BaseUniforms.h

Go to the documentation of this file.

// SPDX-FileCopyrightText: 2026 fuddlesworth
// SPDX-License-Identifier: LGPL-2.1-or-later
 
#pragma once
 
#include <cstddef>
 
namespace PhosphorShaders {
 
constexpr double kShaderTimeWrap = 1024.0;
 
struct alignas(16) BaseUniforms
{
    // Transform and opacity from Qt scene graph (offset 0)
    float qt_Matrix[16]; // mat4: 64 bytes at offset 0
    float qt_Opacity; // float: 4 bytes at offset 64
 
    // Shader timing (Shadertoy-compatible)
    float iTime; // float: 4 bytes at offset 68 (wrapped)
    float iTimeDelta; // float: 4 bytes at offset 72
    int iFrame; // int: 4 bytes at offset 76
 
    // Resolution
    float iResolution[2]; // vec2: 8 bytes at offset 80
 
    // Consumer-defined int slots — see class doc above for the escape-hatch
    // design rationale. Written via ShaderNodeRhi::setAppField0/1.
    int appField0; // offset 88
    int appField1; // offset 92
 
    // Mouse position
    float iMouse[4]; // vec4: 16 bytes at offset 96
 
    // Date/time: year, month (1-12), day (1-31), seconds since midnight
    float iDate[4]; // vec4: 16 bytes at offset 112
 
    // Custom shader parameters (32 float slots in 8 vec4s)
    float customParams[8][4]; // vec4[8]: 128 bytes at offset 128
 
    // Custom colors (16 color slots)
    float customColors[16][4]; // vec4[16]: 256 bytes at offset 256
 
    // Multi-pass: iChannelResolution[i] = buffer texture size
    float iChannelResolution[4][4]; // vec4[4]: 64 bytes at offset 512
 
    // Audio spectrum
    int iAudioSpectrumSize; // offset 576
    int iFlipBufferY; // offset 580 — always 1 for Y-flip
    // The two pad ints at offsets 584 and 588 are explicitly written as zero
    // by the C-side upload path (see BaseUniformProfile::fill in
    // baseuniformprofile.cpp) — readers should not assume the bytes are skipped
    // on the wire. On the
    // GLSL side they are absorbed by std140's vec4 alignment of the following
    // `iTextureResolution` (vec4[4]) member, which forces the next field onto
    // a 16-byte boundary at offset 592. Removing the pad would shift the
    // GLSL view of `iTextureResolution` and break the
    // `data/animations/shared/animation_uniforms.glsl` byte-for-byte
    // contract pinned by the static_asserts below.
    int _pad_after_audioSpectrum[2]; // offset 584
 
    // User texture resolutions (bindings 7-10)
    float iTextureResolution[4][4]; // vec4[4]: 64 bytes at offset 592
 
    // Wrap-offset counterpart of iTime
    float iTimeHi; // offset 656
 
    // Direction signal for asymmetric leg rendering. 1 when the runtime
    // is driving this leg in the "reverse" direction (window.close /
    // going-to-minimized / unmaximize on the kwin path; hide leg on
    // the daemon path), 0 otherwise. Symmetric shaders ignore this and
    // rely on the runtime's iTime flip to auto-mirror; asymmetric
    // shaders (matrix's directional rain, rain windowAlpha trajectory,
    // anything where open and close differ in more than time direction)
    // branch on it. Carved out of the trailing std140 pad so total
    // struct size stays 672 bytes.
    int iIsReversed; // offset 660
    // Ditto: trailing pad zeroed by value-init (BaseUniformProfile's `m_u = {}`)
    // and covered by K_SCENE_HEADER. See the expanded `_pad_after_audioSpectrum`
    // comment above for the full std140 / upload-region rationale.
    int _pad_after_iIsReversed[2]; // std140 struct alignment, total 672 bytes
};
 
static_assert(sizeof(BaseUniforms) == 672, "BaseUniforms must be exactly 672 bytes");
 
// Per-field std140 offset asserts. These pin the layout the
// `data/animations/shared/animation_uniforms.glsl` canonical UBO branch
// depends on — that GLSL declaration is a byte-for-byte std140 prefix of
// `BaseUniforms`, which is what lets a single animation `effect.frag`
// source produce identical visuals on both runtimes (compositor classic
// GL via the canonical header's `#ifdef PLASMAZONES_KWIN` default-block
// branch, daemon Qt RHI via the `binding=0` UBO upload). If anyone
// reorders or inserts a field above any of these, the corresponding
// assert fails at compile time and the canonical GLSL header MUST be
// updated to match (and all in-tree `effect.frag` files re-baked, since
// their `customParams[N]` `#define` macros encode the slot positions).
//
// Every field declared in `animation_uniforms.glsl` is pinned here. A
// previous revision asserted only iTime / iResolution / customParams /
// customColors, which left the door open to a reorder that swapped
// {iTimeDelta, iFrame, appField0, appField1, iMouse, iDate} amongst
// themselves while preserving the four asserted offsets — silent
// miscompile for any future animation shader that reads the in-between
// fields. The full coverage below catches that.
static_assert(offsetof(BaseUniforms, qt_Matrix) == 0,
              "BaseUniforms::qt_Matrix must remain at std140 offset 0 (animation UBO contract)");
static_assert(offsetof(BaseUniforms, qt_Opacity) == 64,
              "BaseUniforms::qt_Opacity must remain at std140 offset 64 (animation UBO contract)");
static_assert(offsetof(BaseUniforms, iTime) == 68,
              "BaseUniforms::iTime must remain at std140 offset 68 (animation UBO contract)");
static_assert(offsetof(BaseUniforms, iTimeDelta) == 72,
              "BaseUniforms::iTimeDelta must remain at std140 offset 72 (animation UBO contract)");
static_assert(offsetof(BaseUniforms, iFrame) == 76,
              "BaseUniforms::iFrame must remain at std140 offset 76 (animation UBO contract)");
static_assert(offsetof(BaseUniforms, iResolution) == 80,
              "BaseUniforms::iResolution must remain at std140 offset 80 (animation UBO contract)");
static_assert(offsetof(BaseUniforms, appField0) == 88,
              "BaseUniforms::appField0 must remain at std140 offset 88 (animation UBO contract)");
static_assert(offsetof(BaseUniforms, appField1) == 92,
              "BaseUniforms::appField1 must remain at std140 offset 92 (animation UBO contract)");
static_assert(offsetof(BaseUniforms, iMouse) == 96,
              "BaseUniforms::iMouse must remain at std140 offset 96 (animation UBO contract)");
static_assert(offsetof(BaseUniforms, iDate) == 112,
              "BaseUniforms::iDate must remain at std140 offset 112 (animation UBO contract)");
static_assert(offsetof(BaseUniforms, customParams) == 128,
              "BaseUniforms::customParams must remain at std140 offset 128 (animation UBO contract)");
static_assert(offsetof(BaseUniforms, customColors) == 256,
              "BaseUniforms::customColors must remain at std140 offset 256 (animation UBO contract)");
static_assert(offsetof(BaseUniforms, iChannelResolution) == 512,
              "BaseUniforms::iChannelResolution must remain at std140 offset 512 (animation UBO contract)");
static_assert(offsetof(BaseUniforms, iAudioSpectrumSize) == 576,
              "BaseUniforms::iAudioSpectrumSize must remain at std140 offset 576 (animation UBO contract)");
static_assert(offsetof(BaseUniforms, iFlipBufferY) == 580,
              "BaseUniforms::iFlipBufferY must remain at std140 offset 580 (animation UBO contract)");
static_assert(offsetof(BaseUniforms, iTextureResolution) == 592,
              "BaseUniforms::iTextureResolution must remain at std140 offset 592 (animation UBO contract)");
static_assert(offsetof(BaseUniforms, iTimeHi) == 656,
              "BaseUniforms::iTimeHi must remain at std140 offset 656 (animation UBO contract)");
static_assert(offsetof(BaseUniforms, iIsReversed) == 660,
              "BaseUniforms::iIsReversed must remain at std140 offset 660 (animation UBO contract)");
 
namespace UboRegions {
 
// Transform and opacity from Qt scene graph (mat4 + float)
constexpr size_t K_MATRIX_OPACITY_OFFSET = 0;
constexpr size_t K_MATRIX_OPACITY_SIZE = offsetof(BaseUniforms, iTime); // 68 bytes
 
// Animation time block (iTime, iTimeDelta, iFrame)
constexpr size_t K_TIME_BLOCK_OFFSET = offsetof(BaseUniforms, iTime);
constexpr size_t K_TIME_BLOCK_SIZE = sizeof(float) + sizeof(float) + sizeof(int); // 12 bytes
 
// App-fields block (appField0, appField1) — 8 bytes at offset 88.
// Uploaded as a tiny standalone region when ONLY the consumer's escape-hatch
// fields changed. Without this granular region, every appField update would
// trigger a full scene-header re-upload (~592 bytes).
constexpr size_t K_APP_FIELDS_OFFSET = offsetof(BaseUniforms, appField0);
constexpr size_t K_APP_FIELDS_SIZE = sizeof(int) * 2;
 
// Scene header: iResolution through end of struct.
// Covers iResolution, appFields, iMouse, iDate, customParams, customColors,
// iChannelResolution, iAudioSpectrumSize, iFlipBufferY, iTextureResolution,
// iTimeHi, iIsReversed, and the trailing std140 pad. Sized to the
// remainder of BaseUniforms so any field added at or after offset 80
// (iResolution) is automatically covered by m_sceneDataDirty's upload
// path without needing a per-field dirty flag.
//
// History: an earlier revision capped K_SCENE_HEADER_SIZE at offsetof(iTimeHi),
// leaving the gap from offsetof(iTimeHi) + sizeof(iTimeHi) (660) to
// sizeof(BaseUniforms) (672) un-uploaded by partial-update paths. The
// new iIsReversed field at offset 660 landed exactly in that gap and
// silently failed to propagate to the GPU after the first full upload —
// asymmetric direction-aware shaders read stale values forever.
//
// WARNING: a new field added BEFORE iResolution (offset < 80) must
// extend K_MATRIX_OPACITY or land in its own region; this scene-header
// range only covers offsets [80, sizeof(BaseUniforms)).
constexpr size_t K_SCENE_HEADER_OFFSET = offsetof(BaseUniforms, iResolution);
constexpr size_t K_SCENE_HEADER_SIZE = sizeof(BaseUniforms) - K_SCENE_HEADER_OFFSET;
 
// iTimeHi block: a granular 4-byte upload region for the time-wrap-only
// path (m_timeHiDirty fires every ~30 s when iTime crosses the wrap
// boundary). Subsumed by K_SCENE_HEADER, so when m_sceneDataDirty also
// fires for the same frame the upload site below skips this granular
// write to avoid the duplicate 4-byte transfer.
constexpr size_t K_TIME_HI_OFFSET = offsetof(BaseUniforms, iTimeHi);
constexpr size_t K_TIME_HI_SIZE = sizeof(float);
 
// Verify K_SCENE_HEADER reaches end of BaseUniforms — a new field added
// at or after offset 80 must land inside this range. Without this assert,
// adding a field beyond the previous K_SCENE_HEADER end (the iTimeHi-
// based cap) would silently regress the gap-bug fixed by extending the
// region. Pin via the actual LAST field's offset+size so a developer
// who manually narrows K_SCENE_HEADER_SIZE (e.g. `= offsetof(iTimeHi) -
// K_SCENE_HEADER_OFFSET`, which is exactly the original regression)
// fails to build. The earlier formulation
// `K_SCENE_HEADER_OFFSET + K_SCENE_HEADER_SIZE == sizeof(BaseUniforms)`
// was tautological because K_SCENE_HEADER_SIZE is itself defined as
// `sizeof(BaseUniforms) - K_SCENE_HEADER_OFFSET` — the assert reduced
// to `sizeof == sizeof` and could not catch the regression it claimed
// to defend.
static_assert(offsetof(BaseUniforms, _pad_after_iIsReversed) + sizeof(BaseUniforms::_pad_after_iIsReversed)
                  <= K_SCENE_HEADER_OFFSET + K_SCENE_HEADER_SIZE,
              "K_SCENE_HEADER must cover the trailing _pad_after_iIsReversed bytes — "
              "narrowing K_SCENE_HEADER_SIZE leaves the iIsReversed gap unmapped");
static_assert(K_SCENE_HEADER_OFFSET + K_SCENE_HEADER_SIZE == sizeof(BaseUniforms),
              "K_SCENE_HEADER must reach end-of-BaseUniforms — defensive companion to "
              "the trailing-field assert above");
// Verify K_TIME_HI is fully nested inside K_SCENE_HEADER so the upload
// site can skip the granular write when both dirty flags fire.
static_assert(K_TIME_HI_OFFSET >= K_SCENE_HEADER_OFFSET
                  && K_TIME_HI_OFFSET + K_TIME_HI_SIZE <= K_SCENE_HEADER_OFFSET + K_SCENE_HEADER_SIZE,
              "K_TIME_HI must be subsumed by K_SCENE_HEADER so a scene-data upload "
              "covers iTimeHi too without needing the m_timeHiDirty granular path");
// Verify K_APP_FIELDS is fully nested inside K_SCENE_HEADER for the
// same reason: the upload site uses an `else if` to skip the granular
// app-fields write when scene-data is also dirty (the broader upload
// already covers it). Pinning the nesting at compile time makes a
// future field-shuffle that breaks containment a build failure rather
// than a silent missed-upload regression.
static_assert(K_APP_FIELDS_OFFSET >= K_SCENE_HEADER_OFFSET
                  && K_APP_FIELDS_OFFSET + K_APP_FIELDS_SIZE <= K_SCENE_HEADER_OFFSET + K_SCENE_HEADER_SIZE,
              "K_APP_FIELDS must be subsumed by K_SCENE_HEADER so the scene-data upload "
              "covers appField0/appField1 too without needing the m_appFieldsDirty granular path");
 
// Total base size (for extension offset calculation)
constexpr size_t K_BASE_SIZE = sizeof(BaseUniforms);
 
} // namespace UboRegions
 
} // namespace PhosphorShaders