screen: add vsync and double buffering

2 files changed, 49 insertions, 0 deletions

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)