From 38fdb591d3630aa895dbe6cb42b964ef0f2106df Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Yaroslav=20de=20la=20Pe=C3=B1a=20Smirnov?=
 <yps@yaroslavps.com>
Date: Sun, 22 Sep 2024 15:21:51 +0300
Subject: gl: animated rgb square

---
 src/main.zig | 48 ++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 38 insertions(+), 10 deletions(-)

(limited to 'src')

diff --git a/src/main.zig b/src/main.zig
index 33e8aba..bcd12d6 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -34,7 +34,7 @@ const frag_shader_src: [*c]const u8 =
     \\
     \\void main()
     \\{
-    \\	frag_color = vec4(color);
+    \\	frag_color = color;
     \\}
 ;
 
@@ -152,12 +152,10 @@ pub const Window = struct {
     width: i32 = 480,
     /// Height in pixels
     height: i32 = 360,
-    /// Offset of our checkerboard animation
-    offset: f32 = 0.0,
     /// Last frame's timestamp in ms
     last_frame: u32 = 0,
     /// Frames per second statistic
-    current_fps: f32 = 0.0,
+    // current_fps: f32 = 0.0,
     /// Should we keep this window open?
     open: bool = true,
 
@@ -227,7 +225,7 @@ pub const Window = struct {
             c.GL_ARRAY_BUFFER,
             @sizeOf(@TypeOf(win.colors)),
             &win.colors,
-            c.GL_STATIC_DRAW,
+            c.GL_DYNAMIC_DRAW,
         );
 
         c.glVertexAttribPointer(1, 3, c.GL_FLOAT, c.GL_FALSE, 4 * @sizeOf(f32), null);
@@ -278,8 +276,39 @@ pub const Window = struct {
         c.glClearColor(0, 0.05, 0.15, 1);
         c.glClear(c.GL_COLOR_BUFFER_BIT);
 
+        var ts: f32 = @floatFromInt(win.last_frame);
+        ts /= 1000;
+        const light_sine = @sin(ts) / 2.0 + 0.5;
+        const dark_sine = @sin(ts-std.math.pi/2.0) / 2.0 + 0.5;
+        // red
+        win.colors[0] = light_sine;
+        win.colors[1] = dark_sine;
+        win.colors[2] = dark_sine;
+        // green
+        win.colors[4] = dark_sine;
+        win.colors[5] = light_sine;
+        win.colors[6] = dark_sine;
+        // blue
+        win.colors[8] = dark_sine;
+        win.colors[9] = dark_sine;
+        win.colors[10] = light_sine;
+        // yellow
+        win.colors[12] = light_sine;
+        win.colors[13] = light_sine;
+        win.colors[14] = dark_sine;
+
         c.glUseProgram(win.shader_prog);
+
         c.glBindVertexArray(win.vao);
+
+        c.glBindBuffer(c.GL_ARRAY_BUFFER, win.cbo);
+        c.glBufferData(
+            c.GL_ARRAY_BUFFER,
+            @sizeOf(@TypeOf(win.colors)),
+            &win.colors,
+            c.GL_DYNAMIC_DRAW,
+        );
+
         c.glDrawElements(c.GL_TRIANGLES, win.indices.len, c.GL_UNSIGNED_INT, null);
 
         try egl_display.swapBuffers(win.egl_surface);
@@ -349,11 +378,10 @@ pub const Window = struct {
                 };
                 new_cb.setListener(*Window, frameListener, win);
 
-                if (win.last_frame != 0) {
-                    const elapsed: f32 = @floatFromInt(done.callback_data -% win.last_frame);
-                    win.offset -= elapsed / 1000.0 * 32.0;
-                    win.current_fps = 1000.0 / elapsed;
-                }
+                // if (win.last_frame != 0) {
+                    // const elapsed: f32 = @floatFromInt(done.callback_data -% win.last_frame);
+                    // win.current_fps = 1000.0 / elapsed;
+                // }
                 win.last_frame = done.callback_data;
 
                 win.drawFrame() catch |err| {
-- 
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