// Copyright (C) 2020 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only

/*!
\page qt-add-shaders.html
\ingroup cmake-commands-qtshadertools

\title qt_add_shaders
\keyword qt6_add_shaders

\summary {Compiles shaders and adds them to a Qt resource.}

\include cmake-find-package-shadertools.qdocinc

\section1 Synopsis

\badcode
qt_add_shaders(<target> <name>
               PREFIX <path>
               FILES <file,...>
               [BASE <path>]
               [GLSL <version,...>]
               [NOGLSL]
               [HLSL <version,...>]
               [NOHLSL]
               [MSL <version,...>]
               [NOMSL]
               [BATCHABLE]
               [ZORDER_LOC <number>]
               [PERTARGETCOMPILE]
               [TESSELLATION]
               [TESSELLATION_VERTEX_COUNT <count>]
               [TESSELLATION_MODE <mode>]
               [VIEW_COUNT <count>]
               [MULTIVIEW]
               [PRECOMPILE]
               [OPTIMIZED]
               [DEBUGINFO]
               [QUIET]
               [DEFINES <name=value,...>]
               [OUTPUTS <file,...>]
               [ORIGINAL_FILES <file,...>]
               [OUTPUT_TARGETS <variable>]
               [MEDIUMP])
\endcode

\versionlessCMakeCommandsNote qt6_add_shaders()

\section1 Description

Invokes the \l{QSB Manual}{qsb} tool at build time on each shader source
file listed in \c FILES, and adds the resulting \c{.qsb} files to the Qt
resource system under the resource prefix given by \c PREFIX.

By default, \c qt_add_shaders invokes \c qsb as follows:

\badcode
qsb --glsl "100 es,120,150" --hlsl 50 --msl 12 -o <output>.qsb <input>
\endcode

This produces a package containing SPIR-V (for Vulkan 1.0), GLSL ES 100
(for OpenGL ES 2.0 and newer), GLSL 120 (for non-core profile OpenGL),
GLSL 150 (for core profile OpenGL), HLSL for Shader Model 5.0 (Direct3D
11.1), and Metal Shading Language 1.2 (Metal).

On WebAssembly, the defaults change to:

\badcode
qsb --glsl "100 es,300 es" -o <output>.qsb <input>
\endcode

which generates shaders compatible with WebGL 1 and WebGL 2.

The original shader source files are not embedded in the application's
executable and do not need to be shipped. Build errors from the
\c glslang compiler are reported at build time and the build fails.
Changes to shader source files are picked up automatically on the next
build, like any other source file.

\note The \c target passed as the first argument must exist before
\c qt_add_shaders is called.

\note Multiple \c qt_add_shaders calls are supported. The \c name
argument must be unique for each call on the same target.

\section1 Shader type

The type of shader is deduced from the file extension:

\list
\li \c .vert — vertex shaders
\li \c .tesc — tessellation control shaders
\li \c .tese — tessellation evaluation shaders
\li \c .geom — geometry shaders
\li \c .frag — fragment (pixel) shaders
\li \c .comp — compute shaders
\endlist

\note Tessellation control and evaluation shaders are not currently
supported with Direct 3D (HLSL). A possible workaround is to manually
create hull and domain shaders and inject them via the
\l{Substituting Hand-Crafted Shaders}{file substitution syntax} in
\c FILES.

\section1 Target language options

\list

\li \c GLSL — Requests GLSL source for the given comma-separated list of
versions. For example, a compute shader typically needs
\c{"310 es,430"} rather than the defaults. The space before the
\c es suffix is optional.

\li \c NOGLSL — Disables GLSL source generation. Suitable for
applications that do not target OpenGL at all.

\li \c HLSL — Requests HLSL source for the given list of Shader Model
versions. \c qsb uses GLSL-style numbering: \c 50 is Shader Model 5.0,
\c 51 is 5.1.

\li \c NOHLSL — Disables HLSL source generation. Suitable for
applications that do not target Direct 3D at all.

\li \c MSL — Requests Metal Shading Language source for the given
version. \c 12 corresponds to MSL 1.2, \c 20 to 2.0.

\li \c NOMSL — Disables MSL source generation. Suitable for applications
that do not target Metal at all.

\endlist

Example — raising the GLSL version for shaders that use OpenGL 3.x
features:

\badcode
qt_add_shaders(exampleapp "res_gl3shaders"
    GLSL "300es,330"
    PREFIX
        "/shaders"
    FILES
        shaders/ssao.vert
        shaders/ssao.frag
        shaders/skybox.vert
        shaders/skybox.frag
)
\endcode

\note The space before the \c es suffix is optional.

\section1 Qt Quick options

\list

\li \c BATCHABLE — Required for vertex shaders used with Qt Quick, either
in a \l ShaderEffect or a \l QSGMaterialShader. Has no effect on fragment
or compute shaders; different shader types can safely be mixed in the same
\c FILES list because the keyword is only applied to \c{.vert} files.
Equivalent to the \c{-b} argument of \c qsb.

\li \c ZORDER_LOC — When \c BATCHABLE is specified, an extra vertex input
is injected at location \c 7 by default. Use this keyword to change the
location to avoid clashing with an existing input.

\endlist

\section1 Tessellation options

\list

\li \c TESSELLATION — Indicates that the shaders belong to a tessellation
pipeline. Relevant only for vertex shaders when MSL generation is not
disabled; enables special processing and translation for those shaders
when targeting Metal.
\cmakeoptionsince 6.5

\li \c TESSELLATION_VERTEX_COUNT — Specifies the output vertex count from
the tessellation control stage. Mandatory for tessellation evaluation
shaders targeting Metal. The default is \c 3. If the value does not match
the control stage, the generated MSL code will not function correctly.
\cmakeoptionsince 6.5

\li \c TESSELLATION_MODE — Specifies the tessellation mode: \c{"triangles"}
(default) or \c{"quads"}. Must be set when a tessellation control shader
is listed in \c FILES, and must match the tessellation evaluation stage.
\cmakeoptionsince 6.5

\endlist

\section1 Multiview options

\list

\li \c VIEW_COUNT — Specifies the number of views for multiview rendering
(GL_OVR_multiview2, VK_KHR_multiview, D3D12 view instancing, etc.).
Set to a value of 2 or greater for the relevant vertex shaders to produce
correct GLSL output. Setting \c VIEW_COUNT injects the
\c{QSHADER_VIEW_COUNT} preprocessor define and, for values of 2 or
greater, automatically adds \c{#extension GL_EXT_multiview : require} in
vertex shaders. Minimum required language versions when using multiview:
GLSL 330 and 300 es, HLSL 61. Avoid setting \c VIEW_COUNT on vertex
shaders that do not use multiview; group them into separate
\c qt_add_shaders() calls instead.
\cmakeoptionsince 6.7

\li \c MULTIVIEW — Generates both a non-multiview and a view-count-2 set
of shaders. This is a convenience equivalent to two separate
\c qt_add_shaders() calls with the appropriate GLSL/HLSL/MSL/VIEW_COUNT
arguments. The implicit settings for the multiview variants are GLSL
\c{330,300es}, HLSL \c 61, MSL \c 21, and VIEW_COUNT \c 2. Multiview
variants are stored with a \c{.mv2qsb} suffix appended to the \c{.qsb}
filename.
\cmakeoptionsince 6.8

\endlist

\section1 External tool options

\list

\li \c PRECOMPILE — On Windows (when HLSL is not disabled), invokes
\c fxc from the Windows SDK to compile HLSL source to DXBC bytecode at
build time rather than at run time. The resulting \c{.qsb} file contains
the compiled intermediate bytecode rather than the original HLSL source.
Equivalent to the \c{-c} argument of \c qsb. Has no effect on
non-Windows platforms.

\li \c OPTIMIZED — Invokes \c spirv-opt from the Vulkan SDK to perform
optimizations on the SPIR-V bytecode. Equivalent to the \c{-O} argument
of \c qsb.

\endlist

\section1 Other options

\list

\li \c BASE — A path prefix used to compute the alias (in-resource name)
of the generated \c{.qsb} files. When \c BASE is set, each output path
is made relative to \c BASE rather than kept as-is. This is analogous to
the \c BASE argument of \l{qt_add_resources}.

\li \c DEFINES — Defines macros active during shader compilation, in the
form \c{"name1=value1;name2=value2"}. Alternatively, entries can be
separated by newlines, just like \c FILES. Equivalent to the \c{-D}
argument of \c qsb.

\li \c OUTPUTS — When the generated \c{.qsb} filename must differ from
the source filename (for example, when one shader file serves as the
source for multiple \c{.qsb} files differentiated by \c DEFINES), provide
one output filename per entry in \c FILES. Each name is passed via the
\c{-o} argument to \c qsb instead of appending \c{.qsb} to the source
filename.

\li \c ORIGINAL_FILES — When the \c{.qsb} files should depend on shader
source files different from those in \c FILES, supply one entry per
\c FILES item here. When present, the corresponding \c ORIGINAL_FILES
entry is written into the CMake dependency file via \c{--orig-file} and
is added to the \c DEPENDS clause of the underlying
\c add_custom_command(). This is useful when the files passed to
\c qt_add_shaders() are intermediate generated assets and the final
\c{.qsb} files should track the original source files.

\li \c PERTARGETCOMPILE — Compiles to SPIR-V and translates to each
output language version separately, once per target language. This is
slower than the default single-pass approach but allows conditional
compilation via the \c{QSHADER_<LANG>[_VERSION]} preprocessor macros.
Equivalent to the \c{-p} argument of \c qsb.

\li \c DEBUGINFO — Generates full debug information for SPIR-V, enabling
tools such as \l{https://renderdoc.org/}{RenderDoc} to display the full
source when inspecting a pipeline or performing vertex/fragment debugging.
When \c PRECOMPILE is also set, instructs \c fxc to embed debug
information in the generated DXBC bytecode. Equivalent to the \c{-g}
argument of \c qsb.

\li \c QUIET — Suppresses debug and warning output from \c qsb. Only
fatal errors are printed. Equivalent to the \c{-s} argument of \c qsb.

\li \c OUTPUT_TARGETS — When using \c qt_add_shaders with static
libraries, one or more special targets are generated. Pass a variable
name to retrieve those targets for further processing.

\li \c MEDIUMP — Requests medium-precision floats as the default in GLSL
ES fragment shaders. Has no effect on other targets, including non-ES
GLSL.

\endlist

\section1 Substituting hand-crafted shaders

The \c FILES list supports a special syntax for replacing a specific
shader variant in the \c{.qsb} package with a hand-crafted file.
This is equivalent to the \c{-r} option of \c qsb:

\badcode
FILES
    "shaders/externalsampler.frag@glsl,100es,shaders/externalsampler_gles.frag"
\endcode

A filename may be followed by any number of \c{@}-separated replacement
specifications. Each specifies the shading language, the version, and the
file to read, separated by commas. \c{@} characters within the filename
or directory path are handled correctly and do not affect parsing. See the
\l{QSB Manual} for details.

\section1 Examples

\section2 Basic usage

\badcode
find_package(Qt6 COMPONENTS ShaderTools)

qt6_add_executable(exampleapp main.cpp)

qt6_add_shaders(exampleapp "exampleapp_shaders"
    PREFIX
        "/"
    FILES
        "wobble.frag"
)
\endcode

This makes \c{:/wobble.frag.qsb} available at run time. The original
\c{wobble.frag} source is not included in the executable.

\section2 Tessellation

A graphics pipeline with four stages — vertex (\c{vertex.vert}),
tessellation control (\c{tess.tesc}), tessellation evaluation
(\c{tess.tese}), and fragment (\c{fragment.frag}) — can be set up as
follows.

The vertex and fragment shaders are compiled first. \c TESSELLATION
enables special Metal translation for the vertex shader, and the GLSL
version is raised because tessellation requires OpenGL 4.x or ES 3.2.

\badcode
qt6_add_shaders(project "shaders_tessellation_part1"
    PREFIX
        "/shaders"
    GLSL
        "410,320es"
    TESSELLATION
    FILES
        "vertex.vert"
        "fragment.frag"
)
\endcode

The tessellation shaders are listed in a separate call because \c NOHLSL
is needed for them—HLSL tessellation shaders must be written manually and
injected. The Metal tessellation parameters are specified explicitly.

\badcode
qt6_add_shaders(project "shaders_tessellation_part2"
    PREFIX
        "/shaders"
    NOHLSL
    GLSL
        "410,320es"
    TESSELLATION_VERTEX_COUNT
        3
    TESSELLATION_MODE
        "triangles"
    FILES
        "tess.tesc@hlsl,50,tess_hull.hlsl"
        "tess.tese@hlsl,50,tess_domain.hlsl"
)
\endcode

\note Writing hull and domain HLSL shaders manually is recommended for
advanced users only. Constructs such as constant buffers require special
care to keep resource interfaces and layouts compatible with the
SPIR-V/GLSL/MSL shaders.
*/
