screen: add vsync and double buffering

6 files changed, 135 insertions, 5 deletions

diff --git a/src/screen/drm/card.zig b/src/screen/drm/card.zig
index d66a5f1..6147cf2 100644
--- a/src/screen/drm/card.zig
+++ b/src/screen/drm/card.zig
@@ -7,7 +7,8 @@ const Resources = @import("resources.zig").Resources;
 const Connector = @import("connector/root.zig").Connector;
 const Encoder = @import("encoder/root.zig").Encoder;
 const Crtc = @import("crtc/root.zig").Crtc;
-const FrameBuffer = @import("frame-buffer/root.zig").FrameBuffer;
+const DoubleBuffer = @import("frame-buffer/root.zig").DoubleBuffer;
+const Event = @import("event.zig").Event;
 
 
 pub const Card = struct {
@@ -25,6 +26,7 @@ pub const Card = struct {
                 .mode = .read_write,
                 .lock_nonblocking = true,
             }),
+
             .allocator = allocator,
         };
     }
@@ -54,7 +56,25 @@ pub const Card = struct {
         return Crtc.init(self, id);
     }
 
-    pub fn create_frame_buffer(self: *Card, width: u32, height: u32, bpp: u32) !FrameBuffer {
-        return FrameBuffer.init(self, width, height, bpp);
+    pub fn create_double_buffer(self: *Card, width: u32, height: u32, bpp: u32) !DoubleBuffer {
+        return DoubleBuffer.init(self, width, height, bpp);
+    }
+
+    pub fn poll_event(self: *Card, timeout: i32) !?Event {
+        var pollfd = os.pollfd {
+            .fd = self.file.handle,
+            .events = os.POLL.IN,
+            .revents = 0
+        };
+
+        try cerror.from_usize(os.poll(@ptrCast(&pollfd), 1, timeout));
+
+        if ((pollfd.revents & os.POLL.IN) != 0) {
+            var event = std.mem.zeroes(Event);
+            try cerror.from_usize(os.read(self.file.handle, @ptrCast(&event), @sizeOf(Event)));
+            return event;
+        }
+
+        return null;
     }
 };
diff --git a/src/screen/drm/crtc/root.zig b/src/screen/drm/crtc/root.zig
index 3c9d6f9..f1f1d5c 100644
--- a/src/screen/drm/crtc/root.zig
+++ b/src/screen/drm/crtc/root.zig
@@ -2,7 +2,9 @@ const std = @import("std");
 const Card = @import("../card.zig").Card;
 const Drm = @import("../request.zig").Drm;
 const Connector = @import("../connector/root.zig").Connector;
-const FrameBuffer = @import("../frame-buffer/root.zig").FrameBuffer;
+const fb = @import("../frame-buffer/root.zig");
+const FrameBuffer = fb.FrameBuffer;
+const DoubleBuffer = fb.DoubleBuffer;
 const Mode = @import("../connector/mode.zig").Mode;
 
 pub const RawCrtc = extern struct {
@@ -17,6 +19,22 @@ pub const RawCrtc = extern struct {
     mode: Mode,
 };
 
+const PageFlipEvent = packed struct(u32) {
+    event: bool,
+    is_async: bool,
+    absolute: bool,
+    relative: bool,
+    __padding: u28,
+};
+
+const PageFlip = extern struct {
+    crtc_id: u32,
+    buffer_id: u32,
+    flags: PageFlipEvent,
+    __reserved: u32,
+    user_data: u64,
+};
+
 pub const Crtc = struct {
     const Self = @This();
 
@@ -65,8 +83,18 @@ pub const Crtc = struct {
         };
 
         try Drm.set_crtc.request(self.card.file.handle, RawCrtc, &crtc);
+    }
+
+    pub fn page_flip(self: *Self, double_buffer: *DoubleBuffer) !void {
+        double_buffer.swap();
+
+        var flip = std.mem.zeroInit(PageFlip, .{
+            .buffer_id = double_buffer.crtc_buffer().id,
+            .crtc_id = self.id,
+            .flags = std.mem.zeroInit(PageFlipEvent, .{ .event = true }),
+        });
 
-        std.debug.print("crtc = {any}\n", .{self});
+        try Drm.page_flip.request(self.card.file.handle, PageFlip, &flip);
     }
 
     pub fn detach(self: *Self) void {
diff --git a/src/screen/drm/event.zig b/src/screen/drm/event.zig
new file mode 100644
index 0000000..201ced3
--- /dev/null
+++ b/src/screen/drm/event.zig
@@ -0,0 +1,31 @@
+
+pub const EventType = enum(u32) {
+    vblank = 1,
+    page_flip_complete = 2,
+    crtc_sequence = 3,
+};
+
+pub const VBlankEvent = extern struct {
+    user_data: u64,
+    tv_sec: u32,
+    tv_usec: u32,
+    sequence: u32,
+    crtc_id: u32,
+};
+
+pub const CrtcSequenceEvent = extern struct {
+    user_data: u64,
+    time_ns: i64,
+    sequence: u64,
+};
+
+pub const EventPayload = extern union {
+    vblank: VBlankEvent,
+    crtc_sequence: CrtcSequenceEvent,
+};
+
+pub const Event = extern struct {
+    type: EventType,
+    length: u32,
+    payload: EventPayload,
+};
diff --git a/src/screen/drm/frame-buffer/page-flip.zig b/src/screen/drm/frame-buffer/page-flip.zig
new file mode 100644
index 0000000..2e41e61
--- /dev/null
+++ b/src/screen/drm/frame-buffer/page-flip.zig
@@ -0,0 +1,8 @@
+
+pub const PageFlip = packed struct(u32) {
+    event: bool,
+    is_async: bool,
+    absolute: bool,
+    relative: bool,
+    _padding: u28,
+}
diff --git a/src/screen/drm/frame-buffer/root.zig b/src/screen/drm/frame-buffer/root.zig
index eb7b47b..0083711 100644
--- a/src/screen/drm/frame-buffer/root.zig
+++ b/src/screen/drm/frame-buffer/root.zig
@@ -33,6 +33,43 @@ const MapDumb = extern struct {
     offset: i64,
 };
 
+pub const DoubleBuffer = struct {
+    const Self = @This();
+
+    back: FrameBuffer,
+    front: FrameBuffer,
+
+    pub fn init(card: *Card, width: u32, height: u32, bpp: u32) !Self {
+        return .{
+            .back = try FrameBuffer.init(card, width, height, bpp),
+            .front = try FrameBuffer.init(card, width, height, bpp),
+        };
+    }
+
+    pub fn swap(self: *Self) void {
+        const back_data = self.back.data;
+        self.back.data = self.front.data;
+        self.front.data = back_data;
+
+        const back_id = self.back.id;
+        self.back.id = self.front.id;
+        self.front.id = back_id;
+    }
+
+    pub fn deinit(self: *Self) void {
+        self.back.deinit();
+        self.front.deinit();
+    }
+
+    pub fn buffer(self: *Self) *FrameBuffer {
+        return &self.back;
+    }
+
+    pub fn crtc_buffer(self: *Self) *FrameBuffer {
+        return &self.front;
+    }
+};
+
 pub const Pixel = packed struct(u32) {
     blue: u8,
     green: u8,
@@ -127,6 +164,10 @@ pub const FrameBuffer = struct {
         self.data[x + self.width * y] = pixel;
     }
 
+    pub fn fill(self: *Self, pixel: Pixel) void {
+        @memset(self.data[0..self.canvas_size], pixel);
+    }
+
     pub fn deinit(self: *Self) void {
         cerror.from_usize(
             os.munmap(@ptrCast(@volatileCast(self.data)), self.data_size)
diff --git a/src/screen/drm/request.zig b/src/screen/drm/request.zig
index 9e0a045..5daf92f 100644
--- a/src/screen/drm/request.zig
+++ b/src/screen/drm/request.zig
@@ -15,6 +15,8 @@ pub const Drm = enum(u8) {
     get_encoder = 0xa6,
     get_connector = 0xa7,
     remove_frame_buffer = 0xaf,
+    page_flip = 0xb0,
+    dirty_frame_buffer = 0xb1,
     create_dumb = 0xb2,
     map_dumb = 0xb3,
     destroy_dumb = 0xb4,