month-based background color

src/main.zig

@@ -11,6 +11,8 @@ pub fn main() !void {
     raylib.SetWindowMaxSize(1920, 1080);
     scales = Scales.init();
 
+    datetime = DateTime{ .secs = @intCast(std.time.timestamp()) };
+
     global_font = raylib.LoadFontEx("font/SCE-PS3-RD-R-LATIN.TTF", 32, 0, 250);
     raylib.SetTextureFilter(global_font.texture, raylib.TEXTURE_FILTER_BILINEAR);
 
@@ -59,7 +61,9 @@ pub fn main() !void {
         if (raylib.IsKeyPressed('D')) debug_draw = !debug_draw;
         if (raylib.IsKeyPressed('S')) raylib.TakeScreenshot("screenshot.png");
 
-        column.updatePositions();
+        datetime.update();
+        background.update();
+        column.update();
 
         raylib.BeginDrawing();
         defer raylib.EndDrawing();
@@ -91,6 +95,8 @@ var screen_height: f32 = 272;
 
 var scales: Scales = undefined;
 
+var datetime: DateTime = undefined;
+
 /// Cached scaling and positioning values for dynamic window resizing.
 pub const Scales = struct {
     font_size_curve: Curve,
@@ -246,7 +252,7 @@ pub const Column = struct {
         self.refresh(false);
     }
 
-    fn updatePositions(self: *Column) void {
+    fn update(self: *Column) void {
         const up = raylib.IsKeyPressed(raylib.KEY_UP) or raylib.IsKeyPressedRepeat(raylib.KEY_UP);
         const down = raylib.IsKeyPressed(raylib.KEY_DOWN) or raylib.IsKeyPressedRepeat(raylib.KEY_DOWN);
         if (up and self.selected > 0) self.selected -= 1;
@@ -375,8 +381,36 @@ pub fn Tweener(comptime T: type, comptime default: T) type {
     };
 }
 
+/// Optimized datetime that only pulls from the system clock every few seconds.
+pub const DateTime = struct {
+    refresh_timer: f32 = 0.0,
+    secs: u64,
+
+    pub fn update(self: *DateTime) void {
+        self.refresh_timer += raylib.GetFrameTime();
+        if (self.refresh_timer >= 5) {
+            self.refresh_timer = 0;
+            self.secs = @intCast(std.time.timestamp());
+        }
+    }
+
+    pub fn getEpochSeconds(self: DateTime) std.time.epoch.EpochSeconds {
+        const secs = self.secs + @as(u64, @intFromFloat(self.refresh_timer));
+        return .{ .secs = secs };
+    }
+
+    pub fn getDaySeconds(self: DateTime) std.time.epoch.DaySeconds {
+        return self.getEpochSeconds().getDaySeconds();
+    }
+
+    pub fn getEpochDay(self: DateTime) std.time.epoch.EpochDay {
+        return self.getEpochSeconds().getEpochDay();
+    }
+};
+
 /// Draws the dynamic gradient background.
-// TODO shift based on time of day
+// TODO subdivided plane gradient
+// TODO smoothly transition between gradients over a couple seconds
 // TODO image wallpaper
 // TODO slideshow wallpaper
 // TODO animated image wallpaper
@@ -388,10 +422,31 @@ pub const Background = struct {
 
     pub fn init() Background {
         var self: Background = undefined;
-        self.setColors(NIGHT_08);
+        self.update();
         return self;
     }
 
+    pub fn update(self: *Background) void {
+        const epoch_day = datetime.getEpochDay();
+        const year_day = epoch_day.calculateYearDay();
+        const month_day = year_day.calculateMonthDay();
+
+        const day_seconds = datetime.getDaySeconds();
+        const t = @sin(raylib.Remap(
+            @floatFromInt(day_seconds.secs),
+            0,
+            std.time.s_per_day / 2,
+            0,
+            std.math.pi,
+        ));
+
+        self.setColors(switch (month_day.month) {
+            .jun => lerpColors(DAY_06, NIGHT_06, t),
+            .aug => lerpColors(DAY_08, NIGHT_08, t),
+            else => @panic("month background colors not implemented"),
+        });
+    }
+
     pub fn setColors(self: *Background, colors: [4]Color) void {
         self.top_left = colors[0];
         self.bottom_right = colors[1];
@@ -421,14 +476,28 @@ pub const Background = struct {
 
         fn toRaylib(self: Color) raylib.Color {
             return .{
-                .r = @intFromFloat(self.r * 255.0),
-                .g = @intFromFloat(self.g * 255.0),
-                .b = @intFromFloat(self.b * 255.0),
+                .r = @intFromFloat(std.math.clamp(self.r, 0.0, 1.0) * 255.0),
+                .g = @intFromFloat(std.math.clamp(self.g, 0.0, 1.0) * 255.0),
+                .b = @intFromFloat(std.math.clamp(self.b, 0.0, 1.0) * 255.0),
                 .a = 255,
             };
         }
+
+        fn lerp(self: Color, other: Color, t: f32) Color {
+            return .{
+                .r = std.math.lerp(self.r, other.r, t),
+                .g = std.math.lerp(self.g, other.g, t),
+                .b = std.math.lerp(self.b, other.b, t),
+            };
+        }
     };
 
+    fn lerpColors(a: [4]Color, b: [4]Color, t: f32) [4]Color {
+        var colors = a;
+        for (&colors, a, b) |*color, aa, bb| color.* = aa.lerp(bb, t);
+        return colors;
+    }
+
     pub const DAY_06 = [4]Color{
         .{ .r = 0.408, .g = 0.333, .b = 0.643 },
         .{ .r = 0.518, .g = 0.365, .b = 0.855 },
@@ -436,6 +505,13 @@ pub const Background = struct {
         .{ .r = 0.569, .g = 0.325, .b = 0.620 },
     };
 
+    pub const NIGHT_06 = [4]Color{
+        .{ .r = 0.039, .g = 0.031, .b = 0.035 },
+        .{ .r = 0.031, .g = 0.039, .b = 0.035 },
+        .{ .r = 0.824, .g = 0.647, .b = 0.878 },
+        .{ .r = 0.784, .g = 0.608, .b = 0.831 },
+    };
+
     pub const DAY_08 = [4]Color{
         .{ .r = 0.243, .g = 0.608, .b = 0.831 },
         .{ .r = 0.039, .g = 0.690, .b = 0.878 },