glscissor 多边形
    English answer：
    The `glScissor` function in OpenGL sets the scissor rectangle, which is a rectangular region of the window that OpenGL will draw to. Anything outside of this rectangle will be clipped, or not drawn.
    The `glScissor` function takes four parameters:
    `x`: The x-coordinate of the lower-left corner of the scissor rectangle.
    `y`: The y-coordinate of the lower-left corner of the scissor rectangle.
    `width`: The width of the scissor rectangle.
    `height`: The height of the scissor rectangle.
    The scissor rectangle is defined in window coordinates, which means that the origin (0, 0) i
s at the lower-left corner of the window. The x-axis extends to the right, and the y-axis extends to the top.
    The scissor rectangle can be used to clip any type of OpenGL primitive, including points, lines, and triangles. To enable scissor testing, you must first call `glEnable(GL_SCISSOR_TEST)`. Once scissor testing is enabled, only the pixels within the scissor rectangle will be drawn.GL甜文推荐
    The scissor rectangle can be used to create a variety of effects, such as:
    Clipping objects to a specific region of the window.
    Creating window borders.
    Masking out certain areas of the window.
    Here is an example of how to use the `glScissor` function:
    // Set the scissor rectangle to the entire window.
    glScissor(0, 0, windowWidth, windowHeight);
    // Enable scissor testing.
    glEnable(GL_SCISSOR_TEST);
    // Draw a rectangle.
    glBegin(GL_QUADS);
    glVertex2f(-1.0f, -1.0f);
    glVertex2f(1.0f, -1.0f);
    glVertex2f(1.0f, 1.0f);
    glVertex2f(-1.0f, 1.0f);
    glEnd();
    // Disable scissor testing.
    glDisable(GL_SCISSOR_TEST);
    This code will draw a rectangle that is the size of the entire window. The scissor rectangle will clip the rectangle so that it only draws within the window.