Class GLShader

java.lang.Object
org.javagi.base.ProxyInstance
org.gnome.gobject.TypeInstance
org.gnome.gobject.GObject
org.gnome.gsk.GLShader
All Implemented Interfaces:
Proxy
@Generated("org.javagi.JavaGI") @Deprecated public class GLShader extends GObject
Deprecated.
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.

GskGLShader 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:

 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 GskGLShaderNode, 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 `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:

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:

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 [method@Gsk.GLShader.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

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;
}

  • Constructor Details

    • GLShader

      public GLShader(MemorySegment address)
      Deprecated.
      Create a GLShader instance for the provided memory address.
      Parameters:
      address - the memory address of the native object

    • GLShader

      public GLShader()
      Deprecated.
      Create a new GLShader.

  • Method Details

    • getType

      public static @Nullable Type getType()
      Deprecated.
      Get the GType of the GLShader class.
      Returns:
      the GType

    • getMemoryLayout

      public static MemoryLayout getMemoryLayout()
      Deprecated.
      The memory layout of the native struct.
      Returns:
      the memory layout

    • asParent

      protected GLShader asParent()
      Deprecated.
      Return this instance as if it were its parent type. Comparable to the Java super keyword, but ensures the parent typeclass is also used in native code.
      Overrides:
      asParent in class GObject
      Returns:
      the instance as if it were its parent type

    • fromBytes

      @Deprecated public static GLShader fromBytes(byte[] sourcecode)
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.
      Creates a GskGLShader that will render pixels using the specified code.
      Parameters:
      sourcecode - GLSL sourcecode for the shader, as a GBytes
      Returns:
      A new GskGLShader

    • fromResource

      @Deprecated public static GLShader fromResource(String resourcePath)
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.
      Creates a GskGLShader that will render pixels using the specified code.
      Parameters:
      resourcePath - path to a resource that contains the GLSL sourcecode for the shader
      Returns:
      A new GskGLShader

    • compile

      @Deprecated public boolean compile(Renderer renderer) throws GErrorException
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

      Tries to compile the this GLShader 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.

      Parameters:
      renderer - a GskRenderer
      Returns:
      true on success, false if an error occurred
      Throws:
      GErrorException - see GError

    • findUniformByName

      @Deprecated public int findUniformByName(String name)
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.
      Looks for a uniform by the name name, and returns the index of the uniform, or -1 if it was not found.
      Parameters:
      name - uniform name
      Returns:
      The index of the uniform, or -1

    • formatArgs

      @Deprecated public byte[] formatArgs(Object... varargs)
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

      Formats the uniform data as needed for feeding the named uniforms values into the shader.

      The argument list is a list of pairs of names, and values for the types that match the declared uniforms (i.e. double/int/guint/gboolean for primitive values and graphene_vecN_t * for vecN uniforms).

      Any uniforms of the shader that are not included in the argument list are zero-initialized.

      Parameters:
      varargs - name-Value pairs for the uniforms of shader, ending with a null name
      Returns:
      A newly allocated block of data which can be passed to GLShaderNode(GLShader, Rect, byte[], RenderNode[]).

    • getArgBool

      @Deprecated public boolean getArgBool(byte[] args, int idx)
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

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

      The uniform must be of bool type.

      Parameters:
      args - uniform arguments
      idx - index of the uniform
      Returns:
      The value

    • getArgFloat

      @Deprecated public float getArgFloat(byte[] args, int idx)
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

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

      The uniform must be of float type.

      Parameters:
      args - uniform arguments
      idx - index of the uniform
      Returns:
      The value

    • getArgInt

      @Deprecated public int getArgInt(byte[] args, int idx)
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

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

      The uniform must be of int type.

      Parameters:
      args - uniform arguments
      idx - index of the uniform
      Returns:
      The value

    • getArgUint

      @Deprecated public int getArgUint(byte[] args, int idx)
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

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

      The uniform must be of uint type.

      Parameters:
      args - uniform arguments
      idx - index of the uniform
      Returns:
      The value

    • getArgVec2

      @Deprecated public void getArgVec2(byte[] args, int idx, Vec2 outValue)
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

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

      The uniform must be of vec2 type.

      Parameters:
      args - uniform arguments
      idx - index of the uniform
      outValue - location to store the uniform value in

    • getArgVec3

      @Deprecated public void getArgVec3(byte[] args, int idx, Vec3 outValue)
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

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

      The uniform must be of vec3 type.

      Parameters:
      args - uniform arguments
      idx - index of the uniform
      outValue - location to store the uniform value in

    • getArgVec4

      @Deprecated public void getArgVec4(byte[] args, int idx, Vec4 outValue)
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

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

      The uniform must be of vec4 type.

      Parameters:
      args - uniform arguments
      idx - index of the uniform
      outValue - location to store set the uniform value in

    • getArgsSize

      @Deprecated public long getArgsSize()
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.
      Get the size of the data block used to specify arguments for this shader.
      Returns:
      The size of the data block

    • getNTextures

      @Deprecated public int getNTextures()
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.

      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.

      Returns:
      The number of texture inputs required by this GLShader

    • getNUniforms

      @Deprecated public int getNUniforms()
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.
      Get the number of declared uniforms for this shader.
      Returns:
      The number of declared uniforms

    • getResource

      @Deprecated public @Nullable String getResource()
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.
      Gets the resource path for the GLSL sourcecode being used to render this shader.
      Returns:
      The resource path for the shader

    • getSource

      @Deprecated public byte[] getSource()
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.
      Gets the GLSL sourcecode being used to render this shader.
      Returns:
      The source code for the shader

    • getUniformName

      @Deprecated public String getUniformName(int idx)
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.
      Get the name of the declared uniform for this shader at index idx.
      Parameters:
      idx - index of the uniform
      Returns:
      The name of the declared uniform

    • getUniformOffset

      @Deprecated public int getUniformOffset(int idx)
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.
      Get the offset into the data block where data for this uniforms is stored.
      Parameters:
      idx - index of the uniform
      Returns:
      The data offset

    • getUniformType

      @Deprecated public GLUniformType getUniformType(int idx)
      Deprecated.
      GTK's new Vulkan-focused rendering does not support this feature. Use GtkGLArea for OpenGL rendering.
      Get the type of the declared uniform for this shader at index idx.
      Parameters:
      idx - index of the uniform
      Returns:
      The type of the declared uniform

    • builder

      public static GLShader.Builder<? extends GLShader.Builder> builder()
      Deprecated.
      A GLShader.Builder object constructs a GLShader with the specified properties. Use the various set...() methods to set properties, and finish construction with GLShader.Builder.build().
      Returns:
      the builder object