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# Context

class Context

  Returned by `moderngl.create_context()`

  Class exposing OpenGL features.

  ModernGL objects can be created from this class.

## Objects

Context.program(vertex_shader: str, fragment_shader: str, geometry_shader: str, tess_control_shader: str, tess_evaluation_shader: str, varyings: Tuple[str, ...], fragment_outputs: Dict[str, int], varyings_capture_mode: str = 'interleaved') → Program

  Create a `Program` object.

  The `varyings` are only used when a transform program is created to specify the names of the output varyings to capture in the output buffer.

  `fragment_outputs` can be used to programmatically map named fragment shader outputs to a framebuffer attachment numbers. This can also be done by using `layout(location=N)` in the fragment shader.

  Parameters:

    - vertex_shader (str) – The vertex shader source.

    - fragment_shader (str) – The fragment shader source.

    - geometry_shader (str) – The geometry shader source.

    - tess_control_shader (str) – The tessellation control shader source.

    - tess_evaluation_shader (str) – The tessellation evaluation shader source.

    - varyings (list) – A list of varyings.

    - fragment_outputs (dict) – A dictionary of fragment outputs.

Context.buffer(data=None, reserve: int = 0, dynamic: bool = False) → Buffer

  Returns a new `Buffer` object.

  The data can be anything supporting the buffer interface.

  The data and reserve parameters are mutually exclusive.

  Parameters:

    - data (bytes) – Content of the new buffer.

    - reserve (int) – The number of bytes to reserve.

    - dynamic (bool) – Treat buffer as dynamic.

Context.vertex_array(program: Program, content: list, index_buffer: Buffer = None, index_element_size: int = 4, mode: int = ...) → VertexArray

  Returns a new `VertexArray` object.

  A VertexArray describes how buffers are read by a shader program. The content is a list of tuples containing a buffer, a format string and any number of attribute names. Attribute names are defined by the user in the Vertex Shader program stage.

  The default mode is `TRIANGLES`.

  Parameters:

    - program (Program) – The program used when rendering

    - content (list) – A list of (buffer, format, attributes). See Buffer Format.

    - index_buffer (Buffer) – An index buffer (optional)

    - index_element_size (int) – byte size of each index element, 1, 2 or 4.

    - skip_errors (bool) – Ignore errors during creation

    - mode (int) – The default draw mode (for example: `TRIANGLES`)

  Examples:

      # Empty vertext array (no attribute input)
      vao = ctx.vertex_array(program)

      # Multiple buffers
      vao = ctx.vertex_array(program, [
          (buffer1, '3f', 'in_position'),
          (buffer2, '3f', 'in_normal'),
      ])
      vao = ctx.vertex_array(
          program,
          [
              (buffer1, '3f', 'in_position'),
              (buffer2, '3f', 'in_normal'),
          ],
          index_buffer=ibo,
          index_element_size=2,  # 16 bit / 'u2' index buffer
      )

  Backward Compatible Version:

      # Simple version with a single buffer
      vao = ctx.vertex_array(program, buffer, 'in_position', 'in_normal')
      vao = ctx.vertex_array(program, buffer, 'in_position', 'in_normal', index_buffer=ibo)

Context.simple_vertex_array(...)

  Deprecated, use `Context.vertex_array()` instead.

Context.texture(size: Tuple[int, int], components: int, data: Any = None, samples: int = 0, alignment: int = 1, dtype: str = 'f1') → Texture

  Returns a new `Texture` object.

  A Texture is a 2D image that can be used for sampler2D uniforms or as render targets if framebuffers.

  Parameters:

    - size (tuple) – The width and height of the texture.

    - components (int) – The number of components 1, 2, 3 or 4.

    - data (bytes) – Content of the texture.

    - samples (int) – The number of samples. Value 0 means no multisample format.

    - alignment (int) – The byte alignment 1, 2, 4 or 8.

    - dtype (str) – Data type.

    - internal_format (int) – Override the internalformat of the texture (IF needed)

  Example:

      from PIL import Image

      img = Image.open(...).convert('RGBA')
      texture = ctx.texture(img.size, components=4, data=img.tobytes())

      # float texture
      texture = ctx.texture((64, 64), components=..., dtype='f4')

      # integer texture
      texture = ctx.texture((64, 64), components=..., dtype='i4')

  Note

  Do not play with `internal_format` unless you know exactly you are doing. This is an override to support sRGB and compressed textures if needed.

Context.framebuffer(color_attachments: List[Texture], depth_attachment: Texture = None) → Framebuffer

  Returns a new `Framebuffer` object.

  A Framebuffer is a collection of images that can be used as render targets. The images of the Framebuffer object can be either Textures or Renderbuffers.

  Parameters:

    - color_attachments (list) – A list of `Texture` or `Renderbuffer` objects.

    - depth_attachment (Texture) – The depth attachment.

Context.sampler(repeat_x: bool, repeat_y: bool, repeat_z: bool, filter: tuple, anisotropy: float, compare_func: str, border_color: tuple, min_lod: float, max_lod: float, texture: Texture) → Sampler

  Returns a new `Sampler` object.

  Samplers bind Textures to uniform samplers within a Program object. Binding a Sampler object also binds the texture object attached to it.

  Parameters:

    - repeat_x (bool) – Repeat texture on x

    - repeat_y (bool) – Repeat texture on y

    - repeat_z (bool) – Repeat texture on z

    - filter (tuple) – The min and max filter

    - anisotropy (float) – Number of samples for anisotropic filtering. Any value greater than 1.0 counts as a use of anisotropic filtering

    - compare_func (str) – Compare function for depth textures

    - border_color (tuple) – The (r, g, b, a) color for the texture border. When this value is set the `repeat_` values are overridden setting the texture wrap to return the border color when outside `[0, 1]` range.

    - min_lod (float) – Minimum level-of-detail parameter (Default `-1000.0`). This floating-point value limits the selection of highest resolution mipmap (lowest mipmap level)

    - max_lod (float) – Minimum level-of-detail parameter (Default `1000.0`). This floating-point value limits the selection of the lowest resolution mipmap (highest mipmap level)

    - texture (Texture) – The texture for this sampler

Context.depth_texture(size: Tuple[int, int], data: Any = None, samples: int = 0, alignment: int = 4) → Texture

  Returns a new `Texture` object.

  A depth texture can be used for sampler2D and sampler2DShadow uniforms and as a depth attachment for framebuffers.

  Parameters:

    - size (tuple) – The width and height of the texture.

    - data (bytes) – Content of the texture.

    - samples (int) – The number of samples. Value 0 means no multisample format.

    - alignment (int) – The byte alignment 1, 2, 4 or 8.

Context.texture3d(size: Tuple[int, int, int], components: int, data: Any = None, alignment: int = 1, dtype: str = 'f1') → Texture3D

  Returns a new `Texture3D` object.

  Parameters:

    - size (tuple) – The width, height and depth of the texture.

    - components (int) – The number of components 1, 2, 3 or 4.

    - data (bytes) – Content of the texture.

    - alignment (int) – The byte alignment 1, 2, 4 or 8.

    - dtype (str) – Data type.

Context.texture_array(size: Tuple[int, int, int], components: int, data: Any = None, *, alignment: int = 1, dtype: str = 'f1') → TextureArray

  Returns a new `TextureArray` object.

  Parameters:

    - size (tuple) – The `(width, height, layers)` of the texture.

    - components (int) – The number of components 1, 2, 3 or 4.

    - data (bytes) – Content of the texture. The size must be `(width, height * layers)` so each layer is stacked vertically.

    - alignment (int) – The byte alignment 1, 2, 4 or 8.

    - dtype (str) – Data type.

Context.texture_cube(size: Tuple[int, int], components: int, data: Any = None, alignment: int = 1, dtype: str = 'f1') → TextureCube

  Returns a new `TextureCube` object.

  Note that the width and height of the cubemap must be the same.

  Parameters:

    - size (tuple) – The width, height of the texture. Each side of the cube will have this size.

    - components (int) – The number of components 1, 2, 3 or 4.

    - data (bytes) – Content of the texture. The data should be have the following ordering: positive_x, negative_x, positive_y, negative_y, positive_z, negative_z

    - alignment (int) – The byte alignment 1, 2, 4 or 8.

    - dtype (str) – Data type.

    - internal_format (int) – Override the internalformat of the texture (IF needed)

Context.depth_texture_cube(size: Tuple[int, int], data: Any | None = None, alignment: int = 4) → TextureCube

  Returns a new `TextureCube` object.

  Parameters:

    - size (tuple) – The width and height of the texture.

    - data (bytes) – Content of the texture.

    - alignment (int) – The byte alignment 1, 2, 4 or 8.

Context.simple_framebuffer(...)

  Deprecated, use `Context.framebuffer()` instead.

Context.renderbuffer(size: Tuple[int, int], components: int = 4, samples: int = 0, dtype: str = 'f1') → Renderbuffer

  Returns a new `Renderbuffer` object.

  Similar to textures, renderbuffers can be attached to framebuffers as render targets, but they cannot be sampled as textures.

  Parameters:

    - size (tuple) – The width and height of the renderbuffer.

    - components (int) – The number of components 1, 2, 3 or 4.

    - samples (int) – The number of samples. Value 0 means no multisample format.

    - dtype (str) – Data type.

Context.depth_renderbuffer(size: Tuple[int, int], samples: int = 0) → Renderbuffer

  Returns a new `Renderbuffer` object.

  Parameters:

    - size (tuple) – The width and height of the renderbuffer.

    - samples (int) – The number of samples. Value 0 means no multisample format.

Context.scope(framebuffer, enable_only, textures, uniform_buffers, storage_buffers, samplers)

  Returns a new `Scope` object.

  Scope objects can be attached to VertexArray objects to minimize the possibility of rendering within the wrong scope. VertexArrays with an attached scope always have the scope settings at render time.

  Parameters:

    - framebuffer (Framebuffer) – The framebuffer to use when entering.

    - enable_only (int) – The enable_only flags to set when entering.

    - textures (tuple) – List of (texture, binding) tuples.

    - uniform_buffers (tuple) – Tuple of (buffer, binding) tuples.

    - storage_buffers (tuple) – Tuple of (buffer, binding) tuples.

    - samplers (tuple) – Tuple of sampler bindings

Context.query(samples: bool, any_samples: bool, time: bool, primitives: bool) → Query

  Returns a new `Query` object.

  Parameters:

    - samples (bool) – Query `GL_SAMPLES_PASSED` or not.

    - any_samples (bool) – Query `GL_ANY_SAMPLES_PASSED` or not.

    - time (bool) – Query `GL_TIME_ELAPSED` or not.

    - primitives (bool) – Query `GL_PRIMITIVES_GENERATED` or not.

Context.compute_shader(...)

  A `ComputeShader` is a Shader Stage that is used entirely for computing arbitrary information. While it can do rendering, it is generally used for tasks not directly related to drawing.

  Parameters:

    source (str) – The source of the compute shader.

## External Objects

External objects are only useful for interoperability with other libraries.

Context.external_buffer(glo: int, size: int, dynamic: bool) → Buffer

  TBD

Context.external_texture(glo: int, size: Tuple[int, int], components: int, samples: int, dtype: str) → Texture

  Returns a new `Texture` object from an existing OpenGL texture object.

  The content of the texture is referenced and it is not copied.

  Parameters:

    - glo (int) – External OpenGL texture object.

    - size (tuple) – The width and height of the texture.

    - components (int) – The number of components 1, 2, 3 or 4.

    - samples (int) – The number of samples. Value 0 means no multisample format.

    - dtype (str) – Data type.

## Methods

Context.clear()

  Clear the bound framebuffer.

  If a viewport passed in, a scissor test will be used to clear the given viewport. This viewport take prescense over the framebuffers `scissor`. Clearing can still be done with scissor if no viewport is passed in.

  This method also respects the `color_mask` and `depth_mask`. It can for example be used to only clear the depth or color buffer or specific components in the color buffer.

  If the viewport is a 2-tuple it will clear the `(0, 0, width, height)` where `(width, height)` is the 2-tuple.

  If the viewport is a 4-tuple it will clear the given viewport.

  Args:

    red (float): color component. green (float): color component. blue (float): color component. alpha (float): alpha component. depth (float): depth value.

  Keyword Args:

    viewport (tuple): The viewport. color (tuple): Optional rgba color tuple

Context.enable_only()

  Clears all existing flags applying new ones.

  Note that the enum values defined in moderngl are not the same as the ones in opengl. These are defined as bit flags so we can logical or them together.

  Available flags:

  - `moderngl.NOTHING`

  - `moderngl.BLEND`

  - `moderngl.DEPTH_TEST`

  - `moderngl.CULL_FACE`

  - `moderngl.RASTERIZER_DISCARD`

  - `moderngl.PROGRAM_POINT_SIZE`

  Examples:

      # Disable all flags
      ctx.enable_only(moderngl.NOTHING)

      # Ensure only depth testing and face culling is enabled
      ctx.enable_only(moderngl.DEPTH_TEST | moderngl.CULL_FACE)

  Args:

    flags (EnableFlag): The flags to enable

Context.enable()

  Enable flags.

  Note that the enum values defined in moderngl are not the same as the ones in opengl. These are defined as bit flags so we can logical or them together.

  For valid flags, please see `enable_only()`.

  Examples:

      # Enable a single flag
      ctx.enable(moderngl.DEPTH_TEST)

      # Enable multiple flags
      ctx.enable(moderngl.DEPTH_TEST | moderngl.CULL_FACE | moderngl.BLEND)

  Args:

    flag (int): The flags to enable.

Context.disable()

  Disable flags.

  For valid flags, please see `enable_only()`.

  Examples:

      # Only disable depth testing
      ctx.disable(moderngl.DEPTH_TEST)

      # Disable depth testing and face culling
      ctx.disable(moderngl.DEPTH_TEST | moderngl.CULL_FACE)

  Args:

    flag (int): The flags to disable.

Context.enable_direct()

  Gives direct access to `glEnable` so unsupported capabilities in ModernGL can be enabled.

  Do not use this to set already supported context flags.

  Example:

      # Enum value from the opengl registry
      GL_CONSERVATIVE_RASTERIZATION_NV = 0x9346
      ctx.enable_direct(GL_CONSERVATIVE_RASTERIZATION_NV)

Context.disable_direct()

  Gives direct access to `glDisable` so unsupported capabilities in ModernGL can be disabled.

  Do not use this to set already supported context flags.

  Example:

      # Enum value from the opengl registry
      GL_CONSERVATIVE_RASTERIZATION_NV = 0x9346
      ctx.disable_direct(GL_CONSERVATIVE_RASTERIZATION_NV)

Context.finish()

  Wait for all drawing commands to finish.

Context.clear_samplers()

  Unbinds samplers from texture units.

  Sampler bindings do clear automatically between every frame, but lingering samplers can still be a source of weird bugs during the frame rendering. This methods provides a fairly brute force and efficient way to ensure texture units are clear.

  Parameters:

    - start (int) – The texture unit index to start the clearing samplers

    - stop (int) – The texture unit index to stop clearing samplers

  Example:

      # Clear texture unit 0, 1, 2, 3, 4
      ctx.clear_samplers(start=0, end=5)

      # Clear texture unit 4, 5, 6, 7
      ctx.clear_samplers(start=4, end=8)

Context.copy_buffer()

  Copy buffer content.

  Args:

    dst (Buffer): The destination buffer. src (Buffer): The source buffer. size (int): The number of bytes to copy.

  Keyword Args:

    read_offset (int): The read offset. write_offset (int): The write offset.

Context.copy_framebuffer()

  Copy framebuffer content.

  Use this method to:

  > - blit framebuffers.

  > - copy framebuffer content into a texture.

  > - downsample framebuffers. (it will allow to read the framebuffer’s content)

  > - downsample a framebuffer directly to a texture.

  Args:

    dst (Framebuffer or Texture): Destination framebuffer or texture. src (Framebuffer): Source framebuffer.

Context.detect_framebuffer()

  Detect a framebuffer.

  This is already done when creating a context, but if the underlying window library for some changes the default framebuffer during the lifetime of the application this might be necessary.

  Args:

    glo (int): Framebuffer object.

Context.memory_barrier()

  Applying a memory barrier.

  The memory barrier is needed in particular to correctly change buffers or textures between each shader. If the same buffer is changed in two shaders, it can cause an effect like ‘depth fighting’ on a buffer or texture.

  The method should be used between `Program` -s, between `ComputeShader` -s, and between `Program` -s and `ComputeShader` -s.

  Keyword Args:

    barriers (int): Affected barriers, default moderngl.ALL_BARRIER_BITS. by_region (bool): Memory barrier mode by region. More read on https://registry.khronos.org/OpenGL-Refpages/gl4/html/glMemoryBarrier.xhtml

Context.gc() → int

  Deletes OpenGL objects. Returns the number of objects deleted.

  This method must be called to garbage collect OpenGL resources when `gc_mode` is `'context_gc'``.

  Calling this method with any other `gc_mode` configuration has no effect and is perfectly safe.

Context.release()

## Attributes

Context.gc_mode: str

  The garbage collection mode.

  The default mode is `None` meaning no automatic garbage collection is done. Other modes are `auto` and `context_gc`. Please see documentation for the appropriate configuration.

  Examples:

      # Disable automatic garbage collection.
      # Each objects needs to be explicitly released.
      ctx.gc_mode = None

      # Collect all dead objects in the context and
      # release them by calling Context.gc()
      ctx.gc_mode = 'context_gc'
      ctx.gc()  # Deletes the collected objects

      # Enable automatic garbage collection like
      # we normally expect in python.
      ctx.gc_mode = 'auto'

Context.objects: deque

  Moderngl objects scheduled for deletion.

  These are deleted when calling `Context.gc()`.

Context.line_width: float

  Set the default line width.

  Warning

  A line width other than 1.0 is not guaranteed to work across different OpenGL implementations. For wide lines you should be using geometry shaders.

Context.point_size: float

  Set/get the point size.

  Point size changes the pixel size of rendered points. The min and max values are limited by `POINT_SIZE_RANGE`. This value usually at least `(1, 100)`, but this depends on the drivers/vendors.

  If variable point size is needed you can enable `PROGRAM_POINT_SIZE` and write to `gl_PointSize` in the vertex or geometry shader.

  Note

  Using a geometry shader to create triangle strips from points is often a safer way to render large points since you don’t have have any size restrictions.

Context.depth_func: str

  Set the default depth func.

  Example:

      ctx.depth_func = '<='  # GL_LEQUAL
      ctx.depth_func = '<'   # GL_LESS
      ctx.depth_func = '>='  # GL_GEQUAL
      ctx.depth_func = '>'   # GL_GREATER
      ctx.depth_func = '=='  # GL_EQUAL
      ctx.depth_func = '!='  # GL_NOTEQUAL
      ctx.depth_func = '0'   # GL_NEVER
      ctx.depth_func = '1'   # GL_ALWAYS

Context.depth_clamp_range: Tuple[float, float]

  Setting up depth clamp range (write only, by default `None`).

  `ctx.depth_clamp_range` offers uniform use of GL_DEPTH_CLAMP and glDepthRange.

  `GL_DEPTH_CLAMP` is needed to disable clipping of fragments outside near limit of projection matrix. For example, this will allow you to draw between 0 and 1 in the Z (depth) coordinate, even if `near` is set to 0.5 in the projection matrix.

  Note

  All fragments outside the `near` of the projection matrix will have a depth of `near`.

  See https://www.khronos.org/opengl/wiki/Vertex_Post-Processing#Depth_clamping for more info.

  `glDepthRange(nearVal, farVal)` is needed to specify mapping of depth values from normalized device coordinates to window coordinates. See https://registry.khronos.org/OpenGL-Refpages/gl4/html/glDepthRange.xhtml for more info.

  Example:

      # For glDisable(GL_DEPTH_CLAMP) and glDepthRange(0, 1)
      ctx.depth_clamp_range = None

      # For glEnable(GL_DEPTH_CLAMP) and glDepthRange(near, far)
      ctx.depth_clamp_range = (near, far)

Context.blend_func: tuple

  Set the blend func (write only).

  Blend func can be set for rgb and alpha separately if needed.

  Supported blend functions are:

      moderngl.ZERO
      moderngl.ONE
      moderngl.SRC_COLOR
      moderngl.ONE_MINUS_SRC_COLOR
      moderngl.DST_COLOR
      moderngl.ONE_MINUS_DST_COLOR
      moderngl.SRC_ALPHA
      moderngl.ONE_MINUS_SRC_ALPHA
      moderngl.DST_ALPHA
      moderngl.ONE_MINUS_DST_ALPHA

      # Shortcuts
      moderngl.DEFAULT_BLENDING     # (SRC_ALPHA, ONE_MINUS_SRC_ALPHA)
      moderngl.ADDITIVE_BLENDING    # (ONE, ONE)
      moderngl.PREMULTIPLIED_ALPHA  # (SRC_ALPHA, ONE)

  Example:

      # For both rgb and alpha
      ctx.blend_func = moderngl.SRC_ALPHA, moderngl.ONE_MINUS_SRC_ALPHA

      # Separate for rgb and alpha
      ctx.blend_func = (
          moderngl.SRC_ALPHA, moderngl.ONE_MINUS_SRC_ALPHA,
          moderngl.ONE, moderngl.ONE
      )

Context.blend_equation: tuple

  Set the blend equation (write only).

  Blend equations specify how source and destination colors are combined in blending operations. By default `FUNC_ADD` is used.

  Blend equation can be set for rgb and alpha separately if needed.

  Supported functions are:

      moderngl.FUNC_ADD               # source + destination
      moderngl.FUNC_SUBTRACT          # source - destination
      moderngl.FUNC_REVERSE_SUBTRACT  # destination - source
      moderngl.MIN                    # Minimum of source and destination
      moderngl.MAX                    # Maximum of source and destination

  Example:

      # For both rgb and alpha channel
      ctx.blend_equation = moderngl.FUNC_ADD

      # Separate for rgb and alpha channel
      ctx.blend_equation = moderngl.FUNC_ADD, moderngl.MAX

Context.multisample: bool

  Enable/disable multisample mode (`GL_MULTISAMPLE`).

  This property is write only.

  Example:

      # Enable
      ctx.multisample = True
      # Disable
      ctx.multisample = False

Context.viewport: tuple

  Get or set the viewport of the active framebuffer.

  Example:

      >>> ctx.viewport
      (0, 0, 1280, 720)
      >>> ctx.viewport = (0, 0, 640, 360)
      >>> ctx.viewport
      (0, 0, 640, 360)

  If no framebuffer is bound `(0, 0, 0, 0)` will be returned.

Context.scissor: tuple

  Get or set the scissor box for the active framebuffer.

  When scissor testing is enabled fragments outside the defined scissor box will be discarded. This applies to rendered geometry or `Context.clear()`.

  Setting is value enables scissor testing in the framebuffer. Setting the scissor to `None` disables scissor testing and reverts the scissor box to match the framebuffer size.

  Example:

      # Enable scissor testing
      >>> ctx.scissor = 100, 100, 200, 100
      # Disable scissor testing
      >>> ctx.scissor = None

  If no framebuffer is bound `(0, 0, 0, 0)` will be returned.

Context.version_code: int

Context.screen: Framebuffer

  A Framebuffer instance representing the screen.

  Normally set when creating a context with `create_context()` attaching to an existing context. This is the special system framebuffer represented by framebuffer `id=0`.

  When creating a standalone context this property is not set since there are no default framebuffer.

Context.fbo: Framebuffer

Context.front_face: str

  The front_face. Acceptable values are `'ccw'` (default) or `'cw'`.

  Face culling must be enabled for this to have any effect: `ctx.enable(moderngl.CULL_FACE)`.

  Example:

      # Triangles winded counter-clockwise considered front facing
      ctx.front_face = 'ccw'
      # Triangles winded clockwise considered front facing
      ctx.front_face = 'cw'

Context.cull_face: str

  The face side to cull. Acceptable values are `'back'` (default) `'front'` or `'front_and_back'`.

  This is similar to `Context.front_face()`

  Face culling must be enabled for this to have any effect: `ctx.enable(moderngl.CULL_FACE)`.

  Example:

      ctx.cull_face = 'front'
      ctx.cull_face = 'back'
      ctx.cull_face = 'front_and_back'

Context.wireframe: bool

  Wireframe settings for debugging.

Context.max_samples: int

  The maximum supported number of samples for multisampling.

Context.max_integer_samples: int

  The max integer samples.

Context.max_texture_units: int

  The max texture units.

Context.max_anisotropy: float

  The maximum value supported for anisotropic filtering.

Context.default_texture_unit: int

  The default texture unit.

Context.patch_vertices: int

  The number of vertices that will be used to make up a single patch primitive.

Context.provoking_vertex: int

  Specifies the vertex to be used as the source of data for flat shaded varyings.

  Flatshading a vertex shader varying output (ie. `flat out vec3 pos`) means to assign all vetices of the primitive the same value for that output. The vertex from which these values is derived is known as the provoking vertex.

  It can be configured to be the first or the last vertex.

  This property is write only.

  Example:

      # Use first vertex
      ctx.provoking_vertex = moderngl.FIRST_VERTEX_CONVENTION

      # Use last vertex
      ctx.provoking_vertex = moderngl.LAST_VERTEX_CONVENTION

Context.polygon_offset: tuple

  Get or set the current polygon offset.

  The tuple values represents two float values: `unit` and a `factor`:

      ctx.polygon_offset = unit, factor

  When drawing polygons, lines or points directly on top of exiting geometry the result is often not visually pleasant. We can experience z-fighting or partially fading fragments due to different primitives not being rasterized in the exact same way or simply depth buffer precision issues.

  For example when visualizing polygons drawing a wireframe version on top of the original mesh, these issues are immediately apparent. Applying decals to surfaces is another common example.

  The official documentation states the following:

      When enabled, the depth value of each fragment is added
      to a calculated offset value. The offset is added before
      the depth test is performed and before the depth value
      is written into the depth buffer. The offset value o is calculated by:
      o = m * factor + r * units
      where m is the maximum depth slope of the polygon and r is the smallest
      value guaranteed to produce a resolvable difference in window coordinate
      depth values. The value r is an implementation-specific int.

  In simpler terms: We use polygon offset to either add a positive offset to the geometry (push it away from you) or a negative offset to geometry (pull it towards you).

  - `units` is a int offset to depth and will do the job alone

      if we are working with geometry parallel to the near/far plane.

  - The `factor` helps you handle sloped geometry (not parallel to near/far plane).

  In most cases you can get away with `[-1.0, 1.0]` for both factor and units, but definitely play around with the values. When both values are set to `0` polygon offset is disabled internally.

  To just get started with something you can try:

      # Either push the geomtry away or pull it towards you
      # with support for handling small to medium sloped geometry
      ctx.polygon_offset = 1.0, 1.0
      ctx.polygon_offset = -1.0, -1.0

      # Disable polygon offset
      ctx.polygon_offset = 0, 0

Context.error: str

  The result of `glGetError()` but human readable.

  This values is provided for debug purposes only and is likely to reduce performace when used in a draw loop.

Context.extensions: Set[str]

  The extensions supported by the context.

  All extensions names have a `GL_` prefix, so if the spec refers to `ARB_compute_shader` we need to look for `GL_ARB_compute_shader`:

      # If compute shaders are supported ...
      >> 'GL_ARB_compute_shader' in ctx.extensions
      True

  Example data:

      {
          'GL_ARB_multi_bind',
          'GL_ARB_shader_objects',
          'GL_ARB_half_float_vertex',
          'GL_ARB_map_buffer_alignment',
          'GL_ARB_arrays_of_arrays',
          'GL_ARB_pipeline_statistics_query',
          'GL_ARB_provoking_vertex',
          'GL_ARB_gpu_shader5',
          'GL_ARB_uniform_buffer_object',
          'GL_EXT_blend_equation_separate',
          'GL_ARB_tessellation_shader',
          'GL_ARB_multi_draw_indirect',
          'GL_ARB_multisample',
          .. etc ..
      }

Context.info: Dict[str, Any]

  OpenGL Limits and information about the context.

  Example:

      # The maximum width and height of a texture
      >> ctx.info['GL_MAX_TEXTURE_SIZE']
      16384

      # Vendor and renderer
      >> ctx.info['GL_VENDOR']
      NVIDIA Corporation
      >> ctx.info['GL_RENDERER']
      NVIDIA GeForce GT 650M OpenGL Engine

  Example data:

      {
          'GL_VENDOR': 'NVIDIA Corporation',
          'GL_RENDERER': 'NVIDIA GeForce GT 650M OpenGL Engine',
          'GL_VERSION': '4.1 NVIDIA-10.32.0 355.11.10.10.40.102',
          'GL_POINT_SIZE_RANGE': (1.0, 2047.0),
          'GL_SMOOTH_LINE_WIDTH_RANGE': (0.5, 1.0),
          'GL_ALIASED_LINE_WIDTH_RANGE': (1.0, 1.0),
          'GL_POINT_FADE_THRESHOLD_SIZE': 1.0,
          'GL_POINT_SIZE_GRANULARITY': 0.125,
          'GL_SMOOTH_LINE_WIDTH_GRANULARITY': 0.125,
          'GL_MIN_PROGRAM_TEXEL_OFFSET': -8.0,
          'GL_MAX_PROGRAM_TEXEL_OFFSET': 7.0,
          'GL_MINOR_VERSION': 1,
          'GL_MAJOR_VERSION': 4,
          'GL_SAMPLE_BUFFERS': 0,
          'GL_SUBPIXEL_BITS': 8,
          'GL_CONTEXT_PROFILE_MASK': 1,
          'GL_UNIFORM_BUFFER_OFFSET_ALIGNMENT': 256,
          'GL_DOUBLEBUFFER': False,
          'GL_STEREO': False,
          'GL_MAX_VIEWPORT_DIMS': (16384, 16384),
          'GL_MAX_3D_TEXTURE_SIZE': 2048,
          'GL_MAX_ARRAY_TEXTURE_LAYERS': 2048,
          'GL_MAX_CLIP_DISTANCES': 8,
          'GL_MAX_COLOR_ATTACHMENTS': 8,
          'GL_MAX_COLOR_TEXTURE_SAMPLES': 8,
          'GL_MAX_COMBINED_FRAGMENT_UNIFORM_COMPONENTS': 233472,
          'GL_MAX_COMBINED_GEOMETRY_UNIFORM_COMPONENTS': 231424,
          'GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS': 80,
          'GL_MAX_COMBINED_UNIFORM_BLOCKS': 70,
          'GL_MAX_COMBINED_VERTEX_UNIFORM_COMPONENTS': 233472,
          'GL_MAX_CUBE_MAP_TEXTURE_SIZE': 16384,
          'GL_MAX_DEPTH_TEXTURE_SAMPLES': 8,
          'GL_MAX_DRAW_BUFFERS': 8,
          'GL_MAX_DUAL_SOURCE_DRAW_BUFFERS': 1,
          'GL_MAX_ELEMENTS_INDICES': 150000,
          'GL_MAX_ELEMENTS_VERTICES': 1048575,
          'GL_MAX_FRAGMENT_INPUT_COMPONENTS': 128,
          'GL_MAX_FRAGMENT_UNIFORM_COMPONENTS': 4096,
          'GL_MAX_FRAGMENT_UNIFORM_VECTORS': 1024,
          'GL_MAX_FRAGMENT_UNIFORM_BLOCKS': 14,
          'GL_MAX_GEOMETRY_INPUT_COMPONENTS': 128,
          'GL_MAX_GEOMETRY_OUTPUT_COMPONENTS': 128,
          'GL_MAX_GEOMETRY_TEXTURE_IMAGE_UNITS': 16,
          'GL_MAX_GEOMETRY_UNIFORM_BLOCKS': 14,
          'GL_MAX_GEOMETRY_UNIFORM_COMPONENTS': 2048,
          'GL_MAX_INTEGER_SAMPLES': 1,
          'GL_MAX_SAMPLES': 8,
          'GL_MAX_RECTANGLE_TEXTURE_SIZE': 16384,
          'GL_MAX_RENDERBUFFER_SIZE': 16384,
          'GL_MAX_SAMPLE_MASK_WORDS': 1,
          'GL_MAX_SERVER_WAIT_TIMEOUT': -1,
          'GL_MAX_TEXTURE_BUFFER_SIZE': 134217728,
          'GL_MAX_TEXTURE_IMAGE_UNITS': 16,
          'GL_MAX_TEXTURE_LOD_BIAS': 15,
          'GL_MAX_TEXTURE_SIZE': 16384,
          'GL_MAX_UNIFORM_BUFFER_BINDINGS': 70,
          'GL_MAX_UNIFORM_BLOCK_SIZE': 65536,
          'GL_MAX_VARYING_COMPONENTS': 0,
          'GL_MAX_VARYING_VECTORS': 31,
          'GL_MAX_VARYING_FLOATS': 0,
          'GL_MAX_VERTEX_ATTRIBS': 16,
          'GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS': 16,
          'GL_MAX_VERTEX_UNIFORM_COMPONENTS': 4096,
          'GL_MAX_VERTEX_UNIFORM_VECTORS': 1024,
          'GL_MAX_VERTEX_OUTPUT_COMPONENTS': 128,
          'GL_MAX_VERTEX_UNIFORM_BLOCKS': 14,
          'GL_MAX_VERTEX_ATTRIB_RELATIVE_OFFSET': 0,
          'GL_MAX_VERTEX_ATTRIB_BINDINGS': 0,
          'GL_VIEWPORT_BOUNDS_RANGE': (-32768, 32768),
          'GL_VIEWPORT_SUBPIXEL_BITS': 0,
          'GL_MAX_VIEWPORTS': 16
      }

Context.includes: Dict[str, str]

  Mapping used for include statements.

Context.extra: Any

  User defined data.

## Context Flags

Context flags are used to enable or disable states in the context. These are not the same enum values as in opengl, but are rather bit flags so we can `or` them together setting multiple states in a simple way.

These values are available in the `Context` object and in the `moderngl` module when you don’t have access to the context.

    import moderngl

    # From moderngl
    ctx.enable_only(moderngl.DEPTH_TEST | moderngl.CULL_FACE)

    # From context
    ctx.enable_only(ctx.DEPTH_TEST | ctx.CULL_FACE)

Context.NOTHING: int

  Represents no states. Can be used with `Context.enable_only()` to disable all states.

Context.BLEND: int

  Enable/disable blending

Context.DEPTH_TEST: int

  Enable/disable depth testing

Context.CULL_FACE: int

  Enable/disable face culling

Context.RASTERIZER_DISCARD: int

  Enable/disable rasterization

  Context flag: Enables `gl_PointSize` in vertex or geometry shaders.

  When enabled we can write to `gl_PointSize` in the vertex shader to specify the point size for each individual point.

  If this value is not set in the shader the behavior is undefined. This means the points may or may not appear depending if the drivers enforce some default value for `gl_PointSize`.

Context.PROGRAM_POINT_SIZE: int

  When disabled `Context.point_size` is used.

## Primitive Modes

Context.POINTS: int

  Each vertex represents a point

Context.LINES: int

  Vertices 0 and 1 are considered a line. Vertices 2 and 3 are considered a line. And so on. If the user specifies a non-even number of vertices, then the extra vertex is ignored.

Context.LINE_LOOP: int

  As line strips, except that the first and last vertices are also used as a line. Thus, you get n lines for n input vertices. If the user only specifies 1 vertex, the drawing command is ignored. The line between the first and last vertices happens after all of the previous lines in the sequence.

Context.LINE_STRIP: int

  The adjacent vertices are considered lines. Thus, if you pass n vertices, you will get n-1 lines. If the user only specifies 1 vertex, the drawing command is ignored.

Context.TRIANGLES: int

  Vertices 0, 1, and 2 form a triangle. Vertices 3, 4, and 5 form a triangle. And so on.

Context.TRIANGLE_STRIP: int

  Every group of 3 adjacent vertices forms a triangle. The face direction of the strip is determined by the winding of the first triangle. Each successive triangle will have its effective face order reversed, so the system compensates for that by testing it in the opposite way. A vertex stream of n length will generate n-2 triangles.

Context.TRIANGLE_FAN: int

  The first vertex is always held fixed. From there on, every group of 2 adjacent vertices form a triangle with the first. So with a vertex stream, you get a list of triangles like so: (0, 1, 2) (0, 2, 3), (0, 3, 4), etc. A vertex stream of n length will generate n-2 triangles.

Context.LINES_ADJACENCY: int

  These are special primitives that are expected to be used specifically with geomtry shaders. These primitives give the geometry shader more vertices to work with for each input primitive. Data needs to be duplicated in buffers.

Context.LINE_STRIP_ADJACENCY: int

  These are special primitives that are expected to be used specifically with geomtry shaders. These primitives give the geometry shader more vertices to work with for each input primitive. Data needs to be duplicated in buffers.

Context.TRIANGLES_ADJACENCY: int

  These are special primitives that are expected to be used specifically with geomtry shaders. These primitives give the geometry shader more vertices to work with for each input primitive. Data needs to be duplicated in buffers.

Context.TRIANGLE_STRIP_ADJACENCY: int

  These are special primitives that are expected to be used specifically with geomtry shaders. These primitives give the geometry shader more vertices to work with for each input primitive. Data needs to be duplicated in buffers.

Context.PATCHES: int

  primitive type can only be used when Tessellation is active. It is a primitive with a user-defined number of vertices, which is then tessellated based on the control and evaluation shaders into regular points, lines, or triangles, depending on the TES’s settings.

### Texture Filters

Also available in the `Context` instance including mode details.

Context.NEAREST: int

  Returns the value of the texture element that is nearest (in Manhattan distance) to the specified texture coordinates.

Context.LINEAR: int

  Returns the weighted average of the four texture elements that are closest to the specified texture coordinates. These can include items wrapped or repeated from other parts of a texture, depending on the values of texture repeat mode, and on the exact mapping.

Context.NEAREST_MIPMAP_NEAREST: int

  Chooses the mipmap that most closely matches the size of the pixel being textured and uses the `NEAREST` criterion (the texture element closest to the specified texture coordinates) to produce a texture value.

Context.LINEAR_MIPMAP_NEAREST: int

  Chooses the mipmap that most closely matches the size of the pixel being textured and uses the `LINEAR` criterion (a weighted average of the four texture elements that are closest to the specified texture coordinates) to produce a texture value.

Context.NEAREST_MIPMAP_LINEAR: int

  Chooses the two mipmaps that most closely match the size of the pixel being textured and uses the `NEAREST` criterion (the texture element closest to the specified texture coordinates ) to produce a texture value from each mipmap. The final texture value is a weighted average of those two values.

Context.LINEAR_MIPMAP_LINEAR: int

  Chooses the two mipmaps that most closely match the size of the pixel being textured and uses the `LINEAR` criterion (a weighted average of the texture elements that are closest to the specified texture coordinates) to produce a texture value from each mipmap. The final texture value is a weighted average of those two values.

## Blend Functions

Blend functions are used with `Context.blend_func` to control blending operations.

    # Default value
    ctx.blend_func = ctx.SRC_ALPHA, ctx.ONE_MINUS_SRC_ALPHA

Context.ZERO: int

  (0,0,0,0)

Context.ONE: int

  (1,1,1,1)

Context.SRC_COLOR: int

  (Rs0/kR,Gs0/kG,Bs0/kB,As0/kA)

Context.ONE_MINUS_SRC_COLOR: int

  (1,1,1,1) - (Rs0/kR,Gs0/kG,Bs0/kB,As0/kA)

Context.SRC_ALPHA: int

  (As0/kA,As0/kA,As0/kA,As0/kA)

Context.ONE_MINUS_SRC_ALPHA: int

  (1,1,1,1) - (As0/kA,As0/kA,As0/kA,As0/kA)

Context.DST_ALPHA: int

  (Ad/kA,Ad/kA,Ad/kA,Ad/kA)

Context.ONE_MINUS_DST_ALPHA: int

  (1,1,1,1) - (Ad/kA,Ad/kA,Ad/kA,Ad/kA)

Context.DST_COLOR: int

  (Rd/kR,Gd/kG,Bd/kB,Ad/kA)

Context.ONE_MINUS_DST_COLOR: int

  (1,1,1,1) - (Rd/kR,Gd/kG,Bd/kB,Ad/kA)

## Blend Function Shortcuts

Context.DEFAULT_BLENDING: tuple

  Shotcut for the default blending `SRC_ALPHA, ONE_MINUS_SRC_ALPHA`

Context.ADDITIVE_BLENDING: tuple

  Shotcut for additive blending `ONE, ONE`

Context.PREMULTIPLIED_ALPHA: tuple

  Shotcut for blend mode when using premultiplied alpha `SRC_ALPHA, ONE`

## Blend Equations

Used with `Context.blend_equation`.

Context.FUNC_ADD: int

  source + destination

Context.FUNC_SUBTRACT: int

  source - destination

Context.FUNC_REVERSE_SUBTRACT: int

  destination - source

Context.MIN: int

  Minimum of source and destination

Context.MAX: int

  Maximum of source and destination

## Other Enums

Context.FIRST_VERTEX_CONVENTION: int

  Specifies the first vertex should be used as the source of data for flat shaded varyings. Used with `Context.provoking_vertex`.

Context.LAST_VERTEX_CONVENTION: int

  Specifies the last vertex should be used as the source of data for flat shaded varyings. Used with `Context.provoking_vertex`.

Context.VERTEX_ATTRIB_ARRAY_BARRIER_BIT: int

  VERTEX_ATTRIB_ARRAY_BARRIER_BIT

Context.ELEMENT_ARRAY_BARRIER_BIT: int

  ELEMENT_ARRAY_BARRIER_BIT

Context.UNIFORM_BARRIER_BIT: int

  UNIFORM_BARRIER_BIT

Context.TEXTURE_FETCH_BARRIER_BIT: int

  TEXTURE_FETCH_BARRIER_BIT

Context.SHADER_IMAGE_ACCESS_BARRIER_BIT: int

  SHADER_IMAGE_ACCESS_BARRIER_BIT

Context.COMMAND_BARRIER_BIT: int

  COMMAND_BARRIER_BIT

Context.PIXEL_BUFFER_BARRIER_BIT: int

  PIXEL_BUFFER_BARRIER_BIT

Context.TEXTURE_UPDATE_BARRIER_BIT: int

  TEXTURE_UPDATE_BARRIER_BIT

Context.BUFFER_UPDATE_BARRIER_BIT: int

  BUFFER_UPDATE_BARRIER_BIT

Context.FRAMEBUFFER_BARRIER_BIT: int

  FRAMEBUFFER_BARRIER_BIT

Context.TRANSFORM_FEEDBACK_BARRIER_BIT: int

  TRANSFORM_FEEDBACK_BARRIER_BIT

Context.ATOMIC_COUNTER_BARRIER_BIT: int

  ATOMIC_COUNTER_BARRIER_BIT

Context.SHADER_STORAGE_BARRIER_BIT: int

  SHADER_STORAGE_BARRIER_BIT

Context.ALL_BARRIER_BITS: int

  ALL_BARRIER_BITS

## Examples

### ModernGL Context

    import moderngl
    # create a window
    ctx = moderngl.create_context()
    print(ctx.version_code)

### Standalone ModernGL Context

    import moderngl
    ctx = moderngl.create_standalone_context()
    print(ctx.version_code)