Understading the stencil buffer

GlStateManager.pushMatrix();
GlStateManager.pushAttrib();

// Clear the stencil buffer
GL11.glClearStencil(0);
GL11.glClear(GL11.GL_STENCIL_BUFFER_BIT);

GL11.glEnable(GL11.GL_STENCIL_TEST);
GL11.glStencilOp(GL11.GL_REPLACE, GL11.GL_REPLACE, GL11.GL_REPLACE);
GL11.glStencilFunc(GL11.GL_ALWAYS, 1, -1); // 1 is written into the buffer when we draw
// Enable color mask
glColorMask(true, true, true, true);
GL11.glColor3f(255, 255, 255);
Gui.drawRect(screen.getScaledWidth() / 2 - 40, screen.getScaledHeight() / 2 - 40, screen.getScaledWidth() / 2 + 40, screen.getScaledHeight() / 2 + 40, new Color(210, 100, 80).getRGB());
// Disable color mask
glColorMask(false, false, false, false);
// Something something makes the fucking thing work (except it's not working)
GL11.glStencilFunc(GL11.GL_NOTEQUAL, 1, -1); // Only draw if not equal to 1
GL11.glStencilOp(GL11.GL_KEEP, GL11.GL_KEEP, GL11.GL_KEEP);
GL11.glColor3f(255, 255, 255);
drawRect(0, 0, width, height, -1);
// Disable color mask again(?)
glColorMask(false, false, false, false);
GlStateManager.popAttrib();
GlStateManager.popMatrix();