Fix #5643, #5064: rounding issues in floating-point -> integer conversions

Currently, various floating-point expressions involving
the coordinates of borders, titlebars and content surfaces
are directly assigned to integers, and so they are rounded
towards zero.

This results in off-by-one distances between these elements
when the signs of their coordinates differ.

Fixed by wrapping these expressions with a call to
floor before the assignment.

sway/desktop/output.c

@@ -105,8 +105,8 @@ static bool get_surface_box(struct surface_iterator_data *data,
 		data->rotation);
 
 	struct wlr_box box = {
-		.x = data->ox + _sx,
+		.x = floor(data->ox + _sx),
-		.y = data->oy + _sy,
+		.y = floor(data->oy + _sy),
 		.width = sw,
 		.height = sh,
 	};

sway/desktop/render.c

@@ -346,8 +346,8 @@ static void render_view(struct sway_output *output, pixman_region32_t *damage,
 	if (state->border_left) {
 		memcpy(&color, colors->child_border, sizeof(float) * 4);
 		premultiply_alpha(color, con->alpha);
-		box.x = state->x;
+		box.x = floor(state->x);
-		box.y = state->content_y;
+		box.y = floor(state->content_y);
 		box.width = state->border_thickness;
 		box.height = state->content_height;
 		scale_box(&box, output_scale);
@@ -365,8 +365,8 @@ static void render_view(struct sway_output *output, pixman_region32_t *damage,
 			memcpy(&color, colors->child_border, sizeof(float) * 4);
 		}
 		premultiply_alpha(color, con->alpha);
-		box.x = state->content_x + state->content_width;
+		box.x = floor(state->content_x + state->content_width);
-		box.y = state->content_y;
+		box.y = floor(state->content_y);
 		box.width = state->border_thickness;
 		box.height = state->content_height;
 		scale_box(&box, output_scale);
@@ -380,8 +380,8 @@ static void render_view(struct sway_output *output, pixman_region32_t *damage,
 			memcpy(&color, colors->child_border, sizeof(float) * 4);
 		}
 		premultiply_alpha(color, con->alpha);
-		box.x = state->x;
+		box.x = floor(state->x);
-		box.y = state->content_y + state->content_height;
+		box.y = floor(state->content_y + state->content_height);
 		box.width = state->width;
 		box.height = state->border_thickness;
 		scale_box(&box, output_scale);
@@ -662,8 +662,8 @@ static void render_top_border(struct sway_output *output,
 	// Child border - top edge
 	memcpy(&color, colors->child_border, sizeof(float) * 4);
 	premultiply_alpha(color, con->alpha);
-	box.x = state->x;
+	box.x = floor(state->x);
-	box.y = state->y;
+	box.y = floor(state->y);
 	box.width = state->width;
 	box.height = state->border_thickness;
 	scale_box(&box, output_scale);
@@ -718,8 +718,8 @@ static void render_containers_linear(struct sway_output *output,
 			}
 
 			if (state->border == B_NORMAL) {
-				render_titlebar(output, damage, child, state->x,
+				render_titlebar(output, damage, child, floor(state->x),
-						state->y, state->width, colors,
+						floor(state->y), state->width, colors,
 						title_texture, marks_texture);
 			} else if (state->border == B_PIXEL) {
 				render_top_border(output, damage, child, colors);
@@ -773,7 +773,7 @@ static void render_containers_tabbed(struct sway_output *output,
 			marks_texture = child->marks_unfocused;
 		}
 
-		int x = cstate->x + tab_width * i;
+		int x = floor(cstate->x + tab_width * i);
 
 		// Make last tab use the remaining width of the parent
 		if (i == parent->children->length - 1) {
@@ -886,8 +886,8 @@ static void render_container(struct sway_output *output,
 	struct parent_data data = {
 		.layout = con->current.layout,
 		.box = {
-			.x = con->current.x,
+			.x = floor(con->current.x),
-			.y = con->current.y,
+			.y = floor(con->current.y),
 			.width = con->current.width,
 			.height = con->current.height,
 		},
@@ -903,8 +903,8 @@ static void render_workspace(struct sway_output *output,
 	struct parent_data data = {
 		.layout = ws->current.layout,
 		.box = {
-			.x = ws->current.x,
+			.x = floor(ws->current.x),
-			.y = ws->current.y,
+			.y = floor(ws->current.y),
 			.width = ws->current.width,
 			.height = ws->current.height,
 		},
@@ -938,8 +938,8 @@ static void render_floating_container(struct sway_output *soutput,
 		}
 
 		if (con->current.border == B_NORMAL) {
-			render_titlebar(soutput, damage, con, con->current.x,
+			render_titlebar(soutput, damage, con, floor(con->current.x),
-					con->current.y, con->current.width, colors,
+					floor(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);