FancyMenu GLSL Shader APIlink

This document describes the GLSL runtime used by FancyMenu's:

• GLSL menu background
• GLSL element
• GLSL decoration overlay

It covers compile modes, multipass routing, supported uniforms, and practical shader authoring patterns.

1. Runtime Overviewlink

FancyMenu renders shaders with an internal OpenGL pipeline (#version 150) and supports:

• single-pass shaders (Image pass only)
• multipass shaders (Buffer A / B / C / D + Image)
• Shadertoy-style entry points (mainImage)
• direct fragment entry points (main)

Shader sources are inline text fields:

• Shader Source (Image pass, required to render)
• Buffer A Source (optional)
• Buffer B Source (optional)
• Buffer C Source (optional)
• Buffer D Source (optional)

If Image source is empty, rendering fails with a "no source" error.

2. Compile Modeslink

FancyMenu supports three compile modes:

• Auto
• Direct Fragment
• Shadertoy

2.1 Shadertoy modelink

Expected entry point:

void mainImage(out vec4 fragColor, in vec2 fragCoord)

FancyMenu wraps it into main() and passes local area coordinates:

mainImage(fmColor_FancyMenu, gl_FragCoord.xy - fmAreaOffset);

The wrapper multiplies output alpha by fmOpacity.

2.2 Direct modelink

Expected entry point:

void main()

Compatibility behavior:

• A gl_FragColor compatibility variant is attempted.
• A no-compat variant is also attempted (for modern explicit out vec4 shaders).

In direct mode, fmOpacity is not automatically applied to your output. Apply it manually if needed.

2.3 Auto modelink

Auto tries compatible variants in sequence (Shadertoy/direct) and uses the first one that compiles.

3. Source Preprocessing and Built-in Macroslink

Before compile, FancyMenu normalizes source:

• removes UTF-8 BOM
• converts CRLF/CR to LF
• strips #version ... lines
• strips precision ...; lines

Runtime-injected preamble includes:

• #version 150
• in vec2 fmUv_FancyMenu (fullscreen UV in [0,1], bottom-left origin)
• #define iGlobalTime iTime
• #define texture2D texture
• #define textureCube texture

Note:

• If your source already declares a known uniform name (e.g. iTime), FancyMenu avoids injecting a duplicate declaration.
• FancyMenu still tries to upload values to that name at runtime.
• textureCube is only an alias macro here; iChannel0..3 are sampler2D uniforms.

4. Pass System (Image + Buffer A-D)link

FancyMenu has 5 pass slots:

• Buffer A
• Buffer B
• Buffer C
• Buffer D
• Image (final on-screen pass)

Behavior:

• Buffer passes only run if their source is non-empty.
• Image pass must be present to render output.
• Buffers are rendered to floating-point textures (GL_RGBA16F), then ping-ponged (read/write swap each frame).

4.1 Channel routing per passlink

Each pass exposes routing for iChannel0..3. Per channel you can select:

• None
• Resource 0
• Resource 1
• Resource 2
• Resource 3
• Buffer A
• Buffer B
• Buffer C
• Buffer D

Resource channels come from the iChannel# Resource settings.

Defaults:

• all iChannel routings default to None
• no buffer pass is active until that buffer source is non-empty

Important:

• Routing to the same buffer pass (feedback) reads previous-frame data (ping-pong read texture).
• If a routed source is missing/inactive, a fallback texture is bound and iChannelResolution[n].z becomes 0.0.

5. Coordinates and Area Semanticslink

Shaders run in an area rectangle:

• Menu background: full screen area
• GLSL element: element rectangle

Coordinate conventions:

• Pixel uniforms are in area-local pixels.
• Y origin is bottom-left for shader-facing pixel coords.
• Mouse coordinates are not clamped; values can be outside area if cursor is outside.

Special fields:

• fmAreaOffset: area bottom-left position in screen pixel space
• fmAreaTopLeft: area top-left position in screen pixel space
• fmAreaSize: area size in pixels

6. Uniform API Referencelink

All uniforms below are available for both background and element shaders.

6.1 Shadertoy-compatible uniformslink

iMouse detailslink

iMouse = vec4(x, y, z, w)

• x, y: current area-local mouse pixel position, or hold/frozen behavior if the toggle is enabled
• z, w: left-click origin
  • positive while left mouse button is held
  • negative after release

Toggle-controlled behavior:

• Update iMouse Position Only While Holding LMB = Off:
  • iMouse.xy updates continuously
• ... = On:
  • iMouse.xy updates only while LMB is down, then remains at last held position

Default value:

• Off (continuous updates)

6.2 FancyMenu-specific uniformslink

Key action values (fmKeyEvent.w):

• 0 = release
• 1 = press
• 2 = repeat

6.3 FancyMenu Variable Uniform APIlink

FancyMenu variables are exposed directly as runtime uniforms (for background, element, and decoration overlay shaders) without shader recompilation when values change.

Naminglink

For each variable <name>, FancyMenu exposes:

• fmVarFloat_<name>
• fmVarInt_<name>
• fmVarBool_<name>
• fmVarVec2_<name>
• fmVarVec3_<name>
• fmVarVec4_<name>
• fmVarExists_<name> (1 = variable currently exists, 0 = not present/removed)

Uniform suffix sanitization for <name>:

• allowed chars are [A-Za-z0-9_]
• all other chars are converted to _
• if the first char is a digit, _ is prepended

Examples:

• variable player_hp -> suffix player_hp
• variable player-hp -> suffix player_hp
• variable 2nd_phase -> suffix _2nd_phase

Important:

• these dynamic variable uniforms are not auto-declared in shader source (declare the ones you use manually)
• avoid variable names that sanitize to the same suffix, because they map to the same GLSL uniform name

Value conversionlink

Given variable text value v:

• fmVarFloat_*: parsed float (0.0 fallback)
• fmVarInt_*: parsed int (0 fallback)
• fmVarBool_*: boolean/int interpretation (true/yes/on/enabled => 1, false/no/off/disabled => 0, otherwise numeric non-zero => 1)
• vector parsing accepts separators: whitespace, ,, ;, |
  • fmVarVec2_*: first 2 parsed components
  • fmVarVec3_*: first 3 parsed components
  • fmVarVec4_*: first 4 parsed components
  • if fewer components are present, the last parsed component is repeated for missing slots
  • if no numeric components are present, all vector components use scalar fallback

If a variable gets removed:

• fmVarExists_* becomes 0
• all corresponding fmVar*_* values are reset to 0

Example declaration and usagelink

uniform float fmVarFloat_player_hp;
uniform int fmVarBool_is_boss_phase;
uniform vec3 fmVarVec3_theme_color;
uniform int fmVarExists_player_hp;

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
    vec2 uv = fragCoord / iResolution.xy;

    float hp = clamp(fmVarFloat_player_hp / 100.0, 0.0, 1.0);
    vec3 theme = fmVarVec3_theme_color;
    float boss = float(fmVarBool_is_boss_phase);

    vec3 col = mix(theme * 0.25, theme, hp);
    col += vec3(0.2, 0.0, 0.0) * boss;

    if (fmVarExists_player_hp == 0) {
        col = vec3(0.15);
    }

    fragColor = vec4(col, 1.0);
}

7. Input Tracking Modellink

FancyMenu tracks input globally and snapshots it per render:

• mouse move/drag
• mouse press/release
• scroll
• key press/release/repeat
• char typed

Mouse robustness:

• Runtime reconciles button states with GLFW polling each frame to prevent stuck-button states.

If Pass Input Events To Shader is disabled:

• input uniforms are reset to neutral values each frame
• counters and events are zeroed in shader-visible data

8. Texture Input Detailslink

Resource channels (iChannel# Resource) expect 2D textures.

Texture state per channel:

• valid resource: bound texture, real width/height, iChannelResolution[n].z = 1.0
• missing/inactive/None: fallback texture, iChannelResolution[n].xyz = (0,0,0)

Buffer textures:

• internal format: RGBA16F (floating point)
• filtering: linear
• wrap: clamp-to-edge

This is suitable for multipass data (including values outside [0,1]).

9. Rendering and Blending Noteslink

• Buffer passes render offscreen without blending.
• Final Image pass uses the Enable Blending setting for compositing.
• Shadertoy wrapper applies fmOpacity to alpha automatically.
• Direct shaders should apply fmOpacity manually if required.

10. Practical Templateslink

10.1 Minimal Shadertoy-style shaderlink

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
    vec2 uv = fragCoord / iResolution.xy;
    vec3 col = vec3(uv, 0.5 + 0.5 * sin(iTime));
    fragColor = vec4(col, 1.0);
}

10.2 Minimal direct fragment shaderlink

out vec4 FragColor;

void main() {
    vec2 uv = gl_FragCoord.xy - fmAreaOffset;
    uv /= iResolution.xy;

    vec3 col = vec3(uv.x, uv.y, 0.5 + 0.5 * sin(iTime));
    FragColor = vec4(col, fmOpacity);
}

10.3 Minimal feedback multipasslink

Buffer A sourcelink

Route: Buffer A iChannel0 Input -> Buffer A

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
    vec2 uv = fragCoord / iResolution.xy;
    vec4 prev = texture(iChannel0, uv);
    vec4 seed = vec4(uv, 0.0, 1.0);
    fragColor = mix(prev, seed, 0.02);
}

Image sourcelink

Route: Image iChannel0 Input -> Buffer A

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
    vec2 uv = fragCoord / iResolution.xy;
    fragColor = texture(iChannel0, uv);
}

11. Troubleshooting Checklistlink

• No output:
  • verify Image source is non-empty
  • verify compile mode matches your entry point (mainImage vs main)
• Purple/invalid textures:
  • verify resource bindings and channel routing
  • check iChannelResolution[n].z (0.0 means invalid/unavailable)
• Wrong coordinates in direct shader:
  • use gl_FragCoord.xy - fmAreaOffset for local area coords
• Drag behavior wrong:
  • use the Update iMouse Position Only While Holding LMB toggle
• Opacity not applied in direct shader:
  • multiply alpha by fmOpacity yourself