From 0fb3650a9ad1a14816cbd0d3870f7d475e4194ca Mon Sep 17 00:00:00 2001
From: Sander Schobers <sander@schobers.eu>
Date: Fri, 2 Jun 2023 14:21:50 +0200
Subject: [PATCH] Added FPS counter. Not forcing vsync.

---
 src/context.zig    | 29 ++++++++++++++++++++++-------
 src/engine.zig     |  1 +
 src/engine/fps.zig | 25 +++++++++++++++++++++++++
 src/main.zig       |  9 +++++++++
 4 files changed, 57 insertions(+), 7 deletions(-)
 create mode 100644 src/engine/fps.zig

diff --git a/src/context.zig b/src/context.zig
index 9051967..7d37823 100644
--- a/src/context.zig
+++ b/src/context.zig
@@ -11,24 +11,38 @@ pub const Context = struct {
     allocator: std.mem.Allocator,
     palette: Palette = undefined,
     shouldQuit: bool = false,
+    showFPS: bool = false,
     scene: ?Scene = null,
 
     display: allegro.Display,
     events: allegro.EventQueue,
 
     viewport: engine.Viewport,
+    fps: engine.FPS,
     fonts: engine.Fonts,
     textures: engine.Textures,
 
     pub fn init(allocator: std.mem.Allocator) !Context {
-        _ = allegro.init();
-        _ = allegro.initImageAddon();
-        _ = allegro.installKeyboard();
-        _ = allegro.installMouse();
-        _ = allegro.initFontAddon();
-        _ = allegro.initTtfAddon();
+        if (!allegro.init()) {
+            return error.FailedToInitialize;
+        }
+        if (!allegro.initImageAddon()) {
+            return error.FailedToInitialize;
+        }
+        if (!allegro.installKeyboard()) {
+            return error.FailedToInitialize;
+        }
+        if (!allegro.installMouse()) {
+            return error.FailedToInitialize;
+        }
+        if (!allegro.initFontAddon()) {
+            return error.FailedToInitialize;
+        }
+        if (!allegro.initTtfAddon()) {
+            return error.FailedToInitialize;
+        }
 
-        allegro.setNewDisplayOption(allegro.NewDisplayOption.VSYNC, 1, allegro.OptionImportance.REQUIRE);
+        allegro.setNewDisplayOption(allegro.NewDisplayOption.VSYNC, 1, allegro.OptionImportance.SUGGEST);
         allegro.setNewDisplayOption(allegro.NewDisplayOption.SAMPLE_BUFFERS, 1, allegro.OptionImportance.REQUIRE);
         allegro.setNewDisplayOption(allegro.NewDisplayOption.SAMPLES, 4, allegro.OptionImportance.REQUIRE);
         allegro.setNewDisplayFlags(allegro.NewDisplayFlags{ .RESIZABLE = true });
@@ -47,6 +61,7 @@ pub const Context = struct {
             .display = display,
             .events = events,
             .viewport = viewport,
+            .fps = engine.FPS{},
             .fonts = engine.Fonts.init(allocator),
             .textures = engine.Textures.init(allocator),
         };
diff --git a/src/engine.zig b/src/engine.zig
index 5ad1421..c2b3520 100644
--- a/src/engine.zig
+++ b/src/engine.zig
@@ -1,6 +1,7 @@
 const assets = @import("engine/assets.zig");
 
 pub const Fonts = assets.Fonts;
+pub const FPS = @import("engine/fps.zig").FPS;
 pub const OpaquePtr = @import("engine/opaque_ptr.zig").OpaquePtr;
 pub const Point = @import("engine/point.zig").Point;
 pub const PointF = @import("engine/point_f.zig").PointF;
diff --git a/src/engine/fps.zig b/src/engine/fps.zig
new file mode 100644
index 0000000..ece6f0e
--- /dev/null
+++ b/src/engine/fps.zig
@@ -0,0 +1,25 @@
+pub const FPS = struct {
+    const Frames: usize = 100;
+
+    frames: [Frames]f32 = [_]f32{0} ** Frames,
+    total: f32 = 0,
+    index: usize = 0,
+    framesCounted: usize = 0,
+
+    pub fn update(self: *FPS, dt: f32) void {
+        self.total -= self.frames[self.index];
+        self.total += dt;
+        self.frames[self.index] = dt;
+        self.index += 1;
+        if (self.index == Frames) {
+            self.index = 0;
+        }
+        if (self.framesCounted < Frames) {
+            self.framesCounted += 1;
+        }
+    }
+
+    pub fn fps(self: FPS) usize {
+        return @floatToInt(usize, @intToFloat(f32, self.framesCounted) / self.total);
+    }
+};
diff --git a/src/main.zig b/src/main.zig
index ad4e4ed..54323f1 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -50,6 +50,7 @@ pub fn main() !void {
     try context.switchToScene(TitleScene, null);
 
     var t = allegro.getTime();
+    var fpsBuffer = [_]u8{0} ** 32;
     while (!context.shouldQuit) {
         const scene = if (context.scene) |scene| scene else {
             break;
@@ -67,6 +68,7 @@ pub fn main() !void {
                 allegro.c.ALLEGRO_EVENT_KEY_CHAR => {
                     switch (event.keyboard.keycode) {
                         allegro.c.ALLEGRO_KEY_ESCAPE => context.quit(),
+                        allegro.c.ALLEGRO_KEY_F9 => context.showFPS = !context.showFPS,
                         allegro.c.ALLEGRO_KEY_F11 => context.toggleFullScreen(),
                         else => {},
                     }
@@ -83,8 +85,15 @@ pub fn main() !void {
         const deltaT = @floatCast(f32, newT - t);
         t = newT;
         scene.update(&context, deltaT);
+        context.fps.update(deltaT);
 
         scene.render(&context);
+        if (context.showFPS) {
+            if (context.fonts.get("default")) |font| {
+                const fps = try std.fmt.bufPrintZ(fpsBuffer[0..], "FPS: {}", .{context.fps.fps()});
+                allegro.drawText(font, context.palette.background.text, 10, 10, allegro.DrawTextFlags.ALIGN_LEFT, fps);
+            }
+        }
 
         allegro.flipDisplay();
     }