box->y,
		box->width, box->height);
	pixman_region32_intersect(&damage, &damage, output_damage);
	bool damaged = pixman_region32_not_empty(&damage);
	if (!damaged) {
		goto damage_finish;
	}

	int nrects;
	pixman_box32_t *rects = pixman_region32_rectangles(&damage, &nrects);
	for (int i = 0; i < nrects; ++i) {
		scissor_output(wlr_output, &rects[i]);
		set_scale_filter(wlr_output, texture, output->scale_filter);
		wlr_render_texture_with_matrix(renderer, texture, matrix, alpha);
	}

damage_finish:
	pixman_region32_fini(&damage);
}

static void render_surface_iterator(struct sway_output *output, struct sway_view *view,
		struct wlr_surface *surface, struct wlr_box *_box, float rotation,
		void *_data) {
	struct render_data *data = _data;
	struct wlr_output *wlr_output = output->wlr_output;
	pixman_region32_t *output_damage = data->damage;
	float alpha = data->alpha;

	struct wlr_texture *texture = wlr_surface_get_texture(surface);
	if (!texture) {
		return;
	}

	struct wlr_box box = *_box;
	scale_box(&box, wlr_output->scale);

	float matrix[9];
	enum wl_output_transform transform =
		wlr_output_transform_invert(surface->current.transform);
	wlr_matrix_project_box(matrix, &box, transform, rotation,
		wlr_output->transform_matrix);

	render_texture(wlr_output, output_damage, texture, &box, matrix, alpha);

	wlr_presentation_surface_sampled_on_output(server.presentation, surface,
		wlr_output);
}

static void render_layer(struct sway_output *output,
		pixman_region32_t *damage, struct wl_list *layer_surfaces) {
	struct render_data data = {
		.damage = damage,
		.alpha = 1.0f,
	};
	output_layer_for_each_surface(output, layer_surfaces,
		render_surface_iterator, &data);
}

#if HAVE_XWAYLAND
static void render_unmanaged(struct sway_output *output,
		pixman_region32_t *damage, struct wl_list *unmanaged) {
	struct render_data data = {
		.damage = damage,
		.alpha = 1.0f,
	};
	output_unmanaged_for_each_surface(output, unmanaged,
		render_surface_iterator, &data);
}
#endif

static void render_drag_icons(struct sway_output *output,
		pixman_region32_t *damage, struct wl_list *drag_icons) {
	struct render_data data = {
		.damage = damage,
		.alpha = 1.0f,
	};
	output_drag_icons_for_each_surface(output, drag_icons,
		render_surface_iterator, &data);
}

// _box.x and .y are expected to be layout-local
// _box.width and .height are expected to be output-buffer-local
void render_rect(struct sway_output *output,
		pixman_region32_t *output_damage, const struct wlr_box *_box,
		float color[static 4]) {
	struct wlr_output *wlr_output = output->wlr_output;
	struct wlr_renderer *renderer =
		wlr_backend_get_renderer(wlr_output->backend);

	struct wlr_box box;
	memcpy(&box, _box, sizeof(struct wlr_box));
	box.x -= output->lx * wlr_output->scale;
	box.y -= output->ly * wlr_output->scale;

	pixman_region32_t damage;
	pixman_region32_init(&damage);
	pixman_region32_union_rect(&damage, &damage, box.x, box.y,
		box.width, box.height);
	pixman_region32_intersect(&damage, &damage, output_damage);
	bool damaged = pixman_region32_not_empty(&damage);
	if (!damaged) {
		goto damage_finish;
	}

	int nrects;
	pixman_box32_t *rects = pixman_region32_rectangles(&damage, &nrects);
	for (int i = 0; i < nrects; ++i) {
		scissor_output(wlr_output, &rects[i]);
		wlr_render_rect(renderer, &box, color,
			wlr_output->transform_matrix);
	}

damage_finish:
	pixman_region32_fini(&damage);
}

void premultiply_alpha(float color[4], float opacity) {
	color[3] *= opacity;
	color[0] *= color[3];
	color[1] *= color[3];
	color[2] *= color[3];
}

static void render_view_toplevels(struct sway_view *view,
		struct sway_output *output, pixman_region32_t *damage, float alpha) {
	struct render_data data = {
		.damage = damage,
		.alpha = alpha,
	};
	// Render all toplevels without descending into popups
	double ox = view->container->surface_x -
		output->lx - view->geometry.x;
	double oy = view->container->surface_y -
		output->ly - view->geometry.y;
	output_surface_for_each_surface(output, view->surface, ox, oy,
			render_surface_iterator, &data);
}

static void render_popup_iterator(struct sway_output *output, struct sway_view *view,
		struct wlr_surface *surface, struct wlr_box *box, float rotation,
		void *data) {
	// Render this popup's surface
	render_surface_iterator(output, view, surface, box, rotation, data);

	// Render this popup's child toplevels
	output_surface_for_each_surface(output, surface, box->x, box->y,
			render_surface_iterator, data);
}

static void render_view_popups(struct sway_view *view,
		struct sway_output *output, pixman_region32_t *damage, float alpha) {
	struct render_data data = {
		.damage = damage,
		.alpha = alpha,
	};
	output_view_for_each_popup(output, view, render_popup_iterator, &data);
}

static void render_saved_view(struct sway_view *view,
		struct sway_output *output, pixman_region32_t *damage, float alpha) {
	struct wlr_output *wlr_output = output->wlr_output;

	if (!view->saved_buffer || !view->saved_buffer->texture) {
		return;
	}
	struct wlr_box box = {
		.x = view->container->surface_x - output->lx -
			view->saved_geometry.x,
		.y = view->container->surface_y - output->ly -
			view->saved_geometry.y,
		.width = view->saved_buffer_width,
		.height = view->saved_buffer_height,
	};

	struct wlr_box output_box = {
		.width = output->width,
		.height = output->height,
	};

	struct wlr_box intersection;
	bool intersects = wlr_box_intersection(&intersection, &output_box, &box);
	if (!intersects) {
		return;
	}

	scale_box(&box, wlr_output->scale);

	float matrix[9];
	wlr_matrix_project_box(matrix, &box, WL_OUTPUT_TRANSFORM_NORMAL, 0,
		wlr_output->transform_matrix);

	render_texture(wlr_output, damage, view->saved_buffer->texture,
			&box, matrix, alpha);

	// FIXME: we should set the surface that this saved buffer originates from
	// as sampled here.
	// https://github.com/swaywm/sway/pull/4465#discussion_r321082059
}

/**
 * Render a view's surface and left/bottom/right borders.
 */
static void render_view(struct sway_output *output, pixman_region32_t *damage,
		struct sway_container *con, struct border_colors *colors) {
	struct sway_view *view = con->view;
	if (view->saved_buffer) {
		render_saved_view(view, output, damage, view->container->alpha);
	} else if (view->surface) {
		render_view_toplevels(view, output, damage, view->container->alpha);
	}

	if (con->current.border == B_NONE || con->current.border == B_CSD) {
		return;
	}

	struct wlr_box box;
	float output_scale = output->wlr_output->scale;
	float color[4];
	struct sway_container_state *state = &con->current;

	if (state->border_left) {
		memcpy(&color, colors->child_border, sizeof(float) * 4);
		premultiply_alpha(color, con->alpha);
		box.x = state->x;
		box.y = state->content_y;
		box.width = state->border_thickness;
		box.height = state->content_height;
		scale_box(&box, output_scale);
		render_rect(output, damage, &box, color);
	}

	list_t *siblings = container_get_current_siblings(con);
	enum sway_container_layout layout =
		container_current_parent_layout(con);

	if (state->border_right) {
		if (con->current.parent && siblings->length == 1 && layout == L_HORIZ) {
			memcpy(&color, colors->indicator, sizeof(float) * 4);
		} else {
			memcpy(&color, colors->child_border, sizeof(float) * 4);
		}
		premultiply_alpha(color, con->alpha);
		box.x = state->content_x + state->content_width;
		box.y = state->content_y;
		box.width = state->border_thickness;
		box.height = state->content_height;
		scale_box(&box, output_scale);
		render_rect(output, damage, &box, color);
	}

	if (state->border_bottom) {
		if (con->current.parent && siblings->length == 1 && layout == L_VERT) {
			memcpy(&color, colors->indicator, sizeof(float) * 4);
		} else {
			memcpy(&color, colors->child_border, sizeof(float) * 4);
		}
		premultiply_alpha(color, con->alpha);
		box.x = state->x;
		box.y = state->content_y + state->content_height;
		box.width = state->width;
		box.height = state->border_thickness;
		scale_box(&box, output_scale);
		render_rect(output, damage, &box, color);
	}
}

/**
 * Render a titlebar.
 *
 * Care must be taken not to render over the same pixel multiple times,
 * otherwise the colors will be incorrect when using opacity.
 *
 * The height is: 1px border, 3px padding, font height, 3px padding, 1px border
 * The left side is: 1px border, 2px padding, title
 */
static void render_titlebar(struct sway_output *output,
		pixman_region32_t *output_damage, struct sway_container *con,
		int x, int y, int width,
		struct border_colors *colors, struct wlr_texture *title_texture,
		struct wlr_texture *marks_texture) {
	struct wlr_box box;
	float color[4];
	float output_scale = output->wlr_output->scale;
	double output_x = output->lx;
	double output_y = output->ly;
	int titlebar_border_thickness = config->titlebar_border_thickness;
	int titlebar_h_padding = config->titlebar_h_padding;
	int titlebar_v_padding = config->titlebar_v_padding;
	enum alignment title_align = config->title_align;

	// Single pixel bar above title
	memcpy(&color, colors->border, sizeof(float) * 4);
	premultiply_alpha(color, con->alpha);
	box.x = x;
	box.y = y;
	box.width = width;
	box.height = titlebar_border_thickness;
	scale_box(&box, output_scale);
	render_rect(output, output_damage, &box, color);

	// Single pixel bar below title
	box.x = x;
	box.y = y + container_titlebar_height() - titlebar_border_thickness;
	box.width = width;
	box.height = titlebar_border_thickness;
	scale_box(&box, output_scale);
	render_rect(output, output_damage, &box, color);

	// Single pixel left edge
	box.x = x;
	box.y = y + titlebar_border_thickness;
	box.width = titlebar_border_thickness;
	box.height = container_titlebar_height() - titlebar_border_thickness * 2;
	scale_box(&box, output_scale);
	render_rect(output, output_damage, &box, color);

	// Single pixel right edge
	box.x = x + width - titlebar_border_thickness;
	box.y = y + titlebar_border_thickness;
	box.width = titlebar_border_thickness;
	box.height = container_titlebar_height() - titlebar_border_thickness * 2;
	scale_box(&box, output_scale);
	render_rect(output, output_damage, &box, color);

	int inner_x = x - output_x + titlebar_h_padding;
	int bg_y = y + titlebar_border_thickness;
	size_t inner_width = width - titlebar_h_padding * 2;

	// output-buffer local
	int ob_inner_x = round(inner_x * output_scale);
	int ob_inner_width = scale_length(inner_width, inner_x, output_scale);
	int ob_bg_height = scale_length(
			(titlebar_v_padding - titlebar_border_thickness) * 2 +
			config->font_height, bg_y, output_scale);

	// Marks
	int ob_marks_x = 0; // output-buffer-local
	int ob_marks_width = 0; // output-buffer-local
	if (config->show_marks && marks_texture) {
		struct wlr_box texture_box;
		wlr_texture_get_size(marks_texture,
			&texture_box.width, &texture_box.height);
		ob_marks_width = texture_box.width;

		// The marks texture might be shorter than the config->font_height, in
		// which case we need to pad it as evenly as possible above and below.
		int ob_padding_total = ob_bg_height - texture_box.height;
		int ob_padding_above = floor(ob_padding_total / 2.0);
		int ob_padding_below = ceil(ob_padding_total / 2.0);

		// Render texture. If the title is on the right, the marks will be on
		// the left. Otherwise, they will be on the right.
		if (title_align == ALIGN_RIGHT || texture_box.width > ob_inner_width) {
			texture_box.x = ob_inner_x;
		} else {
			texture_box.x = ob_inner_x + ob_inner_width - texture_box.width;
		}
		ob_marks_x = texture_box.x;

		texture_box.y = round((bg_y - output_y) * output_scale) +
			ob_padding_above;

		float matrix[9];
		wlr_matrix_project_box(matrix, &texture_box,
			WL_OUTPUT_TRANSFORM_NORMAL,
			0.0, output->wlr_output->transform_matrix);

		if (ob_inner_width < texture_box.width) {
			texture_box.width = ob_inner_width;
		}
		render_texture(output->wlr_output, output_damage, marks_texture,
			&texture_box, matrix, con->alpha);

		// Padding above
		memcpy(&color, colors->background, sizeof(float) * 4);
		premultiply_alpha(color, con->alpha);
		box.x = texture_box.x + round(output_x * output_scale);
		box.y = round((y + titlebar_border_thickness) * output_scale);
		box.width = texture_box.width;
		box.height = ob_padding_above;
		render_rect(output, output_damage, &box, color);

		// Padding below
		box.y += ob_padding_above + texture_box.height;
		box.height = ob_padding_below;
		render_rect(output, output_damage, &box, color);
	}

	// Title text
	int ob_title_x = 0;  // output-buffer-local
	int ob_title_width = 0; // output-buffer-local
	if (title_texture) {
		struct wlr_box texture_box;
		wlr_texture_get_size(title_texture,
			&texture_box.width, &texture_box.height);
		ob_title_width = texture_box.width;

		// The title texture might be shorter than the config->font_height,
		// in which case we need to pad it above and below.
		int ob_padding_above = round((config->font_baseline -
					con->title_baseline + titlebar_v_padding -
					titlebar_border_thickness) * output_scale);
		int ob_padding_below = ob_bg_height - ob_padding_above -
			texture_box.height;

		// Render texture
		if (texture_box.width > ob_inner_width - ob_marks_width) {
			texture_box.x = (title_align == ALIGN_RIGHT && ob_marks_width)
				? ob_marks_x + ob_marks_width : ob_inner_x;
		} else if (title_align == ALIGN_LEFT) {
			texture_box.x = ob_inner_x;
		} else if (title_align == ALIGN_CENTER) {
			// If there are marks visible, center between the edge and marks.
			// Otherwise, center in the inner area.
			if (ob_marks_width) {
				texture_box.x = (ob_inner_x + ob_marks_x) / 2
					- texture_box.width / 2;
			} else {
				texture_box.x = ob_inner_x + ob_inner_width / 2
					- texture_box.width / 2;
			}
		} else {
			texture_box.x = ob_inner_x + ob_inner_width - texture_box.width;
		}
		ob_title_x = texture_box.x;

		texture_box.y =
			round((bg_y - output_y) * output_scale) + ob_padding_above;

		float matrix[9];
		wlr_matrix_project_box(matrix, &texture_box,
			WL_OUTPUT_TRANSFORM_NORMAL,
			0.0, output->wlr_output->transform_matrix);

		if (ob_inner_width - ob_marks_width < texture_box.width) {
			texture_box.width = ob_inner_width - ob_marks_width;
		}

		render_texture(output->wlr_output, output_damage, title_texture,
			&texture_box, matrix, con->alpha);

		// Padding above
		memcpy(&color, colors->background, sizeof(float) * 4);
		premultiply_alpha(color, con->alpha);
		box.x = texture_box.x + round(output_x * output_scale);
		box.y = round((y + titlebar_border_thickness) * output_scale);
		box.width = texture_box.width;
		box.height = ob_padding_above;
		render_rect(output, output_damage, &box, color);

		// Padding below
		box.y += ob_padding_above + texture_box.height;
		box.height = ob_padding_below;
		render_rect(output, output_damage, &box, color);
	}

	// Determine the left + right extends of the textures (output-buffer local)
	int ob_left_x, ob_left_width, ob_right_x, ob_right_width;
	if (ob_title_width == 0 && ob_marks_width == 0) {
		ob_left_x = ob_inner_x;
		ob_left_width = 0;
		ob_right_x = ob_inner_x;
		ob_right_width = 0;
	} else if (ob_title_x < ob_marks_x) {
		ob_left_x = ob_title_x;
		ob_left_width = ob_title_width;
		ob_right_x = ob_marks_x;
		ob_right_width = ob_marks_width;
	} else {
		ob_left_x = ob_marks_x;
		ob_left_width = ob_marks_width;
		ob_right_x = ob_title_x;
		ob_right_width = ob_title_width;
	}
	if (ob_left_x < ob_inner_x) {
		ob_left_x = ob_inner_x;
	} else if (ob_left_x + ob_left_width > ob_right_x + ob_right_width) {
		ob_right_x = ob_left_x;
		ob_right_width = ob_left_width;
	}

	// Filler between title and marks
	box.width = ob_right_x - ob_left_x - ob_left_width;
	if (box.width > 0) {
		box.x = ob_left_x + ob_left_width + round(output_x * output_scale);
		box.y = round(bg_y * output_scale);
		box.height = ob_bg_height;
		render_rect(output, output_damage, &box, color);
	}

	// Padding on left side
	box.x = x + titlebar_border_thickness;
	box.y = y + titlebar_border_thickness;
	box.width = titlebar_h_padding - titlebar_border_thickness;
	box.height = (titlebar_v_padding - titlebar_border_thickness) * 2 +
		config->font_height;
	scale_box(&box, output_scale);
	int left_x = ob_left_x + round(output_x * output_scale);
	if (box.x + box.width < left_x) {
		box.width += left_x - box.x - box.width;
	}
	render_rect(output, output_damage, &box, color);

	// Padding on right side
	box.x = x + width - titlebar_h_padding;
	box.y = y + titlebar_border_thickness;
	box.width = titlebar_h_padding - titlebar_border_thickness;
	box.height = (titlebar_v_padding - titlebar_border_thickness) * 2 +
		config->font_height;
	scale_box(&box, output_scale);
	int right_rx = ob_right_x + ob_right_width + round(output_x * output_scale);
	if (right_rx < box.x) {
		box.width += box.x - right_rx;
		box.x = right_rx;
	}
	render_rect(output, output_damage, &box, color);
}

/**
 * Render the top border line for a view using "border pixel".
 */
static void render_top_border(struct sway_output *output,
		pixman_region32_t *output_damage, struct sway_container *con,
		struct border_colors *colors) {
	struct sway_container_state *state = &con->current;
	if (!state->border_top) {
		return;
	}
	struct wlr_box box;
	float color[4];
	float output_scale = output->wlr_output->scale;

	// Child border - top edge
	memcpy(&color, colors->child_border, sizeof(float) * 4);
	premultiply_alpha(color, con->alpha);
	box.x = state->x;
	box.y = state->y;
	box.width = state->width;
	box.height = state->border_thickness;
	scale_box(&box, output_scale);
	render_rect(output, output_damage, &box, color);
}

struct parent_data {
	enum sway_container_layout layout;
	struct wlr_box box;
	list_t *children;
	bool focused;
	struct sway_container *active_child;
};

static void render_container(struct sway_output *output,
	pixman_region32_t *damage, struct sway_container *con, bool parent_focused);

/**
 * Render a container's children using a L_HORIZ or L_VERT layout.
 *
 * Wrap child views in borders and leave child containers borderless because
 * they'll apply their own borders to their children.
 */
static void render_containers_linear(struct sway_output *output,
		pixman_region32_t *damage, struct parent_data *parent) {
	for (int i = 0; i < parent->children->length; ++i) {
		struct sway_container *child = parent->children->items[i];

		if (child->view) {
			struct sway_view *view = child->view;
			struct border_colors *colors;
			struct wlr_texture *title_texture;
			struct wlr_texture *marks_texture;
			struct sway_container_state *state = &child->current;

			if (view_is_urgent(view)) {
				colors = &config->border_colors.urgent;
				title_texture = child->title_urgent;
				marks_texture = child->marks_urgent;
			} else if (state->focused || parent->focused) {
				colors = &config->border_colors.focused;
				title_texture = child->title_focused;
				marks_texture = child->marks_focused;
			} else if (child == parent->active_child) {
				colors = &config->border_colors.focused_inactive;
				title_texture = child->title_focused_inactive;
				marks_texture = child->marks_focused_inactive;
			} else {
				colors = &config->border_colors.unfocused;
				title_texture = child->title_unfocused;
				marks_texture = child->marks_unfocused;
			}

			if (state->border == B_NORMAL) {
				render_titlebar(output, damage, child, state->x,
						state->y, state->width, colors,
						title_texture, marks_texture);
			} else if (state->border == B_PIXEL) {
				render_top_border(output, damage, child, colors);
			}
			render_view(output, damage, child, colors);
		} else {
			render_container(output, damage, child,
					parent->focused || child->current.focused);
		}
	}
}

/**
 * Render a container's children using the L_TABBED layout.
 */
static void render_containers_tabbed(struct sway_output *output,
		pixman_region32_t *damage, struct parent_data *parent) {
	if (!parent->children->length) {
		return;
	}
	struct sway_container *current = parent->active_child;
	struct border_colors *current_colors = &config->border_colors.unfocused;
	int tab_width = parent->box.width / parent->children->length;

	// Render tabs
	for (int i = 0; i < parent->children->length; ++i) {
		struct sway_container *child = parent->children->items[i];
		struct sway_view *view = child->view;
		struct sway_container_state *cstate = &child->current;
		struct border_colors *colors;
		struct wlr_texture *title_texture;
		struct wlr_texture *marks_texture;
		bool urgent = view ?
			view_is_urgent(view) : container_has_urgent_child(child);

		if (urgent) {
			colors = &config->border_colors.urgent;
			title_texture = child->title_urgent;
			marks_texture = child->marks_urgent;
		} else if (cstate->focused || parent->focused) {
			colors = &config->border_colors.focused;
			title_texture = child->title_focused;
			marks_texture = child->marks_focused;
		} else if (child == parent->active_child) {
			colors = &config->border_colors.focused_inactive;
			title_texture = child->title_focused_inactive;
			marks_texture = child->marks_focused_inactive;
		} else {
			colors = &config->border_colors.unfocused;
			title_texture = child->title_unfocused;
			marks_texture = child->marks_unfocused;
		}

		int x = cstate->x + tab_width * i;

		// Make last tab use the remaining width of the parent
		if (i == parent->children->length - 1) {
			tab_width = parent->box.width - tab_width * i;
		}

		render_titlebar(output, damage, child, x, parent->box.y, tab_width,
				colors, title_texture, marks_texture);

		if (child == current) {
			current_colors = colors;
		}
	}

	// Render surface and left/right/bottom borders
	if (current->view) {
		render_view(output, damage, current, current_colors);
	} else {
		render_container(output, damage, current,
				parent->focused || current->current.focused);
	}
}

/**
 * Render a container's children using the L_STACKED layout.
 */
static void render_containers_stacked(struct sway_output *output,
		pixman_region32_t *damage, struct parent_data *parent) {
	if (!parent->children->length) {
		return;
	}
	struct sway_container *current = parent->active_child;
	struct border_colors *current_colors = &config->border_colors.unfocused;
	size_t titlebar_height = container_titlebar_height();

	// Render titles
	for (int i = 0; i < parent->children->length; ++i) {
		struct sway_container *child = parent->children->items[i];
		struct sway_view *view = child->view;
		struct sway_container_state *cstate = &child->current;
		struct border_colors *colors;
		struct wlr_texture *title_texture;
		struct wlr_texture *marks_texture;
		bool urgent = view ?
			view_is_urgent(view) : container_has_urgent_child(child);

		if (urgent) {
			colors = &config->border_colors.urgent;
			title_texture = child->title_urgent;
			marks_texture = child->marks_urgent;
		} else if (cstate->focused || parent->focused) {
			colors = &config->border_colors.focused;
			title_texture = child->title_focused;
			marks_texture = child->marks_focused;
		} else if (child == parent->active_child) {
			colors = &config->border_colors.focused_inactive;
			title_texture = child->title_focused_inactive;
			marks_texture = child->marks_focused_inactive;
		} else {
			colors = &config->border_colors.unfocused;
			title_texture = child->title_unfocused;
			marks_texture = child->marks_unfocused;
		}

		int y = parent->box.y + titlebar_height * i;
		render_titlebar(output, damage, child, parent->box.x, y,
				parent->box.width, colors, title_texture, marks_texture);

		if (child == current) {
			current_colors = colors;
		}
	}

	// Render surface and left/right/bottom borders
	if (current->view) {
		render_view(output, damage, current, current_colors);
	} else {
		render_container(output, damage, current,
				parent->focused || current->current.focused);
	}
}

static void render_containers(struct sway_output *output,
		pixman_region32_t *damage, struct parent_data *parent) {
	if (config->hide_lone_tab && parent->children->length == 1) {
		struct sway_container *child = parent->children->items[0];
		if (child->view) {
			render_containers_linear(output,damage, parent);
			return;
		}
	}

	switch (parent->layout) {
	case L_NONE:
	case L_HORIZ:
	case L_VERT:
		render_containers_linear(output, damage, parent);
		break;
	case L_STACKED:
		render_containers_stacked(output, damage, parent);
		break;
	case L_TABBED:
		render_containers_tabbed(output, damage, parent);
		break;
	}
}

static void render_container(struct sway_output *output,
		pixman_region32_t *damage, struct sway_container *con, bool focused) {
	struct parent_data data = {
		.layout = con->current.layout,
		.box = {
			.x = con->current.x,
			.y = con->current.y,
			.width = con->current.width,
			.height = con->current.height,
		},
		.children = con->current.children,
		.focused = focused,
		.active_child = con->current.focused_inactive_child,
	};
	render_containers(output, damage, &data);
}

static void render_workspace(struct sway_output *output,
		pixman_region32_t *damage, struct sway_workspace *ws, bool focused) {
	struct parent_data data = {
		.layout = ws->current.layout,
		.box = {
			.x = ws->current.x,
			.y = ws->current.y,
			.width = ws->current.width,
			.height = ws->current.height,
		},
		.children = ws->current.tiling,
		.focused = focused,
		.active_child = ws->current.focused_inactive_child,
	};
	render_containers(output, damage, &data);
}

static void render_floating_container(struct sway_output *soutput,
		pixman_region32_t *damage, struct sway_container *con) {
	if (con->view) {
		struct sway_view *view = con->view;
		struct border_colors *colors;
		struct wlr_texture *title_texture;
		struct wlr_texture *marks_texture;

		if (view_is_urgent(view)) {
			colors = &config->border_colors.urgent;
			title_texture = con->title_urgent;
			marks_texture = con->marks_urgent;
		} else if (con->current.focused) {
			colors = &config->border_colors.focused;
			title_texture = con->title_focused;
			marks_texture = con->marks_focused;
		} else {
			colors = &config->border_colors.unfocused;
			title_texture = con->title_unfocused;
			marks_texture = con->marks_unfocused;
		}

		if (con->current.border == B_NORMAL) {
			render_titlebar(soutput, damage, con, con->current.x,
					con->current.y, con->current.width, colors,
					title_texture, marks_texture);
		} else if (con->current.border == B_PIXEL) {
			render_top_border(soutput, damage, con, colors);
		}
		render_view(soutput, damage, con, colors);
	} else {
		render_container(soutput, damage, con, con->current.focused);
	}
}

static void render_floating(struct sway_output *soutput,
		pixman_region32_t *damage) {
	for (int i = 0; i < root->outputs->length; ++i) {
		struct sway_output *output = root->outputs->items[i];
		for (int j = 0; j < output->current.workspaces->length; ++j) {
			struct sway_workspace *ws = output->current.workspaces->items[j];
			if (!workspace_is_visible(ws)) {
				continue;
			}
			for (int k = 0; k < ws->current.floating->length; ++k) {
				struct sway_container *floater = ws->current.floating->items[k];
				if (floater->fullscreen_mode != FULLSCREEN_NONE) {
					continue;
				}
				render_floating_container(soutput, damage, floater);
			}
		}
	}
}

static void render_seatops(struct sway_output *output,
		pixman_region32_t *damage) {
	struct sway_seat *seat;
	wl_list_for_each(seat, &server.input->seats, link) {
		seatop_render(seat, output, damage);
	}
}

void output_render(struct sway_output *output, struct timespec *when,
		pixman_region32_t *damage) {
	struct wlr_output *wlr_output = output->wlr_output;

	struct wlr_renderer *renderer =
		wlr_backend_get_renderer(wlr_output->backend);
	if (!sway_assert(renderer != NULL,
			"expected the output backend to have a renderer")) {
		return;
	}

	struct sway_workspace *workspace = output->current.active_workspace;
	if (workspace == NULL) {
		return;
	}

	struct sway_container *fullscreen_con = root->fullscreen_global;
	if (!fullscreen_con) {
		fullscreen_con = workspace->current.fullscreen;
	}

	wlr_renderer_begin(renderer, wlr_output->width, wlr_output->height);

	if (!pixman_region32_not_empty(damage)) {
		// Output isn't damaged but needs buffer swap
		goto renderer_end;
	}

	if (debug.damage == DAMAGE_HIGHLIGHT) {
		wlr_renderer_clear(renderer, (float[]){1, 1, 0, 1});
	} else if (debug.damage == DAMAGE_RERENDER) {
		int width, height;
		wlr_output_transformed_resolution(wlr_output, &width, &height);
		pixman_region32_union_rect(damage, damage, 0, 0, width, height);
	}

	if (output_has_opaque_overlay_layer_surface(output)) {
		goto render_overlay;
	}

	if (fullscreen_con) {
		float clear_color[] = {0.0f, 0.0f, 0.0f, 1.0f};

		int nrects;
		pixman_box32_t *rects = pixman_region32_rectangles(damage, &nrects);
		for (int i = 0; i < nrects; ++i) {
			scissor_output(wlr_output, &rects[i]);
			wlr_renderer_clear(renderer, clear_color);
		}

		if (fullscreen_con->view) {
			if (fullscreen_con->view->saved_buffer) {
				render_saved_view(fullscreen_con->view, output, damage, 1.0f);
			} else if (fullscreen_con->view->surface) {
				render_view_toplevels(fullscreen_con->view,
						output, damage, 1.0f);
			}
		} else {
			render_container(output, damage, fullscreen_con,
					fullscreen_con->current.focused);
		}

		for (int i = 0; i < workspace->current.floating->length; ++i) {
			struct sway_container *floater =
				workspace->current.floating->items[i];
			if (container_is_transient_for(floater, fullscreen_con)) {
				render_floating_container(output, damage, floater);
			}
		}
#if HAVE_XWAYLAND
		render_unmanaged(output, damage, &root->xwayland_unmanaged);
#endif
	} else {
		float clear_color[] = {0.25f, 0.25f, 0.25f, 1.0f};

		int nrects;
		pixman_box32_t *rects = pixman_region32_rectangles(damage, &nrects);
		for (int i = 0; i < nrects; ++i) {
			scissor_output(wlr_output, &rects[i]);
			wlr_renderer_clear(renderer, clear_color);
		}

		render_layer(output, damage,
			&output->layers[ZWLR_LAYER_SHELL_V1_LAYER_BACKGROUND]);
		render_layer(output, damage,
			&output->layers[ZWLR_LAYER_SHELL_V1_LAYER_BOTTOM]);

		render_workspace(output, damage, workspace, workspace->current.focused);
		render_floating(output, damage);
#if HAVE_XWAYLAND
		render_unmanaged(output, damage, &root->xwayland_unmanaged);
#endif
		render_layer(output, damage,
			&output->layers[ZWLR_LAYER_SHELL_V1_LAYER_TOP]);
	}

	render_seatops(output, damage);

	struct sway_seat *seat = input_manager_current_seat();
	struct sway_container *focus = seat_get_focused_container(seat);
	if (focus && focus->view) {
		render_view_popups(focus->view, output, damage, focus->alpha);
	}

render_overlay:
	render_layer(output, damage,
		&output->layers[ZWLR_LAYER_SHELL_V1_LAYER_OVERLAY]);
	render_drag_icons(output, damage, &root->drag_icons);

renderer_end:
	wlr_renderer_scissor(renderer, NULL);
	wlr_output_render_software_cursors(wlr_output, damage);
	wlr_renderer_end(renderer);

	int width, height;
	wlr_output_transformed_resolution(wlr_output, &width, &height);

	pixman_region32_t frame_damage;
	pixman_region32_init(&frame_damage);

	enum wl_output_transform transform =
		wlr_output_transform_invert(wlr_output->transform);
	wlr_region_transform(&frame_damage, &output->damage->current,
		transform, width, height);

	if (debug.damage == DAMAGE_HIGHLIGHT) {
		pixman_region32_union_rect(&frame_damage, &frame_damage,
			0, 0, wlr_output->width, wlr_output->height);
	}

	wlr_output_set_damage(wlr_output, &frame_damage);
	pixman_region32_fini(&frame_damage);

	if (!wlr_output_commit(wlr_output)) {
		return;
	}
	output->last_frame = *when;
}