/*
 * MIT License
 * Author: Mark Allyn
 *
 * text.vert — vertex shader for FreeType glyph-atlas text rendering.
 * Each glyph is a textured quad. Vertices are in window pixels
 * (top-left origin); the shader converts to NDC and passes the
 * glyph atlas UV coordinates to the fragment shader.
 */
#version 330 core

layout(location = 0) in vec4 aVertex;  // xy = screen pos (px), zw = atlas UV

out vec2 vTexCoord;

uniform vec2 u_viewportSize;   // (WINDOW_WIDTH, WINDOW_HEIGHT)

void main() {
    vec2 pos = aVertex.xy;
    vTexCoord = aVertex.zw;

    vec2 ndc = vec2(
         pos.x / u_viewportSize.x * 2.0 - 1.0,
        -pos.y / u_viewportSize.y * 2.0 + 1.0
    );
    gl_Position = vec4(ndc, 0.0, 1.0);
}