river/src/output.zig

const std = @import("std");
const c = @import("c.zig");
const render = @import("render.zig");

const Box = @import("box.zig").Box;
const LayerSurface = @import("layer_surface.zig").LayerSurface;
const Log = @import("log.zig").Log;
const Root = @import("root.zig").Root;
const ViewStack = @import("view_stack.zig").ViewStack;

pub const Output = struct {
    const Self = @This();

    root: *Root,
    wlr_output: *c.wlr_output,

    /// All layer surfaces on the output, indexed by the layer enum.
    layers: [4]std.TailQueue(LayerSurface),

    /// The area left for views and other layer surfaces after applying the
    /// exclusive zones of exclusive layer surfaces.
    usable_box: Box,

    /// The top of the stack is the "most important" view.
    views: ViewStack,

    /// A bit field of focused tags
    current_focused_tags: u32,
    pending_focused_tags: ?u32,

    /// Number of views in "master" section of the screen.
    master_count: u32,

    /// Percentage of the total screen that the master section takes up.
    master_factor: f64,

    listen_frame: c.wl_listener,

    pub fn init(self: *Self, root: *Root, wlr_output: *c.wlr_output) !void {
        // Some backends don't have modes. DRM+KMS does, and we need to set a mode
        // before we can use the output. The mode is a tuple of (width, height,
        // refresh rate), and each monitor supports only a specific set of modes. We
        // just pick the monitor's preferred mode, a more sophisticated compositor
        // would let the user configure it.

        // if not empty
        if (c.wl_list_empty(&wlr_output.modes) == 0) {
            // TODO: handle failure
            const mode = c.wlr_output_preferred_mode(wlr_output);
            c.wlr_output_set_mode(wlr_output, mode);
            c.wlr_output_enable(wlr_output, true);
            if (!c.wlr_output_commit(wlr_output)) {
                return error.CantCommitWlrOutputMode;
            }
        }

        self.root = root;
        self.wlr_output = wlr_output;

        for (self.layers) |*layer| {
            layer.* = std.TailQueue(LayerSurface).init();
        }

        self.usable_box = undefined;

        self.views.init();

        self.current_focused_tags = 1 << 0;
        self.pending_focused_tags = null;

        self.master_count = 1;

        self.master_factor = 0.6;

        // Sets up a listener for the frame notify event.
        self.listen_frame.notify = handleFrame;
        c.wl_signal_add(&wlr_output.events.frame, &self.listen_frame);

        // Add the new output to the layout. The add_auto function arranges outputs
        // from left-to-right in the order they appear. A more sophisticated
        // compositor would let the user configure the arrangement of outputs in the
        // layout.
        c.wlr_output_layout_add_auto(root.wlr_output_layout, wlr_output);

        // Creating the global adds a wl_output global to the display, which Wayland
        // clients can see to find out information about the output (such as
        // DPI, scale factor, manufacturer, etc).
        c.wlr_output_create_global(wlr_output);
    }

    /// Add a new view to the output. arrangeViews() will be called by the view
    /// when it is mapped.
    pub fn addView(self: *Self, wlr_xdg_surface: *c.wlr_xdg_surface) void {
        const node = self.root.server.allocator.create(ViewStack.Node) catch unreachable;
        node.view.init(self, wlr_xdg_surface, self.current_focused_tags);
        self.views.push(node);
    }

    /// Add a newly created layer surface to the output.
    pub fn addLayerSurface(self: *Self, wlr_layer_surface: *c.wlr_layer_surface_v1) !void {
        const layer = wlr_layer_surface.client_pending.layer;
        const node = try self.layers[@intCast(usize, @enumToInt(layer))].allocateNode(self.root.server.allocator);
        node.data.init(self, wlr_layer_surface, layer);
        self.layers[@intCast(usize, @enumToInt(layer))].append(node);
        self.arrangeLayers();
    }

    pub fn arrange(self: *Self) void {
        // TODO: properly handle output events instead of calling arrangeLayers() here
        self.arrangeLayers();
        self.arrangeViews();
    }

    /// Arrange all views on the output for the current layout. Modifies only
    /// pending state, the changes are not appplied until a transaction is started
    /// and completed.
    fn arrangeViews(self: *Self) void {
        const output_tags = if (self.pending_focused_tags) |tags|
            tags
        else
            self.current_focused_tags;

        const visible_count = blk: {
            var count: u32 = 0;
            var it = ViewStack.pendingIterator(self.views.first, output_tags);
            while (it.next() != null) count += 1;
            break :blk count;
        };

        const master_count = std.math.min(self.master_count, visible_count);
        const slave_count = if (master_count >= visible_count) 0 else visible_count - master_count;

        const outer_padding = self.root.server.config.outer_padding;

        const layout_width = @intCast(u32, self.usable_box.width) - outer_padding * 2;
        const layout_height = @intCast(u32, self.usable_box.height) - outer_padding * 2;

        var master_column_width: u32 = undefined;
        var slave_column_width: u32 = undefined;
        if (master_count > 0 and slave_count > 0) {
            // If both master and slave views are present
            master_column_width = @floatToInt(u32, @round(@intToFloat(f64, layout_width) * self.master_factor));
            slave_column_width = layout_width - master_column_width;
        } else if (master_count > 0) {
            master_column_width = layout_width;
            slave_column_width = 0;
        } else {
            slave_column_width = layout_width;
            master_column_width = 0;
        }

        var i: u32 = 0;
        var it = ViewStack.pendingIterator(self.views.first, output_tags);
        while (it.next()) |view| {
            if (i < master_count) {
                // Add the remainder to the first master to ensure every pixel of height is used
                const master_height = @divTrunc(layout_height, master_count);
                const master_height_rem = layout_height % master_count;

                view.pending_box = Box{
                    .x = @intCast(i32, outer_padding),
                    .y = @intCast(i32, outer_padding + i * master_height +
                        if (i > 0) master_height_rem else 0),

                    .width = master_column_width,
                    .height = master_height + if (i == 0) master_height_rem else 0,
                };
            } else {
                // Add the remainder to the first slave to ensure every pixel of height is used
                const slave_height = @divTrunc(layout_height, slave_count);
                const slave_height_rem = layout_height % slave_count;

                view.pending_box = Box{
                    .x = @intCast(i32, outer_padding + master_column_width),
                    .y = @intCast(i32, outer_padding + (i - master_count) * slave_height +
                        if (i > master_count) slave_height_rem else 0),

                    .width = slave_column_width,
                    .height = slave_height +
                        if (i == master_count) slave_height_rem else 0,
                };
            }

            i += 1;
        }
    }

    /// Arrange all layer surfaces of this output and addjust the usable aread
    pub fn arrangeLayers(self: *Self) void {
        // TODO: handle exclusive zones
        const bounds = blk: {
            var width: c_int = undefined;
            var height: c_int = undefined;
            c.wlr_output_effective_resolution(self.wlr_output, &width, &height);
            break :blk Box{
                .x = 0,
                .y = 0,
                .width = @intCast(u32, width),
                .height = @intCast(u32, height),
            };
        };

        for (self.layers) |layer| {
            self.arrangeLayer(layer, bounds);
        }

        self.usable_box = bounds;

        // TODO: handle seat focus
    }

    /// Arrange the layer surfaces of a given layer
    fn arrangeLayer(self: *Self, layer: std.TailQueue(LayerSurface), bounds: Box) void {
        var it = layer.first;
        while (it) |node| : (it = node.next) {
            const layer_surface = &node.data;
            const current_state = layer_surface.wlr_layer_surface.current;

            var new_box: Box = undefined;

            // Horizontal alignment
            if (current_state.anchor & (@intCast(u32, c.ZWLR_LAYER_SURFACE_V1_ANCHOR_LEFT) |
                @intCast(u32, c.ZWLR_LAYER_SURFACE_V1_ANCHOR_RIGHT)) != 0 and
                current_state.desired_width == 0)
            {
                new_box.x = bounds.x + @intCast(i32, current_state.margin.left);
                new_box.width = bounds.width -
                    (current_state.margin.left + current_state.margin.right);
            } else if (current_state.anchor & @intCast(u32, c.ZWLR_LAYER_SURFACE_V1_ANCHOR_LEFT) != 0) {
                new_box.x = bounds.x + @intCast(i32, current_state.margin.left);
                new_box.width = current_state.desired_width;
            } else if (current_state.anchor & @intCast(u32, c.ZWLR_LAYER_SURFACE_V1_ANCHOR_RIGHT) != 0) {
                new_box.x = bounds.x + @intCast(i32, bounds.width - current_state.desired_width -
                    current_state.margin.right);
                new_box.width = current_state.desired_width;
            } else {
                new_box.x = bounds.x + @intCast(i32, bounds.width / 2 - current_state.desired_width / 2);
                new_box.width = current_state.desired_width;
            }

            // Vertical alignment
            if (current_state.anchor & (@intCast(u32, c.ZWLR_LAYER_SURFACE_V1_ANCHOR_TOP) |
                @intCast(u32, c.ZWLR_LAYER_SURFACE_V1_ANCHOR_BOTTOM)) != 0 and
                current_state.desired_height == 0)
            {
                new_box.y = bounds.y + @intCast(i32, current_state.margin.top);
                new_box.height = bounds.height -
                    (current_state.margin.top + current_state.margin.bottom);
            } else if (current_state.anchor & @intCast(u32, c.ZWLR_LAYER_SURFACE_V1_ANCHOR_TOP) != 0) {
                new_box.y = bounds.y + @intCast(i32, current_state.margin.top);
                new_box.height = current_state.desired_height;
            } else if (current_state.anchor & @intCast(u32, c.ZWLR_LAYER_SURFACE_V1_ANCHOR_BOTTOM) != 0) {
                new_box.y = bounds.y + @intCast(i32, bounds.height - current_state.desired_height -
                    current_state.margin.bottom);
                new_box.height = current_state.desired_height;
            } else {
                new_box.y = bounds.y + @intCast(i32, bounds.height / 2 - current_state.desired_height / 2);
                new_box.height = current_state.desired_height;
            }

            layer_surface.box = new_box;
            layer_surface.sendConfigure();
        }
    }

    fn handleFrame(listener: ?*c.wl_listener, data: ?*c_void) callconv(.C) void {
        // This function is called every time an output is ready to display a frame,
        // generally at the output's refresh rate (e.g. 60Hz).
        const output = @fieldParentPtr(Output, "listen_frame", listener.?);
        render.renderOutput(output);
    }
};