Alternative f => [f a] -> f a -fgl +opengl
Push the current matrix stack down by one, duplicating the current matrix, excute the given action, and pop the current matrix stack, replacing the current matrix with the one below it on the stack (i.e. restoring it to its previous state). The returned value is that of the given action. Note that a round-trip to the server is probably required. For a more efficient version, see unsafePreservingMatrix.
A more efficient, but potentially dangerous version of preservingMatrix: The given action is not allowed to throw an exception or change the current matrix mode permanently.
Delimit the vertices that define a primitive or a group of like primitives.
Only a subset of GL commands can be used in the delimited action: Those for specifying vertex coordinates (vertex, vertexv), vertex colors (color, colorv, secondaryColor, secondaryColorv, index, indexv), normal (normal, normalv), texture coordinates (texCoord, texCoordv, multiTexCoord, multiTexCoordv), and fog coordinates (fogCoord, fogCoordv). Additionally, evalPoint1, evalPoint2, evalCoord1, evalCoord1v, evalCoord2, evalCoord2v, materialAmbient, materialDiffuse, materialAmbientAndDiffuse, materialSpecular, materialEmission, materialShininess, callList, callLists, and setting edgeFlag are allowed. Writing the respective state variables is allowed in the delimited action, too.
Regardless of the chosen PrimitiveMode, there is no limit to the number of vertices that can be defined during a single renderPrimitive. Lines, triangles, quadrilaterals, and polygons that are incompletely specified are not drawn. Incomplete specification results when either too few vertices are provided to specify even a single primitive or when an incorrect multiple of vertices is specified. The incomplete primitive is ignored; the rest are drawn.
The minimum specification of vertices for each primitive is as follows: 1 for a point, 2 for a line, 3 for a triangle, 4 for a quadrilateral, and 3 for a polygon. Modes that require a certain multiple of vertices are Lines (2), Triangles (3), Quads (4), and QuadStrip (2).
A more efficient, but potentially dangerous version of renderPrimitive: The given action is not allowed to throw an exception.
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