Struct GLShader 

pub struct GLShader { /* private fields */ }

👎Deprecated:

Since 4.16

This feature was deprecated in GTK 4.16 after the new rendering infrastructure introduced in 4.14 did not support it. The lack of Vulkan integration would have made it a very hard feature to support. If you want to use OpenGL directly, you should look at GtkGLArea, which uses a different approach and is still well-supported. Implements a fragment shader using GLSL.

A fragment shader gets the coordinates being rendered as input and produces the pixel values for that particular pixel. Additionally, the shader can declare a set of other input arguments, called uniforms (as they are uniform over all the calls to your shader in each instance of use). A shader can also receive up to 4 textures that it can use as input when producing the pixel data.

GLShader is usually used with gtk_snapshot_push_gl_shader() to produce a GLShaderNode in the rendering hierarchy, and then its input textures are constructed by rendering the child nodes to textures before rendering the shader node itself. (You can pass texture nodes as children if you want to directly use a texture as input).

The actual shader code is GLSL code that gets combined with some other code into the fragment shader. Since the exact capabilities of the GPU driver differs between different OpenGL drivers and hardware, GTK adds some defines that you can use to ensure your GLSL code runs on as many drivers as it can.

If the OpenGL driver is GLES, then the shader language version is set to 100, and GSK_GLES will be defined in the shader.

Otherwise, if the OpenGL driver does not support the 3.2 core profile, then the shader will run with language version 110 for GL2 and 130 for GL3, and GSK_LEGACY will be defined in the shader.

If the OpenGL driver supports the 3.2 code profile, it will be used, the shader language version is set to 150, and GSK_GL3 will be defined in the shader.

The main function the shader must implement is:

⚠️ The following code is in glsl ⚠️

 void mainImage(out vec4 fragColor,
                in vec2 fragCoord,
                in vec2 resolution,
                in vec2 uv)

Where the input @fragCoord is the coordinate of the pixel we’re currently rendering, relative to the boundary rectangle that was specified in the GLShaderNode, and @resolution is the width and height of that rectangle. This is in the typical GTK coordinate system with the origin in the top left. @uv contains the u and v coordinates that can be used to index a texture at the corresponding point. These coordinates are in the [0..1]x[0..1] region, with 0, 0 being in the lower left corder (which is typical for OpenGL).

The output @fragColor should be a RGBA color (with premultiplied alpha) that will be used as the output for the specified pixel location. Note that this output will be automatically clipped to the clip region of the glshader node.

In addition to the function arguments the shader can define up to 4 uniforms for textures which must be called u_textureN (i.e. u_texture1 to u_texture4) as well as any custom uniforms you want of types int, uint, bool, float, vec2, vec3 or vec4.

All textures sources contain premultiplied alpha colors, but if some there are outer sources of colors there is a gsk_premultiply() helper to compute premultiplication when needed.

Note that GTK parses the uniform declarations, so each uniform has to be on a line by itself with no other code, like so:

⚠️ The following code is in glsl ⚠️

uniform float u_time;
uniform vec3 u_color;
uniform sampler2D u_texture1;
uniform sampler2D u_texture2;

GTK uses the “gsk” namespace in the symbols it uses in the shader, so your code should not use any symbols with the prefix gsk or GSK. There are some helper functions declared that you can use:

⚠️ The following code is in glsl ⚠️

vec4 GskTexture(sampler2D sampler, vec2 texCoords);

This samples a texture (e.g. u_texture1) at the specified coordinates, and contains some helper ifdefs to ensure that it works on all OpenGL versions.

You can compile the shader yourself using compile(), otherwise the GSK renderer will do it when it handling the glshader node. If errors occurs, the returned @error will include the glsl sources, so you can see what GSK was passing to the compiler. You can also set GSK_DEBUG=shaders in the environment to see the sources and other relevant information about all shaders that GSK is handling.

An example shader

⚠️ The following code is in glsl ⚠️

uniform float position;
uniform sampler2D u_texture1;
uniform sampler2D u_texture2;

void mainImage(out vec4 fragColor,
               in vec2 fragCoord,
               in vec2 resolution,
               in vec2 uv) {
  vec4 source1 = GskTexture(u_texture1, uv);
  vec4 source2 = GskTexture(u_texture2, uv);

  fragColor = position * source1 + (1.0 - position) * source2;
}

Properties

resource

Resource containing the source code for the shader.

If the shader source is not coming from a resource, this will be None.

Readable | Writable | Construct Only

source

The source code for the shader, as a GBytes.

Readable | Writable | Construct Only

GLib type: GObject with reference counted clone semantics.

Implementations

impl GLShader

pub fn from_bytes(sourcecode: &Bytes) -> GLShader

👎Deprecated:

Since 4.16

Creates a GLShader that will render pixels using the specified code.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

sourcecode

GLSL sourcecode for the shader, as a GBytes

Returns

A new GLShader

pub fn from_resource(resource_path: &str) -> GLShader

👎Deprecated:

Since 4.16

Creates a GLShader that will render pixels using the specified code.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

resource_path

path to a resource that contains the GLSL sourcecode for the shader

Returns

A new GLShader

pub fn builder() -> GLShaderBuilder

👎Deprecated:

Since 4.16

Creates a new builder-pattern struct instance to construct GLShader objects.

This method returns an instance of GLShaderBuilder which can be used to create GLShader objects.

pub fn compile(&self, renderer: &impl IsA<Renderer>) -> Result<(), Error>

👎Deprecated:

Since 4.16

Tries to compile the @self for the given @renderer.

If there is a problem, this function returns false and reports an error. You should use this function before relying on the shader for rendering and use a fallback with a simpler shader or without shaders if it fails.

Note that this will modify the rendering state (for example change the current GL context) and requires the renderer to be set up. This means that the widget has to be realized. Commonly you want to call this from the realize signal of a widget, or during widget snapshot.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

renderer

a Renderer

Returns

true on success, false if an error occurred

pub fn find_uniform_by_name(&self, name: &str) -> i32

👎Deprecated:

Since 4.16

Looks for a uniform by the name @name, and returns the index of the uniform, or -1 if it was not found.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

name

uniform name

Returns

The index of the uniform, or -1

pub fn arg_bool(&self, args: &Bytes, idx: i32) -> bool

👎Deprecated:

Since 4.16

Gets the value of the uniform @idx in the @args block.

The uniform must be of bool type.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

args

uniform arguments

idx

index of the uniform

Returns

The value

pub fn arg_float(&self, args: &Bytes, idx: i32) -> f32

👎Deprecated:

Since 4.16

Gets the value of the uniform @idx in the @args block.

The uniform must be of float type.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

args

uniform arguments

idx

index of the uniform

Returns

The value

pub fn arg_int(&self, args: &Bytes, idx: i32) -> i32

👎Deprecated:

Since 4.16

Gets the value of the uniform @idx in the @args block.

The uniform must be of int type.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

args

uniform arguments

idx

index of the uniform

Returns

The value

pub fn arg_uint(&self, args: &Bytes, idx: i32) -> u32

👎Deprecated:

Since 4.16

Gets the value of the uniform @idx in the @args block.

The uniform must be of uint type.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

args

uniform arguments

idx

index of the uniform

Returns

The value

pub fn args_size(&self) -> usize

👎Deprecated:

Since 4.16

Get the size of the data block used to specify arguments for this shader.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

Returns

The size of the data block

pub fn n_textures(&self) -> i32

👎Deprecated:

Since 4.16

Returns the number of textures that the shader requires.

This can be used to check that the a passed shader works in your usecase. It is determined by looking at the highest u_textureN value that the shader defines.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

Returns

The number of texture inputs required by @self

pub fn n_uniforms(&self) -> i32

👎Deprecated:

Since 4.16

Get the number of declared uniforms for this shader.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

Returns

The number of declared uniforms

pub fn resource(&self) -> Option<GString>

👎Deprecated:

Since 4.16

Gets the resource path for the GLSL sourcecode being used to render this shader.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

Returns

The resource path for the shader

pub fn source(&self) -> Bytes

👎Deprecated:

Since 4.16

Gets the GLSL sourcecode being used to render this shader.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

Returns

The source code for the shader

pub fn uniform_name(&self, idx: i32) -> GString

👎Deprecated:

Since 4.16

Get the name of the declared uniform for this shader at index @idx.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

idx

index of the uniform

Returns

The name of the declared uniform

pub fn uniform_offset(&self, idx: i32) -> i32

👎Deprecated:

Since 4.16

Get the offset into the data block where data for this uniforms is stored.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

idx

index of the uniform

Returns

The data offset

pub fn uniform_type(&self, idx: i32) -> GLUniformType

👎Deprecated:

Since 4.16

Get the type of the declared uniform for this shader at index @idx.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

idx

index of the uniform

Returns

The type of the declared uniform

impl GLShader

pub fn arg_vec2(&self, args: &Bytes, idx: i32) -> Vec2

Gets the value of the uniform @idx in the @args block.

The uniform must be of vec2 type.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

args

uniform arguments

idx

index of the uniform

out_value

location to store the uniform value in

pub fn arg_vec3(&self, args: &Bytes, idx: i32) -> Vec3

Gets the value of the uniform @idx in the @args block.

The uniform must be of vec3 type.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

args

uniform arguments

idx

index of the uniform

out_value

location to store the uniform value in

pub fn arg_vec4(&self, args: &Bytes, idx: i32) -> Vec4

Gets the value of the uniform @idx in the @args block.

The uniform must be of vec4 type.

Deprecated since 4.16

GTK’s new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

args

uniform arguments

idx

index of the uniform

out_value

location to store set the uniform value in

Trait Implementations

impl Clone for GLShader

fn clone(&self) -> Self

Makes a clone of this shared reference.

This increments the strong reference count of the object. Dropping the object will decrement it again.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for GLShader

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for GLShader

impl HasParamSpec for GLShader

type ParamSpec = ParamSpecObject

type SetValue = GLShader

Preferred value to be used as setter for the associated ParamSpec.

type BuilderFn = fn(&str) -> ParamSpecObjectBuilder<'_, GLShader>

fn param_spec_builder() -> Self::BuilderFn

impl Hash for GLShader

fn hash<H>(&self, state: &mut H)

where H: Hasher,

Hashes the memory address of this object.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for GLShader

fn cmp(&self, other: &Self) -> Ordering

Comparison for two GObjects.

Compares the memory addresses of the provided objects.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl ParentClassIs for GLShader

type Parent = Object

impl<OT: ObjectType> PartialEq<OT> for GLShader

fn eq(&self, other: &OT) -> bool

Equality for two GObjects.

Two GObjects are equal if their memory addresses are equal.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<OT: ObjectType> PartialOrd<OT> for GLShader

fn partial_cmp(&self, other: &OT) -> Option<Ordering>

Partial comparison for two GObjects.

Compares the memory addresses of the provided objects.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl StaticType for GLShader

fn static_type() -> Type

Returns the type identifier of Self.