From 44a1263cbbe6a19f796d6fb05e74396703482340 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Yaroslav=20de=20la=20Pe=C3=B1a=20Smirnov?=
 <yps@yaroslavps.com>
Date: Sat, 21 Sep 2024 23:40:37 +0300
Subject: gl: rgb triangle

---
 src/main.zig | 46 ++++++++++++++++++++++++++++++++++------------
 1 file changed, 34 insertions(+), 12 deletions(-)

diff --git a/src/main.zig b/src/main.zig
index 13ff58b..8b9f927 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -17,20 +17,24 @@ const egl = @import("egl.zig");
 const vertex_shader_src: [*c]const u8 =
     \\#version 330 core
     \\layout (location = 0) in vec3 pos;
+    \\layout (location = 1) in vec4 in_color;
+    \\out vec4 color;
     \\
     \\void main()
     \\{
+    \\  color = in_color;
     \\	gl_Position = vec4(pos.x, pos.y, pos.z, 1.0);
     \\}
 ;
 
 const frag_shader_src: [*c]const u8 =
     \\#version 330 core
+    \\in vec4 color;
     \\out vec4 frag_color;
     \\
     \\void main()
     \\{
-    \\	frag_color = vec4(1.0f, 0.2f, 0.2f, 1.0f);
+    \\	frag_color = vec4(color);
     \\}
 ;
 
@@ -117,19 +121,24 @@ pub const Window = struct {
     /// OpenGl triangle shader program
     shader_prog: c_uint = undefined,
     /// Triangle vertices
-    vertices: [12]f32 = .{
+    vertices: [9]f32 = .{
         -0.5, -0.5, 0.0, // bl
-        0.5,  -0.5, 0.0, // br
-        0.5,   0.5, 0.0, // tr
-        -0.5,  0.5, 0.0, // tl
+        0.5, -0.5, 0.0, // br
+        0.0, 0.5, 0.0, // t
+    },
+    colors: [12]f32 = .{
+        1.0, 0.0, 0.0, 1.0,
+        0.0, 1.0, 0.0, 1.0,
+        0.0, 0.0, 1.0, 1.0,
     },
     /// Triangles indices
-    indices: [6]c_uint = .{
+    indices: [3]c_uint = .{
         0, 1, 2,
-        2, 3, 0,
     },
     /// OpenGL vertex buffer object
     vbo: c_uint = undefined,
+    /// OpenGL color vbo
+    cbo: c_uint = undefined,
     /// OpenGL vertex array object
     vao: c_uint = undefined,
     // OpenGL element buffer object
@@ -194,6 +203,7 @@ pub const Window = struct {
 
         c.glGenVertexArrays(1, &win.vao);
         c.glGenBuffers(1, &win.vbo);
+        c.glGenBuffers(1, &win.cbo);
         c.glGenBuffers(1, &win.ebo);
 
         c.glBindVertexArray(win.vao);
@@ -206,6 +216,20 @@ pub const Window = struct {
             c.GL_STATIC_DRAW,
         );
 
+        c.glVertexAttribPointer(0, 3, c.GL_FLOAT, c.GL_FALSE, 3 * @sizeOf(f32), null);
+        c.glEnableVertexAttribArray(0);
+
+        c.glBindBuffer(c.GL_ARRAY_BUFFER, win.cbo);
+        c.glBufferData(
+            c.GL_ARRAY_BUFFER,
+            @sizeOf(@TypeOf(win.colors)),
+            &win.colors,
+            c.GL_STATIC_DRAW,
+        );
+
+        c.glVertexAttribPointer(1, 3, c.GL_FLOAT, c.GL_FALSE, 4 * @sizeOf(f32), null);
+        c.glEnableVertexAttribArray(1);
+
         c.glBindBuffer(c.GL_ELEMENT_ARRAY_BUFFER, win.ebo);
         c.glBufferData(
             c.GL_ELEMENT_ARRAY_BUFFER,
@@ -214,9 +238,6 @@ pub const Window = struct {
             c.GL_STATIC_DRAW,
         );
 
-        c.glVertexAttribPointer(0, 3, c.GL_FLOAT, c.GL_FALSE, 3 * @sizeOf(f32), null);
-        c.glEnableVertexAttribArray(0);
-
         c.glBindBuffer(c.GL_ARRAY_BUFFER, 0);
         c.glBindVertexArray(0);
 
@@ -251,12 +272,12 @@ pub const Window = struct {
     pub fn drawFrame(win: *Window) !void {
         try egl_display.swapInterval(0);
 
-        c.glClearColor(0, 0.5, 1, 1);
+        c.glClearColor(0, 0.05, 0.15, 1);
         c.glClear(c.GL_COLOR_BUFFER_BIT);
 
         c.glUseProgram(win.shader_prog);
         c.glBindVertexArray(win.vao);
-        c.glDrawElements(c.GL_TRIANGLES, 6, c.GL_UNSIGNED_INT, null);
+        c.glDrawElements(c.GL_TRIANGLES, win.indices.len, c.GL_UNSIGNED_INT, null);
 
         try egl_display.swapBuffers(win.egl_surface);
     }
@@ -361,6 +382,7 @@ pub fn main() !void {
         .{ .type = .red_size, .value = 8 },
         .{ .type = .green_size, .value = 8 },
         .{ .type = .blue_size, .value = 8 },
+        .{ .type = .alpha_size, .value = 8 },
         .{ .type = .none, .value = 0 },
     };
     egl_display = try egl.Display.get(display);
-- 
cgit v1.2.3