| HOpenGL Libraries (GLUT package) | Contents | Index

Graphics.UI.GLUT.Initialization

Portability | portable
Stability | stable
Maintainer | sven.panne@aedion.de

Contents

Primary initialization
Initial window geometry
Setting the initial display mode (I)
Setting the initial display mode (II)
Controlling the creation of rendering contexts
Direct/indirect rendering

Description

Actions and state variables in this module are used to initialize GLUT state. The primary initialization routine is `initialize`, which should only be called exactly once in a GLUT program. No other GLUT or OpenGL actions should be called before `initialize`, apart from getting or setting the state variables in this module.

The reason is that these state variables can be used to set default window initialization state that might be modified by the command processing done in `initialize`. For example, `initialWindowSize` can be set to `(`Size` 400 400)` before `initialize` is called to indicate 400 by 400 is the program's default window size. Setting the initial window size or position before `initialize` allows the GLUT program user to specify the initial size or position using command line arguments.

Synopsis

initialize :: String -> [String] -> IO [String]
getArgsAndInitialize :: IO (String, [String])
initialWindowPosition :: StateVar Position
initialWindowSize :: StateVar Size

data DisplayMode

= RGBAMode
| RGBMode
| IndexMode
| LuminanceMode
| WithAlphaComponent
| WithAccumBuffer
| WithDepthBuffer
| WithStencilBuffer
| SingleBuffered
| DoubleBuffered
| Multisampling
| Stereoscopic

initialDisplayMode :: StateVar [DisplayMode]
displayModePossible :: GettableStateVar Bool

data DisplayCapability

= DisplayRGBA
| DisplayRGB
| DisplayRed
| DisplayGreen
| DisplayBlue
| DisplayIndex
| DisplayBuffer
| DisplaySingle
| DisplayDouble
| DisplayAccA
| DisplayAcc
| DisplayAlpha
| DisplayDepth
| DisplayStencil
| DisplaySamples
| DisplayStereo
| DisplayLuminance
| DisplayNum
| DisplayConformant
| DisplaySlow
| DisplayWin32PFD
| DisplayXVisual
| DisplayXStaticGray
| DisplayXGrayScale
| DisplayXStaticColor
| DisplayXPseudoColor
| DisplayXTrueColor
| DisplayXDirectColor

data Relation

= IsEqualTo
| IsNotEqualTo
| IsLessThan
| IsNotGreaterThan
| IsGreaterThan
| IsAtLeast
| IsNotLessThan

data DisplayCapabilityDescription

= Where DisplayCapability Relation Int
| With DisplayCapability

initialDisplayCapabilities :: SettableStateVar [DisplayCapabilityDescription]

data RenderingContext

= CreateNewContext
| UseCurrentContext

renderingContext :: StateVar RenderingContext

data DirectRendering

= ForceIndirectContext
| AllowDirectContext
| TryDirectContext
| ForceDirectContext

directRendering :: StateVar DirectRendering

Primary initialization
initialize

:: String | The program name.
-> [String] | The command line arguments
-> IO [String] | Non-GLUT command line arguments

Given the program name and command line arguments, initialize the GLUT library and negotiate a session with the window system. During this process, `initialize` may cause the termination of the GLUT program with an error message to the user if GLUT cannot be properly initialized. Examples of this situation include the failure to connect to the window system, the lack of window system support for OpenGL, and invalid command line options.

`initialize` also processes command line options, but the specific options parsed are window system dependent. Any command line arguments which are not GLUT-specific are returned.

X Implementation Notes: The X Window System specific options parsed by `initialize` are as follows:

- `-display DISPLAY`: Specify the X server to connect to. If not specified, the value of the `DISPLAY` environment variable is used.
- `-geometry WxH+X+Y`: Determines where windows should be created on the screen. The parameter following `-geometry` should be formatted as a standard X geometry specification. The effect of using this option is to change the GLUT initial size and initial position the same as if `initialWindowSize` or `initialWindowPosition` were modified directly.
- `-iconic`: Requests all top-level windows be created in an iconic state.
- `-indirect`: Force the use of indirect OpenGL rendering contexts.
- `-direct`: Force the use of direct OpenGL rendering contexts (not all GLX implementations support direct rendering contexts). A fatal error is generated if direct rendering is not supported by the OpenGL implementation. If neither `-indirect` or `-direct` are used to force a particular behavior, GLUT will attempt to use direct rendering if possible and otherwise fallback to indirect rendering.
- `-gldebug`: After processing callbacks and/or events, call `reportErrors` to check if there are any pending OpenGL errors. Using this option is helpful in detecting OpenGL run-time errors.
- `-sync`: Enable synchronous X protocol transactions. This option makes it easier to track down potential X protocol errors.

getArgsAndInitialize :: IO (String, [String])
Convenience action: Initialize GLUT, returning the program name and any non-GLUT command line arguments.
Initial window geometry
initialWindowPosition :: StateVar Position

Controls the initial window position. Windows created by `createWindow` will be requested to be created with the current initial window position. The initial value of the initial window position GLUT state is ``Size` (-1) (-1)`. If either the X or Y component of the initial window position is negative, the actual window position is left to the window system to determine.

The intent of the initial window position is to provide a suggestion to the window system for a window's initial position. The window system is not obligated to use this information. Therefore, GLUT programs should not assume the window was created at the specified position.

initialWindowSize :: StateVar Size

Controls the initial window size. Windows created by `createWindow` will be requested to be created with the current initial window size. The initial value of the initial window size GLUT state is ``Size` 300 300`. If either the width or the height component of the initial window size is non-positive, the actual window size is left to the window system to determine.

The intent of the initial window size is to provide a suggestion to the window system for a window's initial size. The window system is not obligated to use this information. Therefore, GLUT programs should not assume the window was created at the specified size. A GLUT program should use the window's reshape callback to determine the true size of the window.

Setting the initial display mode (I)
data DisplayMode

A single aspect of a window which is to be created, used in conjunction with `initialDisplayMode`.
Constructors

RGBAMode | Select an RGBA mode window. This is the default if neither `RGBAMode` nor `IndexMode` are specified.
RGBMode | An alias for `RGBAMode`.
IndexMode | Select a color index mode window. This overrides `RGBAMode` if it is also specified.

LuminanceMode

Select a window with a "luminance" color model. This model provides the functionality of OpenGL's RGBA color model, but the green and blue components are not maintained in the frame buffer. Instead each pixel's red component is converted to an index between zero and `numColorMapEntries` and looked up in a per-window color map to determine the color of pixels within the window. The initial colormap of `LuminanceMode` windows is initialized to be a linear gray ramp, but can be modified with GLUT's colormap actions. Implementation Notes: `LuminanceMode` is not supported on most OpenGL platforms.

WithAlphaComponent | Select a window with an alpha component to the color buffer(s).
WithAccumBuffer | Select a window with an accumulation buffer.
WithDepthBuffer | Select a window with a depth buffer.
WithStencilBuffer | Select a window with a stencil buffer.
SingleBuffered | Select a single buffered window. This is the default if neither `DoubleBuffered` nor `SingleBuffered` are specified.
DoubleBuffered | Select a double buffered window. This overrides `SingleBuffered` if it is also specified.
Multisampling | Select a window with multisampling support. If multisampling is not available, a non-multisampling window will automatically be chosen. Note: both the OpenGL client-side and server-side implementations must support the `GLX_SAMPLE_SGIS` extension for multisampling to be available.
Stereoscopic | Select A Stereo Window.

Instances

Eq DisplayMode
Ord DisplayMode
Show DisplayMode

initialDisplayMode :: StateVar [DisplayMode]

Controls the initial display mode used when creating top-level windows, subwindows, and overlays to determine the OpenGL display mode for the to-be-created window or overlay.

Note that `RGBAMode` selects the RGBA color model, but it does not request any bits of alpha (sometimes called an alpha buffer or destination alpha) be allocated. To request alpha, specify `WithAlphaComponent`. The same applies to `LuminanceMode`.

displayModePossible :: GettableStateVar Bool
Contains `True` if the current display mode is supported, `False` otherwise.
Setting the initial display mode (II)
data DisplayCapability

Capabilities for `initialDisplayCapabilities`, most of them are extensions of the constructors of `DisplayMode`.
Constructors

DisplayRGBA | Number of bits of red, green, blue, and alpha in the RGBA color buffer. Default is "`IsAtLeast` `1`" for red, green, blue, and alpha capabilities, and "`IsEqualTo` `1`" for the RGBA color model capability.
DisplayRGB | Number of bits of red, green, and blue in the RGBA color buffer and zero bits of alpha color buffer precision. Default is "`IsAtLeast` `1`" for the red, green, and blue capabilities, and "`IsNotLessThan` `0`" for alpha capability, and "`IsEqualTo` `1`" for the RGBA color model capability.
DisplayRed | Red color buffer precision in bits. Default is "`IsAtLeast` `1`".
DisplayGreen | Green color buffer precision in bits. Default is "`IsAtLeast` `1`".
DisplayBlue | Blue color buffer precision in bits. Default is "`IsAtLeast` `1`".
DisplayIndex | Boolean if the color model is color index or not. True is color index. Default is "`IsAtLeast` `1`".
DisplayBuffer | Number of bits in the color index color buffer. Default is "`IsAtLeast` `1`".
DisplaySingle | Boolean indicate the color buffer is single buffered. Default is "`IsEqualTo` `1`".
DisplayDouble | Boolean indicating if the color buffer is double buffered. Default is "`IsEqualTo` `1`".
DisplayAccA | Red, green, blue, and alpha accumulation buffer precision in bits. Default is "`IsAtLeast` `1`" for red, green, blue, and alpha capabilities.
DisplayAcc | Red, green, and green accumulation buffer precision in bits and zero bits of alpha accumulation buffer precision. Default is "`IsAtLeast` `1`" for red, green, and blue capabilities, and "`IsNotLessThan` `0`" for the alpha capability.
DisplayAlpha | Alpha color buffer precision in bits. Default is "`IsAtLeast` `1`".
DisplayDepth | Number of bits of precsion in the depth buffer. Default is "`IsAtLeast` `12`".
DisplayStencil | Number of bits in the stencil buffer. Default is "`IsNotLessThan` `1`".
DisplaySamples | Indicates the number of multisamples to use based on GLX's `SGIS_multisample` extension (for antialiasing). Default is "`IsNotGreaterThan` `4`". This default means that a GLUT application can request multisampling if available by simply specifying "`With` `DisplaySamples`".
DisplayStereo | Boolean indicating the color buffer is supports OpenGL-style stereo. Default is "`IsEqualTo` `1`".

DisplayLuminance

Number of bits of red in the RGBA and zero bits of green, blue (alpha not specified) of color buffer precision. Default is "`IsAtLeast` `1`" for the red capabilitis, and "`IsEqualTo` `0`" for the green and blue capabilities, and "`IsEqualTo` `1`" for the RGBA color model capability, and, for X11, "`IsEqualTo` `1`" for the `DisplayXStaticGray` capability. SGI InfiniteReality (and other future machines) support a 16-bit luminance (single channel) display mode (an additional 16-bit alpha channel can also be requested). The red channel maps to gray scale and green and blue channels are not available. A 16-bit precision luminance display mode is often appropriate for medical imaging applications. Do not expect many machines to support extended precision luminance display modes.

DisplayNum | A special capability name indicating where the value represents the Nth frame buffer configuration matching the description string. When not specified, `initialDisplayCapabilities` also uses the first (best matching) configuration. `Num` requires a relation and numeric value.
DisplayConformant | Boolean indicating if the frame buffer configuration is conformant or not. Conformance information is based on GLX's `EXT_visual_rating` extension if supported. If the extension is not supported, all visuals are assumed conformant. Default is "`IsEqualTo` `1`".

DisplaySlow

Boolean indicating if the frame buffer configuration is slow or not. Slowness information is based on GLX's `EXT_visual_rating` extension if supported. If the extension is not supported, all visuals are assumed fast. Note that slowness is a relative designation relative to other frame buffer configurations available. The intent of the slow capability is to help programs avoid frame buffer configurations that are slower (but perhaps higher precision) for the current machine. Default is "`IsAtLeast` `0`". This default means that slow visuals are used in preference to fast visuals, but fast visuals will still be allowed.

DisplayWin32PFD | Only recognized on GLUT implementations for Win32, this capability name matches the Win32 Pixel Format Descriptor by number. `DisplayWin32PFD` can only be used with `Where`.
DisplayXVisual | Only recongized on GLUT implementations for the X Window System, this capability name matches the X visual ID by number. `DisplayXVisual` requires a relation and numeric value.
DisplayXStaticGray | Only recongized on GLUT implementations for the X Window System, boolean indicating if the frame buffer configuration's X visual is of type `StaticGray`. Default is "`IsEqualTo` `1`".
DisplayXGrayScale | Only recongized on GLUT implementations for the X Window System, boolean indicating if the frame buffer configuration's X visual is of type `GrayScale`. Default is "`IsEqualTo` `1`".
DisplayXStaticColor | Only recongized on GLUT implementations for the X Window System, boolean indicating if the frame buffer configuration's X visual is of type `StaticColor`. Default is "`IsEqualTo` `1`".
DisplayXPseudoColor | Only recongized on GLUT implementations for the X Window System, boolean indicating if the frame buffer configuration's X visual is of type `PsuedoColor`. Default is "`IsEqualTo` `1`".
DisplayXTrueColor | Only recongized on GLUT implementations for the X Window System, boolean indicating if the frame buffer configuration's X visual is of type `TrueColor`. Default is "`IsEqualTo` `1`".
DisplayXDirectColor | Only recongized on GLUT implementations for the X Window System, boolean indicating if the frame buffer configuration's X visual is of type `DirectColor`. Default is "`IsEqualTo` `1`".

Instances

Eq DisplayCapability
Ord DisplayCapability
Show DisplayCapability

data Relation

A relation between a `DisplayCapability` and a numeric value.
Constructors

IsEqualTo | Equal.
IsNotEqualTo | Not equal.
IsLessThan | Less than and preferring larger difference (the least is best).
IsNotGreaterThan | Less than or equal and preferring larger difference (the least is best).
IsGreaterThan | Greater than and preferring larger differences (the most is best).
IsAtLeast | Greater than or equal and preferring more instead of less. This relation is useful for allocating resources like color precision or depth buffer precision where the maximum precision is generally preferred. Contrast with `IsNotLessThan` relation.
IsNotLessThan | Greater than or equal but preferring less instead of more. This relation is useful for allocating resources such as stencil bits or auxillary color buffers where you would rather not over-allocate.

Instances

Eq Relation
Ord Relation
Show Relation

data DisplayCapabilityDescription

A single capability description for `initialDisplayCapabilities`.
Constructors

Where DisplayCapability Relation Int | A description of a capability with a specific relation to a numeric value.
With DisplayCapability | When the relation and numeric value are not specified, each capability has a different default, see the different constructors of `DisplayCapability`.

Instances

Eq DisplayCapabilityDescription
Ord DisplayCapabilityDescription
Show DisplayCapabilityDescription

initialDisplayCapabilities :: SettableStateVar [DisplayCapabilityDescription]

Controls the initial display mode used when creating top-level windows, subwindows, and overlays to determine the OpenGL display mode for the to-be-created window or overlay. It is described by a list of zero or more capability descriptions, which are translated into a set of criteria used to select the appropriate frame buffer configuration. The criteria are matched in strict left to right order of precdence. That is, the first specified criterion (leftmost) takes precedence over the later criteria for non-exact criteria (`IsGreaterThan`, `IsLessThan`, etc.). Exact criteria (`IsEqualTo`, `IsNotEqualTo`) must match exactly so precedence is not relevant.

Unspecified capability descriptions will result in unspecified criteria being generated. These unspecified criteria help `initialDisplayCapabilities` behave sensibly with terse display mode descriptions.

Here is an example using `initialDisplayCapabilities`:

        initialDisplayCapabilities $= [ With  DisplayRGB,
                                        Where DisplayDepth IsAtLeast 16,
                                        With  DisplaySamples,
                                        Where DisplayStencil IsNotLessThan 2,
                                        With  DisplayDouble ]

The above call requests a window with an RGBA color model (but requesting no bits of alpha), a depth buffer with at least 16 bits of precision but preferring more, multisampling if available, at least 2 bits of stencil (favoring less stencil to more as long as 2 bits are available), and double buffering.

Controlling the creation of rendering contexts
data RenderingContext

How rendering context for new windows are created.
Constructors

CreateNewContext | Create a new context via `glXCreateContext` or `wglCreateContext` (default).
UseCurrentContext | Re-use the current rendering context.

Instances

Eq RenderingContext
Ord RenderingContext
Show RenderingContext

renderingContext :: StateVar RenderingContext
(freeglut only) Controls the creation of rendering contexts for new windows.
Direct/indirect rendering
data DirectRendering

The kind of GLX rendering context used. Direct rendering provides a performance advantage in some implementations. However, direct rendering contexts cannot be shared outside a single process, and they may be unable to render to GLX pixmaps.
Constructors

ForceIndirectContext | Rendering is always done through the X server. This corresponds to the command line argument `-indirect`, see `initialize`.
AllowDirectContext | Try to use direct rendering, silently using indirect rendering if this is not possible.
TryDirectContext | Try to use direct rendering, issue a warning and use indirect rendering if this is not possible.
ForceDirectContext | Try to use direct rendering, issue an error and terminate the program if this is not possible.This corresponds to the command line argument `-direct`, see `initialize`.

Instances

Eq DirectRendering
Ord DirectRendering
Show DirectRendering

directRendering :: StateVar DirectRendering
(freeglut on X11 only) Controls which kind of rendering context is created when a new one is required.
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