@@ -696,14 +696,10 @@ static void damage_from_surface(struct wlr_surface *surface, int sx, int sy,
 	int center_x = box.x + box.width/2;
 	int center_y = box.y + box.height/2;
 
-	enum wl_output_transform transform =
-		wlr_output_transform_invert(surface->current.transform);
-
 	pixman_region32_t damage;
 	pixman_region32_init(&damage);
-	pixman_region32_copy(&damage, &surface->buffer_damage);
-	wlr_region_transform(&damage, &damage, transform,
-		surface->current.buffer_width, surface->current.buffer_height);
+	wlr_surface_get_effective_damage(surface, &damage);
+
 	wlr_region_scale(&damage, &damage,
 		wlr_output->scale / (float)surface->current.scale);
 	if (ceil(wlr_output->scale) > surface->current.scale) {
#define _POSIX_C_SOURCE 200809L
#include <assert.h>
#include <stdbool.h>
#include <stdlib.h>
#include <time.h>
#include <wlr/backend/drm.h>
#include <wlr/config.h>
#include <wlr/types/wlr_matrix.h>
#include <wlr/types/wlr_compositor.h>
#include <wlr/types/wlr_output_layout.h>
#include <wlr/types/wlr_wl_shell.h>
#include <wlr/types/wlr_xdg_shell_v6.h>
#include <wlr/types/wlr_xdg_shell.h>
#include <wlr/util/log.h>
#include <wlr/util/region.h>
#include "rootston/config.h"
#include "rootston/layers.h"
#include "rootston/output.h"
#include "rootston/server.h"

/**
 * Rotate a child's position relative to a parent. The parent size is (pw, ph),
 * the child position is (*sx, *sy) and its size is (sw, sh).
 */
static void rotate_child_position(double *sx, double *sy, double sw, double sh,
		double pw, double ph, float rotation) {
	if (rotation != 0.0) {
		// Coordinates relative to the center of the subsurface
		double ox = *sx - pw/2 + sw/2,
			oy = *sy - ph/2 + sh/2;
		// Rotated coordinates
		double rx = cos(rotation)*ox - sin(rotation)*oy,
			ry = cos(rotation)*oy + sin(rotation)*ox;
		*sx = rx + pw/2 - sw/2;
		*sy = ry + ph/2 - sh/2;
	}
}

struct layout_data {
	double x, y;
	int width, height;
	float rotation;
};

static void get_layout_position(struct layout_data *data, double *lx, double *ly,
		const struct wlr_surface *surface, int sx, int sy) {
	double _sx = sx, _sy = sy;
	rotate_child_position(&_sx, &_sy, surface->current.width,
		surface->current.height, data->width, data->height, data->rotation);
	*lx = data->x + _sx;
	*ly = data->y + _sy;
}

static void surface_for_each_surface(struct wlr_surface *surface,
		double lx, double ly, float rotation, struct layout_data *layout_data,
		wlr_surface_iterator_func_t iterator, void *user_data) {
	layout_data->x = lx;
	layout_data->y = ly;
	layout_data->width = surface->current.width;
	layout_data->height = surface->current.height;
	layout_data->rotation = rotation;

	wlr_surface_for_each_surface(surface, iterator, user_data);
}

static void view_for_each_surface(struct roots_view *view,
		struct layout_data *layout_data, wlr_surface_iterator_func_t iterator,
		void *user_data) {
	layout_data->x = view->x;
	layout_data->y = view->y;
	layout_data->width = view->wlr_surface->current.width;
	layout_data->height = view->wlr_surface->current.height;
	layout_data->rotation = view->rotation;

	switch (view->type) {
	case ROOTS_XDG_SHELL_V6_VIEW:
		wlr_xdg_surface_v6_for_each_surface(view->xdg_surface_v6, iterator,
			user_data);
		break;
	case ROOTS_XDG_SHELL_VIEW:
		wlr_xdg_surface_for_each_surface(view->xdg_surface, iterator,
			user_data);
		break;
	case ROOTS_WL_SHELL_VIEW:
		wlr_wl_shell_surface_for_each_surface(view->wl_shell_surface, iterator,
			user_data);
		break;
#ifdef WLR_HAS_XWAYLAND
	case ROOTS_XWAYLAND_VIEW:
		wlr_surface_for_each_surface(view->wlr_surface, iterator, user_data);
		break;
#endif
	}
}

#ifdef WLR_HAS_XWAYLAND
static void xwayland_children_for_each_surface(
		struct wlr_xwayland_surface *surface,
		wlr_surface_iterator_func_t iterator, struct layout_data *layout_data,
		void *user_data) {
	struct wlr_xwayland_surface *child;
	wl_list_for_each(child, &surface->children, parent_link) {
		if (child->mapped) {
			surface_for_each_surface(child->surface, child->x, child->y, 0,
				layout_data, iterator, user_data);
		}
		xwayland_children_for_each_surface(child, iterator, layout_data,
			user_data);
	}
}
#endif

static void drag_icons_for_each_surface(struct roots_input *input,
		wlr_surface_iterator_func_t iterator, struct layout_data *layout_data,
		void *user_data) {
	struct roots_seat *seat;
	wl_list_for_each(seat, &input->seats, link) {
		struct roots_drag_icon *drag_icon;
		wl_list_for_each(drag_icon, &seat->drag_icons, link) {
			if (!drag_icon->wlr_drag_icon->mapped) {
				continue;
			}
			surface_for_each_surface(drag_icon->wlr_drag_icon->surface,
				drag_icon->x, drag_icon->y, 0, layout_data,
				iterator, user_data);
		}
	}
}


struct render_data {
	struct layout_data layout;
	struct roots_output *output;
	struct timespec *when;
	pixman_region32_t *damage;
	float alpha;
};

/**
 * Checks whether a surface at (lx, ly) intersects an output. If `box` is not
 * NULL, it populates it with the surface box in the output, in output-local
 * coordinates.
 */
static bool surface_intersect_output(struct wlr_surface *surface,
		struct wlr_output_layout *output_layout, struct wlr_output *wlr_output,
		double lx, double ly, float rotation, struct wlr_box *box) {
	double ox = lx, oy = ly;
	wlr_output_layout_output_coords(output_layout, wlr_output, &ox, &oy);

	ox += surface->sx;
	oy += surface->sy;

	if (box != NULL) {
		box->x = ox * wlr_output->scale;
		box->y = oy * wlr_output->scale;
		box->width = surface->current.width * wlr_output->scale;
		box->height = surface->current.height * wlr_output->scale;
	}

	struct wlr_box layout_box = {
		.x = lx, .y = ly,
		.width = surface->current.width, .height = surface->current.height,
	};
	wlr_box_rotated_bounds(&layout_box, rotation, &layout_box);
	return wlr_output_layout_intersects(output_layout, wlr_output, &layout_box);
}

static void scissor_output(struct roots_output *output, pixman_box32_t *rect) {
	struct wlr_output *wlr_output = output->wlr_output;
	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, transform, ow, oh, &box);

	wlr_renderer_scissor(renderer, &box);
}

static void render_surface(struct wlr_surface *surface, int sx, int sy,
		void *_data) {
	struct render_data *data = _data;
	struct roots_output *output = data->output;
	float rotation = data->layout.rotation;

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

	struct wlr_renderer *renderer =
		wlr_backend_get_renderer(output->wlr_output->backend);
	assert(renderer);

	double lx, ly;
	get_layout_position(&data->layout, &lx, &ly, surface, sx, sy);

	struct wlr_box box;
	bool intersects = surface_intersect_output(surface, output->desktop->layout,
		output->wlr_output, lx, ly, rotation, &box);
	if (!intersects) {
		return;
	}

	struct wlr_box rotated;
	wlr_box_rotated_bounds(&box, rotation, &rotated);

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

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

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

damage_finish:
	pixman_region32_fini(&damage);
}

static void get_decoration_box(struct roots_view *view,
		struct roots_output *output, struct wlr_box *box) {
	struct wlr_output *wlr_output = output->wlr_output;

	struct wlr_box deco_box;
	view_get_deco_box(view, &deco_box);
	double sx = deco_box.x - view->x;
	double sy = deco_box.y - view->y;
	rotate_child_position(&sx, &sy, deco_box.width, deco_box.height,
		view->wlr_surface->current.width,
		view->wlr_surface->current.height, view->rotation);
	double x = sx + view->x;
	double y = sy + view->y;

	wlr_output_layout_output_coords(output->desktop->layout, wlr_output, &x, &y);

	box->x = x * wlr_output->scale;
	box->y = y * wlr_output->scale;
	box->width = deco_box.width * wlr_output->scale;
	box->height = deco_box.height * wlr_output->scale;
}

static void render_decorations(struct roots_view *view,
		struct render_data *data) {
	if (!view->decorated || view->wlr_surface == NULL) {
		return;
	}

	struct roots_output *output = data->output;
	struct wlr_renderer *renderer =
		wlr_backend_get_renderer(output->wlr_output->backend);
	assert(renderer);

	struct wlr_box box;
	get_decoration_box(view, output, &box);

	struct wlr_box rotated;
	wlr_box_rotated_bounds(&box, view->rotation, &rotated);

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

	float matrix[9];
	wlr_matrix_project_box(matrix, &box, WL_OUTPUT_TRANSFORM_NORMAL,
		view->rotation, output->wlr_output->transform_matrix);
	float color[] = { 0.2, 0.2, 0.2, view->alpha };

	int nrects;
	pixman_box32_t *rects =
		pixman_region32_rectangles(&damage, &nrects);
	for (int i = 0; i < nrects; ++i) {
		scissor_output(output, &rects[i]);
		wlr_render_quad_with_matrix(renderer, color, matrix);
	}

damage_finish:
	pixman_region32_fini(&damage);
}

static void render_view(struct roots_view *view, struct render_data *data) {
	// Do not render views fullscreened on other outputs
	if (view->fullscreen_output != NULL &&
			view->fullscreen_output != data->output) {
		return;
	}

	data->alpha = view->alpha;
	render_decorations(view, data);
	view_for_each_surface(view, &data->layout, render_surface, data);
}

static bool has_standalone_surface(struct roots_view *view) {
	if (!wl_list_empty(&view->wlr_surface->subsurfaces)) {
		return false;
	}

	switch (view->type) {
	case ROOTS_XDG_SHELL_V6_VIEW:
		return wl_list_empty(&view->xdg_surface_v6->popups);
	case ROOTS_XDG_SHELL_VIEW:
		return wl_list_empty(&view->xdg_surface->popups);
	case ROOTS_WL_SHELL_VIEW:
		return wl_list_empty(&view->wl_shell_surface->popups);
#ifdef WLR_HAS_XWAYLAND
	case ROOTS_XWAYLAND_VIEW:
		return wl_list_empty(&view->xwayland_surface->children);
#endif
	}
	return true;
}

static void surface_send_frame_done(struct wlr_surface *surface, int sx, int sy,
		void *_data) {
	struct render_data *data = _data;
	struct roots_output *output = data->output;
	struct timespec *when = data->when;
	float rotation = data->layout.rotation;

	double lx, ly;
	get_layout_position(&data->layout, &lx, &ly, surface, sx, sy);

	if (!surface_intersect_output(surface, output->desktop->layout,
			output->wlr_output, lx, ly, rotation, NULL)) {
		return;
	}

	wlr_surface_send_frame_done(surface, when);
}

static void render_layer(struct roots_output *output,
		const struct wlr_box *output_layout_box, struct render_data *data,
		struct wl_list *layer) {
	struct roots_layer_surface *roots_surface;
	wl_list_for_each(roots_surface, layer, link) {
		struct wlr_layer_surface_v1 *layer = roots_surface->layer_surface;

		surface_for_each_surface(layer->surface,
			roots_surface->geo.x + output_layout_box->x,
			roots_surface->geo.y + output_layout_box->y,
			0, &data->layout, render_surface, data);

		wlr_layer_surface_v1_for_each_surface(layer, render_surface, data);
	}
}

static void layers_send_done(
		struct roots_output *output, struct timespec *when) {
	size_t len = sizeof(output->layers) / sizeof(output->layers[0]);
	for (size_t i = 0; i < len; ++i) {
		struct roots_layer_surface *roots_surface;
		wl_list_for_each(roots_surface, &output->layers[i], link) {
			struct wlr_layer_surface_v1 *layer = roots_surface->layer_surface;
			wlr_surface_send_frame_done(layer->surface, when);
			struct wlr_xdg_popup *popup;
			wl_list_for_each(popup, &roots_surface->layer_surface->popups, link) {
				wlr_surface_send_frame_done(popup->base->surface, when);
			}
		}
	}
}

static void render_output(struct roots_output *output) {
	struct wlr_output *wlr_output = output->wlr_output;
	struct roots_desktop *desktop = output->desktop;
	struct roots_server *server = desktop->server;
	struct wlr_renderer *renderer = wlr_backend_get_renderer(wlr_output->backend);
	assert(renderer);

	if (!wlr_output->enabled) {
		return;
	}

	struct timespec now;
	clock_gettime(CLOCK_MONOTONIC, &now);

	float clear_color[] = {0.25f, 0.25f, 0.25f, 1.0f};

	const struct wlr_box *output_box =
		wlr_output_layout_get_box(desktop->layout, wlr_output);

	// Check if we can delegate the fullscreen surface to the output
	if (output->fullscreen_view != NULL &&
			output->fullscreen_view->wlr_surface != NULL) {
		struct roots_view *view = output->fullscreen_view;

		// Make sure the view is centered on screen
		struct wlr_box view_box;
		view_get_box(view, &view_box);
		double view_x = (double)(output_box->width - view_box.width) / 2 +
			output_box->x;
		double view_y = (double)(output_box->height - view_box.height) / 2 +
			output_box->y;
		view_move(view, view_x, view_y);

		if (has_standalone_surface(view)) {
			wlr_output_set_fullscreen_surface(wlr_output, view->wlr_surface);
		} else {
			wlr_output_set_fullscreen_surface(wlr_output, NULL);
		}

		// Fullscreen views are rendered on a black background
		clear_color[0] = clear_color[1] = clear_color[2] = 0;
	} else {
		wlr_output_set_fullscreen_surface(wlr_output, NULL);
	}

	bool needs_swap;
	pixman_region32_t damage;
	pixman_region32_init(&damage);
	if (!wlr_output_damage_make_current(output->damage, &needs_swap, &damage)) {
		return;
	}

	struct render_data data = {
		.output = output,
		.when = &now,
		.damage = &damage,
		.alpha = 1.0,
	};

	if (!needs_swap) {
		// Output doesn't need swap and isn't damaged, skip rendering completely
		goto damage_finish;
	}

	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 (server->config->debug_damage_tracking) {
		wlr_renderer_clear(renderer, (float[]){1, 1, 0, 1});
	}

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

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

	// If a view is fullscreen on this output, render it
	if (output->fullscreen_view != NULL) {
		struct roots_view *view = output->fullscreen_view;

		if (wlr_output->fullscreen_surface == view->wlr_surface) {
			// The output will render the fullscreen view
			goto renderer_end;
		}

		if (view->wlr_surface != NULL) {
			view_for_each_surface(view, &data.layout, render_surface, &data);
		}

		// During normal rendering the xwayland window tree isn't traversed
		// because all windows are rendered. Here we only want to render
		// the fullscreen window's children so we have to traverse the tree.
#ifdef WLR_HAS_XWAYLAND
		if (view->type == ROOTS_XWAYLAND_VIEW) {
			xwayland_children_for_each_surface(view->xwayland_surface,
				render_surface, &data.layout, &data);
		}
#endif
	} else {
		// Render all views
		struct roots_view *view;
		wl_list_for_each_reverse(view, &desktop->views, link) {
			render_view(view, &data);
		}
		// Render top layer above shell views
		render_layer(output, output_box, &data,
				&output->layers[ZWLR_LAYER_SHELL_V1_LAYER_TOP]);
	}

	// Render drag icons
	data.alpha = 1.0;
	drag_icons_for_each_surface(server->input, render_surface, &data.layout,
		&data);

	render_layer(output, output_box, &data,
			&output->layers[ZWLR_LAYER_SHELL_V1_LAYER_OVERLAY]);

renderer_end:
	wlr_renderer_scissor(renderer, NULL);
	wlr_renderer_end(renderer);

	if (server->config->debug_damage_tracking) {
		int width, height;
		wlr_output_transformed_resolution(wlr_output, &width, &height);
		pixman_region32_union_rect(&damage, &damage, 0, 0, width, height);
	}

	if (!wlr_output_damage_swap_buffers(output->damage, &now, &damage)) {
		goto damage_finish;
	}
	output->last_frame = desktop->last_frame = now;

damage_finish:
	pixman_region32_fini(&damage);

	// Send frame done events to all surfaces
	if (output->fullscreen_view != NULL) {
		struct roots_view *view = output->fullscreen_view;
		if (wlr_output->fullscreen_surface == view->wlr_surface) {
			// The surface is managed by the wlr_output
			return;
		}

		view_for_each_surface(view, &data.layout, surface_send_frame_done,
			&data);

#ifdef WLR_HAS_XWAYLAND
		if (view->type == ROOTS_XWAYLAND_VIEW) {
			xwayland_children_for_each_surface(view->xwayland_surface,
				surface_send_frame_done, &data.layout, &data);
		}
#endif
	} else {
		struct roots_view *view;
		wl_list_for_each_reverse(view, &desktop->views, link) {
			view_for_each_surface(view, &data.layout, surface_send_frame_done,
				&data);
		}

		drag_icons_for_each_surface(server->input, surface_send_frame_done,
			&data.layout, &data);
	}
	layers_send_done(output, data.when);
}

void output_damage_whole(struct roots_output *output) {
	wlr_output_damage_add_whole(output->damage);
}

static bool view_accept_damage(struct roots_output *output,
		struct roots_view *view) {
	if (view->wlr_surface == NULL) {
		return false;
	}
	if (output->fullscreen_view == NULL) {
		return true;
	}
	if (output->fullscreen_view == view) {
		return true;
	}
#ifdef WLR_HAS_XWAYLAND
	if (output->fullscreen_view->type == ROOTS_XWAYLAND_VIEW &&
			view->type == ROOTS_XWAYLAND_VIEW) {
		// Special case: accept damage from children
		struct wlr_xwayland_surface *xsurface = view->xwayland_surface;
		while (xsurface != NULL) {
			if (output->fullscreen_view->xwayland_surface == xsurface) {
				return true;
			}
			xsurface = xsurface->parent;
		}
	}
#endif
	return false;
}

struct damage_data {
	struct layout_data layout;
	struct roots_output *output;
};

static void damage_whole_surface(struct wlr_surface *surface, int sx, int sy,
		void *_data) {
	struct damage_data *data = _data;
	struct roots_output *output = data->output;
	float rotation = data->layout.rotation;

	double lx, ly;
	get_layout_position(&data->layout, &lx, &ly, surface, sx, sy);

	if (!wlr_surface_has_buffer(surface)) {
		return;
	}

	int ow, oh;
	wlr_output_transformed_resolution(output->wlr_output, &ow, &oh);

	struct wlr_box box;
	bool intersects = surface_intersect_output(surface, output->desktop->layout,
		output->wlr_output, lx, ly, rotation, &box);
	if (!intersects) {
		return;
	}

	wlr_box_rotated_bounds(&box, rotation, &box);

	wlr_output_damage_add_box(output->damage, &box);
}

void output_damage_whole_local_surface(struct roots_output *output,
		struct wlr_surface *surface, double ox, double oy, float rotation) {
	struct wlr_output_layout_output *layout = wlr_output_layout_get(
		output->desktop->layout, output->wlr_output);
	struct damage_data data = { .output = output };
	surface_for_each_surface(surface, ox + layout->x, oy + layout->y, 0,
		&data.layout, damage_whole_surface, &data);
}

static void damage_whole_decoration(struct roots_view *view,
		struct roots_output *output) {
	if (!view->decorated || view->wlr_surface == NULL) {
		return;
	}

	struct wlr_box box;
	get_decoration_box(view, output, &box);

	wlr_box_rotated_bounds(&box, view->rotation, &box);

	wlr_output_damage_add_box(output->damage, &box);
}

void output_damage_whole_view(struct roots_output *output,
		struct roots_view *view) {
	if (!view_accept_damage(output, view)) {
		return;
	}

	damage_whole_decoration(view, output);

	struct damage_data data = { .output = output };
	view_for_each_surface(view, &data.layout, damage_whole_surface, &data);
}

void output_damage_whole_drag_icon(struct roots_output *output,
		struct roots_drag_icon *icon) {
	struct damage_data data = { .output = output };
	surface_for_each_surface(icon->wlr_drag_icon->surface, icon->x, icon->y, 0,
		&data.layout, damage_whole_surface, &data);
}

static void damage_from_surface(struct wlr_surface *surface, int sx, int sy,
		void *_data) {
	struct damage_data *data = _data;
	struct roots_output *output = data->output;
	struct wlr_output *wlr_output = output->wlr_output;
	float rotation = data->layout.rotation;

	double lx, ly;
	get_layout_position(&data->layout, &lx, &ly, surface, sx, sy);

	if (!wlr_surface_has_buffer(surface)) {
		return;
	}

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

	struct wlr_box box;
	surface_intersect_output(surface, output->desktop->layout,
		wlr_output, lx, ly, rotation, &box);

	int center_x = box.x + box.width/2;
	int center_y = box.y + box.height/2;

	enum wl_output_transform transform =
		wlr_output_transform_invert(surface->current.transform);

	pixman_region32_t damage;
	pixman_region32_init(&damage);
	pixman_region32_copy(&damage, &surface->buffer_damage);
	wlr_region_transform(&damage, &damage, transform,
		surface->current.buffer_width, surface->current.buffer_height);
	wlr_region_scale(&damage, &damage,
		wlr_output->scale / (float)surface->current.scale);
	if (ceil(wlr_output->scale) > surface->current.scale) {
		// When scaling up a surface, it'll become blurry so we need to
		// expand the damage region
		wlr_region_expand(&damage, &damage,
			ceil(wlr_output->scale) - surface->current.scale);
	}
	pixman_region32_translate(&damage, box.x, box.y);
	wlr_region_rotated_bounds(&damage, &damage, rotation, center_x, center_y);
	wlr_output_damage_add(output->damage, &damage);
	pixman_region32_fini(&damage);
}

void output_damage_from_local_surface(struct roots_output *output,
		struct wlr_surface *surface, double ox, double oy, float rotation) {
	struct wlr_output_layout_output *layout = wlr_output_layout_get(
		output->desktop->layout, output->wlr_output);
	struct damage_data data = { .output = output };
	surface_for_each_surface(surface, ox + layout->x, oy + layout->y, 0,
		&data.layout, damage_from_surface, &data);
}

void output_damage_from_view(struct roots_output *output,
		struct roots_view *view) {
	if (!view_accept_damage(output, view)) {
		return;
	}

	struct damage_data data = { .output = output };
	view_for_each_surface(view, &data.layout, damage_from_surface, &data);
}

static void set_mode(struct wlr_output *output,
		struct roots_output_config *oc) {
	int mhz = (int)(oc->mode.refresh_rate * 1000);

	if (wl_list_empty(&output->modes)) {
		// Output has no mode, try setting a custom one
		wlr_output_set_custom_mode(output, oc->mode.width, oc->mode.height, mhz);
		return;
	}

	struct wlr_output_mode *mode, *best = NULL;
	wl_list_for_each(mode, &output->modes, link) {
		if (mode->width == oc->mode.width && mode->height == oc->mode.height) {
			if (mode->refresh == mhz) {
				best = mode;
				break;
			}
			best = mode;
		}
	}
	if (!best) {
		wlr_log(WLR_ERROR, "Configured mode for %s not available", output->name);
	} else {
		wlr_log(WLR_DEBUG, "Assigning configured mode to %s", output->name);
		wlr_output_set_mode(output, best);
	}
}

static void output_destroy(struct roots_output *output) {
	// TODO: cursor
	//example_config_configure_cursor(sample->config, sample->cursor,
	//	sample->compositor);

	wl_list_remove(&output->link);
	wl_list_remove(&output->destroy.link);
	wl_list_remove(&output->mode.link);
	wl_list_remove(&output->transform.link);
	wl_list_remove(&output->damage_frame.link);
	wl_list_remove(&output->damage_destroy.link);
	free(output);
}

static void output_handle_destroy(struct wl_listener *listener, void *data) {
	struct roots_output *output = wl_container_of(listener, output, destroy);
	output_destroy(output);
}

static void output_damage_handle_frame(struct wl_listener *listener,
		void *data) {
	struct roots_output *output =
		wl_container_of(listener, output, damage_frame);
	render_output(output);
}

static void output_damage_handle_destroy(struct wl_listener *listener,
		void *data) {
	struct roots_output *output =
		wl_container_of(listener, output, damage_destroy);
	output_destroy(output);
}

static void output_handle_mode(struct wl_listener *listener, void *data) {
	struct roots_output *output =
		wl_container_of(listener, output, mode);
	arrange_layers(output);
}

static void output_handle_transform(struct wl_listener *listener, void *data) {
	struct roots_output *output =
		wl_container_of(listener, output, transform);
	arrange_layers(output);
}

void handle_new_output(struct wl_listener *listener, void *data) {
	struct roots_desktop *desktop = wl_container_of(listener, desktop,
		new_output);
	struct wlr_output *wlr_output = data;
	struct roots_input *input = desktop->server->input;
	struct roots_config *config = desktop->config;

	wlr_log(WLR_DEBUG, "Output '%s' added", wlr_output->name);
	wlr_log(WLR_DEBUG, "'%s %s %s' %"PRId32"mm x %"PRId32"mm", wlr_output->make,
		wlr_output->model, wlr_output->serial, wlr_output->phys_width,
		wlr_output->phys_height);

	struct roots_output *output = calloc(1, sizeof(struct roots_output));
	clock_gettime(CLOCK_MONOTONIC, &output->last_frame);
	output->desktop = desktop;
	output->wlr_output = wlr_output;
	wlr_output->data = output;
	wl_list_insert(&desktop->outputs, &output->link);

	output->damage = wlr_output_damage_create(wlr_output);

	output->destroy.notify = output_handle_destroy;
	wl_signal_add(&wlr_output->events.destroy, &output->destroy);
	output->mode.notify = output_handle_mode;
	wl_signal_add(&wlr_output->events.mode, &output->mode);
	output->transform.notify = output_handle_transform;
	wl_signal_add(&wlr_output->events.transform, &output->transform);

	output->damage_frame.notify = output_damage_handle_frame;
	wl_signal_add(&output->damage->events.frame, &output->damage_frame);
	output->damage_destroy.notify = output_damage_handle_destroy;
	wl_signal_add(&output->damage->events.destroy, &output->damage_destroy);

	size_t len = sizeof(output->layers) / sizeof(output->layers[0]);
	for (size_t i = 0; i < len; ++i) {
		wl_list_init(&output->layers[i]);
	}

	struct roots_output_config *output_config =
		roots_config_get_output(config, wlr_output);

	if ((!output_config || output_config->enable) && !wl_list_empty(&wlr_output->modes)) {
		struct wlr_output_mode *mode =
			wl_container_of(wlr_output->modes.prev, mode, link);
		wlr_output_set_mode(wlr_output, mode);
	}

	if (output_config) {
		if (output_config->enable) {
			if (wlr_output_is_drm(wlr_output)) {
				struct roots_output_mode_config *mode_config;
				wl_list_for_each(mode_config, &output_config->modes, link) {
					wlr_drm_connector_add_mode(wlr_output, &mode_config->info);
				}
			} else if (!wl_list_empty(&output_config->modes)) {
				wlr_log(WLR_ERROR, "Can only add modes for DRM backend");
			}

			if (output_config->mode.width) {
				set_mode(wlr_output, output_config);
			}

			wlr_output_set_scale(wlr_output, output_config->scale);
			wlr_output_set_transform(wlr_output, output_config->transform);
			wlr_output_layout_add(desktop->layout, wlr_output, output_config->x,
				output_config->y);
		} else {
			wlr_output_enable(wlr_output, false);
		}
	} else {
		wlr_output_layout_add_auto(desktop->layout, wlr_output);
	}

	struct roots_seat *seat;
	wl_list_for_each(seat, &input->seats, link) {
		roots_seat_configure_cursor(seat);
		roots_seat_configure_xcursor(seat);
	}

	arrange_layers(output);
	output_damage_whole(output);
}

You need to remove `surface->current.scale` here. Can you test with `scale=2` in your config file?