HP Workstation zx2000 OpenGL 1.1 Reference for HP-UX 11.x - Page 396

S glScissor glScissor glScissor: define the scissor box. C Specification void glScissor( GLint x, GLint y, GLsizei width, GLsizei height) Parameters x, y width, height Specify the lower left corner of the scissor box. Initially (0, 0). Specify the width and height of the scissor box. When a GL context is first attached to a window, width and height are set to the dimensions of that window. Description glScissor defines a rectangle, called the scissor box, in window coordinates. The first two arguments, x and y, specify the lower left corner of the box. width and height specify the width and height of the box. To enable and disable the scissor test, call glEnable and glDisable with argument GL_SCISSOR_TEST. The test is initially disabled. While the test is enabled, only pixels that lie within the scissor box can be modified by drawing commands. Window coordinates have integer values at the shared corners of frame buffer pixels. glScissor(0, 0, 1, 1) allows modification of only the lower left pixel in the window, and glScissor(0, 0, 0, 0) doesn't allow modification of any pixels in the window. When the scissor test is disabled, it is as though the scissor box includes the entire window. Errors • GL_INVALID_VALUE is generated if either width or height is negative. • GL_INVALID_OPERATION is generated if glScissor is executed between the execution of glBegin and the corresponding execution of glEnd. Associated Gets glGet with argument GL_SCISSOR_BOX glIsEnabled with argument GL_SCISSOR_TEST 396 Chapter 17